bluuebunny/crossref_metadata_2025_split huggingface dataset:
Locomotion and cell-substratum contacts ofXenopusepidermal cellsin vitroandin situ
Authors: Radice Gary P. 
Published: April 2021

ABSTRACTStudies of tissue cell locomotion in culture have revealed much about cell motility, but whether behaviour in vitro resembles movement of the same cells in the animal is not clear. To investigate this, I compared the locomotion and cell-substratum contacts of epidermal cells from Xenopus tadpoles, migrating from explants on glass and plastic, with the same cells spreading in vivo during wound closure. Time-lapse cinemicrography showed that in both cases, cells spread by extending broad lamellipodia across the substratum, and did not form microspikes, filopodia, or blebs. The net rate of translocation was significantly slower in vitro, however, because cells both protruded lamellipodia slower and spent more time stationary or withdrawing, compared with cells in situ. The increased fluctuation seemed in part due to greater tension within the expanding sheet in vitro, since when tension was reduced, for example by wounding, the cells spread with less fluctuation and at a greater rate (6·5 μm/min compared with 0·77 μm/min). Micromanipulation showed that cells adhered to the substratum, both in situ and in vitro, by a broad contact where transmission electron microscopy (TEM) of sectioned material showed the cells to be less than 30 nm from the substratum. A similar separation was observed beneath cells in vitro when viewed in life with interference-reflexion optics (IRM). A few focal contacts (adhesion plaques) were also seen with IRM and TEM of cells in vitro, but were not seen with TEM of cells in situ. Submarginal as well as marginal basal cells of the advancing sheet adhere and spread on the substratum in both situations, whereas cells of the outer layer are passive. Hence, the overall pattern of migration of these cells is similar in vitro and in situ, the differences in rates of movement may be explained in part by the different degree of tension in the epithelium under the 2 conditions.
Adhesion and spreading ofLimulusblood cells on artificial surfaces
Authors: Armstrong Peter B. 
Published: April 2021

ABSTRACTThe horseshoe crab Limulus has a single cell type in the blood, the granular amoebocyte. These cells, which are non-adhesive and non-motile in the blood, transform to an adhesive and motile state following extravasation. In the present study, the events of transformation were studied by time-lapse microcinematography of cells plated on to glass. Following attachment of cells to the glass, the cells protrude filopods and engage in active motility. Motile cells show 2 convertible forms; a contracted form and a reversibly flattened form. Eventually the motile cells undergo irreversible flattening which is accompanied by spontaneous degranulation. The shapes of irreversibly spread cells are influenced by the arrangement of cell-substrate contacts established prior to degranulation, and by the pattern of contact of domains of granule-derived membrane introduced into the cell surface during granule exocytosis and their subsequent endoctyosis by the cell. The clottable protein released by spontaneous degranulation of the amoebocytes undergoes gelation in the absence of bacterial endotoxin. The ability to undergo spontaneous gelation stands in marked contrast to the absolute requirement for endotoxin for gelation of the clottable protein present in ‘Limulus amoebocyte lysate’, a commercially valuable preparation obtained from amoebocytes used to detect endotoxin.
Regulation of macrophage lysosomal enzyme secretion: Role of arachidonate metabolites, divalent cations and cyclic amp
Authors: Mcmillan Rodger M. , Macintyre D. Euan , Beesley Julian E. , Gordon John L. 
Published: April 2021

ABSTRACT
We have investigated the role in macrophage lysosomal enzyme release of arachidonate metabolites, extracellular divalent cations and cyclic AMP (cAMP) which modulate secretion in other cell types. Lysosomal enzyme secretion induced by zymosan was accompanied by release of malondialdehyde (MDA), which is derived from arachidonic acid via prostaglandin synthase. Blockade of MDA formation, by aspirin or indomethacin, was associated with only a small inhibitory effect on lysosomal enzyme release by zymosan: arachidonate metabolites thus play only a minor role in mediating macrophage lysosomal enzyme release.
Zymosan-induced secretion of lysosomal enzymes from macrophages did not require extracellular magnesium or calcium although release was enhanced by magnesium and inhibited by calcium. These effects may be related to an influence of the ions on phagocytosis. Elevation of intracellular divalent cation concentrations, by ionophore A23187, induced release of lysosomal enzymes but this was a result of cell lysis.
Adenylate cyclase stimulants and dibutyryl cAMP produced slight inhibition of zymosan-induced lysosomal enzyme release. Aminophylline and papaverine caused more marked inhibition but their effects may be due to actions independent of phosphodiesterase inhibition.
Our data indicate that arachidonate metabolites and cAMP do not play a major role in regulating zymosan-induced enzyme release from macrophages. Extracellular calcium and magnesium may modulate secretion but the role of intracellular divalent cations remains to be established. We conclude that macrophage lysosomal enzyme secretion is controlled by regulatory mechanisms different from those which control similar degranulation processes in other cell types.
Ultrastructure and histochemistry of the watermelon stigma
Authors: Sedgley Margaret 
Published: April 2021

ABSTRACT
The ultrastructure and histochemistry of the watermelon stigma were followed from 6 days before flower opening to anthesis. Starch and lipid were present in the immature papilla cells but had largely disappeared from the cells by anthesis, when carbohydrate and lipid were present in the stigma secretion external to the cell wall. The mature papilla cells had simple wall thickenings and were transfer cells. The wall thickenings were associated with dictyosomes and secretory vesicles. Other characteristics indicating a secretory function for the papilla cells included plastid—ER complexes and close associations between ER and secretory vesicles at the plasmalemma. Granulocrine secretion involving dictyosomes and ER is suggested for the carbohydrate component of the secretion.
Studies on the surface properties of hybrid cells: III. A membrane glycoprotein found on the surface of a wide range of malignant cells
Authors: Atkinson M. A. L. , Bramwell M. E. 
Published: April 2021

ABSTRACT
We report here the presence of a glycoprotein of apparent molecular mass 90000 daltons on the surface of membranes of malignant cells, which is absent or very much reduced on the surface of non-malignant cells. This glycoprotein is rich in sialic acid and appears to be sensitive to the concentration of cAMP under certain conditions.
Analysis of the labelled sugars present in the glycoproteins of cells metabolically labelled with [14C]glucosamine suggests that all the enzymes necessary for the conversion of the tracer precursor into the sugars normally found to be labelled are present in both the malignant and the non-malignant cells.
Analysis of skin fibroblast aggregation in duchenne muscular dystrophy
Authors: Jones G. E. , Witkowski J. A. 
Published: April 2021

ABSTRACT
Skin fibroblasts from patients with Duchenne muscular dystrophy have a low intercellular adhesiveness compared with normal cells when aggregated in a Couette viscometer (collison efficiencies of 2-52 and 4-62, respectively). The pattern of aggregation was quantitated using a digitizer system to measure the areas of particles (single cells and aggregates) formed after 20 min aggregation. This size analysis showed that the majority of dystrophic cells remained unaggregated but that a small number of very large aggregates was always formed. Normal cell suspensions only rarely contained large aggregates but contained many intermediate-size aggregates. These differences in intercellular adhesiveness and aggregate pattern formation indicate that there may be an alteration in the surface of dystrophic cells.
Comparison of multiple injections with continuous infusion of tritiated thymidine, and estimation of the cell cycle time
Authors: Blenkinsopp W. K. , Gilbert C. W. 
Published: April 2021

ABSTRACT
Labelled nuclei were counted in stratified squamous epithelium in mice killed after 24 h intraperitoneal administration of tritiated thymidine to label cells synthesizing deoxyribonucleic acid. Multiple injections produced the same result as an infusion of tritiated thymidine given after 24 h infusion of saline, but infusion of tritiated thymidine alone produced a different result. Thus, cell proliferation was depressed during the first 24 h of continuous infusion but was normal during the second 24 h.
Comparison of proliferation of the oesophageal epithelium at the level of the thyroid and at the level of the diaphragm showed no difference between the two.
Comparison of male with female mice given 72-h infusions of tritiated thymidine showed that cell proliferation occurred at the same rate in both.
The cell cycle time was estimated in the epithelium of the oesophagus and tongue by comparison of mice given a single injection with mice given multiple injections of tritiated thymidine.
Sodium butyrate blocks hela cells preferentially in early G
1 phase of the cell cycle
Authors: Xue Shaobai , Rao Potu N. 
Published: April 2021

ABSTRACT
The effects of sodium butyrate on the cell-cycle traverse of HeLa cells was re-examined using the kinetic and the premature chromosome condensation methods of cell-cycle analysis. The results of this study indicate that the sodium butyrate effects are dose-dependent and cell-cycle phase-specific. Cells in the early G1 period are the most sensitive to the inhibitory effects of the drug. When HeLa cells in exponential growth were exposed to a 5 mM concentration of butyrate for 48 h, 67% of the cell population was preferentially arrested in the early G1 period as indicated by the condensed morphology of the prematurely condensed chromosomes (PCC). There was no accumulation of cells in the G1 period. The results of this study suggest that hyperacetylation of histones induced by sodium butyrate does not necessarily result in decondensation of chromatin and the butyrate-enhanced protein, which has been reported to be present in butryate-treated cells, may have a role in the regulation of the transition of cells from early G1 to the subsequent phases of the cell cycle.
High-resolution electron microscopy of glycoproteins: The crystalline cell wall of lobomonas
Authors: Roberts K. , Shaw P. J. , Hills G. J. 
Published: April 2021

ABSTRACT
Lobomonas piriformis is a member of an order of green algae (Volvocales) that have crystalline glycoprotein cell walls. As part of a program of investigation of these glycoproteins and their architecture we have studied the cell wall of Lobomonas by a variety of chemical, electron- microscopical and image-analysis techniques. Lobomonas and Vitreochlamys incisa show a very similar structure in their cell walls and represent 1 of the 4 classes into which all the structures of the walls of these algae that we have so far examined fall. The 2 classes that we have previously studied in detail, represented by Chlamydomonas reinhardii and Chlorogonium elongatum, have a crystalline component of the wall that is a more or less smooth continuous surface overlying an amorphous inner wall layer. Although Lobomonas also has this 2-layer structure, the crystalline layer consists of distinct plates, each of which is built around a single, very coherent crystal lattice. The polar nature of the architecture of the cell wall is shown by sectioning and by examination of the cell-wall surface by metal-shadowing of carbon replicas, both of intact cells and of isolated cell-wall plates.
There are great similarities in chemical composition between the glycoproteins of the cell wall of C. reinhardii and those of Lobomonas. Both have a large content of hydroxyproline in their amino acid composition and a sugar/hydroxyproline ratio of about 6·0, and both contain sugar sulphates. Lobomonas however has a large glucose content, whereas Chlamydomonas has almost none. Electron micrographs of walls stained with methylamine tungstate and shadowed specimens show that the Lobomonas crystal structure is entirely different from that of C. reinhardii, and that there is a distinctly different structure in the centre of the plates from that at their edges, although the transition between the 2 areas occurs with no distortion of the crystal lattice. Computer image analysis has been used to calculate reconstructed images of the 2 areas, and by using minimal-dose techniques has yielded 2-dimensional maps of the negatively stained structure at a resolution of 1·8 nm. The 2-sided plane group of both areas of the crystal is P2, and the centre area contains 2 distinct structural units, both centred on dyad axes, together with other more complex features. In the edge structure, one of the structural units appears unchanged, but the other unit has a considerably different appearance. The most likely interpretation of this is as a conformational or positional change in one of the subunits. However, because the underlying lattice is so accurately maintained across this transition, it seems probable that the basic structural arrangement that defines the lattice is common to the 2 areas. Some of the computational and mathematical techniques used in the image analysis have not been previously published and are described in detail and compared with published techniques in an Appendix.
Cell-to-substrate contacts in an adhesion-defective mutant of balb/c3T3 cells
Authors: Yates James R. , Izzard Colin S. 
Published: April 2021

ABSTRACT
The cell-to-substrate contacts of the adhesion-defective mutant, AD6, have been examined by interference reflexion microscopy and compared with those of the wild-type Balb/c3T3 cell. The 2 cell-types differed in their ability to produce focal contacts with the substrate (10–15 nm separation distance). Only 10% of AD6 versus 92% of Balb/c3T3 cells formed these contacts. When present in AD6 the focal contacts were smaller and fewer in number per cell than in Balb/c3T3. Close contact with the substrate (approx. 30 nm separation distance) was formed by both cell types. The absence of the stronger focal contacts accounts for the reduced substrate adhesion of the mutant cells and for other phenotypic characteristics such as reduced spreading, rounded shape, altered pattern of movement, and absence of stress fibres. The reduced adhesion of the mutant has been attributed to a change in the pattern of glycoproteins exposed at the cell surface, which results from a defect in glycosylation. This suggests that normal glycosylation and correct exposure of one or more cell surface components are required for the formation of a specific substrate adhesion, the focal contact, and offers the possibility of identifying individual surface components involved in formation of this adhesion.
Attention is drawn to zero-order minima originating from cell thickness and not cell-to-substrate separation distance in the interference reflexion image.
The amphibian epidermis: distribution of mitochondria-rich cells and the effect of oxytocin
Authors: Brown D. , Grosso A. , Sousa R. C. De 
Published: April 2021

ABSTRACT
It is known that the ion-transporting capacity and the permeability to water of amphibian skins vary greatly both between and within species. Furthermore, the extent to which different skins respond to hormonal stimulation of these parameters also shows considerable inter- and intra-specific variation. As a first step towards defining a possible morphological basis for this physiological heterogeneity, we examined different regions of skins from 3 anurans, Bufo bufo, Rana ridibunda and Xenopus laevis, that are species with widely differing habitats. The mitochondria-rich cell population of the epidermis was counted and the epidermal thickness was measured. There were large differences in the mitochondria-rich cell content and in the epidermal thickness of the skins from different species and from different regions of skin from the same animal.
In a second set of studies, the same morphological features were examined and, in addition, routine functional parameters were measured to monitor some transport properties of the skins used. The skins also varied considerably with respect to short-circuit current, potential difference, water permeability and sensitivity to oxytocin. Although no apparent relationship was noted between either basal or hormone-stimulated physiological parameters and the morphological features of the individual skins, the striking variation in the density of mitochondria-rich cells in amphibian epidermis merits further studies, including the use of techniques or experimental designs that allow the movement of individual species of ion across the skin to be followed.
The structure and chemistry of plastid differentiation during male meiosis in Lilium Henryi
Authors: Dickinson H. G. 
Published: April 2021

ABSTRACT
The unusual content of the plastids characteristic of male meiosis and microsporogenesis in Lilium henryi has been investigated using enzymic digestion of material prepared for electron microscopy. Apart from membranous tubules and osmiophilic droplets, commonly regarded as normal constituents of the stroma of undifferentiated plastids, these organelles contained a single conspicuous association between membrane and particulate material and wefts of filaments. Enzymic digestion revealed the membrane-particle association (MPA) to contain RNA and some protein, and the filaments to be entirely proteinaceous. The use of DNase on this material proved both unreliable and, on occasions, unspecific, so no new information has emerged as to the disposition of DNA within these organelles. Many of the plastids divide immediately after meiosis and the MPAs normally divide in step with the orgenelles. The activities of the MPA and those of the filaments are discussed in terms of changes in the organelle population as a whole, and also in consideration of the fundamental events occurring elsewhere in the cells during the alternation from the diploid sporophyte to the haploid gametophyte.
Growth and differentiation of the Golgi apparatus and wall formation during carposporogenesis in the red alga, Gigartina teedii (Roth) Lamour
Authors: Tsekos Ioannes 
Published: April 2021

ABSTRACTThe fine structure of the Golgi apparatus during development of carposporangia of Gigartina teedii has been studied. Dictyosomes in differentiating carposporangia undergo extraordinary changes in size and morphology.Dictyosomes of gonimoblast cells and the auxiliary cell are composed of a stack of 5–7 straight cistemae and are approximately 0·18μm thick; from the structural and functional viewpoint, these are similar to dictyosomes in most other plants.Hypertrophied Golgi cistemae with fibrillar contents occur in immature and nearly mature carposporangia. Secretory vesicles originate from the ends of cistemae and by complete vésiculation of terminal cistemae; vesicles with a diameter of 0·2–0·6 μm and fibrillar contents are abundant throughout the cytoplasm of immature and nearly mature carposporangia. Some vesicles secrete their contents into the carpospore wall. At this stage the dictyosomes are straight in profile and only some Golgi cistemae and Golgi vesicles show acid phosphatase activity.Mucilage sacs appearing to be derived from either dilating endoplasmic reticulum or membraneous formations with a lysosomal character exist in both the mature gonimoblast cells and the immature carposporangia. These mucilage sacs constitute a considerable portion of the cytoplasmic volume and ultimately migrate to the outside of the cytoplasm. The mucilage sacs disappear completely in the mature carposporangia.Throughout the development of the wall of immature and nearly mature carposporangia, multi-vesicular lomasome-like bodies, showing acid phosphatase activity, are released through the plasmalemma. Apart from any other possible activities, these bodies seem to contribute to the plasticity of the expanding cell wall.The older carposporangia are recognized by having very active dictyosomes with a semicircular profile, producing vesicles with an electron-opaque centre (cored vesicles). These vesicles are likely to contain glycoproteins and to contribute to the formation of vacuoles with fibrous contents, as they are dominant in the carpospores before their liberation.The dictyosomes of older carposporangia are composed of a polarized stack usually composed of 7 to 11 cistemae. They exhibit anomalous, densely staining, laminated mid-regions, which are formed due to close apposition of 6—7 adjacent cistemae from the forming face. The mid-regions of the rest of the cistemae towards the maturing face have large intercistemal spaces, which usually contain darkly staining small vesicles probably originating from the endoplasmic reticulum. The cistemae towards the maturing face contain dense granules.Observations suggest that materials polymerize into fibrils within the Golgi system and the inflated Golgi-derived vesicles participate directly in the formation of the fibrillar network of the carpospore wall in the Gigartina teedii.
Immunological delineation in normal and malignant cells of a membrane protein involved in glucose transport: I. Preparation and properties of the antibody
Authors: Gingrich R. D. , Wouters M. , Bramwell M. E. , Harris H. 
Published: April 2021

ABSTRACT
Partially purified preparations of the 200000 Mt membrane glycoprotein described by Bramwell & Harris were used as antigens to generate monoclonal antibodies. Whether the protein was prepared from human or mouse tumours, the mice immunized with it yielded monoclonal antibodies of broadly similar specificities. All the antibodies obtained were of the immunoglobulin M class, despite a prolonged immunization schedule, and recognized an antigen that was present on the surface of mouse, rat and human cells. One such antibody, M/27, was studied in detail. With the exception of 2 rat kidney cell lines, the antigen detected by M/27 was found on the surface of all cells grown in culture, whether malignant or not. However, in the mouse, the species in which the antibody was generated, M/27 discriminated sharply between malignant tumours and normal tissues excised directly from the animal. In normal adult or embryonic mouse tissues, whether they were composed of multiplying cells or not, the antigen detected by M/27 was present on the cell surface only at the lower limit of detection, if at all. Malignant mouse tumours grown in the animal produced large amounts of the antigen. Explantation of embryonic mouse fibroblasts induced the expression of the antigen, which was not detected on these same cells in their normal habitat in the growing embryo. Conversely, non-malignant cells that express the antigen in vitro cease to do so when they are re-introduced into the animal. The antigenic determinant appeared to be polypeptide in nature rather than polysaccharide.