bluuebunny/crossref_metadata_2025_split huggingface dataset:
Similarity of sister-cell trajectories in fibroblast clones
Authors: Levinstone D. , Eden M. , Bell E. 
Published: April 2021

ABSTRACTThe observation that sister cells of a fibroblast division execute somewhat symmetric trajectories has led to the controversial hypothesis that cell pathways on a substrate are preprogrammed in detail. We have investigated symmetry and structure in the paths of 170 human AG1519 sister-fibroblast pairs recorded on film and analysed by interactive computer techniques.In a set of plots of sister-cell trajectories recorded immediately after cell division, we found an average of 31 % mirror symmetry and 14 % rotation identity after rejecting tracks that crossed over each other, a result in substantial agreement with published data. Such ‘symmetries’ are quite inexact, however. A symmetry-controlled perceptual experiment using a stimulus set based on real tracks showed a bias towards mirror symmetry over identity. A large fraction of paired random trajectories of few independent steps and turning angles can be expected to exhibit true turn symmetry on the basis of chance alone. But as the number of turning angles increases the number of rigorously symmetrical pairs decreases sharply. Subjects classified nearly 50% of 10-step computer generated random persistent trajectory pairs as symmetrical while only a fraction of a per cent are rigorously so. In fact, they were classified as though they contained only three to four random independent steps. The bias of the human observer and chance may thus account for the perception of a high occurrence of sister trajectory symmetry in vitro.Since branching patterns of sister trajectories do not possess rigorous symmetry, we feel they cannot be taken as evidence of preprogramming. However, the dissimilarity of the structure of sister-cell walks does not rule out the possibility that sister cells are alike in other respects. We found a significant correlation between the time-average velocities of newly born sister cells, and suggest that it and other similarities may be due to the equipartitive character of mitosis. The correlation decays over a 2 · 5-day period after mitosis. But phenotypic sister-cell similarities do not appear to determine the sequence of turning angles in cell walks. If they did a claim might be made for the preprogramming of locomotion.
Phagocytosis by macrophages: III. Effects of heat-labile opsonin and poly(L-lysine)
Authors: Matsui Hiroshi , Ito Tadanao , Ohnishi Shun-Ichi 
Published: April 2021

ABSTRACT
To study the mechanism of action of fresh serum (heat-labile opsonin) and poly(L-lysine) (a non-physiological opsonin) on particle uptake by phagocytes, a kinetic analysis of attachment and ingestion of lipopolysaccharide-coated particles during phagocytosis by mouse peritoneal macrophages was undertaken. The relative attachment rate was obtained from the initial overall rate of phagocytosis. The ingestion rate constant was obtained from the time-course of ingestion of the particles attached to the cell surface into the cytoplasm, using spin-labelled paraffin particles and ascorbate, a membrane-impermeable reducing reagent.
Although the lipopolysaccharide-coated particles readily attached to the cell surface, they were ingested to only a small extent. Treatment of the particles with poly(L-lysine) and fresh serum influenced both attachment and ingestion. Poly(L-lysine) greatly increased the attachment rate, whereas fresh serum decreased it. The attachment rate was found to be closely correlated with the difference in surface charge density of the particles caused by such treatments, increasing with the decrease in negative charge density. Attachment of particles treated with fresh serum was strongly dependent on incubation temperature, and was inhibited by treatment of the cells with cytochalasin B or trypsin, whereas attachment of poly(L-lysine)-treated particles was only slightly, if at all, dependent on incubation temperature or treatment. Divalent cations in the incubation medium stimulated attachment of fresh-serum-treated particles. Treatment of the particles with both poly(L-lysine) and fresh serum made it possible for the particles to be ingested into the cytoplasm. The ingestion rate constants (k) for the two types of particles were almost identical (k = 1’2 × 10−1/min at 37°C), and they showed a similar temperature dependence. They were independent of the divalent cations in the incubation medium. Treatment of the cells with cytochalasin B inhibited ingestion. These results suggest that ingestion of the poly(L-lysine)-treated particles results from electrostatic non-specific interaction between the particles and the cell surface, whereas ingestion of the fresh-serum-treated particles results from specific interaction via ‘ligand-specific receptor)’ on the cell surface. Ingestion proceeded independently of such differences in the interaction, though attachment was strongly dependent on the electrostatic environment of the particle surface.
The quantitative utilization of amino acids and glucose and contact inhibition of growth in cultures of the human diploid cell, WI-38
Authors: Griffiths J. B. 
Published: April 2021

ABSTRACT
There are many reports in the literature showing that contact inhibition of growth is affected by the culture medium. A quantitative study of amino acid and glucose uptake by the human diploid cell line, WI-38 was carried out to determine more precisely what effect nutritional factors have on contact inhibition of growth.
Eagle’s minimal essential medium (MEM) was found to support higher cell yields than Eagle’s basal medium (BME) and for growth to continue beyond 96 h a medium change was essential. However, analysis of the used growth media showed that neither amino acids nor glucose were fully depleted after 96 h. The rate of glucose utilization was in the range 65–100 μg/mg dry wt./h and this agreed very closely with the results of other authors. The pattern of amino acid uptake also closely resembled that for other cell lines except that the utilization of cystine was higher. The nutritional requirements were further studied as the results from the medium analyses failed to explain the growth-promoting activity of MEM. Daily medium changes greatly increased cell yields even though the medium nutrients were not exhausted. This effect was dependent upon fresh medium being used and the only medium component found to be of importance was the amino acid complement. These results are discussed in relation to the low saturation density of diploid cells in culture and a possible explanation is proposed in terms of differences in the cell membrane between normal and altered cells.
A micromass culture method for rat embryonic neural cells
Authors: Flint O. P. 
Published: April 2021

ABSTRACT
A method of culturing early (13-day) rat embryo neural cells is described. Undifferentiated neural epithelium is disaggregated and cultured in small discrete islands. Cells that are destined to differentiate as neurons actively segregate from the other cells in the island and aggregate together into small clumps. Other cells flatten and attach to the substrate and resemble typical fibroblasts throughout the culture period. The clumps of preneuron cells spread out forming large irregular foci. Spreading is mediated by active cell movements. Cells in the foci differentiate as a pure population of neurons identifiable by specific inhibition of 3H-labelled y-amino butyric acid incorporation or by labelling with a monoclonal antibody to GQ-ganglioside. The ganglioside is not found on the cell surface at the start of culture after trypsinization, but emerges during the 5 days of culture. The antigen is similarly not present in the embryonic mesencephalon in vivo at 13 days post coitum, only emerging later in the differentiated midbrain. There is thus an apparent de novo synthesis, which is paralleled in vivo and in vitro.
Fibrinogen And Fibronectin As Substrates For Epidermal Cell Migration During Wound Closure
Authors: Donaldson Donald J. , Mahan James T. 
Published: April 2021

ABSTRACT
Pieces of glass coverslip coated with human fibronectin or human fibrinogen were implanted under one margin of a skin wound on adult newt (Notophthalmus viridescens) hind limbs. In contrast to uncoated glass or glass coated with newt serum, bovine serum or bovine serum albumin, glass treated with either fibronectin or fibrinogen supported considerable epidermal cell migration. When optimal amounts of each protein were used, the amount of migration on fibrinogen-coated glass did not differ from the amount on fibronectin-coated glass or from the amount on the wound bed. Migration on a fibronectin substrate could be blocked by treating the substrate with an antiserum against fibronectin just prior to implantation. Similarly, migration on a fibrinogen substrate could be blocked by exposing it to an antiserum against fibrinogen. While we have yet to determine if fibrinogen and fibronectin are interacting directly with the cell surface, our observations suggest that these two proteins may play an important role in wound closure by providing a suitable substrate for epithelial cell migration.
Cell fractionation with affinity ligands conjugated to agarose-polyacrolein microsphere beads
Authors: Margel S. , Ofarim M. , Eshhar Z. 
Published: April 2021

ABSTRACT
A new effective insoluble support useful for cell fractionation based on agarose-polyacrolein microsphere beads (APAMB) of diameters 150–250 μm has been developed. The synthesized polyacrolein (PA) microspheres, of average diameter 0·2 μm, are provided with reactive aldehyde groups through which various ligands containing primary amino groups are bound covalently in a single step at physiological pH. Antibodies coupled to the microspheres are very effective for labelling of cell surface receptors on human red blood cells and mouse lymphoid cells.
APAMB were obtained by encapsulating the PA microspheres with agarose. Antibodies and lectins bound to the APAMB served to construct affinity columns for the separation of red blood cells and murine lymphocyte subpopulations. Anti-human red blood cell antibodies coupled to antiimmunoglobulin APAMB are effective in separating human from turkey red blood cells, whereas either anti-Thy l·2 anti-immunoglobulin antibodies or soybean agglutinin coupled to APAMB have proved useful for the separation of T and B cells from heterogeneous population of spleen cells. The separation procedure is simple, rapid and effective. The viability of the fractionated cells is unaffected by the procedure and the recovery of the cells is high: between 80 % and 100 %.
Theoretical Analysis Of A Method For Determining The Pattern Of Macromolecular Synthesis During The Cell Cycle
Authors: Fraser R. S. S. , Barnes A. 
Published: April 2021

ABSTRACT
The dual-labelling centrifugal-elutriation method has been extensively used to study patterns of macromolecular synthesis and accumulation in the yeast cell cycle. Cells are long-term labelled with a radioactive precursor for about 1· 5 cycles (a measure of macromolecular mass), then pulse-labelled with a precursor containing a different radioactive isotope for the final 0·1 cycle (a measure of rate of synthesis). Harvested cells are fractionated into cell cycle stages by centrifugal elutriation, and changes in pulse: long-term labelling during the cycle determined. This pattern of change is compared with theoretical changes in rate: mass calculated for various patterns of synthesis. Using this method, it has been suggested that rates of synthesis and accumulation of several types of RNA and protein all increase exponentially through the cycle.
In contrast, experiments using synchronous cultures or zonal centrifugation for cell cycle analysis have suggested other synthetic patterns, including periodic doubling in rate in each cycle. In this paper we analyse whether the dual-labelling, centrifugal-elutriation method is capable of discriminating between exponential and periodic rate-doubling patterns. Three possible sources of imprecision in the method and its application are examined.
(1) Theoretical rate: mass curves have been simulated for macromolecules with a wider range of properties than previously considered. It is shown that for some important classes, such as messenger RNAs, with turnover rates in the range measured experimentally, and proteins, differences between rate: mass curves for exponential and periodic rate-doubling models are considerably smaller than previously suggested.
(2) Long-term labelling is shown to be an accurate measure of macromolecular mass, but pulse-labelling can be inadequate as a measure of rate of synthesis. The error is greater with RNAs with faster turnover, and again reduces the ability of the method to discriminate exponential and periodic rate-doubling models of synthesis.
(3) Imperfections in cell cycle fractionation by centrifugal elutriation are examined, and by computer simulation it is shown that these also reduce the ability of the method to distinguish between the two models of synthesis.
The three sources of imprecision are cumulative. It is concluded from simulation analyses that the differences between exponential and periodic rate-doubling patterns analysed by the method would be so small as to be almost impossible to establish against the background of error in experimental measurement. We therefore suggest that in practice, the dual-labelling centrifugal-elutriation method is unable to discriminate between the exponentially increasing and periodic ratedoubling models.
The mathematical treatment developed in this paper should be applicable to analysis of other methods and cell cycle events.
Regulation Of Ciliary Pattern In Dileptus (CILIATA) : II. Formation Of A Cortical Domain Of Sensory Cilia From A Domain Of Locomotor Cilia
Authors: Golinska K. 
Published: April 2021

ABSTRACT
The surface of the ciliate Dileptus contains locomotor and sensory domains. Each domain contains cilia of its own kind, arranged in a characteristic pattern. Transformation of a portion of the locomotor area into the sensory domain has been studied. Locomotor ciliary units in the transforming area undergo resorption of ciliary shafts, which are subsequently replaced by shafts of a sensory type. Anterior to each transforming ciliary unit a new one is formed, and both acquire sensory rootlets. As a result, a double-kinetosomal sensory unit emerges. A regulatory change in structure occurs over a definite area that is determined to become the sensory cortical domain.
Ca2 +-dependent regulation of beat frequency of cilia in Paramecium
Authors: Nakaoka Yasuo , Tanaka Haruhiko , Oosawa Fumio 
Published: April 2021

ABSTRACT
Triton-extracted models of Paramecium cells prepared in the presence of Mg2+ and EGTA showed Ca2+ sensitivity not only in the direction of beat but also in the beat frequency of cilia. The beat frequency increased over a range of concentration of Ca2+ from 2 × 10−7to 4 × 10−7 M, in which the model swam forwards. The frequency increased also above 10−6M-Ca2+, in which the model swam backwards. The increase in frequency was inhibited by calmodulin antagonists. Intracellular injection of a Ca2+ buffer giving a free Ca2+ concentration of 2 × 10−7 to 5 × 10−7M in intact cells induced an increase in the beat frequency. Therefore, it is very likely that the beat frequency of cilia is regulated by the intracellular concentration of Ca2+.
Desmosomes in hamster cheek pouch epithelium: Their quantitative characterization during epithelial differentiation
Authors: White F. H. , Gohari K. 
Published: April 2021

ABSTRACT
Desmosomes in stratified squamous epithelia appear to exhibit quantitative alterations during differentiation. In this work we use stereological and other morphometric methods to quantify these structures in epithelial cells from defined basal, spinous and granular strata. Hamster cheek pouch mucosa from five animals was processed for electron microscopy using strictly standardized techniques and a stratified random sampling procedure was used to obtain micrographs of cells from basal, spinous and granular layers. Stereological intersection counting techniques were used to determine for each layer the relative surface area of plasma membrane occupied by desmosomes (Ss), the number of desmosomesper unit surface area of plasma membrane (NS), the mean individual desmosomal diameter and the mean individual desmosomal surface area . In addition, estimates of nuclear volume were obtained by direct measurement of nuclear profiles and volume-to-surface ratios were obtained by a combination of point and intersection counting, which enabled estimates for the volume (Vccell) and plasma membrane surface area (SPM) of the ‘average’ cell within each stratum to be acquired. Using this information, it was then possible to calculate both the total surface area (S) and the number (N) of desmosomes on the plasma membranes of average cells.
The parameters SS and NS showed progressive increases between basal and granular layers, whereas values for and were lower in granular cells when compared with basal and spinous cells. The parameters Vccell, SPM, S and N all increased progressively and significantly during differentiation. Between basal and granular layers, the mean cell volume and surface area had each increased approximately threefold, whereas the surface area and number of desmosomes on the average cell plasma membrane had increased approximately seven- and eleven-fold, respectively. Granular cells thus possess more numerous desmosomes, which occupy a greater proportion of the plasma membrane area but which are individually smaller, when compared with basal and spinous layers.
A neurofibrillar method stains solitary (primary) cilia in the mammalian retina: Their distribution and age-related changes
Authors: Boycott B. B. , Hopkins J. M. 
Published: April 2021

ABSTRACT
Richardson’s reduced silver method, developed for the staining of autonomic nerve fibres in the mammalian intestine, is shown consistently to stain solitary (primary) cilia and diplosomes of the cells of the retinae of cats and rabbits. The cilia comprise a centriole, a basal body and an axoneme with a 9+0 complement of microtubules.
Probably all retinal cells possess a cilium during their development but, contrary to previous reports, not all retain the axoneme after birth. Axonemes are absent from horizontal, bipolar, microglia, Müllerian, and probably some other glial, cells; all of which showed paired centrioles (diplosomes) after staining. Photoreceptor, amacrine, Interplexiform, displaced amacrine and ganglion cells have each one cilium. These differences between cell types persist, without significant change, in the retina of adult rabbits up to the age of 2 years, and in the cat up to 5 years.
The alpha-type ganglion cells of the cat are an exception. In 4 to 8-week-old kittens they are all ciliated, like other types of ganglion cells. But by two years about 30% of central area α-cells lack an axoneme. Individual cells may have only diplosomes, unusual dispositions of the centrioles in the perikaryal cytoplasm, or even show complete loss of the whole ciliary apparatus. By 5 years of age the proportion of those α-cells showing unusual arrangements has increased to approximately 70%, while less than 5% of the other types of ganglion cells are so affected. Cilia of peripheral α-cells change at a different rate and by 5 years of age are approximately like the 2-year-old central area population.
Role Of Glycosaminoglycans And Collagen In The Development Of A Fibronectin-Rich Extracellular Matrix In Cultured Embryonic Corneal Epithelial Cells
Authors: Mattey D. L. , Garrod D. R. 
Published: April 2021

ABSTRACT
Corneal epithelial cells from 15-day chick embryos produce a fibronectin-rich extracellular matrix when cultured on glass, plastic and fibronectin-coated substrata. Cell culture in the presence of Streptomyces hyaluronidase or chondroitinase ABC resulted in considerable reduction of the matrix; collagenase had a lesser effect but nevertheless also reduced the matrix. In all enzyme treatments the cells attached and spread to form characteristic epithelial cell islands, but the margi nal cells of these islands showed a marked reduction in the number of lamellipodia and focal contacts. Also, the immunoAuorescent staining pattern for fibronectin was considerably reduced. Control cells cultured on a fibronectin-coated surface were able to reorganize the fibronectin into fibrils, whereas cells cultured in enzymes showed little or no ability to do so. The cellular reorganiza tion of fibronectin could also be inhibited by the addition of L-azetidine-2-carboxylic acid (LACA), an inhibitor of collagen secretion. Cells plated out in the presence of LACA spread much better on collagen substrata than on plastic, glass or fibronectin. However, in all cases very little fibronectin matrix was detectable in the epithelial islands.
The results suggest that components of the extracellular matrix (ECM) such as collagen, hyaluronic acid and chondroitin sulphates are not essential for the initial attachment and spreading of corneal epithelial cells in culture, but are important in the development of the ECM, and in maintaining a flattened morphology and spreading behaviour. It is suggested that fibronectin plays an important role in these interactions and that the ability of cells to organize fibronectin into fibrils is dependent on the presence of other ECM components such as glycosaminoglycans and collagen.
The cytoskeleton of the apical border of the lateral cells of freshwater mussel gill: Structural integration of microtubule and actin filament-based organelles
Authors: Reed William , Avolio Jock , Satir Peter 
Published: April 2021

ABSTRACT
The coexistence of densely packed microtubule- and microfilament-based elements in the apex of ciliated epithelial cells, such as the lateral (L) cells of freshwater mussel gill, suggests that with this system it may be possible to define structural connections and interactions that permit integrated cytoskeletal responses to known physiological stimuli. In this study we examine the structure of the L cell apex in detail. The central elements of the elaborate cytoskeleton of the cortex are the basal bodies whose specialized accessory processes are points of integration and the focus of cortical microtubule and microfilament networks. Each basal body supports a cilium and interacts with adjacent basal bodies and with the cell periphery via a dual set of fibre-containing flat trabeculae, both of which are attached to a special organizing centre, the basal foot cap. The distal trabecula is composed of microtubules and the proximal of microfilaments. Connecting the trabeculae, at vertices in the filamentous grids, are core bundles of microfilaments from apical microvilli. In this way, a zig-zag pattern that characterizes microvillar organization at the cell surface is generated. At the cell periphery, the microfilaments from basal foot caps join a peripheral band of microfilaments that underlies the cell border and is associated with four special sites, one in each corner of the cell. Mussel gill epithelial cells contain a polypeptide that resembles actin in its mobility in sodium dodecyl sulphate/10% (w/v) polyacrylamide gels and its affinity for DNase I. Decoration with heavy meromyosin demonstrates that many microfilaments of the L cell apex contain actin, including the microvillar core and peripheral band microfilaments. Actin-associated proteins are also present in these epithelial cells. The actin filaments of the peripheral band are organized to support contraction of the cell border, which would also affect each element of the cortex. This structural complexity, combined with the limited number of modes of interaction between various elements, suggests that the L cell apical cytoskeleton endows the cell with significant positional and morphogenetic information that could be used to compute organellar and cytoskeletal lengths, spacing and changes upon stimulation.