bluuebunny/crossref_metadata_2025_split huggingface dataset:
The cell cycle of symbiotic Chlorella I. the relationship between host feeding and algal cell growth and division
Authors: McAuley P. J. 
Published: April 2021

ABSTRACT
When green hydra were starved, cell division of the symbiotic algae within their digestive cells was inhibited, but algal cell growth, measured as increase in either mean volume or protein content per cell, was not. Therefore, control of algal division by the host digestive cells must be effected by direct inhibition of algal mitosis rather than by controlling algal cell growth. The number of algae per digestive cell increased slightly during starvation, eventually reaching a new stable level.
A number of experiments demonstrated that although there was a relationship between host cell and algal mitosis, this was not causal: the apparent entrainment of algal mitosis to that of the host cells could be disrupted. Thus, there was a delay in algal but not host cell mitosis when hydra were fed after prolonged starvation, and algae repopulated starved hydra with lower than normal numbers of algae (reinfected aposymbionts or hydra transferred to light after growth in continuous darkness). Two experiments demonstrated a direct stimulation of algal cell division by host feeding. Relationships of algal and host cell mitosis to numbers of Artemia digested per hydra were different, and in hydra fed extracted Artemia algal, but not host cell, mitosis was reduced in comparison to that in control hydra fed live shrimp.
It is proposed that algal division may be dependent on a division factor, derived from host digestion of prey, whose supply is controlled by the host cells. Numbers of algae per cell would be regulated by competition for division factor, except at host cell mitosis, when the algae may have temporarily uncontrolled access to host pools of division factor. The identity of the division factor is not known, but presumably is a metabolite needed by both host cells and algae.
Changes in nucleoli and nucleolar fibrillar centres of chromaffin cells in rat adrenal medulla over a 24-hour period: An ultrastructural and stereological analysis
Authors: Robaglia Andrée , Seïte Raymond 
Published: April 2021

ABSTRACT
A stereological and ultrastructural study was performed on the nucleoli of the adrenal medulla chromaffin cells of rats exposed to a standardized 12 h light/12 h dark cycle with free access to food and water. The animals were killed three at a time, every 4h during the 24-h span and fixed by intracardiac perfusion.
In these reticulated nucleoli, the stereological analysis over a 24-h period showed a variation dependent on the time of killing for the two parameters investigated, the mean nucleolar volume, , and the mean volume of the fibrillar centres, . The minimal value occurred at 0300 h (dark span) and the maximal one at 0700 h (at the onset of the light span). Between these two extreme values, increased 1’8-fold and 5’3-fold.
These data are compared with a previous description from our laboratory of circadian rhythm in nucleoli of sympathetic neurons of superior cervical ganglion in the same animals. Analogies and differences are pointed out, but apart from these considerations the present study provides a new example of temporal organization at the cellular level in the organelle involved in ribosomal RNA synthesis and ribosome assembly.
Rebinding of Tetrahymena 13 s and 21 s dynein atpases to extracted doublet microtubules the inner row and outer row dynein arms
Authors: Warner Fred D. , Perreault John G. , Mcilvain Jane H. 
Published: April 2021

ABSTRACT
Ciliary axonemes from Tetrahymena contain a second salt-extractable ATPase distinguishable from outer arm 21 S dynein by sedimentation velocity (≃ 13 S), electrophoretic mobility and substrate specificity. As characterized by turbidimetric assay, gel electrophoresis in the presence of sodium dodecyl sulphate, ATPase activity and electron microscopy, the 13 S dynein ATPase rebinds to extracted doublet microtubules. Compared to structural-side (ATP-insensitive) 21 S dynein binding, which is moderately specific for the 24 nm outer row arm position, rebinding of 13 S dynein is highly specific but for the inner row arm position. However, 13 S dynein rebinds to the A subfibre with a spacing that coincides with the triplet spacing of the radial spokes (24–32–40 nm periods; 96 nm repeat). All of the major protein components present in the 13 S or 21 S fractions rebind to extracted doublets under conditions that both restore and activate dynein ATPase activity. Unlike active-side (ATP-sensitive) rebound 21 S dynein, rebound 13 S dynein is completely insensitive to dissociation by ATP-vanadate and does not independently decorate the B subfibre. The saturation profile for rebinding of 13 S dynein exhibits a lack of cooperativity between binding events (h = 1·0) similar to structural-side rebinding of 21 S dynein. At low 21 S/doublet stoichiometry there is no measureable competition between the 13 S and 21 S dyneins for binding sites on the A subfibre lattice, although at saturating concentrations of 21 S dynein, rebinding of 13 S dynein is blocked completely.
Surface features of human natural killer cells and antibody-dependent cytotoxic cells
Authors: Payne Claire M. , Linde Alec , Kibler Ruth , Poulos Bonnie , Glasser Lewis , Fiederlein Roger 
Published: April 2021

ABSTRACT
The purpose of the present study was to examine the surface features of purified large granular lymphocytes (LGLs) (natural killer (NK) cells, antibody-dependent cytotoxic lymphoid (ADCL) cells, K-cells, Fcγ (+) third population (non-T, non-B) lymphoid cells, Tγ cells) by scanning electron microscopy (SEM) and to compare their surface features with granulocytes, monocytes and Fcγ (—) lymphoid cells that were all fixed for SEM under identical conditions. We have determined that 72–80% of LGLs enriched by rosette formation with sensitized erythrocytes or using Percoli gradients, have a complex microvillous surface (CMS) pattern identical to that of lymphocytes. The LGL fraction appears by SEM to represent a morphologically homogeneous population of cells. Monocytes prepared for SEM under identical conditions had distinct surface folds and granulocytes displayed numerous broad-based ridge-like profiles. The majority of lymphoid cells in an unfrac- tioned population have a CMS pattern when incubated at room temperature (25 °C) before fixation, and a sparse microvillous surface (SMS) pattern when incubated at body temperature (37°C). Ficoll-Hypaque (FH) also had a direct effect on the cell surface pattern. Over half of the unfractionated lymphoid cells displayed a CMS pattern after cells were washed free of FH and incubated at 37 °C before fixation. The CMS pattern is therefore not unique to LGLs but can be produced by the surface alteration of non-LGLs found in unfractionated buffy coat and mononuclear fractions. The interactions between LGLs and sensitized erythrocytes in an antibody-dependent cytotoxic assay system, and LGLs and K562 target cells in an NK assay system, were also examined. This is the first report that describes the surface features of human LGLs interacting with K562 target cells in an NK assay system. The LGL populations studied by SEM were determined to have a high percentage ofLeu-ll (+) and Leu-7 (+) cells. These same populations were also shown to have high antibody-dependent cytotoxicity and NK activity using the 51Cr release assay.
Changes in the transport of mitochondrial Ca2+ during the culture growth cycle of Tetrahymena pyriformis
Authors: Kim Yuri V. , Kudzina Ludmila Yu. , Zinchenko Valeri P. , Evtodienko Yuri V. 
Published: April 2021

ABSTRACT
The properties of the Ca2+ transport system of mitochondria, isolated in various phases of growth of static cultures of Tetrahymena pyriformis, were studied. A large increase in the endogenous energy-dependent Ca2+ content of mitochondria was observed as cultures of T. pyriformis passed through the exponential and stationary phases of growth (approx. 0·25 and 50 nmol Ca2+ per mg mitochondrial protein, respectively). Simultaneously, the mitochondria dramatically lost their ability to withstand large concentrations of Ca2+ and ADP. However, in the latter case they were able to phosphorylate a large amount of ADP if the strong Ca2+chelator, ethylene glycol bis-β-aminoethyl ether)-N,N,N’,N’-tetraacetic acid, was initially present in the incubation medium.
Furthermore, all the changes observed in mitochondria from the stationary phase cells were completely reversed when cell proliferation was re-activated after the lag phase, either by reseeding the stationery cells in fresh growth medium or by oxygenation of the old medium. In aerobic conditions even a small addition of Ca2+ was able to induce rapid release of Ca2+ from mitochondria isolated during the stationary phase of growth. It is suggested that the redistribution of Ca2+between the mitochondria and the cytoplasm at the onset of the lag phase may serve as the main trigger for the subsequent biochemical and morphological changes observed in T. pyriformis.
Density-dependent survival of ehrlich ascites tumour cells in the presence of various substrates for energy metabolism
Authors: Zaporowska-Siwiak E. , Michalik M. , Kajstura J. , Korohoda W. 
Published: April 2021

ABSTRACT
We have found that Ehrlich ascites tumour (EAT) cells, deprived of any carbon source, and suspended at a density of 2 ×105 cells/cm3, begin to die only after 12h of starvation, though it is known that under these conditions they lose over 80% of their ATP within 30 min. Moreover, we have found that the viability of the cells incubated in the absence of any substrate for energy metabolism is strongly dependent on the density of the cell suspension, and can be significantly improved simply by increasing the suspension density. This prompted us to investigate the density dependence of the maintenance of EAT cell viability in the presence of various substrates for energy metabolism and metabolic intermediates. It was found that:
(1) Glucose ensures 48 h viability of EAT cells irrespective of suspension density.
(2) Fatty acids and pyruvate as sole carbon source do not improve EAT cell survival.
(3) In the presence of glutamine as sole carbon source the EAT cell survival shows dependence on cell-suspension density. At densities of 1·6 ×106 to 3·2 × 106 cells/cm3 the cell viability is maintained at least as well as in the presence of glucose, but at low cell-suspension densities glutamine does not support cell viability.
(4) In the presence of glutamine, addition of 1 mM-inosine and 1 mM-uridine ensures high cell survival irrespective of the cell-suspension density.
(5) In the presence of inosine or uridine (10 mid) as sole carbon source, the EAT cell survival is the same as in the presence of glucose and does not depend upon cell-suspension density. Guanosine is less effective, whereas adenosine has no effect at all on the maintenance of EAT cell viability for 48 h.
(6)There is no correlation at all between EAT cell survival and the rate of lactic acid production. At a cell-suspension density of 1·6 × 106 cells/cm3 the cell survival is of the same order in the presence of glutamine as in the presence of glucose, in spite of the fact that in the first case the rate of lactic acid production is more than 20 times lower.
(7) There is no correlation between the capacity of particular nucleosides to support EAT cell survival and their effects on glycolysis and oxygen consumption.
The cystoskeleton of unstimulated blood platelets: Structure and composition of the isolated marginal microtubular band
Authors: Kenney Dianne M. , Linck Richard W. 
Published: April 2021

ABSTRACT
Detergent-insoluble, marginal microtubular band (MB) cytoskeletons were isolated from unstimulated blood platelets after pretreatment with glycerol or with Taxol. MB cytoskeletons retained the shape of intact platelets and behaved in suspension as coherent structural units. The major structural component was a continuous coil of long microtubule(s), often with granular/amorphous material present in the centre; few typical actin filaments were observed. The coiled microtubules often had an amorphous surface coating, but no discrete inter-microtubule bridges were seen. Tubulin and actin (identified by immunochemical staining) were major polypeptides. None of the minor (&gt; 10) polypeptide components comigrated with high molecular weight microtubule-associated proteins in brain tubulin. A novel polypeptide, resolved by two-dimensional electrophoresis and designated IEF-51K, was present in MB cytoskeletons in amounts approximately equivalent to each of the tubulin polypeptides. Evidence suggests that IEF-51K is a distinct, previously undescribed component of the platelet cytoskeletal system.
High density mammalian cell growth in leibovitz bicarbonate-free medium: Effects of fructose and galactose on culture biochemistry
Authors: Barngrover D. , Thomas J. , Thilly W. G. 
Published: April 2021

ABSTRACT
The most commonly used buffering system for mammalian cell cultures is a bicarbonate/CO2 system, which requires CO2 regulators and incubators to supply a constant level of CO2. As a replacement, Leibovitz developed a bicarbonate-free medium, L15, with relatively high levels of certain amino acids in the free base form. We found that a modified form of L15, containing 10 mM-fructose instead of galactose, supported high density growth of Vero and MDCK cells, with maintenance of a stable pH and lactate/pyruvate ratio. We report here investigations of Vero and MDCK cell growth and culture biochemistry at different concentrations of the two carbohydrates. The initial fructose concentration in the medium affected the eventual pH of the medium, the rate of production of lactic acid and ammonia, and the fructose utilization rate. The initial galactose concentration affected the growth rate but did not affect eventual culture pH, the rates of lactate and ammonia production, or the rate of its own utilization. Thus, Leibovitz’ formula, modified to contain 10mM-fructose, appears to yield satisfactory stability of culture pH and the lactate/pyruvate ratio. At all concentrations of galactose tested, the lactate/pyruvate ratio drifted out of the physiological range.
Cell junctions and locomotion of the blastoderm edge in gastrulating chick and quail embryos
Authors: Andries L. , Harrisson F. , Hertsens R. , Vakaet L. 
Published: April 2021

ABSTRACT
The blastoderm edge migrates by the active locomotion of a multilayer of epithelial cells, the so-called margin of overgrowth (MO), that uses the vitelline membrane as its substratum. The structural unity formed by the margin of overgrowth cells and their rapid migration suggest coordination of locomotion between individual cells. Using transmission electron microscopy of thin sections and freeze-fracture, we attempted to determine if the pattern of junctions of the migrating margin of overgrowth is related to the suggested cell-cell cooperation between individual cells in this region. In the leading edge there are large areas of closely apposed cell membranes. Incipient desmosomes and small gap junctions were observed. Tight junctions consisted of isolated strands or isolated networks of tight-junctional strands. In the proximal part of the margin of overgrowth the size of the gap junctions increased and the desmosomes were fully developed. Tight-junctional strands were either isolated or arranged into an isolated network. A broad belt of tight junctions was observed at the transition between margin of overgrowth and non-marginal cells. The distribution of the junctional elements in the MO suggests that junctions contribute to the maintenance of the structural and functional organization of the margin of overgrowth. Furthermore, the spatial distribution of the junctions might give information about the mechanism of locomotion of the margin of overgrowth.
Correlation of Na+, K+-ATPase content and plasma membrane surface area in adapted and de-adapted salt glands of ducklings
Authors: Merchant Juanita L. , Papermaster David S. , Barrnett Russell J. 
Published: April 2021

ABSTRACT
During salt-water adaptation, an increase occurs in Na+, K+-ATPase content and surface area of the basolateral plasma membrane of the principal cell of the duck salt gland. To determine the degree to which these changes are correlated, accepted morphometric methods were used to determine numerical cell densities and plasma membrane surface densities of peripheral and principal cells. After adaptation, the plasma membrane surface area per principal cell was five times greater than in controls. Following de-adaptation, the plasma membrane content in principal cells returned to L9 times control levels. Two other cell constituents, mitochondria and lipid droplets, displayed similar quantitative changes. Na+, K+-ATPase content increased about fourfold with adaptation and decreased to near control levels with de-adaptation. Thus, changes in Na+, K+—ATPase content and basolateral plasma membrane surface area in adapting and de-adapting secretory epithelia of the salt gland occur nearly in parallel. These quantitative data enable Na+, K+-ATPase synthesis and degradation to be investigated in relation to membrane biogenesis.
Involvement of sperm sulphatases in early sperm–zona interactions in the hamster
Authors: Ahuja Kamal K. , Gilburt David J. 
Published: April 2021

ABSTRACT
Sulphatase preparations from Abalone entrails, the limpet Patella vulgata and ox liver, as well as artificial substrates for these enzymes, were used in the hamster in -vitro fertilization system to study the possible roles of sperm sulphatases in sperm-zona pellucida interactions, p-nitrophenyl sulphate, p-nitrocatechol sulphate, ascorbate 2-sulphate, as well as D-glucopyranose and D-galactopyranose, both sulphated at the 3, 4 or 6 position but not the 2 position, inhibited fertilization in a dose-dependent manner. Sperm-egg fusion was not inhibited by the substrates used and eggs pre-treated with sulphates could readily be fertilized. Sperm motility and therefore viability was unaffected by inhibitory concentrations of substrates as determined by rhodamine 123 labelling of motile spermatozoa. Acrosomal integrity of rhodamine-labelled spermatozoa was assessed and found to be unaffected by inhibitory levels of substrates. Fertilization was inhibited by high concentrations of the two molluscan sulphatases but not by purified ox liver sulphatase. Pre-treatment of eggs with these enzymes did not prevent fertilization. Long-term exposure of hamster oocytes to N-acetylhexosaminidase or limpet sulphatase caused thinning and distension of the zona pellucida but these changes were not observed with the ox liver sulphatase. The results suggest that a glycosulphatase is probably released from hamster spermatozoa during sperm-egg adhesion and, or, penetration. If sperm-egg adhesion molecules are sulphated, the commercially available sulphatases would be unsuitable for their characterization.
Protein secretion in Tetrahymena thermophila: Characterization of the secretory mutant strain sb281
Authors: Maihle Nita J. , Satir Birgit H. 
Published: April 2021

ABSTRACT
The ciliated protozoon Tetrahymena thermophila contains membrane-bounded secretory organelles termed mucocysts, the release of which has previously been characterized ultrastructurally as a model system for the events occurring during membrane fusion and protein secretion. Recently, a series of secretory mutant strains of Tetrahymena has been isolated following mutagenesis of a parental wild-type strain designated SB210. In this study, the correlates of non-release in one unique mutant strain of this series, designated SB281, are described. SB281 appears to express a diminished (undetectable) level of the major 34000 Mr proteinaceous secretory product of Tetrahymena, as determined by Western immunoblot analysis and indirect immunofluorescence labelling. Thin-section electron-microscopic studies of these cells reveal that they possess no docked or free mature mucocysts. In addition, freeze-fracture electron microscopy demonstrates that an intramembrane particle array termed the rosette, present in the plasma membrane of wild-type cells above sites of docked mucocysts, is absent in the plasma membrane of mutant SB281 cells. A morphometric analysis of intramembrane particles in the plasma membrane of both wild-type and mutant cells indicates that both strains have a similar intramembrane particle density in both leaflets of the the plasma membrane. Although assembled rosettes are missing in the plasma membrane of mutant cells, a 15 nm intramembrane particle size class does exist in the plasma membrane of the mutant, but this size class is significantly reduced in number relative to wild-type.
Effect of cytochalasin b on somatic cell hybrids between normal and transformed cells
Authors: Hickey Ivor , Mcconville Carmel , Mcmenamin Mary , Neill Rosemary 
Published: April 2021

ABSTRACT
Cytochalasin B (CB) prevents cytokinesis in animal cells. In normal cells nuclear division and DNA synthesis are also blocked and the cells, held in the G1 phase of the cell cycle, remain either mononucleate or binucleate. In transformed cell lines DNA synthesis and nuclear division continue and the cells become multinucleate. We have examined the response to CB in two sets of somatic cell hybrids made between cells that display multinucleation after CB treatment and cells that do not. In a cross between transformed mouse LMTK cells and normal rat embryo lung cells, very little multinucleation was observed after treatment with CB for 7 days. The ability of the LMTK cells to form clones in soft agar was also significantly reduced in these hybrids. Segregant sub-clones that re-expressed both of these transformation phenotypes were isolated. These had reduced chromosome numbers.
A second cross was made between two variants of the BHK cell line, one of which displayed a high level of multinucleation in CB while the other did not. Again the hybrids showed a response similar to that of the non-multinucleating parent. From the results obtained with these two hybrids we conclude that the multinucleation induced in transformed cells by CB behaves as a recessive character in crosses with normal cells.
The kinetic polarities of spindle microtubules in vivo, in crane-fly spermatocytes. i. kinetochore microtubules that re-form after treatment with colcemid
Authors: Czaban B. Barbara , Forer Arthur 
Published: April 2021

ABSTRACT
In newly formed chromosomal spindle fibres we determined the kinetic polarities of the microtubules, that is, the ends to which tubulin monomers add. Spindles disappeared after cells were continuously immersed in colcemid; then portions of the cells were continuously irradiated with a microbeam of near-ultraviolet light to reverse locally the effect of the colcemid. From the following lines of evidence we conclude: (a) that microtubules are organized by the chromosomes; and (b) that tubulin monomers add to the chromosomal spindle fibres at the kinetochore.
When chromosomes were irradiated chromosomal spindle fibres grew in different directions, not necessarily focussed to a common pole; this would not occur if the chromosomal spindle fibres were organized by poles. Chromosomal spindle fibres were sometimes associated with only some of the chromosomes; this would not occur if the fibres were organized by the poles. Thus, chromosomal spindle fibres are organized solely by chromosomes; these spindle fibres are functional since the associated chromosomes moved in anaphase.
When chromosomes were irradiated the re-formed spindle fibres grew up to 10 μm past the edges of the irradiating spot. Experimentally, free tubulin did not diffuse more than 4—5 μm from the irradiated spot. Thus we conclude that the tubulin monomers add at the kinetochores and not at the distal ends of the fibres.