bluuebunny/crossref_metadata_2025_split huggingface dataset:
Coordinate expression of Mn-containing superoxide dismutase and Cu,Zn-containing superoxide dismutase in human fibroblasts with trisomy 21
Authors: Crosti N. , Bajer J. , Serra A. , Rigo A. , Scarpa M. , Viglino P. 
Published: April 2021

ABSTRACT
The amount of Mn superoxide dismutase (MnSOD) and the activity of Cu.Zn-superoxide dismutase (CuZnSOD) have been studied in human fibroblasts of five subjects with trisomy 21 and five subjects with normal karyotype, using nuclear magnetic relaxation and polarographic methods. In the trisomic fibroblasts we have found a mean molar amount of MnSOD 25·4% lower than in the control, and an amount of CuZnSOD 54·7% higher. A positive significant correlation between the activities of both enzymes has been observed indicating that the two enzymes dismute the O2− cooperatively. However, the increase of MnSOD per unit of CuZnSOD appears significantly lower in the trisomic fibroblasts, an effect that is not due to a diminished inducibility of MnSOD. These findings suggest that the MnSOD and CuZnSOD genes interact to preserve the normal level of total SOD activity.
Observations on the membranous components of amphibian oocyte nucleoli
Authors: Kezer J. , Macgregor H. C. , Schabtach E. 
Published: April 2021

ABSTRACT
Nucleoli in some large yolky oocytes of Plethodon cinerens and Ascaphus truei have attached to them a filament which may or may not have a beaded appearance. These filaments have been called ‘nucleolar tails’. One nucleus may contain several hundred of them. They may be up to 200 μm long and are usually about 1 μm wide. The beads which are sometimes attached to the filament are round, refractile and up to 3 μm in diameter. The tails are a feature of nuclei in which the nucleoli have left the nuclear envelope and migrated inward to cluster around the chromosomes in the centre of the nucleus. The tails project radially outwards from the central mass of nucleoli. Tails may be attached to round solid nucleoli, as is usually the case in A. truei, or they may be attached to ring nucleoli, as is often the case in P. cinereus, or they may lie free in the nuclear sap. Those nucleoli which remain attached to the nucleolar organizing site on the lampbrush chromosomes of P. cinereus never have tails. Nucleolar tails are Feulgen-negative and do not stain with gallocyanine when it is used under the proper conditions for staining nucleic acids. Tails are unaffected by deoxyribonuclease and ribonuclease but are destroyed by proteolytic enzymes.
Thin sections of oocytes whose nuclei contained nucleolar tails showed chains of membranous vesicles lying near to many of the nucleoli. These vesicles appeared empty, some of them were confluent with their neighbours, all were bounded by a unit membrane and all were coated on their outer surfaces by a fine fibrous material. The chains of vesicles commonly ended near a depression on the surface of the core of a nucleolus. Chains of vesicles sometimes extended into a long membranous tube. We have interpreted these chains of vesicles and tubes as sections through nucleolar tails.
It is suggested that nucleolar tails may be associated with the replication of nucleolar DNA, or with the division of nucleolar cores and nucleoli, or with the production of nuclear membrane at a time when the nucleus is enlarging rapidly. Each of these suggestions is discussed. A likeness between nucleolar tails and the mesosomes of bacteria is proposed and discussed.
Fine structure study of pollen development in Haemanthus katherinae baker: II. microtubules and elongation of the generative cells
Authors: Sanger Jean M. , Jackson W. T. 
Published: April 2021

ABSTRACT
The newly formed generative cell of the pollen grain of the African blood lily is spheroidal after its detachment from the pollen wall. Plastids are almost always excluded from the generative cell, while dictyosomes, mitochondria, ribosomes, endoplasmic reticulum, and micro-tubules are present throughout development of the cell. During the time that the generative cell is spheroidal, microtubules are found scattered randomly throughout the cytoplasm. The cell subsequently elongates and concurrently an oriented system of microtubules appears along the wall of the cell. The microtubules are aligned with their long axes parallel to the long axis of the cell. This system of microtubules persists in the generative cell throughout its development. The microtubules can be destroyed by exposure to isopropyl N-phenylcarbamate or colchicine and as a result the generative cell reverts to a near spheroidal shape.
Isolation and characterization of secretory vesicles in germinated pollen of Lilium longiflorum
Authors: Vandbrwoude W. J. , Morré D. J. , Bracker C. E. 
Published: April 2021

ABSTRACT
Secretory vesicles containing polysaccharide were isolated from germinated pollen of Lilium longiflorum and characterized by biochemical and ultrastructural investigation. Pollen tubes exhibit a secretory pathway in which the vesicles concentrated in the tube apex are produced by the Golgi apparatus and contributed to the cell wall at the apex upon fusion of the vesicle membrane with the plasma membrane.
Secretory vesicles were isolated by a method involving the size discrimination of cytoplasmic components using Millipore filters. Cells were disrupted under conditions which minimized membrane vesiculation. Identification was made by electron-microscopic comparison of the periodic acid-silver hexamine (PASH) reactivities of in situ and isolated secretory vesicles.
The secretory vesicles contained polysaccharides which were high in galacturonic acid and similar in sugar composition to those of the hot-water-soluble fraction of pollen tube cell wall. A hot-water-insoluble, non-cellulosic glucan was the major component of the cell wall. Less than 7 % of the wall was cellulosic. Chitin was absent. Similarities in the ultrastructure and PASH staining of apical secretory vesicles and an amorphous component of the cell wall support a precursor-product relationship between these 2 cell components. Ultrastructural investigations revealed complexes of the endoplasmic reticulum (ER) associated with electron-translucent regions of cytoplasm, suggesting a possible function of the ER in cell wall formation. Additionally, patterns of PASH staining show that changes in polysaccharides occur in secretory vesicles after vesicles have been formed by dictyosomes. Therefore, secretory vesicles may have a role in polysaccharide synthesis as well as in membrane and product transport.
The effects of sucrose and various salts on the growth and lysosomal enzyme activity of L5178Y cells
Authors: Bernacki R. J. , Bosmann H. B. 
Published: April 2021

ABSTRACT
L5178 Y murine leukemic cells do not seem to be affected by sucrose in the same manner as other mammalian cells. Although there is active uptake of sucrose with no concomitant metabolism, there is no increase in vacuolation or cell size and there is only a slight increase in acid phosphatase, acid protease and β-glucuronidase activities. However, the glycosidases are significantly elevated in the presence of 0·08 M sucrose. This may be due to a specific induction of these enzymes by the sucrose not related to a general increase in lysosomes.
As the sucrose concentration is raised, a depression of the growth rate and an elevation of glycosidase activities occurs, reaching a maximum at 0·08 M sucrose. This depression of growth with a concomitant increase in generation time is primarily a result of the increased osmolarity of the medium; the same effect is observed with increased concentrations of NaCl. Although the growth effects are similar with either sucrose or NaCl, the elevation of glycosidase activity occurs only with increased concentrations of sucrose.
Sucrose-induced vacuolation with an increase in cell size is not evident in L5178Y cells; therefore this effect does not seem to be common to all mammalian cells, even though it has been reported for LS cells, Chinese hamster fibroblasts, and chick bone rudiments and in vivo for liver cells.
The form of haemoglobin in the erythrocytes of the cod, Gadus callarias
Authors: Thomas N. W. 
Published: April 2021

ABSTRACT
The erythrocytes of the cod, Gadus callarias have a flattened discoid shape; each contains a peripheral marginal band of approximately 10 microtubules and a centrally placed nucleus. The cytoplasmic and nuclear haemoglobins have a paracrystalline organization; individual filaments, presumably polymers of haemoglobin, are grouped into bundles which course in all directions through the cell. This organization shows a remarkable similarity to that of deoxygenated haemoglobin in sickled human red cells. However, paracrystalline haemoglobin in the cod is characteristic of the normal red cells and is not associated with a crenated shape.
Incorporation of [me-3H] methionine into wool follicle proteins: a biochemical and ultrastructural study
Authors: Wilson Patricia A. , Henrikson R. C. , Downes A. M. 
Published: April 2021

ABSTRACT
The formation of the ‘low-sulphur’ group of proteins which constitutes more than half the cortical cell content of wool was investigated. Of the amino acids present in the low- and high-sulphur proteins isolated from wool, methionine is the only one which is exclusive to the low-S group. The incorporation of [Me-3H]methionine, administered intradermally to a sheep, was examined using both biochemical and autoradiographic procedures.
During the first hour after injection, most of the [3H]methionine appeared in the blood, but some was incorporated into the wool follicle proteins at the injection sites. Most of the radio-activity incorporated by the fibre during this period was subsequently retained. Initially, more than 90 % of the activity was present in the prekeratin (8 M urea-soluble) portion of the fibre; 50 h elapsed before half of the radioactive material appeared in the keratinized (8 M urea-insoluble) part of the fibre. Methionine and its oxidation products accounted for more than 80 % of the radioactivity present in hydrolysates of wool removed from injection sites after 4 h or 22 days. Analysis of labelled wool showed that the specific radioactivities of those fractions low in sulphur (α- and β-keratose) were 7 and 14 times greater than that of the high-S (γ-keratose) fraction.
Autoradiographic studies showed that the main site of formation of the low-S proteins was in the bulb region of the follicle. Here there was no specific intracellular site of low-S protein synthesis, the [3H]methionine being incorporated into the nucleus, cytoplasm, the various cell organelles and intercellular membranes. The amount of radioactivity incorporated by the cortical cells diminished at progressively higher levels in the fibre. In the keratinization zone, the various cell components showed limited protein synthesis, but 1–8 h after injection there was a localization of tritium over the keratin fibrils. It is suggested that a large proportion of the low-S proteins formed within the developing cortical cell ultimately contribute to the keratin microfibrils. The results provide further evidence for the formation of the low-S and high-S proteins at different sites in the follicle.
The development of a simple pattern: Spaced hairs in Oncopeltus fasciatus
Authors: Lawrence P. A. , Hayward P. 
Published: April 2021

ABSTRACT
Adults of Oncopeltus fasciatus, the milkweed bug, are covered with an evenly spaced mat of hairs. Each of these hairs develops from a single selected epidermal cell which divides and differentiates in situ. The process which picks out the particular epidermal cell is a simple example of pattern formation. Using a measure of uniformity of distribution an attempt was made to analyse the development of the hair pattern in time and space. Three methods were used: (i) Direct mapping of epidermis undergoing hair differentiation which allowed analysis of the spatial and temporal order in a single developing pattern: (ii) The injection of an agent which killed cells in DNA synthesis and which allowed the development of only those hairs that had completed DNA synthesis at the time of injection. Thus adults developed in which only the first-formed hairs differentiated, (iii) Treatment with the insect moulting hormone ecdysone which led to premature deposition of cuticle and curtailed hair development.
Results from these 3 approaches showed that the first hairs, far from being a random sample of the complete hair population in the normal adult, were a highly dispersed group. It is concluded that the hair pattern is built up in a precise order, with the centre of the largest available spaces being the sites where differentiation begins.
Microtubules and a contractile ring of microfilaments associated with a cleavage furrow
Authors: Tucker J. B. 
Published: April 2021

ABSTRACT
A ring composed largely of microfilaments is situated underneath the pellicle and at the base of the cleavage furrow in the ciliate Nassula during binary fission. The microfilaments have diameters ranging from 4 to 10 run. There are substantial indications that the ring actively constricts in a sphincter-like fashion and is the main contractile agent causing furrowing. As cleavage proceeds the ring thickens and the dense layer of the pellicle becomes progressively more deeply folded. The longitudinal axes of the folds are at right angles to the longitudinal axes of the microfilaments and the plane of the ring. Folds form only where the pellicle overlies the ring. Two distinct phases of cleavage have been distinguished. The furrow constricts the organism at a progressively more rapid rate until the cleavage constriction has a diameter of about 5 μm and the microfilaments plug the constriction. After this furrowing proceeds much more slowly. A girdle of several thousand microtubules embedded in a densely staining material forms between the ring and the pellicular folds during the final stages of cleavage. Constriction and severance of the narrow cleavage constriction joining daughter oiganisms during the final phase of cleavage involve mechanisms different from those acting during the earlier phase of furrow development.
Dynamic rearrangements of erythrocyte membrane internal architecture induced by infection with Plasmodium falciparum
Authors: Allred David R. , Gruenberg Jean E. , Sherman Irwin W. 
Published: April 2021

ABSTRACT
Cultured human erythrocytes infected with Plasmodium falciparum were studied by freezefracture electron microscopy. Special emphasis was placed upon the formation of the membrane surface excrescences (‘knobs’) found on red cells containing mature parasites. Knobs were visualized as conoid projections of the protoplasmic fracture face (PF) and depressions of the exoplasmic fracture face (EF). Knob formation was correlated with parasite growth and, on the basis of the organization of intramembranous particles (IMP) in the PF leaflet, a series of changes associated with parasite maturation was discerned:’ (1) a focal IMP cluster with minimal erythrocyte membrane elevation; (2) an elevated central IMP cluster surrounded by an IMP-free zone and concentric IMP ring; (3) maximal erythrocyte membrane deformation, concomitant with a loss of obvious IMP organization. Subtle changes in PF IMP organization were seen with knob formation and parasite maturation, including an apparent lateral partitioning of endogenous red cell membrane proteins between knobby or knob-free membrane areas in trophozoite-infected cells. IMP size distributions of the PF were shifted toward smaller particles in schizont-infected cells. Parasite development did not affect IMP densities in the PF; however, a decrease from 464 ± 106 µm−2 to 374 ± 94 µm−2 was seen in the EF of schizont-infected cells. IMP densities were similar over knobs and knob-free areas of either membrane leaflet, and there was no apparent EF IMP reorganization associated with the presence of knobs. These findings indicate that dynamic membrane changes are associated with knob formation and parasite maturation.
Characterization of a specific antiserum for mammalian collagenase from several species: immunolocalization of collagenase in rabbit chondrocytes and uterus
Authors: Hembry Rosalind M. , Murphy Gillian , Cawston Tim E. , Dingle John T. , Reynolds John J. 
Published: April 2021

ABSTRACT
A specific antiserum to rabbit bone collagenase was raised in a sheep and shown to react with collagenase from several mammalian species. This antiserum was used to demonstrate that only active collagenase binds to and can be immunolocalized on collagen fibrils and, by indirect immunofluorescence, the secretion of latent collagenase by stimulated rabbit chondrocytes and cells’ of the post-partum involuting rabbit uterus. The ionophore monensin was used to demonstrate intracellular accumulation of collagenase in the Golgi apparatus of both stimulated chondrocytes and involuting uterine cells. Collagenase was not detectable in either normal cartilage or non-gravid uterus. These results are discussed in relation to other studies of collagenase immunolocalization reported in the literature.
Analysing collisions between fibroblasts and fibrosarcoma cells: fibrosarcoma cells show an active invasionary response
Authors: Paddock S. W. , Dunn G. A. 
Published: April 2021

ABSTRACT
We describe a direct way of measuring contact inhibition of locomotion by analysing the changes in motion of pairs of colliding cells. This allows values to be assigned to each type of cell in mixed collisions and will enable certain hypotheses about the relationship between contact inhibition and invasion in culture to be tested critically. We find that fibrosarcoma (FS9) cells, on colliding with chick heart fibroblasts, show a reversed contact-inhibition response that we call contact promotion of locomotion. We also describe a measure of the lateral changes in motion that result from collisions between cells and show that this is dependent on the type of colliding cell but, unlike contact inhibition, it does not appear to be dependent on the type of cell with which it collides for the types studied here. Finally, we analyse how the total response is dependent on the dispositions and motions of the cells before collision and we find that FS9 cells, on colliding with fibroblasts, tend to turn towards the point of initial marginal contact. We conclude that the FS9 cells show a pronounced response on colliding with the fibroblasts, which is in contrast to the subjective impression that the FS9 cells do not respond much. These findings support the thesis of Abercrombie and colleagues, that the infiltration of a population of normal cells by a population of invasive cells in culture is dependent on the nature of the response of each cell type to collision with the other and that the invasive cells fail to show contact inhibition in these heterotypic collisions; but the findings further suggest that these invasive cells show an active invasionary response as opposed to merely failing to show contact inhibition.
Intracellular electrical potential measurements in Drosophila follicles
Authors: Bohrmann Johannes , Huebner Erwin , Sander Klaus , Gutzeit Herwig 
Published: April 2021

ABSTRACT
We measured the intracellular electrical potential in oocyte and nurse cells of Drosophila follicles at different developmental stages (6–14) and determined the intrafollicular potential difference. During stages 8—10B, when intrafollicular transport is known to occur, no significant potential difference was found. During late vitellogenic stages the nurse cells assume a more positive potential than the oocyte. This result contrasts with the published data on Hyalophora follicles, in which intercellular electrophoresis of negatively charged proteins occurs from nurse cells to oocyte as a result of an intrafollicular potential difference (nurse cells more negative than the oocyte). Such a potential difference was not observed in Drosophila follicles at any stage, not even after application of juvenile hormone. The extrafollicular electrical field is described with a dipole model. The hypothetical dipole is located in the long axis of the follicle and changes its calculated length stage-specifically.
Anti-tubulin antibodies locate the blepharoplast during spermatogenesis in the fern Platyzoma microphyllum R.BR.: A correlated immunofluorescence and electron-microscopic study
Authors: Doonan John H. , Lloyd Clive W. , Duckett Jeffrey G. 
Published: April 2021

ABSTRACT
The discovery that the monoclonal anti-tubulin antibody YOL 1/34 recognizes a microtubule organizing centre, the BIepharoplast (which arises de novo during the latter stages of spermatogenesis in the fern, Platyzoma microphyHum), has enabled us to follow it and associated microtubules throughout most of its ontogeny. By correlating electron-microscopic and immunofluorescence observations, YOL 1/34 is seen to stain the BIepharoplast uniformly at a time when no microtubules are present within the organelle. Later, staining becomes intense at the surface, concomitant with the re-location of cylindrical channels to the periphery of the BIepharoplast.
During anaphase of the ultimate division of the spermatid mother cell the BIepharoplast moves to the spindle poles and sharpens the otherwise barrel-shaped mitotic apparatus. Prior to this stage the BIepharoplast is, however, off-centre and at variable positions around the poles.
Later still, in the differentiating spermatids, the BIepharoplast is the focus for radiating cytoplasmic microtubules that abut directly onto the electron-dense organelle, penetrating the ribosome-free halo.
The three main conclusions are: (1) that tubulin in a pre-microtubular form is associated with the cylindrical channels that arise de novo within the previously amorphous BIepharoplast and act as a template in basal body formation; (2) that the late appearance of the BIepharoplast as a focus for the spindle poles during the final mitosis provides strong argument against its functioning during spindle pole initiation (despite its ability to sharpen the poles at anaphase); (3) that the BIepharoplast does seem to act as a microtubule organizing centre in the mitotically quiescent spermatid.
Elemental concentration gradients between subcellular compartments
Authors: Cameron Ivan L. , Hansen John T. , Hunter Keithley E. , Padilla George M. 
Published: April 2021

ABSTRACT
To gain information on the mechanisms involved in the establishment and maintenance of subcellular gradients of Na, K, Cl and other elements in the flagellate, Euglena gracilis, we turned to the technique of ultracentrifugal stratification of its intracellular contents, which is achieved without loss of viability or cell rupture. Stratified and non-stratified Euglena were cryofixed for energy-dispersive X-ray microanalysis of Na, K, Cl and other elements in thin freeze-dried cryosections. A number of significant elemental concentration differences (expressed as mmol kg−1 dry weight) were found between chloroplast, nucleus, paramylon granules and open cytoplasm (which contained ribosomes, membranes and macromolecules associated with the cytomatrix) in the non-stratified cells. Stratification caused several ions to be redistributed. For example, we observed a significant increase in K and Cl in the nucleus, which was correlated with the condensation of chromatin. Also Cl, but not Na, decreased significantly in the region of cytoplasm that was cleared of observable ribosomes, membranes and macromolecules associated with the cytomatrix, as well as of observable cytochemical enzyme activity. We conclude from the data that more than half of the Cl in open cytoplasm was adsorbed to or entrapped in material that was removed by ultracentrifugation. Thus, it appears that a close association of at least one ion, Cl, with ultracentrifugable material is involved in maintenance of the measured Cl concentration in the open cytoplasm of the non-stratified cell.