bluuebunny/crossref_metadata_2025_split huggingface dataset:
Molecular cloning of the cDNA for ligatin
Authors: Jakoi Emma R. , Brown Alison L. , Ho Ye-Shih , Snyderman Ralph 
Published: April 2021

ABSTRACT
We describe the first isolation and sequence of a partial cDNA clone encoding ligatin, a trafficking receptor for phosphoglycoproteins. The clone was isolated from a human U937 promonocyte λgtll cDNA library using rabbit antiserum to rat ileal ligatin. RNA blot hybridization revealed that the intact receptor transcript in human cells is 2-4 kilobases (kb). DNA sequencing together with expression of protein fusion products in Escherichia coli demonstrated that the cloned segment begins with a 1·2 kb open reading frame potentially encoding a 7·5×10 Mr section of the 10×103 Mr receptor followed by a 3′ tail of 948 bases. The 225 bases of coding sequence correspond to the carboxyl region of ligatin and contain a potential acceptor site for asparagine-linked glycosylation. Neither a poly(A) sequence nor polyadenylation signal was found at the 3′ end of the clone. In the 3′ untranslated region there is a paired consensus sequence that is analogous to a conserved 12 base-pair sequence present in clusters in several growth-controlled mRNAs, including those for c-fos and β-actin. The identity of this clone as ligatin was confirmed immunologically using antisera to an encoded fusion protein and three independent regions of its derived sequence. In addition, one of these antibodies produced a punctate immunofluorescence pattern within the cytosol of U937 cells in a similar fashion to anti-ligatin serum.
Changes in microvilli and golgi-associated membranes of lepidopteran cells induced by an insecticidally active bacterial δ-endotoxin
Authors: Lane Nancy J. , Harrison J. B. , Lee W. M. 
Published: April 2021

ABSTRACT
The δendotoxin from Bacillus thuringiensis var. kurstaki was fed to late larvae of the tobacco hornworm, Manduca sexta, to determine its effect on the anterior midgut epithelium, which was examined ultrastructurally at intervals thereafter. The cells of the midgut are primarily of the columnar and goblet variety and the effects of the toxin were more pronounced on the former. Tissues examined after only 1·5 min of exposure to the toxin already revealed fine-structural alterations. These were most notably changes in the microvilli and membranes associated spatially with the Golgi complex: vacuoles associated with its maturing face became enlarged. This effect was intensified with more-extensive exposure to the toxin, resulting in an increase in both vacuoles and the number of lysosomal bodies, many containing myelin-like formations; some of these arose as autophagicvacuoles. There seemed to be no consistent increase in endocytotic activity at the apical border, however. The intramembranous particle population of the microvilli of the columnar cells showed some slight changes with toxin treatment; alterations in microvillar contours also occured. The intercellular septate and gap junctions on the lateral borders were sometimes disrupted and with time often became internalized. It seems, then, that the toxin initially modifies the microvillar membranes and subsequently the Golgi-associated saccules are affected, giving rise to vacuoles and lysosomes.
Computer-generated three-dimensional representation of dictyosomes reconstructed from electron micrographs of serial ultrathin sections
Authors: Kristen U. , Lockhausen J. , Menhardt W. , Dallas W. J. 
Published: April 2021

ABSTRACT
Computer-generated three-dimensional reconstructions of higher plant dictyosomes from electron micrographs are presented from different viewing angles in the form of shaded perspective displays. The image processing has revealed complicated structures indicating a central cisternal stack surrounded by a cloud of vesicles and vesicular and tubular protrusions. The entire dictyosome is suggested as being an approximately spherical body that is marginally penetrated by plates and tubules of the endoplasmic reticulum.
Colony-stimulating factor-1 induces rapid behavioural responses in the mouse macrophage cell line, BAC1.2F5
Authors: Boocock C. A. , Jones G. E. , Stanley E. R. , Pollard J. W. 
Published: April 2021

ABSTRACT
The cloned, SV40-immortalized mouse macrophage cell line, BAC1.2F5, resembles primary macrophages in its dependence on colony-stimulating factor-1 (CSF-1) for both viability and proliferation. Re-addition of CSF-1 stimulates rapid, transient behavioural changes in starved cells, which are rounded, with diffusely organized F-actin and few intracellular vesicles. Within 1 min, cells begin to spread, forming prominent, F-actin-rich ruffles. Small vesicles (0·5–1·0μm), formed throughout extending lamellar processes, move centripetally and, after 3–5 min, fuse to form larger vesicles (2·0–4·0μm), clustered around the nucleus. Immunofluorescence demonstrates that CSF-1, bound to cell-surface receptors, is internalized via these vesicles. Cell spreading and ruffling peak about 5 min after restimulation. Interference reflection microscopy indicates no corresponding change in the mode of cell-substratum adhesion: a single area of close adhesion underlies most of the cell and simply broadens during spreading. Analysis of cell aggregation kinetics shows no effect of CSF-1 on intercellular adhesiveness. Measurement of cell areas after starvation and restimulation demonstrates quantitatively the time-course and concentrationdependence of cell spreading. Mean area doubles within 5 min and, after a transient peak, decreases within 30 min to the value measured before starvation. This time-course corresponds to that of CSF-1 internalization and of the phosphorylation and subsequent degradation of CSF-1 receptors. The concentration-dependence of the spreading response resembles that of CSF-1-dependent survival and proliferation. The minimum detectable stimulation of spreading occurs at the concentration (22 pM) that supports survival without proliferation. Increasing stimulation of spreading occurs over the range of concentrations that elicit increasing proliferation.
Bimodal redistribution of surface transmembrane glycoproteins during Ca2+-dependent secretion (acrosome reaction) in boar spermatozoa
Authors: Aguas Artur P. , Da Silva Pedro Pinto 
Published: April 2021

ABSTRACT
We used the acrosome reaction of boar sperm cells to study the dynamics of surface transmembrane glycoproteins (TMG) during a secretory process. The acrosome reaction is the Ca2+-dependent fusion of a large cytoplasmic vesicle (the acrosome) with the overlying segment of the plasma membrane (acrosomal cap) that leads to the release of the acrosomal enzymes. After triggering the acrosome reaction in vitro (2 mM-CaCU in the presence of 10μM-A23187), we used freeze-fracture electron microscopy to follow the topographical rearrangement of a population of acrosomal-cap large intramembrane particles that correspond to transmembrane proteins that bind wheat germ agglutinin. We found that these TMG move in the direction of either one of two opposite poles, proximal and distal, of the acrosomal cap. This bimodal movement of the TMG reorganizes the acrosomal cap into three extensive domains. The first two, on the apical rim and on the equator, are membrane domains to which the TMG are directed and where they accumulate. The third, a large in-between area of protein clearing, corresponds to the region from which TMG were preferentially located before displacement induced by the Ca2+ effect. The topography of these new membrane domains of the acrosomal cap becomes coincident with that of the structural domains of the subjacent acrosomal membrane. Mirroring of the acrosomal membrane by the plasma membrane is followed by fusion between the two membranes, formation of an exquisite labyrinth of hybrid-membrane tubules, followed by fission and release of the acrosomal contents through intertubular fenestrae.
A non-connexon protein (MIP) is involved in eye lens gap-junction formation
Authors: Gruijters W. T. M. 
Published: April 2021

ABSTRACT
New immunolocalization data put the role of the lens MP26 (MIP) protein in a new perspective. During maturation of lens fibre cells, MIP is found to associate specifically with two structures, gap junctions and cell interlocking processes (known as ball and socket domains). It is significant that the zone in which these associations are most striking is discrete, coinciding with the zone of rapidly enlarging junctional plaques and newly forming ball and socket domains. Observation of domain-specific interactions of MIP with forming gap junctions and ball and socket domains suggests that MIP may be involved in the formation of close membrane appositions. Furthermore, previous ambiguities in the literature over the presence of MIP in gap junctions are clarified by the knowledge that, in situ, MIP associates strongly with gap junctions for only a brief period (with less than about 5 % of all lens gap junctions at any one time) during the assembly of junctional plaques.
Differential expression of membrane sialoglycoproteins in exudate and resident mouse peritoneal macrophages
Authors: Rabinowitz Stephen , Gordon Siamon 
Published: April 2021

ABSTRACT
Wheat germ agglutinin (WGA) has been used to define biochemical differences between exudate and resident macrophages in the peritoneal cavity of mice. Western blotting with 125I-WGA identifies a restricted set of glycoproteins in elicited peritoneal macrophages (MΦ) (recruited with thioglycollate or periodate) and fully activated MΦ (recruited with live Bacille Calmette-Guérin, or heat-killed Corynebacterium parvum); the major species migrates with Mt 89-115 kDa in 10 % acrylamide gels. These glycoproteins are not detected in resident peritoneal MΦ, nor in thymocytes, neutrophils, lymphocytes and a variety of non-MΦ cell lines.
The binding of WGA is sensitive to neuraminidase, which exposes binding sites on these proteins for peanut agglutinin and reduces their electrophoretic mobility; these features are typical of O-linked sialo-oligosaccharides. In culture, exudate MΦ increase their WGA-binding content over 48 h, and continue to display a phenotype distinct from that of resident peritoneal MΦ.
The stable differential expression of these sialoglycoproteins, by elicited and activated versus resident peritoneal MΦ, suggests that biochemical modification during the synthesis and expression of membrane glycoproteins accompanies MΦ recruitment to an inflammatory focus.
Regulatory subunits of cyclic AMP-dependent protein kinase: presence in granules and secretion by exocrine and endocrine cells
Authors: Hand A. R. , Mednieks M. I. 
Published: April 2021

ABSTRACT
Cyclic AMP-dependent protein kinase (cAPK) is the intracellular mediator of signal transduction events involving the adenylate cyclase-cyclic AMP system. A monoclonal antibody (MAb BB1) to the type II regulatory subunit (RII) of cAPK was used in a post-embedding immunogold-labeling procedure to determine the ultrastructural localization of RH in several different secretory cells of the rat. Label was present in nuclei, especially over the heterochromatin, and in the cytoplasm, particularly in areas containing rough endoplasmic reticulum. Immunolabeled RH was also present in secretory granules of the parotid gland, exocrine and endocrine pancreas, seminal vesicle, anterior and intermediate pituitary, and intestinal endocrine cells. Photoaffinity labeling of parotid saliva, pancreatic and seminal fluids with the cyclic AMP analogue, 32P-labeled-8-azido-cyclic AMP, revealed the presence of cyclic AMP-binding proteins with electrophoretic mobilities similar to those of authentic cAPK regulatory subunits. These results confirm our previous observations on the localization of cAPK regulatory subunits in the rat parotid using polyclonal antibodies, and extend them to a number of other exocrine and endocrine cells. The apparent widespread occurrence of cAPK subunits in secretory granules and secretory fluids suggests that cAPK may be involved in specific intragranular regulatory and/or phosphorylation events, or that it has an unidentified extracellular function.
Immunological detection of spectrin during differentiation and in mature ciliated cells from quail oviduct
Authors: Chailley Bernadette , Frappier Thierry , Regnouf Franqoise , Laine Marie-Christine 
Published: April 2021

ABSTRACT
A protein that was immunologically related to the erythrocyte and brain α-240-subunit and to the brain β-235-subunit of spectrin was characterized by immunoblotting and was detected by immunofluorescence in the apical part of ciliated cells from quail oviduct. After immunogold-labeling electron immunocytochemistry, spectrin was detected mainly in a fibrillar meshwork located between the proximal parts of the basal bodies. It was also observed to be in contact with the basal foot of basal bodies, but was not found to be associated with the apical plasma membrane. Cilia and microvilli were unlabeled. In contrast, spectrin was detected in close contact with the lateral plasma membrane of mature ciliated cells as well as in stem epithelial cells in unstimulated oviduct. During ciliogenesis induced by estrogen, spectrin gradually appeared at the apex of the cells as the apical cytoskeleton differentiated.
Nerve growth in the absence of growth cone filopodia and the effects of a small applied electric field
Authors: Mccaig Colin D. 
Published: April 2021

ABSTRACT
Nerve orientation may involve a biasing of the distribution of tension at the growth cone. Chemical and electrical guidance cues cause more filopodia to appear on one side of the growth cone and this may determine turning behaviour. In a small applied electric field, filopodia predominate on the cathodal side of the growth cone and nerves turn towards the cathode. Removing all filopodia by treatment with cytochalasin D did not prevent nerves from continued slow growth and nerves still oriented towards the cathode. It is concluded that nerves can perform some types of orienting behaviour in the complete absence of filopodia.
Eurythermic and stenothermic growth of cultured fish cells and their thermosensitivity
Authors: Mitani Hiroshi , Naruse Kiyoshi , Shima Akihiro 
Published: April 2021

ABSTRACT
RBCF-1 cells derived from the caudal fin of the goldfish (Carassius auratus) have been established at 37°C, and could grow at a wide range of temperatures (20-37°C). To examine the mechanism(s) of this eurythermic property, we isolated clones from RBCF-1 cells with different optimal growth temperatures. R37 clone grew continuously at 37°C but could not grow at 27°C. R27 clone grew continuously at 27°C but could not grow at 37°C. Thus R37 and R27 cells may be referred to as stenothermic. The R3727 clone, which was derived from R37 cells selected at 27°C, and the cell hybrids of R37 and R27 cells, could proliferate for a long time and form colonies at 27–37°C, like progenitor RBCF-1 cells, so they may be referred to as eurythermic. The shape of colonies of R3727 cells changed with incubation temperature; they resembled those of R37 cells at a higher temperature (37°C), while at a lower temperature, (27°C), they were like those of R27 cells.
The lethal effects of heat treatment were compared among RBCF-1 clones. R27 cells were most sensitive, and R37 cells were most resistant. The heat treatment could induce the four major heatshock proteins (hsp30, hsp42, hsp70 and hsp90). Marked induction of hsp70 and hsp30 was observed at 33°C for R27, at 37°C for R3727 and at 40°C for R37. With R3727 cells, induction of hsps and thermosensitivity were highly dependent on the incubation temperature before heat treatment.
Confocal scanning optical microscopy and its applications for biological specimens
Authors: Shotton David M. 
Published: April 2021

ABSTRACT
Confocal scanning optical microscopy (CSOM) is a new optical microscopic technique, which offers significant advantages over conventional microscopy. In laser scanning optical microscopy (SOM), the specimen is scanned by a diffractionlimited spot of laser light, and light transmitted or reflected by the in-focus illuminated volume element (voxel) of the specimen, or the fluorescence emission excited within it by the incident light, is focused onto a photodetector. As the illuminating spot is scanned over the specimen, the electrical output from this detector is displayed at the appropriate spatial position on a TV monitor, thus building up a two-dimensional image.
In the confocal mode, an aperture, usually slightly smaller in diameter than the Airy disc image, is positioned in the image plane in front of the detector, at a position confocal with the in-focus voxel. Light emanating from this in-focus voxel thus passes through the aperture to the detector, while that from any region above or below the focal plane is defocused at the aperture plane and is thus largely prevented from reaching the detector, contributing essentially nothing to the confocal image. It is this ability to reduce out-of-focus blur, and thus permit accurate non-invasive optical sectioning, that makes confocal scanning microscopy so well suited for the imaging and three-dimensional tomography of stained biological specimens.
In this review, I explain the principles of scanning optical microscopy and blur-free confocal imaging, discuss the various imaging modes of confocal microscopy, and illustrate some of its early applications.
The localization of the divergent β2-tubulin isotype in the microtubular arrays of Physarum polycephalum
Authors: Diggins-Gilicinski Maureen , Solnica-Krezel Lilianna , Burland Timothy G. , Paul Eileen C. A. , Dove William F. 
Published: April 2021

ABSTRACT
The β2-tubulin isotype of Physarum polycephalum is only 83 % identical in amino acid sequence with the constitutively expressed β1B-tubulin and the myxamoeba-specific βlα-tubulin isotypes. A poly-clonal antibody specific for β2-tubulin was used to monitor the subcellular distribution of the β2-tubu-lin antigen in the mitotic spindle of the mature plasmodium – the sole microtubular array in that stage of Physarum. By immunofluorescence, the β2-tubulin antigen was detected throughout this an-astral mitotic spindle, at all stages of mitosis. Physarum myxamoebae contain astral mitotic spindles and cytoskeletal microtubules. No β2-tubulin antigen was detected in the myxamoebal stage. However, as cultures of myxamoebae developed into plasmodia, the β2-tubulin antigen was found in the astral mitotic spindles and cytoskeletons in developing cells. Thus, the presence of the plasmodial β2-tubulin isotype in a mitotic spindle does not determine a closed, anastral mitosis.
Microtubules rich in modified α-tubulin characterize the tail processes of motile fibroblasts
Authors: Prescott A. R. , Vestberg M. , Warn R. M. 
Published: April 2021

ABSTRACT
The organisation of microtubules rich in post-transiationaily modified α-tubulin has been investigated in a fibroblast cell line (NIH–3T3–T15) that can be reversibly transformed. An immunofluorescence microscopy study of the static non-trans-formed cells has revealed a central distribution of wavy microtubules showing post-translational modifications. When transformed there is a marked increase in cell motility and the appearance of long thin cytoplasmic ‘tails’. These tails have been found to contain conspicuous bundles of post-trans-lationally modified microtubules that run down the length of the processes and terminate close to the plasmalemma. Both detyrosinated and acetylated α-tubulin are present as major species in these modified microtubules. Such a pattern of modified microtubules is only occasionally seen in the untransformed NIH–3T3–T15 cells. We have also found them to be present in other transformed fibroblast lines. The presence of bundles of micro-tubules rich in modified α-tubulin in the cell tails is correlated with a marked reduction in the numbers of F-actin stress fibres. The possible role of these modified stable microtubules in cell motility is discussed.
The fate of the centrosome–microtubule network in monocyte-derived giant cells
Authors: Moudjou Mohammed , Lanotte Michel , Bornens Michel 
Published: April 2021

ABSTRACT
Avian monocyte-derived giant cells in vitro, which are in many respects similar to osteoclasts, display a complex microtubule array that plays a prominent role in cell spreading. It is organized by a polygonal row of regularly spaced centrosomes surrounding an irregular cluster of nuclei. The immediate progenitor cells are binucleate cells with a single microtubule- organising center (MTOC), the result of the congregation of the two individual centrosomes. The one-to-one correspondence between numbers of centrosomes and nuclei in giant cells suggests that the centrosome of each precursor cell has been conserved through the fusion process. This is in marked contrast to the absence of centrosomes in myotubes, another example of a differentiated cell derived from the fusion of progenitor cells.
Stringency at four regions of the plant cell cycle where proteins regulating its progression are synthesized*
Authors: torre C. De la , Gonzalez-fernandez A. , Gimenez-martin G. 
Published: April 2021

ABSTRACT
Different responses were detected when inhibiting protein synthesis (by 1μg ml-1 anisomycin) for similar times (3 h) in each of the four regions of the plant cell cycle where synthesis of specific proteins seems to control further cycle progression. Synchronous cells, labelled as binucleate by 1-h, 5 mM-caffeine treatment, were used for this study in Allium cepa L. root meristems proliferating under steady-state kinetics.
In the experimental conditions used, G1 lasts 8 h in the synchronous control populations. G1 houses two such regions. The first region is located in early G1. Inhibition of protein synthesis in this region produced 8·2 h of delay in reaching the S period. Moreover, the treatment halved the prolUerative fraction of the population, behaving as a restriction area where cells should be rendered competent to go on cycling by newly synthesized proteins. The second region, located in late G1 (before the 6th hour of the cycle), produced, when inhibiting protein synthesis in the population, a delay of 2·4h (shorter than the treatment) in reaching the S period and no decrease of its proliferative fraction.
A similar inhibition of protein synthesis in the third region mapped in early G2 (before the 20th hour of the cell cycle) produced 4·4h of delay in reaching mitosis and a 20 % decrease in the proliferative fraction. Finally, there is a fourth region in early prophase (before the 25th hour of the cell cycle) where all the cells seemed to abandon the cycle during inhibition of protein synthesis.