bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrophoretic and chemical characterization of the charged groups at the surface of murine CL3 ascites leukaemia cells
Authors: Ward P. D. , Ambrose E. J. 
Published: April 2021

ABSTRACT
The electrophoretic characteristics of the murine CL3 ascites tumour were investigated.
Treatment of the cells with formaldehyde raised the electrophoretic mobility (E.P.M.) from—1· 06 to—1 ·28 μ/sec/V/cm; subsequent treatment with diazomethane reduced their mobility to zero. The E.P.M. of the diazomethane-treated cells did not alter over the pH range 3·0–8·0. This proved that the only ionic groups at this cell surface were amino and carboxyl groups. The absence of phosphate groups, another possibility, was confirmed by the lack of calcium-ion binding from 10 mM Ca+ solutions.
Neuraminidase treatment reduced the E.P.M. from—1·06 to—0·55 μ/sec/V/cm and free sialic acid was identified in the enzyme supernatant. Subsequent treatment of the cells with formaldehyde raised the mobility to—1·22 μ/sec/V/cm indicating that the change in E.P.M. on neuraminidase treatment was not due solely to the removal of the carboxyl groups of sialic acid but also to a change in the ionic nature of the surface. This change is ascribed to a change in the conformation of the surface protein. The reason for this change and a suggestion for the possible role of sialic acid at the cell surface are mentioned.
Treatment of the cells with trypsin did not affect the viable cells in any way, suggesting that the surface proteins lack the basic amino acids lysine and arginine. Pronase treatment served only to show that much of the sialic acid was bound to protein; the total amount was not determined.
Particles present in the haemolymph and defensive secretions of insects
Authors: Kay D. , Rothschild Miriam , Aplin R. 
Published: April 2021

ABSTRACT
Defensive fluids obtained from the Garden Tiger, Scarlet Tiger and Burnet Moths and from the Monarch Butterfly and the Seven-Spot Ladybird Beetle, haemolymphs taken from the wasp, the Burying Beetle and the Rat Flea, and fluids from the eggs of the Garden Tiger, Gypsy Moth and Oak Eggar Moth were examined in the electron microscope after negative staining.
Except for the ladybird all the defensive fluids, haemolymphs and egg fluids contained particles 100–150 Å across which frequently had rectangular or square outlines. In some species the particles were occasionally arranged in groups of 2 and 4 and in the egg fluid of the Garden Tiger they were arranged in rows which were aligned side by side to form strands of considerable length.
The particles are believed to be protein. They correspond in size to the 16 s component of the haemocyanins of Limulus and Homarus and the protein particles found in Calliphora by other workers.
Alteration of nuclear distribution in B-mutant strains of Schizophyllum Commune
Authors: Koltin Y. , Flexer A. S. 
Published: April 2021

ABSTRACT
Sexual morphogenesis in Schizophyltum commune, a higher basidiomycete, is controlled by two incompatibility factors, A and B. A key event, the migration of nuclei from each mate throughout the mycelium of the other, is controlled by the B factor and occurs in A = B ‡ = matings. The distribution of nuclei in the resulting heterokaryon is irregular, and anucleate, uninucleate, binucleate and multinucleate cells are found. A similar distribution of nuclei is found in homokaryons carrying a mutation in the B factor. Because of their developmental history, strains that carry a mutated B factor offer a relatively simple system for the study of the events associated with nuclear migration. Growth of mutant-B germlings occurs in three stages: (I) most cells are binucleate; (II) most cells are uninucleate; (III) cells contain varied numbers of nuclei. The ratio of nuclei: cells remains constant during the transition from stage II to stage III. Changes in nuclear distribution result from movement of the nuclei from cell to cell, and the movement is associated with the disruption of the dolipore septum. The mutant-B system appears to offer an opportunity for the biochemical resolution of the events related to nuclear migration.
Karyotype analysis of the plant-parasitic nematode Heterodera glycines by electron microscopy I. the diploid
Authors: Goldstein Paul , Triantaphyllou A. C. 
Published: April 2021

ABSTRACT
Heterodera glycines is a diploid amphimictic nematode with n = 9 chromosomes. Nine normal synaptonemal complexes (SC) were detected following 3-dimensional reconstruction of pachytene nuclei from electron microscopy of serial sections. Regions of unique ‘modified synaptonemal complexes’ (M.SC) were observed along 2 SCs. These consist of a heterochromatic knob within which the SC appears either disorganized or stacked in layers of lateral elements. Its function is not known. Recombination nodules and ‘cylindrical granular complexes’, were not observed in H. glycines.
Directional change of ciliary beat effected with Mg2+ in Paramecium
Authors: Nakaoka Yasuo , Toyotama Hideki 
Published: April 2021

ABSTRACT
Two types of Triton X-100 extracted model of Paramecium caudatum were prepared and effects of the ionic compositions of the reactivating medium on the swimming behaviour of the extracted models were examined. Type I, prepared by the method of Naitoh and Kaneko, did not change swimming direction depending on the concentrations of Mg2+ and K+ in the reactivating medium. Type II, prepared by a different method, however, reversed the swimming direction depending on the concentrations of Mg2+ and K + in the reactivating medium, even when the concentration of Ca2+ was kept at an extremely low level (below 10−8 M). Decreasing the concentration of Mg2+ induced the type II model to swim backwards.
Intracellular injection of EDTA into a live paramecium cell induced reversal of the direction of ciliary beat. The concentration of Mg2+ at which the reversal of swimming direction occurred varied with the concentration of adenosine triphosphate (ATP) in a manner which suggested that the concentration of free ATP4- might be the critical determinant of swimming direction.
Infiltration and survival: the behaviour of normal, invasive cells implanted to the developing chick wing
Authors: Tickle C. , Crawley A. 
Published: April 2021

ABSTRACT
The invasiveness of mouse lymphocytes and thymocytes, rabbit peritoneal neutrophil granulocytes (PMNs), mouse peritoneal macrophages (both activated and non-activated) and pig endothelial cells was assayed by implanting these cells to the chick wing bud. Ceils of each type moved into the wing mesenchyme, although activated macrophages invaded poorly. PMNs were the most invasive cells and had moved well into the limb after only a few hours. PMNs, lymphocytes and thymocytes were ingested by wing mesenchyme cells. Endothelial cells, however, ingested chick blood cells. The implanted cells showed differences in ability to survive in the limb: PMNs disappeared rapidly, lymphocytes and thymocytes sometimes persisted for 24 h, while grafts of macrophages and endothelial cells were present at 24 h. Mechanisms which might be involved in the invasiveness of these cells, and also in their different abilities to survive in the chick wing, are discussed with particular reference to the production of plasminogen activator.
Necessary amino acids and vitamins for the growth of human diploid fibroblasts
Authors: Litwin Jack 
Published: April 2021

ABSTRACT
Only 2 amino acids and one vitamin were found to be essential for the growth of human embryonic diploid lung fibroblasts when 10% undialysed calf serum was used as a medium supplement. These amino acids were either glutamine + cysteine or serine + homocysteine. Replacing cysteine or homocysteine with cystine or homocystine, respectively, reduced growth. The growth rate in the glutamine+ cysteine medium was slightly less than that in Eagle’s medium, but the in vitro life time was similar.
Folic acid was the only vitamin needed to support cell growth in vitro. The addition of other vitamins had no stimulatory effect with the possible exception of nicotinamide.
When other amino acids were added to glutamine + cysteine none showed stimulatory effects but tryptophan was either toxic or inhibitory for the 3 human diploid strains examined. Serine was inhibitory for WI-38 but not for MRC5 cells.
Subtle nutritional differences appear to exist between fibroblasts of the same type obtained from different embryos.
Ultrastructural cytochemistry of the nucleus in zea mays embryos during germination
Authors: Deltour R. , Gautier A. , Fakan J. 
Published: April 2021

ABSTRACT
The ultrastructure of embryonic root cells of Zea mays was studied from the quiescent stage (dry seeds) to 72 h of germination. Semithin and ultrathin sections of tissues fixed with only glutaraldehyde and embedded in Epon were observed after usual section staining and after cytochemical reactions specific for DNA or preferential for ribonucleoproteins.
In quiescent cells, dense chromatin forms a network which fills a great part of the nucleoplasm. Following germination, gradual dispersion of chromatin occurs: total dispersion is reached at 24 h. After 48 h the chromatin appears moderately condensed again.
The nucleolus is compact and predominantly fibrillar in dry cells. At 48 h a typical pars granulosa is differentiated. At 8 h a pronounced vacuolation of the nucleolus is observed; nucleolar vacuoles persist until 72 h but become less numerous. During the first 8 h of germination a nucleolus organizer region (NOR) in an eccentric position is associated with the nucleolus; by 24 h and later this NOR has disappeared.
No DNA can be visualized in the nucleolar matrix between o and 8 h of germination, whereas later, when the nucleolus is reactivated, DNA is always detected in the nucleolar matrix and vacuoles.
During the first 72 h of germination, heavily contrasted areas, rich in ribonucleoproteins and appearing to be of fibrillar texture, are found in the nucleoplasm, often in close contact with the dense chromatin.
In quiescent cells dense ribonucleoprotein granules, approximately 40 nm in diameter are found dispersed or clustered in the nucleoplasm; after 8h larger (50 nm), dense ribonucleoprotein granules are found frequently clustered in granular areas in the extranucleolar space.
At 8 h of germination, when the nucleolus is temporarily highly vacuolated, unusual 35-nm ribonucleoprotein granules are found both in the smallest vacuoles and on the periphery of the nucleolus.
Different cytoskeletal domains in murine fibroblasts
Authors: Temmink J. H. M. , Spiele H. 
Published: April 2021

ABSTRACTThe morphology of the cytoskeleton of normal 3T3 fibroblasts was studied in the electron microscope on embedded and sectioned cells as well as on critical-point-dried whole mounts. Four ultrastructurally different cytoplasmic domains could be distinguished within every 3T3 cell, namely: Cytocortex, ruffle area, endoplasm, and stress fibre. However, many transitions between the different domains were also found. In addition, 2 other domains were occasionally encountered in the same cells. Based on the knowledge that actin is present in relatively high concentration throughout non-muscle cells and that it can, under different physiological conditions, assume different morphological appearances, an attempt has been made to formulate a hypothesis that links the ultrastructural domains to different cellular functions. Many experimental approaches are available to test the hypothesis and at the same time increase our knowledge of the cytoskeleton of 3T3 cells.
Evidence that spectrin binds to macromolecular complexes on the inner surface of the red cell membrane
Authors: Litman D. , Hsu C. J. , Marchesi V. T. 
Published: April 2021

ABSTRACT
Spectrin binds to a population of high-affinity sites on the exposed surfaces of inverted vesicles prepared from human red blood cell ghost membranes. Optimal spectrin binding requires the presence of monovalent salts but does not require calcium or magnesium. The band 2 subunit of spectrin, prepared in SDS, can also bind to vesicles, but isolated band 1 is inactive.
Pre-incubation of inverted vesicles with antibodies directed against the cytoplasmic segment of band 3 or against bands 4.1–4.2 inhibits the binding of spectrin to the same vesicles. Antibodies against the cytoplasmic portion of glycophorin A have no effect.
These results suggest that spectrin binds to a protein acceptor on the cytoplasmic surface of the red cell membrane which is close to the cytoplasmic segments of bands 3 and 4.1 and/or 4.2.
Role of cell surface receptor mobility in concanavalin a-induced agglutination of novikoff hepatoma and normal rat liver cells
Authors: Mastromarino Paola , Neri Giovanni , Serra Angelo , Walborg Earl F. 
Published: April 2021

ABSTRACT
The relationship between Con A-receptor mobility and Con A-induced agglutination of Novikoff hepatoma and normal rat liver cells was investigated. Novikoff cells, incubated with fluorescein-labelled Con A at 3 °C displayed uniform, ring-like surface fluorescence. Increasing the temperature of the cells to 37 °C caused capping of Con A receptors in approximately 65% of the cells, a phenomenon that could be prevented by prefixing the cells with glutaraldehyde. In spite of these variations in Con A-receptor distribution, Con A-induced agglutination was remarkably constant over a temperature range from 3 to 37 °C. In contrast to Novikoff cells, normal hepatocytes displayed a uniform, ringlike surface fluorescence at both 3 and 37 °C. No capping was observed. However, hepatocytes, similar to Novikoff cells, were agglutinable by low concentrations of Con A. These findings indicate that, in this model system, Con A-induced cytoagglutination is not dependent upon long-range lateral mobility of Con A receptors. The qualitative differences in the lateral mobility of cell-surface Con A receptors of normal and malignant rat liver cells may represent a marker for neoplastic transformation during hepatocarcinogenesis, adaptation to growth in ascitic form, or progression of a tumour to a more malignant state.
Origin and development of free kinetosomes in the flagellates Deltotrichonympha and Koruga
Authors: Tamm Signhild , Tamm Sidney L. 
Published: April 2021

ABSTRACT
The formation of more than half a million free (non-flagellated) kinetosomes in post-mitotic Deltotrichonympha and Koruga from Mastotermes is described. Ladder-like configurations of prokinetosomes extend from the 2 fibrous walls of the centriolar apparatus in the rostrum. The prokinetosomes within the ladders are arranged side by side in 2 layers. Because the fibrous walls are oriented perpendicular to each other, the 2 groups of prokinetosomal ladders are also mutually perpendicular. The prokinetosomes arise continously next to the fibrous walls, and migrate outward along the ladders as they develop. Consequently, progressive stages in kineto-some formation occur sequentially along the ladders in a polarized fashion. A cartwheelstructure appears first. This is followed by the formation of A tubules, B tubules and C tubules in an orderly sequence around the cartwheel (counter-clockwise, viewed from the distal end). The cartwheel ring disappears after the triplets have formed. The new free kinetosomes accumulate in a disorganized mass at the ends of the ladders. Later, the kinetosomes become organized end to end into the polarized chains found in interphase cells. The fibrous wall of the centriolar apparatus is thus a new type of intermediate structure associated with the mass production of basal bodies. It appears to determine the spatial organization of the ‘assembly lines’ of developing kinetosomes.
The effects of applied electric fields on Micrasterias: I. morphogenesis and the pattern of cell wall deposition
Authors: Brower Danny L. , Mcintosh J. Richard 
Published: April 2021

ABSTRACT
Applied electric fields of approximately 14 V/cm have profound effects on the morphogenesis of the unicellular green alga, Micrasterias denticulata. This field corresponds to a potential drop of 15–40 mV across lobes oriented perpendicular to the applied field. These lobes show a galvanotropism toward the cathode. Lobes growing parallel to the field are stunted to varying degrees, depending on their orientation.
As shown by other investigators, most cell wall material is normally deposited at the tips of growing lobes. If, however, cell expansion is osmotically inhibited in electric fields, wall material also accumulates along the cathode-facing (CF) sides of lobes oriented perpendicular to the field. Similarly, in cells growing under the influence of an applied field, radioactively abelled glucose and the methyl groups from methionine are incorporated along the CF sides of lobes as well as the lobe tips. This is also true when the label is added immediately after cells are removed from the fields, indicating that the wall-depositing machinery itself has been temporarily altered by the field.
These results demonstrate that applied electric fields can be a valuable tool in elucidating the mechanisms of growth localization in Micrasterias cells.
Eosinophil interaction with antibody-coated, non-phagocytosable surfaces: Changes in cell surface proteins
Authors: Thorne Kareen J. I. , Oliver Rhonda C. , Glauert Audrey M. 
Published: April 2021

ABSTRACT
Plasma membrane changes during the interaction of human eosinophils with large, antibody-coated, non-phagocytosable surfaces have been investigated in a model system. Human peripheral blood eosinophils were incubated with layers of agar into which tetanus toxoid and human anti-tetanus immunoglobulin, together with an eosinophil chemotactic factor (EOF), were incorporated. Changes in organization of the eosinophil plasma membrane proteins during interaction with the agar layer were detected by lactoperoxidase-catalysed iodination with [125]iodide.
A protein of apparent mol. wt 55000 became newly accessible on the eosinophil surface as a specific consequence of interaction with antigen-antibody complexes in the agar layer. This protein appeared in the early attachment phase of the interaction which preceded extracellular degranulation. Cytochalasin D enhanced its appearance, while Mg2+-deficiency prevented it. A second newly accessible protein of apparent mol. wt 58000 was blocked when ECF was present and may therefore be a receptor for ECF. Other proteins of apparent mol. wt 68000 and 46000 newly appeared at the surface of eosinophils even after incubation in suspension, apparently as a consequence of the rapid cycling of membrane components which occurs in eosinophils.
Microtubule-organizing centres in mammalian cells in culture
Authors: Watt Fiona M. , Harris H. 
Published: April 2021

ABSTRACT
When microtubules in animal cells are dissociated and then allowed to recover, they re-grow from discrete points in the cytoplasm known as microtubule-organizing centres (MTOC). The microtubules may be dissociated by antimitotic drugs such as colcemid, vinblastine and griseofulvin, or by chilling the cells. Immunofluorescence studies show that the number of MTOC seen does not depend on the concentration of antimitotic drug used or the duration of exposure to the drug; the same results are obtained with vinblastine, griseofulvin and colcemid. However, after cold treatment, the proportion of cells showing only a single MTOC is greater than that seen with the antimitotic drugs and may exceed 90 %. Evidence is presented for the view that procedures involving the use of antimitotic drugs give artificially high values for the number of MTOC per cell.
Microtubule-organizing centres in binucleate cells and homosynkaryons
Authors: Watt Fiona M. , Sidebottom E. , Harris H. 
Published: April 2021

ABSTRACT
Immunofluorescence studies showed that most binucleate Vero cells formed by virus-induced fusion or by inhibition of cytokinesis had a single microtubule-organizing centre (MTOC) when examined during the reassembly of microtubules after chilling, but two or more organizing centres when examined after exposure to colcemid. These findings suggest that although binucleate cells initially contain more MTOC than mononucleate cells, the extra MTOC are normally aggregated, so that the number of MTOC in binucleate cells tends to be reduced very quickly to that in mononucleate cells.
Sliding velocity between outer doublet microtubules of sea-urchin sperm axonemes
Authors: Yano Y. , Miki-Noumura T. 
Published: April 2021

ABSTRACT
Using a dark-field microscope equipped with a high-efficiency TV camera including a video tape-recorder, we recorded the sliding movement between outer doublet microtubules of the demembranated axonemes of sea-urchin (Pseudocentrotus depressus and Heniicentrotus puleherrimus) sperm flagella by adding ATP and trypsin at 25 °C. The time and length of the sliding doublet microtubules from axonemes were measured directly from the image on the picture monitor from the video tape.
The sliding velocity was almost constant in the range from o to 2 % polyethylene glycol concentration in the reactivation medium and decreased a little at more than 2 %. We prepared various lengths of axoneme fragments by homogenizing whole axonemes and found that the shorter fragments showed similar sliding velocity to that of longer ones at less than 200 μM ATP, but slightly decreased speed at more than 500 μM ATP. The sliding movement sometimes stopped and the percentage of sliding axonemes was lower below 2 μg/ml trypsin. Above 3 μg/ml the process appeared to be more like disintegration than sliding movement, which may be due to excess digestion by trypsin. Sliding speed was therefore measured in a reactivation medium containing 2 % polyethylene glycol with the addition of ATP and 2 μg/ml trypsin. The velocity increased in proportion to the increase in ATP concentration. was approximately 14 μm/s at 1 mM ATP.
In order to compare the Km for the sliding velocity with that of the ATPase activity of the axonemes, we measured ATPase activity of axonemes prepared and assayed under conditions in which sliding movement in the axonemes could be induced. Neither the curve of ATPase activity nor the curve of sliding velocity plotted against ATP concentration obeyed Michaelis-Menten kinetics. The close relationship between ATPase activity and sliding velocity suggested that ‘sliding-movement-coupled ATPase activity’ may well be reflected in the axoneme ATPase reported here.