bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ultrastructural and enzymic modulation of hela cells induced by sodium butyrate and the effects of cytochalasin b and colcemid
Authors: Deutsch S. I. , Silvers D. N. , Cox R. P. , Griffin M. J. , Ghosh N. K. 
Published: April 2021

ABSTRACT
Sodium, butyrate causes HeLa cells to assume an elongated and jagged shape. Ultrastructurally this change is associated with the formation of bundles of microfilaments. Desmosomes were present between adjacent cells. No increase in microtubules was observed in the butyrate-treated cells.
Butyrate induces an increase in the activity of 2 membrane-bound enzymes, alkaline phosphatase and 5’-nucleotidase; however, the activity of a third membrane enzyme, acetylcholine esterase, is reduced. The activities of the several other enzymes with different subcellular localizations are not significantly increased. Colcemid and cytochalasin B prevent or reverse the butyrate-mediated change in HeLa cell morphology and also partially inhibit the induction of alkaline phosphatase activity in these cells. The effect of cytochalasin B on alkaline phosphatase induction may be caused by a reduction in protein synthesis produced by this fungal metabolite.
Neutral protease activity of rous sarcoma (RSV) transformed chick embryo fibroblasts
Authors: Spataro Ann C. , Morgan H. R. , Bosmann H. B. 
Published: April 2021

ABSTRACT
The proteolytic activities of normal, Schmidt Ruppin Rous sarcoma virus (SR-RSV transformed, and infected (RAV) chick embryo fibroblasts (CEF) have been measured by a highly sensitive technique using 3H-acetylated haemoglobin as a substrate. When all 3 types of CEF cells were maintained in serumless media, no differences were detected in the amount of pH 3·4 protease activity released into the media over a 24–h period, and only negligible amounts of pH 7·6 proteolytic activity were found. When normal, transformed, and infected cells were maintained in serumless media and later incubated with 3H-acetylated haemoglobin, a significant proteolysis of the haemoglobin, a 6-fold increase compared to the normal CEF cells, was associated only with plates containing SR–RSV–CEF cells. A fluorescent assay for peptides confirmed that SR–RSV–CEF cells have increased cell-associated proteolytic activity. The net surface charge of the transformed CEF cells was unchanged by maintenance in serumless media but the net surface negativity of the normal and RAV-CEF cells was significantly increased by incubation in media minus serum for 24 h. This suggests that normal CEF cells, maintained in media plus serum, have a substance masking their surface charge which is absent from the surface of transformed cells, possibly because of proteolytic degradation.
Aggregation in Polysphondylium
Authors: Jones Michael E. 
Published: April 2021

ABSTRACT
Dense aggregating fields of P. violaceum and P. pallidum exhibit propagated waves which may be analogous to those seen in Dictyostelhim discoideum. As in D. discoideum the wave velocity is determined by an intracellular delay between stimulation and response, rather than by the diffusion coefficient of the acrasin.
The frequency of the propagated wave overlaps that of aggregating D. discoideum, so that absence of coaggregation reported by Raper & Thom is unlikely to be based on specificity of the propagated wave parameters, but rather on a difference in the chemical acrasin itself, as argued on independent evidence by Bonner. Despite this difference in the chemical nature of the acrasin, the presence of propagated waves in Polysphondylium with frequencies similar to those in D. discoideum, taken together with evidence for a diffusible acrasin, suggests that the mechanism of aggregation is substantially the same in both genera.
Electron-microscopic study of the spindle and chromosome movement in the yeast Saccharomyces Cerevisiae
Authors: Peterson Joan B. , Ris Hans 
Published: April 2021

ABSTRACT
Mitosis in the yeast Saccharomyces cerevisiae was investigated in thick (0·25–1 μm) serial sections with a high voltage electron microscope and in preparations of spheroplasts spread on a water surface. Spindle microtubules originate from a plaque-like structure called the spindle pole body (SPB) which is inserted within the persisting nuclear envelope. Early in mitosis the SPB duplicates and a set of long and short microtubules develops on each SPB. The spindle arises as the SPBs separate on the nuclear membrane and reorient so that the microtubules fall into line. Chromosomes do not condense and are not individually visible. Genetic studies, however, have indicated that there are 17 linkage groups. The number of microtubules was determined in diploid and haploid spindles on serial stereo micrographs. In diploid mitosis about 40 microtubules issue from a SPB. Most are non-continuous and often they are visibly associated with a chromatin fibre. The spindle in haploid cells is similar except that the number of microtubules is about half that in diploid cells and the SPB is smaller. The pole-to-pole microtubules vary in number from spindle to spindle, but in each case enough microtubules are present to account for each linkage group being associated with a single non-continuous microtubule. We conclude that mitosis in yeast is comparable in its general aspect to that observed in typical eukaryotes.
Lectin receptor sites on rat liver cell nuclear membranes
Authors: Virtanen Ismo , Wartiovaara Jorma 
Published: April 2021

ABSTRACT
The presence and localization of lectin receptor sites on rat liver cell nuclear and other endomembranes was studied by light and electron microscopy using fluorescein and ferritin-coupled lectin conjugates.
Isolated nuclei labelled with fluorescein-conjugated Concanavalin A (Con A) or wheat germ agglutinin (WGA) often showed membrane staining, which sometimes was especially bright on small stretches of the nuclear surface. Unlabelled nuclei and nuclei with a complete ring fluorescence were also seen. The nuclear fluorescence corresponded in intensity to that seen on the surface of isolated rat liver cells.
Con A-ferritin particles were seldom detected on the cytoplasmic surface of the intact nuclear envelope. However, at places where the 2 leaflets of the envelope were widely separated or where the outer nuclear membrane was partly torn away, heavy labelling was seen on the cisternal surface of both the inner and outer nuclear membranes. Labelling with Con A-ferritin was also found on the cisternal side of rough endoplasmic reticulum present in the specimens. No labelling was seen on the cytoplasmic surface of mitochondrial outer membrane.
The results demonstrate the presence of binding sites for Con A and WGA in nuclei and an asymmetric localization of these sites on the cisternal side of ribosome-carrying endomembranes in rat liver cells.
Ultrastructural studies on the surface membrane of the mouse egg
Authors: Eager Deborah D. , Johnson M. H. , Thurley K. W. 
Published: April 2021

ABSTRACT
Fertilized and unfertilized mouse eggs were examined by scanning and transmission electron microscopy for evidence of mosaicism in the organization and concanavalin A-binding properties of their surface membranes. No obvious quantitative mosaicism in concanavalin A binding was noted. The egg membrane was microvillous over most of its surface, but was smooth in the region overlying the 2nd metaphase spindle of the unfertilized egg and on the polar body of the fertilized egg.
Morphological changes in frog pronephric cell surfaces after transformation by herpes virus
Authors: Tweedell Kenyon S. , Williams Daniel C. 
Published: April 2021

ABSTRACT
A scanning electron-microscope study has established that there are major modifications in the surface membranes of malignant cells transformed from the pronephric kidney of the frog. Tumours were induced in vivo after exposure of embryos to Lucké Herpes virus. A pronephric cell line from normal embryos and 3 tumour cell lines derived from experimentally induced adenocarcinomas of the pronephros were observed. The normal embryonic kidney cells have their surfaces covered with long fingerlike microvilli throughout the cell cycle. In contrast, the surface of the pronephric tumour cells are mainly covered by multiple, ruffled or parallel straight microridges and short, stubby microvilli. These comparisons were made on cells subject to similar culture conditions. The topographic changes in the tumour cells are considered significant since the characteristic microridges and stubby villi were consistently found in all 3 pronephric tumour lines.
The preprophase band: Possible involvement in the formation of the cell wall
Authors: Packard Mary J. , Stack Stephen M. 
Published: April 2021

ABSTRACT
Numerous vesicles were observed among the microtubules of the ‘preprophase’ band in prophase cells from root tips of Allium cepa. The content of these vesicles looks similar to the matrix of adjacent cell walls, and these vesicles often appear to be involved in exocytosis. In addition, the cell walls perpendicular to the plane of (beneath) the preprophase band are often differentially thickened compared to the walls lying parallel to the plane of the band. Our interpretation of these observations is that the preprophase band may direct or channel vesicles containing precursors of the cell wall to localized regions of wall synthesis. The incorporation of constituents of the cell wall into a narrow region defined by the position of the preprophase band may be a mechanism that ensures unidirectional growth of meristematic cells.
Interrelationships between golgi, gerl and synaptic vesicles in the nerve cells of insect and gastropod ganglia
Authors: Lane Nancy J. , Swales Lesley S. 
Published: April 2021

ABSTRACT
In addition to demonstrating synaptic vesicles, staining with the zinc-iodide-osmium tetroxide (ZIO) method reveals the presence of positively reacting GERL membranes in association with the Golgi complex and lysosomes in the nerve cell bodies within ganglia from the locust Schistocerca gregaria and the gastropod molluscs, Limnaea stagnalis and Helix aspersa. A positive response to ZIO occurs in certain Golgi vesicles and saccules, in GERL (Golgi-endoplasmic-reticulum-lysosomes), in multivesicular bodies as well as residual bodies and in small vesicles and cisternae of axonal smooth endoplasmic reticulum (ER). The interrelationships between these organelles are considered in view of the similarity of the ZIO localization to phosphatase-rich sites in the neuronal perikarya and with respect to the possibility that components of the synaptic vesicles are formed in the Golgi region of the cell and migrate via the axonal smooth ER to the synaptic regions.
The effects of spectinomycin and ethidium bromide on the synthesis of organelle rrna and on ultrastructure in Ochromonas danica
Authors: Smith-Johannsen Heidi , Fromson David , Gibbs Sarah P. 
Published: April 2021

ABSTRACT
The effects of 24-h exposure to spectinomycin (100 μg/ml) and ethidium bromide (1 μg/ml) on the accumulation of chloroplast and mitochondrial rRNAs and on organelle ultra-structure were studied in greening cells of Ochromonas danica. Cells treated with ethidium bromide for 24 h divide at the same rate as controls but contain less than one third the normal amount of mitochondrial rRNA. Ultrastructural observations showed that these cells contain only 10% the number of mitochondrial ribosomes found in controls as well as fewer mitochondrial cristae. Ethidium bromide has no effect on chloroplast ultrastructure in Ochromonas.
Greening cells treated with spectinomycin grow at close to control rates but contain 30–40% less chloroplast rRNA than do controls. Electron microscopy showed that spectino-mycin disrupts the organization of chloroplast membranes and reduces the number of chloroplast ribosomes by 30%. Under these conditions, spectinomycin has no effect on mitochondrial rRNA or ultrastructure. Since spectinomycin is a specific inhibitor of translation on 70s ribosomes, these results are consistent with the possibility that at least some chloroplast ribosomal proteins are synthesized in the chloroplast of Ochromonas.
Fertilization in brown algae: III. preliminary characterization of putative gamete receptors from eggs and sperm of Fucus serratus
Authors: Bolwell G. P. , Callow J. A. , Evans L. V. 
Published: April 2021

ABSTRACT
Membrane fractions have been isolated from eggs of Fucus serratus which inhibit fertilization in a species-specific manner. This activity is destroyed by α-fucosidase and a-mannosidase. Some 6% of the protein of this membrane fraction binds to Con A-agarose, following SDS solubilization, and when eluted with α-methyl mannoside inhibits fertilization when preincubated with sperm, but not eggs. This inhibitory activity is species-specific and destroyed by α-fucosidase but not by trypsin. SDS-gel electrophoresis reveals 1 band staining strongly with Coomassie Brilliant Blue G and weakly with the PAS reagent. This major band represents a glycoprotein with an approximate molecular weight of 30000 Daltons.
Membrane fractions from sperm of Fucus serratus solubilized in KC1 yielded a proteincontaining fraction, after affinity chromatography on desulphated fucoidan-Sepharose. This fraction is 100-fold more effective in inhibiting fertilization after preincubation with eggs than either Con A or fucose-binding protein. It is species-specific and inhibition is reversed when pretreated eggs are washed with fucoidan. Activity is destroyed by heat and trypsin and only one diffuse band is apparent on SDS gels. This stains positively with Coomassie Brilliant Blue G but not with PAS and has a molecular weight of approximately 60000 Daltons.
Tentative calculation of the numbers of putative receptor molecules gives a figure of 2·5 × 106 receptors per egg and 1·8 × 105 receptors per sperm.
Isolation of plasma membranes from purified mouse spermatogenic cells
Authors: Millette Clarke F. , O’Brien Deborah A. , Moulding Christopher T. 
Published: April 2021

ABSTRACTPlasma membranes have been prepared from purified pachytene spermatocytes, round spermatids and residual bodies of the adult mouse testis using procedures modified from other authors’. Isolated membranes have been examined using electron microscopy, lectin binding and enzymic assays. Ultrastructural observation reveals smooth unit-membrane vesicles from 0 · 4 – 1 · 7 μ m diameter. No contamination by nuclei, mitochondria or lysosomes is detected microscopically. Radiolabelled lectin-binding experiments [125I-RCA1, 125]-green pea lectin] indicate that cell surface label cofractionates with material identified morphologically as plasma membrane. Estimates of total recovery of membrane, based upon the lectin data, average 33%. Biochemical analysis of subcellular markers reveal that no detectable DNA and only 1.2% of the total cellular RNA cofractionate with membranes. A variety of enzyme assays suggests little contamination by cytosol enzymes, Golgi material or mitochondria. Assays of 5 ‘-nucleotidase (E.C. 3.1.3.5) indicate that this enzyme is not a major component of developing mouse spermatogenic cell membranes. Instead, Sertoli cells represent the most important source of this enzyme in the adult seminiferous tubule. Polyacrylamide gel analysis of membranes isolated from purified germ cells reveals significant differences in the protein compositions of pachytene spermatocyte and round spermatid membranes. The preparation of highly purified plasma membranes from homogeneous populations of spermatogenic cells should facilitate the biochemical characterization of cell surface antigens specific to developing male germ cells.
The myocardial plasma membrane during development: influence of glutaraldehyde fixation on the density and size of intramembranous particles
Authors: Gros Daniel , Potreau Daniel , Mocquard Jean-Pierre 
Published: April 2021

ABSTRACTThe ultrastructure of the plasma membrane of mouse myocardial cells has been studied during development (from 10 days post-coïtum to the adult stage) using the freeze-cleave method, and the effect of glutaraldehyde-fixat10n on this structure has also been evaluated. Blebs, free of intramembranous particles (IMP), were found to be dependent upon the developmental stage and upon fixation with glutaraldehyde. On P and E fracture faces, the presence of IMP-free areas was age-dependent and fixation-independent. No difference was demonstrated in the IMP density during heart development. Fixation with glutaraldehyde retains in the plasma membrane approximately 40% of IMP, probably by preventing an alteration induced by glycerol. Whatever the developmental stage, E face-associated particles are significantly larger than P face-associated particles. The diameter of both types of particle increases slightly but irregularly as myocardial cells mature. Fixation reduces the particle size on both fracture faces in such a way that no significant difference between them can be demonstrated.
Evidence of low molecular weight rnas involved in permanent character changes in amoebae
Authors: Hawkins Shirley E. 
Published: April 2021

ABSTRACT
Previous studies have established that ‘informational molecules’ present in cytoplasmic fractions of A. discoides may be transferred by microinjection into A. proteus. Clones derived from injected cells showed various changes, including lowered sensitivity to growth in streptomycin and neomycin, in which respects they resembled A. discoides. These changes in response to antibiotics were transferred independently and were permanent, the information being replicated over many generations. The most ‘active’ material in terms of the number of clones showing character changes was found following injection of 16s ribonucleoprotein obtained after sucrose density gradient centrifugation of the microsomal fraction. Polyacrylamide gel electrophoresis of the 16s material showed 3 small peaks of RNA. In order to obtain adequate amounts of material, these peaks of RNA were identified in electrophoresis profiles of RNA extracted from the whole microsomal fraction, and RNA eluted from these latter gels was injected into A. proteus. Although the number of surviving clones was low, all were examined for their response to growth in either streptomycin, neomycin, erythromycin or chloroquine. After injection of RNA eluted from the 3 small peaks of RNA (slices 26-33), 8 out of 10 and 9 out of 10 clones showed lowered sensitivity to growth in streptomycin and neomycin respectively, and resembled the donor A. discoides. No changes in response to antibiotics were obtained from clones derived from cells injected with RNA eluted from another region of the gel, or after ribonuclease treatment of the RNA from slices 26-33. The relative molecular weights of these ‘informational’ RNA molecules were found to be between 9 and 13 × 104 Daltons.
Spontaneous spatio-temporal organization in yeast cell suspension
Authors: Jacobsen H. , Busse H. G. , Havsteen B. 
Published: April 2021

ABSTRACT
Under suitable conditions of substrate supply, cell suspensions of yeast Saccharomyces uvarum may display synchronized oscillations of glycolytic metabolism.
Also in an unstirred suspension, spatial patterns can be induced by continuously feeding enzymically liberated glucose into the system. The absorption of NADH in the suspension was measured in an annular cuvette. The observed structures display moving waves, which travel over a distance of some centimetres in the cell suspension and seem to originate from a volume element in which the phase is ahead of those of its neighbours. The wavelength is estimated to be about 10 cm and the velocity of spreading of the wave is about 5 cm/min. Waves are only observed in the beginning of glycolytic oscillations. Subsequently the spatial synchrony usually increases and destroys the previous organization.
Similar spatio-temporal structures are observed during aggregation of the slime mould Dictyostelium discoideum and in the chemical reaction system of Belousov and Zhabotinsky.
Cytoskeleton changes in fibroblast adhesion and detachment
Authors: Badley R. Andrew , Woods Anne , Carruthers Linda , Rees David A. 
Published: April 2021

ABSTRACT
The organization of the cytoskeleton in several anchorage-dependent fibroblast types has been compared with the pattern of adhesions to a glass substratum which will support either their growth or just their spreading. Components were stained separately for immunofluorescence microscopy using specific antisera against actin, tubulin, and gizzard 10-nm filament protein, and the adhesions were visualized by interference-reflexion microscopy.
Of the cytoskeleton features, only stress fibres could be related to the pattern of focal adhesions; as shown before, each focal adhesion lies directly beneath a stress fibre, often near the terminus. Cells spread on fibronectin-treated glass in serum-free medium to arrest the development of focal adhesions, show correspondingly underdeveloped stress fibres. Actin geodesic domes, microtubules, and 10-nm filaments showed no relations with the adhesion pattern. During cell rounding leading to detachment with either EGTA or trypsin, stress fibres begin to disperse in advance of shape change whereas microtubules and 10-nm filaments seem to alter their distribution as a consequence of shape change. We therefore confirm that stress fibres are the cytoskeleton features most directly related to focal adhesions and are cytoskeleton targets for 2 agents which cause rounding and hence detachment.
The sequences of events in dispersal of stress fibres by EGTA and by trypsin showed significant differences in detail. With trypsin, fibres higher in the cell and terminating at the cell edge were more sensitive than most basal fibres and, during disintegration, all types of fibre went through an intermediate ‘beaded’ structure. With EGTA, all stress fibres seemed to be similarly susceptible and the beaded stage was not seen. The implications of these differences for our understanding of the mechanisms of dispersal of stress fibres are discussed.
Analysis of the cell adhesion mechanism using somatic cell hybrids: I. aggregation of hybrid cells between adhesive v79 and non-adhesive ehrlich’s ascites tumour cells
Authors: Aoyama Hirohiko , Okada T. S. , Takeichi Masatoshi 
Published: April 2021

ABSTRACT
V79 Chinese hamster cells dissociated with 1 mM EDTA retain 2 kinds of cell adhesion mechanisms, one dependent on Ca2+ and the other independent of Ca2+. Ehrlich’s ascites tumour (EAT) cells are provided with neither Caa+-dependent nor Ca2+-independent mechanisms. Studies on the aggregation of cells of 25 different hybrid clones obtained by fusing these 2 lined cells revealed the following points with regard to adhesive properties of hybrid cells. (1) The activity of the Ca2+-independent mechanism was lower in most hybrid clones than in parental V79 cells. (2) There were a few hybrid clones whose Ca2+-dependent mechanism activity was lower than in V79 cells. In these clones, the Ca2+-independent mechanism was also less active than the parental cells. (3) A hybrid clone with reduced Ca2+-dependent mechanism activity only was not found. (4) All the hybrid clones have at least one set of chromosomes derived from V79. (5) The number of chromosomes derived from EAT cells tended to be less in hybrid clones with lower aggregative ability.
These results can be explained by assuming that the activity of the Ca2+-independent and Ca2+-dependent mechanisms of V79 cells may be differently inhibited by genes contained in EAT cells.