bluuebunny/crossref_metadata_2025_split huggingface dataset:
Migration of cultured vascular cells in response to plasma and platelet-derived factors
Authors: Bernstein Lori R. , Antoniades Harry , Zetter Bruce R. 
Published: April 2021

ABSTRACT
Phagokinetic migration of cultured vascular cells was tested in response to human plateletrich serum (‘serum’) and human platelet-poor plasma serum (‘plasma’). The cell types tested included bovine aortic endothelial cells, human umbilical vein endothelial cells, human haemangiomal capillary endothelial cells, bovine adrenal microvascular pericytes, and bovine aortic smooth muscle cells. Human serum stimulated a significant increase in the rate of migration for all five cell types. Human plasma stimulated the endothelial cells to migrate but had no effect on the migration of pericytes or smooth muscle cells.
Highly purified platelet-derived growth factor (PDGF) stimulated dose-dependent migration of smooth muscle cells causing a 50 % increase in phagokinetic track area relative to controls. Neither pericyte nor endothelial cell migration was stimulated by PDGF. Rabbit antiserum to human PDGF completely blocked the smooth muscle cell migration induced by either 10% serum or 1 ng/ml pure PDGF. Purified platelet factor IV (PF4) stimulated migration of pericytes but not of smooth muscle cells nor endothelial cells. Sheep antiserum to human PF4 completely blocked the pericyte migration induced by either 10 % serum or 1 μg/ml pure PF4. These results indicate that PDGF is the primary factor in serum responsible for the migration of cultured aortic smooth muscle cells and that PF4 is a critical factor required to induce the migration of pericytes. Other factors present in both plasma and serum control the migration of vascular endothelial cells.
Effects of conditioned medium on nucleoside uptake, cell cycle progression and apparent DNA repair
Authors: Downes C. S. , Johnson R. T. , Yew F. F. 
Published: April 2021

ABSTRACT
Cells in culture can condition the medium they grow in so as to inhibit cellular uptake of nucleosides. Some conditioned media specifically block the uptake of cytosine arabinoside and deoxycytidine, but not other deoxyribonucleosides; some also block thymidine uptake; some have no effect. Detransformation of cells by sodium butyrate can alter their medium-conditioning properties. The inhibition of uptake acts at the level of nucleoside phosphorylation; it is not affected by inhibitors of nucleoside degradation. Cell cycle progression is also blocked by conditioned medium. Inhibition of nucleoside uptake by conditioned medium can cause serious errors in estimations of the incision step of DNA repair, or of DNA replication.
Inhibition of Dictyostelium discoideum differentiation in monolayers in vitro by endogenous and exogenous lectins
Authors: Laroy Kathy , Weeks Gerald 
Published: April 2021

ABSTRACT
Spore-cell differentiation in monolayers in vitro of two sporagenous mutants of Dictyostelium discoideum, HM18 and HM15, is markedly inhibited by relatively low concentrations of the exogenous lectins, Concanavalin A (ConA) and wheat germ agglutinin (WGA) and by somewhat higher concentrations of the endogenous lectin, discoidin. The selective inhibition of spore cell formation by ConA occurs toward the end of the differentiation process, as shown by studies involving the addition or removal of ConA at various times during the period of differentiation. In addition, ConA has no deleterious effect on the expression of the pre-spore cell specific enzyme, UDP-galactosyl transferase. It is likely, therefore, that the maturation of pre-spore cells into spore cells is the most sensitive locus of lectin inhibition.
At higher concentrations of WGA and ConA, both stalk- and spore-cell formation are inhibited, but increased concentrations of discoidin do not have this effect.
Conditioning of a culture substratum by the ectodermal layer promotes attachment and oriented locomotion by amphibian gastrula mesodermal cells
Authors: Nakatsuji Norio , Johnson Kurt E. 
Published: April 2021

ABSTRACTWe have found that ectodermal fragments of Ambystoma maculatum gastrulae deposit immense numbers of 0-1 pm diameter extracellular fibrils on plastic coverslips. When migrating mesodermal cells from A. maculatum gastrulae are seeded on such conditioned plastic substrata, they attach and begin migrating after 15-30 min in vitro. We did a detailed analysis of the relationship between fibril orientation and cell migration using time-lapse cinemicrography, scanning electron microscopy, and a microcomputer with a graphics tablet and morphometric program. We found that cells move in directions closely related to the orientation of fibrils. Usually fibrils are oriented in dense arrays with a predominance of fibrils running parallel to the blastopore-animal pole axis of the explant, and cells move preferentially along lines parallel to the blastopore-animal pole axis. When fibrils are unaligned, cells move at random. We have also shown that cells move with a slightly stronger tendency towards the animal pole direction. These results are discussed concerning the mechanism of specific cell migration during amphibian gastrulation.
Osmium-impregnation patterns of the golgi complex in the epididymal epithelial cells of castrated and testosterone-injected mice
Authors: Yamaoka Ikuo , Yamamoto Kozo , Urabe Nobuko , Nagatani Yoshimi 
Published: April 2021

ABSTRACT
After prolonged exposure of mouse epididymal epithelial cells to a solution of osmium tetroxide, reduced osmium compounds were detected in the Golgi cisternae and in the cytoplasm adjacent to the Golgi complex. Their appearance changed in time under certain conditions. Eight days after castration each cisterna of the regularly arranged Golgi lamellae fragmented into small vesicles, in which deposits of reduced osmium compound were in reduced amounts or completely absent, but no notable decrease of the fine reduced osmium particles in the cytoplasm adjacent to the Golgi complex occurred. The amount of deposit in the Golgi cisternae in castrated mice recovered to the normal level after the subcutaneous injection of testosterone for two weeks. On the other hand, the osmium particles observed in the cytoplasm adjacent to the Golgi complex during the recovery process of the lamellar structure increased in amount. This study showed that the reduced osmium compounds were of two kinds, and that the deposits contained in the Golgi cisternae were related to secretory products, and might be controlled by hormonal factors, but the fine reduced osmium particles that appeared in the cytoplasm adjacent to the Golgi complex might be regulated by other factors.
Characterization of proteins from the cytoskeleton of Giardia lamblia
Authors: Crossley Richard , Holberton David V. 
Published: April 2021

ABSTRACT
Proteins from the axonemes and disc cytoskeleton of Giardia lamblia have been examined by sodium dodecyl sulphate/polyacrylamide gel electrophoresis. In addition to tubulin and the 30 × 103 molecular weight disc protein, at least 18 minor components copurify with the two major proteins in Triton-insoluble structures. The most prominent minor bands have the apparent molecular weights of 110 × 103, 95 × 103 and 81 × 103.
Protein of 30 × 103 molecular weight accounts for about 20% of organelle protein on gels. In continuous 25 mM-Tris-glycine buffer it migrates mostly as a close-spaced doublet of polypeptides, which are here given the name giardins.
Giardia tubulin and giardin have been purified by gel filtration chromatography in the presence of sodium dodecyl sulphate. Well-separated fractions were obtained that could be further characterized.
Both proteins are heterogeneous when examined by isoelectric focusing. Five tubulin chains were detected by PAGE Blue 83 dye-binding after focusing in a broad-range ampholyte gel. Giardin is slightly less acidic than tubulin. On gels it splits into four major and four minor chains with isoelectric points in the pl range from 5· 8 to 6’2.
The amino acid composition of the giardin fraction has been determined, and compared to Giardia tubulin and a rat brain tubulin standard. Giardins are rich in helix-forming residues, particularly leucine. They have a low content of proline and glycine; therefore they may have extensive a-helical regions and be rod-shaped.
As integral proteins of disc microribbons, giardins in vivo associate closely with tubulin. The properties of giardins indicate that in a number of respects -molecular size, charge, stoichiometry -their structural interaction with tubulin assemblies will be different from other tubulin-accessory protein copolymers studied in vitro.
Differential effects of K+ and Na+ on specific bands of isolated polytene chromosomes of Chironomus Tentans
Authors: Lezzi M. , Gilbert L. I. 
Published: April 2021

ABSTRACT
Previous investigations on the effects of monovalent cations on the gene activities (formation of puffs) of polytene chromosomes utilized whole salivary glands or nuclei and suggested that the K+/Na+ ratio in the nuclear sap was of primary importance in influencing gene activities. To determine whether these effects of ions were direct or indirect, we have employed isolated polytene chromosomes incubated in salt solutions of varying ionic composition. Our observations reveal differential effects of K+, Na+, Mg2+, Ca2+ and combinations thereof on specific chromosome regions. The band at region I-18-C that is specifically affected by K+ is the same one that puffs when salivary gland nuclei are incubated in a K+-rich medium and this is believed to be an ecdysone-specific puff. Bands at region I-19-A are specifically affected by Na+ and are the same ones that form puffs when salivary gland nuclei are incubated in a Na+-rich medium. This region is believed to be juvenile hormone-specific. Effects on the chromosome are also described that are the result of incubation in solutions containing Mg2+ and Ca2+. Analogies are drawn between the observed effects of ions on isolated chromosomes and their effects on chromatin isolated from mammalian cells. For example, when chromatin is exposed to solutions of increasing ionic strength, hydration is followed by aggregation and histone dissociation. This may be analogous to what is observed in the isolated chromosome under similar conditions; namely, expansion, contraction and expansion.
The effects of some metabolic inhibitors on the ability of SV40 virus in transformed cells to be detected by cell fusion
Authors: Watkins J. F. 
Published: April 2021

ABSTRACT
When mouse fibroblasts transformed by SV 40 virus are fused with African Green Monkey kidney cells about 5 % of the heterokaryons produce infective SV 40 virus. If the transformed mouse cells are treated with iododeoxyuridine before fusion, the percentage of heterokaryons producing SV40 virus is increased to between 50 and 80 %; if the transformed cells are treated with 8-azaguanine, the percentage of heterokaryons yielding virus is increased to between 59 % and 96 %. This shows that whether the SV40 virus can be detected by cell fusion depends on the state of the transformed cells beforehand. A new method for titrating SV 40 virus is described.
Studies on the ‘incisures’ of schmidt and lanterman
Authors: Hall Susan M. , Williams P. L. 
Published: April 2021

ABSTRACT
Since its initial description over a century ago the ‘incisure’ of Schmidt-Lanterman has usually been regarded as a histological artifact, or a post-mortem change. With the establish ment of in vivo discrete zones in the myelin sheath, an ultrastructural study was undertaken and correlation attempted between their electron-microscopical appearances and their range of states seen in vivo and produced in vitro.
It was demonstrated that under conditions of hypotonicity the incisure dilates and further that it closes in hypertonic solutions. Such behaviour is reversible within certain limits. Ultrastructurally, the incisural region appears as a highly complex zone in which the repeat characteristics of the compact myelin sheath are drastically altered. At the incisure, the major dense line of the myelin splits to enclose a granular Schwann cytoplasm which frequently contains a single central helical microtubule, dense bodies and small vesicles. The intraperiod line also splits, dilatation of the incisure involving further widening of this intraperiod line gap beyond the normal confines of the incisure. Desmosomoid stacks are a common feature, particularly of the outer layers of incisures of both mature and immature fibres. Surface invaginations, vesicles, longitudinal microtubules, filaments, mitochondria and granular endoplasmic reticulum are typical constituents of peri-incisural Schwann cytoplasm. The incisure may be related to fibre growth, remodelling and degeneration; to dynamic changes of internodal contour—possibly peristaltic; or may operate as a fluid-satellite cell-neuron interchange pathway.
The three cortical membranes of the gregarines: I. Ultrastructural organization of Gregarina blaberae
Authors: Schrével J. , E. Caigneaux D. , Gros D. , Philippe M. 
Published: April 2021

ABSTRACT
Gregarines, parasitic protozoa of invertebrates, possess a highly differentiated cell surface, with three cortical membranes and associated structures. Transmission electron microscopy and freezefracture reveal the presence of two cytomembranes lying uniformly under the plasma membrane. The density and the distribution of the intramembraneous particles (IMPs) in the plasma membrane of Gregarina blaberae are similar to those reported for other eukaryotic cells. The IMP density is lower in the cytomembranes than in the plasma membrane. The distribution of IMPs in the different fracture faces of the two cytomembranes suggests that they are in topological continuity, forming either side of a flattened vesicle or cisterna. The sizes of the cytomembrane IMPs show a high variability. The nature of the IMPs, both for the plasma membrane and the cytomembranes, is discussed with regard to the integral proteins and glycoproteins of the ghost.
The cell surface of G. blaberae exhibits numerous longitudinal folds with three types of cortical membrane-associated structures: 12 nm filaments, an internal lamina, and homogeneous structures described as ‘rippled dense structures’. The 12 nm filaments, running under the cytomembranes along the longitudinal axis of each fold, exhibit the properties of intermediate filaments. Their distribution in mature cells and during the growth process suggests a participation in cell surface morphogenesis. The internal lamina, also localized under the cytomembranes, would stabilize each fold and assure a scaffolding function between the numerous folds. The rippled dense structures, settled on the external cytomembrane, show a regular distribution at the top of each fold. The membrane-associated structures are discussed with regard to the gliding movement mechanism.
Cytasters induced within unfertilized sea-urchin eggs
Authors: Kuriyama Ryoko , Borisy Gary G. 
Published: April 2021

ABSTRACT
Conditions that induce the formation of asters in unfertilized sea-urchin eggs have been investigated. Monasters were formed by treatment of eggs with acidic or basic sea-water, or procaine- or thymol-containing sea-water. A second treatment step, incubation with D2O-containing, ethanol-containing or hypertonic sea-water induced multiple cytasters. The number and size of cytasters varied according to the concentration of agents and duration of the first and second treatments, and also upon the species of eggs and the season in which the eggs were obtained. Generally, a longer second treatment or a higher concentration of the second medium resulted in a higher number of cytasters per egg.
Asters were isolated and then examined by light and electron microscopy. Isolated monasters apparently lacked centrioles, whereas cytasters obtained from eggs undergoing the two-step treatment contained one or more centrioles. Up to eight centrioles were seen in a single aster; the centrioles appeared to have been produced during the second incubation. Centrospheres prepared from isolated asters retained the capacity to nucleate the formation of microtubules in vitro as assayed by light and electron microscopy.
Many microtubules radiated from the centre of isolated asters, whether they contained centrioles or not. This observation is consistent with many other reports that microtubule-organizing centres need not contain centrioles.
Mutational disruption of the 9 + 2 structure of the axoneme of Chlamydomonas Flagella
Authors: Forest Charlene L. 
Published: April 2021

ABSTRACT
A mutant of Chlamydomonas, gam-5, which has short but variable-length, paralysed flagella has been characterized using electron microscopy and genetics. The flagellar axoneme shows varying degrees of disorganization of its 9 + 2 structure, and the structures that attach to the microtubule pairs may be wholly or partly missing or, if present, abnormal. Flagellar length is inversely related to temperature, and gametes of this mutant are generally incapable of mating at higher temperatures. This pleiotropic mutation shows Mendelian (2:2) segregation and is unlinked to the mating-type locus. It is suggested thatgiwz-5 leads to the production of a thermal-sensitive flagellar component, which results in increased assembly and/or maintenance difficulties as temperature is increased.
Mitochondria of Tetrahymena pyriformis: Enumeration and sizing of isolated organelles using a coulter counter and pulse-height analyser
Authors: POOLE R. K. 
Published: April 2021

ABSTRACT
An electronic particle counter (Coulter Counter ZBI) and pulse-height analyser (Channelyzer C1000) have been used to measure numbers and sizes of mitochondria isolated from the ciliated protozoon Tetrahymena pyriformis. Differential centrifugation of disrupted organisms, followed by single-step sub-fractionation of the mitochondrial fraction on sucrose gradients yielded a population of organelles extensively enriched in the activities of mitochondrial marker enzymes. Gradient-purified mitochondria (approx. 3 × 109 particles (mg protein)-1) were stable in electrolyte, exhibited unimodal volume distributions and were somewhat larger (0·93 ± 0·13(S.D.) μm3; 19 preparations) than organelles in a crude mitochondrial fraction. Glutaraldehyde fixation of mitochondria in sucrose gradients decreased the apparent volume to 0·6 ± 0·06 μm3 (6 preparations). Based on the recovery in the mitochondrial fraction of mitochondrial membrane-bound cytochromes from a suspension of intact cells, the number of mitochondria per cell was estimated to be approximately 1440, representing 15 % of the total cell volume. Isolated mitochondria were osmotically sensitive and exhibited an apparent marked contraction on adding Ca2+ (10 μM-10mM). Addition of chloramphenicol (500 μgml-1) to exponentially growing Tetrahymena cultures resulted in an almost immediate cessation of cell division and a dramatic decrease in cell volume. Mitochondria purified from such cells were much smaller than control mitochondria (0·21 ± 0·02 μm3; 7 measurements); their population density was approximately 900 per cell, equivalent to 11 % of total cell volume. The measurements of mitochondrial populations using the Coulter Counter and electron microscopy are in good agreement.
Effects Of Culture Conditions On The Proliferation, Morphology And Migration Of Bovine Aortic Endothelial Cells
Authors: Schor A. M. , Schor S. L. , Allen T. D. 
Published: April 2021

ABSTRACT
Various culture conditions, such as the presence of ascorbic acid, initial plating density and the nature of the substratum (plastic, gelatin or native collagen gels), influenced the growth, morphology and migration of three cloned populations of adult bovine aorta endothelial cells.
Aorta endothelial cells showed two distinctive and reversible morphological phenotypes. Cells presenting a free apical surface were polygonal and formed sheets of overlapping or non-overlapping cells, depending on the culture conditions. When the cells were able to establish adhesive interactions over their entire cell surface they adopted an elongated shape and formed meshworks of interconnected ‘sprouting’ cells. The cells were capable of migrating into a collagen gel from both their basal and apical surfaces. Once in the gel, they formed characteristic, compact, threedimensional meshworks.
Meiosis and early cleavage in Drosophila melanogaster eggs: Effects of the claret-non-disjunctional mutation
Authors: Kimble Mary , Church Kathleen 
Published: April 2021

ABSTRACT
The claret-non-disjunctional (cand) mutation is a female-specific mutation in Drosophila melanogaster, which causes a high frequency of mortality (89–90 %) in eggs laid by the homozygous females. Among the progeny that survive to the adult stage, greater than 50 % are aneuploid and/ or mosaic for the X and number 4 chromosomes. The genetic studies of cand indicate that it is homologous to the claret mutation (ca-simulans) in Drosophila simulons.
The cytological effect of the cand mutation on meiosis I and the early cleavage divisions has been observed at the light microscope level in stage 14 ovarian and fertilized uterine eggs, respectively. Four classes of metaphase I figures were observed. These include those with: (1) two or more spindles; (2) spindles that were abnormally wide and the bivalents widely separated; (3) unipolar spindles; and (4) apparently normal bipolar spindles. The three abnormal classes of metaphase I figures included 80 % of the eggs examined at this stage. Among the cleavage stage eggs examined 69 % showed highly abnormal mitotic figures, including multipolar spindles, and the nuclei in these eggs were found in clusters, rather than dispersed throughout the ooplasm.
In addition to the cytological abnormalities observed, 17–23 % of the eggs produced by the cand females showed morphological abnormalities. These abnormalities included eggs having three or four dorsal filaments, eggs that had a truncated shape, and abnormally small eggs. These abnormalities may not be an aspect of the cand syndrome, but they are due to recessive genes located on the third chromosome.
Although the cand and ca-simulans mutations both affect the formation of the spindle apparatus during meiosis and the early cleavage divisions, the effects of these two mutations differ considerably in detail. The effect of the ca-simulans mutation appears to be more severe than the effect of cand.
A model to explain the relationship between the effect of the cand mutation on meiosis I and the early cleavage divisions is presented, and evidence to support the model is discussed.