bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reorganization of hydrated collagen lattices by human skin fibroblasts
Authors: Grinnell Frederick , Lamke Cheryl R. 
Published: April 2021

ABSTRACT
Fibroblasts were cultured on top of or at the bottom of hydrated collagen lattices. Shortly after initially interacting with the collagen lattices, fibroblasts appeared to attach to individual collagen fibrils and in many cases cell processes were found wrapped around clusters of collagen fibrils. Tension generated by cells during spreading resulted in proximal collagen fibrils becoming aligned in the plane of spreading and more densely packed. During subsequent culture, the collagen fibrils distal to the cells underwent a similar reorganization and the lattice thinned to one-tenth of its original thickness. The rate of thinning was similar regardless of whether the cells were originally above or at the bottom of the lattices. The presence of cells distributed throughout the lattice was unnecessary for lattice reorganization to occur. When the lattices were allowed to come off the underlying substratum, compaction of the collagen gels was observed, and the resulting matrix had the typical appearance of dermis as observed by both light and electron microscopy. Collagen fibrils associated with the cell surface often appeared to be under tension and, in regions of close fibril binding, there was a prominent reorganization of submembranous microfilaments. It is suggested that reorganization of the collagen lattice by fibroblasts may depend upon secreted cell factors as well as physical forces generated by the cells.
Isolation And Phenotypic Characterization Of Tetrahymena Thermophila Size Mutants: The Relationship Between Cell Size And Regulation Of Dna Content
Authors: Seyfert H. M. , Hipke H. , Schmidt W. 
Published: April 2021

ABSTRACT
Temperature-sensitive size mutants of the ciliate Telrahymena thermophila were selected following chemical mutagenesis. Phenotypical characteristics are given for seven cell lines, which have a range of average cell volumes from 8000μm3 to more than 100 000μm3. Wild-type Tetrahymena cells have an average cell volume of 15 000 μm3. Two of the mutagenized cell lines have comparatively small cells at 29°C but normal cells at 37°C; whereas the other five lines are normal at 29°C but large at 37°C. While the small cells are poor growers, the large cells grow excellently at 37°C. Measurements of DNA, RNA and protein contents indicate a significant correlation between all parameters and cell size. However, since the cells tolerate considerably different concentrations of each class of macromolecules, the amount of any of these macromolecules cannot be tightly controlled by cell size.
The Cellular Program For The Formation And Dissolution Of The Synaptonemal Complex In Coprinus
Authors: Lu B. C. 
Published: April 2021

ABSTRACT
Inhibition of protein synthesis by cycloheximide on processes in meiosis was used to probe the cellular program for the formation and dissolution of the synaptonemal complex (SC) in the synchronous meiotic system of Coprinus cinereus.
The pathway for the synthesis and assembly of the synaptonemal complex is proposed to be as follows: (1) synthesis and assembly of lateral components on the chromosomes; (2) synthesis and assembly of the central components in the nucleolus; (3) the lateral components of the homologous chromosomes are brought together to pair when the homologous pairing occurs at zygotene; (4) the transport of the central components from the nucleolus to join the paired lateral components and thus complete the synaptonemal complex.
Continued protein synthesis is required for all steps. Step (1) is nearly complete 2 h after the onset of karyogamy, because continued assembly is possible in the presence of cycloheximide. The transition point for step (2) is 4 h after the onset of karyogamy, as inhibition at this point results in accumulation of central components in the nucleolar dense body. The paired lateral components of step (3) are deprived of the central component. The transition point for step (4) is 5 h after the onset of karyogamy, for inhibition at this point no longer prevents transport.
Two steps are proposed for dissociation and dissolution of the SC at the end of pachytene. Protein synthesis is required for the dissolution of SC. Inhibition at this point causes accumulation of polycomplexes.
Mutations in various organisms from the literature relating to the SC support the validity of the proposed pathway.
The concentrations of water, sodium and potassium in the nucleus and cytoplasm of amphibian oocytes
Authors: Century T. J. , Fenichel I. R. , Horowitz S. B. 
Published: April 2021

ABSTRACT
Techniques are described for the isolation of nuclei and cytoplasm from frozen amphibian oocytes at − 40 °C and their analysis for water, sodium, and potassium contents. Nuclei of the 4 species studied contain 74–85% water while cytoplasm is only 35–50% water. Nuclei contain 7–17 μequiv. Na/ml H2O and 123-129 μequiv. K/ml H,O; cytoplasm contains 50–84 μequiv. Na/ml H2O and 81–94 μequiv. K/ml H2O. Mechanisms suggested to explain the observed nucleo-cytoplasmic asymmetries are the selective sequestering of sodium in the cytoplasm and a fraction of cytoplasmic water which does not act as solvent. Asymmetric cation transport by the nuclear membrane is not indicated.
An ultrastructural study of pyrenoids from Chlorella pyrenoidosa
Authors: Bertagnolli B. L. , Nadakavukaren M. J. 
Published: April 2021

ABSTRACT
The fine structure of pyrenoids from Chlorella pyrenoidosa shows a crystalline matrix with an8-o-nm periodicity. In certain areas of the pyrenoid 2 sets of parallel lines intersect at approximately 80° to give a criss-crossed appearance to the matrix. The recognition of the crystalline structure depends on the portion of the pyrenoid that is sectioned, as well as the plane of sectioning.
A distinct crystal-like body which is closely associated with the thylakoid lamellae that traverse the pyrenoid matrix is observed in one cell.
Although 2 pairs of thylakoid lamellae run separately through the pyrenoid matrix of a cell, they appear to be continuous with each other outside the pyrenoid.
The fine structure of the pyrenoid, at any given time, seems to be a reflection of its metabolic state. A lack of understanding of the exact function or functions of pyrenoids makes a more rational interpretation of pyrenoid ultrastructure difficult.
The mitral and short axon cells of the olfactory bulb
Authors: Price J. L. , Powell T. P. S. 
Published: April 2021

ABSTRACT
A description is given of the mitral and short axon cells of the olfactory bulb of the rat from Golgi material examined with the light microscope and from material examined with the electron microscope. The mitral cells are large neurons with primary and secondary dendrites which both extend into the overlying external plexiform layer, although only the primary dendrite enters the glomerular formations. No predominant antero-posterior orientation of the secondary dendrites has been found. Within the glomeruli the mitral cell dendrites are in synaptic contact with the olfactory nerves and also with the periglomeiular cells, but elsewhere the only synapses on the mitral cells are the ‘reciprocal synapses’ with the granule cells. Synaptic-type vesicles are found in all parts of the mitral cells, including the axon initial segments; they appear to be especially concentrated in the distal portions of the dendrites.
Several types of short axon cells have been found in the granule cell layer in Golgi-impregnated material. Their cell bodies can also be distinguished with the electron microscope, and from previous work it is probable that the axons of at least some of these cells form flattened vesicle symmetrical synapses upon the granule cells.
Destruction of immaturin activity in early mature mutants of Paramecium caudatum
Authors: Miwa Isoji 
Published: April 2021

ABSTRACT
Cells of Paramecium in the sexually immature period of the clonal life cycle contain a protein called immaturin, which represses mating activity when injected into sexually mature cells. The amount of immaturin at various stages of the immaturity period was examined by injecting cytoplasm from immature cells of one wild-type and two early mature mutant clones into mature cells of wild-type. The proportion of immature cells brought about by the injection increased until about 10-15 fissions after conjugation of the donor cells in all three clones. But the percentage of immature cells induced by the injection decreased rapidly from the 25th to the 30th fission of both early mature donors, while the percentage was still high with a wild-type donor of the same fission age. When cytoplasm of the Emt A (early mature mutant) homozygote taken immediately before maturation (about 27 fissions) was injected into the wild-type immature cells of 45 fissions after conjugation, 13% of the recipient cells expressed mating reactivity. But when cytoplasm of Emt A cells 20 and 50 fissions after conjugation was injected into the same cells, no reactive cell appeared. The results suggest that cytoplasm of the early mature mutant immediately before maturation contains some material that accelerates maturation when injected into wild-type cells in the late stage of immaturity. On the other hand, the immature cytoplasm of wild-type cells about 25 fissions after conjugation showed no effect when injected into early mature cells immediately before maturation. The function of the early mature gene product was suggested to be the destruction of immaturin activity.
Unique calcium-dependent hydrophobic binding proteins: Possible independent mediators of intracellular calcium distinct from calmodulin
Authors: Moore Pamela B. , Kraus-Friedmann Naomi , Dedman John R. 
Published: April 2021

ABSTRACT
Calcium-dependent regulation of cellular processes is mediated by specific intracellular proteins. A newly described set of proteins isolated from chicken gizzard with Mr of 67 × 103, 35 × 103, 33 × 103 and 30 × 103 also express a hydrophobic site in the presence of calcium. These proteins are isolated from several other cellular tissues and are termed calcimedins. These proteins differ from calmodulin in isoelectric point, DEAE-cellulose binding characteristics and heat stability. The calcimedins do not activate calmodulin-dependent cyclic nucleotide phosphodiesterase but do activate a hepatic microsomal Ca2+-ATPase system. Hence, the possibility is opened that calcium regulation of cellular processes is mediated by calcium-binding proteins in addition to calmodulin.
Ultrastructural analysis of the initiation and development of cytasters in sea-urchin eggs
Authors: Kallenbach Rein J. 
Published: April 2021

ABSTRACT
Two approaches were used to study the origin and overall development of cytasters in relation to the emergence and maturation of new centrioles in sea-urchin eggs. A continuous hypertonic treatment was used to gather information on cytoplasmic areas of potential cytaster formation and the subsequent development of these cytastral areas. A two-step parthenogenetic stimulation procedure was used to analyse various cytastral changes during and after mitosis. Potential cytastral areas are associated with extensive Golgi complexes and astral formation occurs only about newly induced centrioles. The construction of a single aster involves a large redistribution of local cytoplasmic structures, concentrating some components, excluding others and orienting more and more microtubules in an increasingly focussed arrangement. These events are correlated with an extensive accumulation of astral endoplasmic reticulum, an increase in the size of the astral area, and a gradual acquisition of a more typical radial configuration. The astral shape becomes more pronounced during mitosis, after which the cytasters regress, but retain the mature centrioles. The data reveal that cytaster formation is initiated after the activation and appearance of centriolar precursor bodies, and that both centrioles and associated cytasters are complementary structures, which develop in unison. The results suggest that developing centrioles, from the moment of their emergence, control and direct the events of cytastral formation.
Proliferation of a human embryonal carcinoma-derived cell line in serum-free medium: Inter-relationship between growth factor requirements and membrane receptor expression
Authors: Engström Wilhelm , Rees Anthony R. , Heath John K. 
Published: April 2021

ABSTRACT
Substantial multiplication in vitro of cloned cells from a human embryonal carcinoma cell line, Tera 2, has been obtained in a basal medium (DMEM/Ham’s F12,50:50, v/v) supplemented with 10μg low density lipoprotein/ml, 100μeg high density lipoprotein/ml, 100ng multiplication stimulating activity/ml, 100 ng insulin/ml and 1 μg transferrin/ml. The growth rate appears to be similar to that obtained in 10% serum. Furthermore, studies on the expression of cell surface receptors revealed that cloned Tera 2 cells express high-affinity receptors for IGF-II but not for insulin. The cells also express receptors for Epidermal Growth Factor (EGF) even though the addition of EGF does not stimulate their proliferation in serum-free medium. These results suggest that the expression of specific growth factor receptors is not an absolute determinant of hormone responsiveness.
Consequences of parental exposure to serum-free medium for progeny cell division
Authors: Larsson Olle , Zetterberg Anders , Engströmi Wilhelm 
Published: April 2021

ABSTRACT
Proliferating serum-dependent 3T3 cells prolong their intermitotic time by 9-10 h after exposure to serum-free medium for only 1 h. This delay was only observed in cells younger than 4h, i.e. cells in the postmitotic G1 phase (G 1 pm), as defined by time elapsed since previous mitosis. These data confirm earlier findings that cells are very sensitive to growth factor or serum depletion during the first part of G1 and that only a short exposure to serum-free medium is sufficient for the cells to leave the cell cycle. However, such cells that have delayed their first cell cycle in response to a short exposure to serum-free medium in early G1 exhibit a reduced capacity to delay the subsequent cycle in response to a repeated exposure to serum-free medium. In contrast cells older than 4 h that are exposed for short periods to serum-free medium undergo cell division on schedule, but delay the subsequent cell cycle by several hours. This delay of the progeny cycle is mainly ascribable to the postmitotic part of G1 (G1pm). These data suggest that short exposures to serum-free medium exert an indirect effect on the progeny cell cycle and demonstrate that cycle times are not necessarily determined de novo in the lifetime of every cell, but may be influenced by events in the preceding cycle.
Caveolae intracellulares and sarcoplasmic reticulum in smooth muscle
Authors: Gabella G. 
Published: April 2021

ABSTRACT
In the smooth-muscle cells from guinea-pig ileum a highly developed sarcoplasmic reticulum has been observed immediately underneath the plasma membrane in close relationship to the caveolae intracellulares. It is suggested that sarcoplasmic reticulum in smooth muscle may play a similar role as in skeletal muscle, constituting the main intracellular store for calcium.
Bound lipid in the tissues of mammal and insect: A new histochemical method
Authors: Wigglesworth V. B. 
Published: April 2021

ABSTRACT
‘Bound’ lipids persist in ester wax sections of tissues fixed in glutaraldehyde. They do not take up Sudan black B. They are unmasked by dilute sodium hypochlorite and then stain readily with the Sudan dye and are extractable in warm chloroform and methanol.
Bound lipids have been studied in tissues from the mouse and from the insects Rhodnius, Periplaneta and Calliphora. They are so widely distributed that Sudan staining alone gives an informative histological picture.
They occur in nucleoli and the nuclear envelope, in the nuclear matrix and in the cytoplasm (especially when rich in endoplasmic reticulum), in plasma membranes and their invaginations and évaginations (microvilli), in septate desmosomes, and particularly in mitochondria, dictyosomes and myelin.
In erythrocytes they are not only concentrated in the surface membrane but are distributed throughout the interior of the cell. In muscle fibrils (papillary muscle of the ventricle and fibrillar flight muscle of Calliphora) bound lipid occurs in small amounts in the dark regions of the unstained muscle (‘A’-bands) but is normally absent from the ‘Z’-line and from the ‘I’-bands. In highly contracted muscle this relation is reversed: lipid is concentrated around the ‘Z’-line. The elastic layers and fibrils in arteries are rich in bound lipid.
Bound lipids are presumably lipoproteins. Purified lipoprotein from egg yolk examined histochemically has the same properties.
Immunolocalization of keratan sulphate in the human embryonic cornea and other human foetal organs
Authors: Hyldahl Louise , Aspinall Richard , Watt Fiona M. 
Published: April 2021

ABSTRACT
An antibody raised against keratan sulphate was used to localize keratan sulphate in the human embryonic cornea and other human foetal organs. It was found that keratan sulphate was present in the corneal endothelium, as well as in the corneal stroma. In contrast, no keratan sulphate could be demonstrated in the corneal epithelium or in any posterior parts of the human foetal eye. Human corneal stromal cells grown in monolayers in tissue culture lost their capacity to bind this antibody. This suggests that explantation in vitro decreases or alters the expression of keratan sulphate in this cell type. Keratan sulphate was found to be present in abundant quantities in human embryonic cartilage and to a lesser extent in placenta. In contrast, keratan sulphate could not be detected in the foetal intestine, liver, suprarenal glands, the umbilical cord or in the foetal yolk sack.
Stylar peroxidase and incompatibility reactions in Petunia hybrida
Authors: Carraro Luisa , Lombardo Giuliana , Gerola F. M. 
Published: April 2021

ABSTRACT
Self-, cross- and non-pollinated styles of Petunia hybrida were treated with 3-3’-diamino-benzidine for the ultrastructural localization of peroxidase activity. Wall peroxidases were absent in cross-pollinated styles, but they were detectable as an osmiophilic deposit on the cell walls of the outer portion of the transmitting tissue in self- and non-pollinated styles. The cell layer showing peroxidase activity was thicker in the self-pollinated styles than in the non-pollinated ones. In accordance with current hypotheses on the mechanism involved in pollen incompatibility process, it is suggested : (1) that wall peroxidases present in the cells of the outer portion of the transmitting tissue are involved in the gametophytic self-incompatibility of Petunia ; (2) that self-pollination causes an increase in the number of cells involved in the rejection process; (3) that non-pollinated styles, which are characterized by the presence of cell wall peroxidases in the outer portion of the transmitting tissue, are ‘prepared’ to a certain extent for the rejection of incompatible pollen tubes. The removal of peroxidase activity thus seems to be an important step in the compatible pollination process.
Homotypic pair formation during conjugation in Tetrahymena thermophila
Authors: Kitamura Akio , Sugai Toshiro , Kitamura Yasuko 
Published: April 2021

ABSTRACT
In the ciliate Tetrahymena thermophila, conjugation has been believed to occur only between cells of different mating types. We found the formation of homotypic pairs during normal conjugation by using micronuclear morphological markers. Homotypic pairs formed preferentially during the first 10 min following the first pair formation and comprised about half of the pairs. These results suggest the involvement of mating-type non-specific adhesion of cells in the initial step of conjugation. Homotypic pairs apparently persist for at least 30 min and then separate into single cells. Homotypic pairs are also formed when conjugant pairs re-form after mechanical separation of heterotypic pairs. Five kinds of glycosidases, three kinds of proteases and phospholipase C showed no effect on either the formation of homotypic pairs or their separation. The relation between the mating-type substances and the molecules responsible for mating-type nonspecific adhesion of cells is discussed.
Cell surface glycoproteins change during gastrulation in Pleurodeles waltlh
Authors: Riou Jean-François , Darribère Thierry , Boucaut Jean-Claude 
Published: April 2021

ABSTRACT
Identification of the cell surface glycoproteins is an essential requirement for elucidating the mechanisms that mediate intercellular adhesion and cell migration in gastrulating amphibian embryos. In our experiments the glycoproteins present at the surface of isolated cells at blastula and gastrula stages were labelled with 3H-labelled sodium borohydride. The procedure included the oxidation of either galactosyl and, or,.’V-acetylgalactosaminyl residues with galactose oxidase or sialic acid with sodium metaperiodate. The tritiated components were analysed by two-dimensional gel electrophoresis. On the surface of isolated embryonic cells, 23 glycoproteins have been identified. The most important observation was the labelling of 15 new glycoproteins during gastrulation. At the late blastula stage, eight glycoproteins containing galactosyl or N-acetyl-galactosaminyl residues are labelled, while 23 are labelled at the late gastrula stage. In other experiments, glycoproteins labelled by [3H] fucose or [3H] mannose or precipitated by concanavalin A(ConA)-, or wheat-germ agglutinin (WGA)-Sepharose were studied by two-dimensional gel electrophoresis in order to provide supplementary data on the synthesis and lectin-binding properties of major cell surface glycoproteins. It appears that approximately 100 different glycoproteins are revealed by these methods. Among them, 13 have been identified as major cell surface glycoproteins, 12 being labelled by [3H]mannose, four by [3H]fucose, 10 bearing an affinity for ConA and five for WGA. These 13 glycoproteins are synthesized throughout gastrulation without qualitative variation.
Biochemical aspects of bupivacaine-induced acute muscle degradation
Authors: Ishiura Shoichi , Nonaka Ikuya , Sugita Hideo 
Published: April 2021

ABSTRACT
A single injection of a local anaesthetic, bupivacaine, into the soleus muscle of adult rat has a severe mytoxic effect, i.e. rapid dissolution of myofilaments and degradation of myofibrillar proteins shortly after injection. Increased lysosomal enzymes were observed in homogenates of affected muscle. The activity of potent proteolytic enzyme, cathepsins B and L (assayed against a new synthetic substrate succinyl-Tyr-Met-naphthylamide), gradually increased and reached a plateau value that was 11-fold greater than the control 48 h after bupivacaine injection. The chronological change in the activity of cathepsins B and L was reflected in the myofibrillar protein pattern in bupivacaine-treated muscle. To determine whether the increase in lysosomal peptide hydrolases is due to activation of muscle lysosomes or not, mononuclear cells were separated from both injected and control muscles. The activity of cathepsins B and L in the lysate from injured muscle was 180-fold higher than the control. Affinity-purified antibody was used to study the intracellular localization of cathepsin B by immunohistochemical procedures. The results were consistent with the biochemical observation that the main source of cathepsin B in muscle homogenates was infiltrated mononuclear cells. Therefore, we conclude that the increased lysosomal enzymes may be derived mainly from mononuclear cells (macrophages), not from muscle lysosomes, in bupivacaine-induced acute muscle degeneration.