bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mutual desmosome formation between all binary combinations of human, bovine, canine, avian and amphibian cells: Desmosome formation is not tissue- or species-specific
Authors: Mattey D. L. , Garrod D. R. 
Published: April 2021

ABSTRACT
Our previous work has suggested that the molecular components of desmosomes are highly conserved between different tissues and different vertebrate species. In order to determine whether the adhesion recognition mechanism of desmosomes is also conserved we have examined the specificity of desmosome formation between different epithelial cell types by co-culturing binary combinations of cells from different species and from epidermal and non-epidermal origin. The following cell types were used: human (HeLa, cervical carcinoma), bovine (Madin Darby bovine kidney, MDBK), canine (Madin Darby canine kidney, MDCK), avian (chick embryonic corneal epithelium) and amphibian (Rana pipiens, adult corneal epithelium). Different cells in co-culture were identified on the basis of at least one of the following criteria: (1) morphology by phase-contrast microscopy; (2) presence or absence of staining of cytokeratin with monoclonal antibody LE6l; (3) morphology at the electron microscope level. Mutual desmosome formation between different cell types was assessed using fluorescent antibody staining with anti-desmoplàkin antibodies and confirmed using electron microscopy. We have found that mutual desmosome formation occurred between all binary combinations of human, bovine, canine, avian and amphibian cells. Thus there is complete non-selectivity of desmosome formation between five different epithelial cell types from three vertebrate classes. Our results suggest that desmosome formation is not tissue- or speciesspecific and that the mechanism for intercellular binding involved in desmosomal adhesion is highly conserved.
The analysis of malignancy by cell fusion: III. hybrids between diploid fibroblasts and other tumour cells
Authors: Wiener F. , Klein G. , Harris H. 
Published: April 2021

ABSTRACT
Diploid fibroblasts were fused with cells of two highly malignant near euploid tumours, a sarcoma induced by polyoma virus and a spontaneous carcinoma; the resulting hybrid cells were tested for their ability to grow progressively in vivo. In the case of the sarcoma/fibroblast hybrids, 15 clonal populations, each derived from a separate primary fusion, were examined. Most of these populations already showed substantial losses of chromosomes by the time enough cells had been generated to permit chromosomal analysis; but a few clones were isolated with chromosomal constitutions approximating to the sum of the 2 parental chromosome sets. Those clones that had undergone substantial chromosomal losses were highly tumorigenic, but some of the clones that contained the complete, or almost complete, chromosome sets of both parent cells, showed a greatly reduced take incidence. Initially these clones produced very few tumours, but the take incidence rose as continued cultivation of the cells in vitro resulted in progressive loss of chromosomes. In the case of the carcinoma/fibroblast hybrids, clonal populations with very high chromosome numbers were selected for special study. These were also found to have a very low take incidence, comparable to that of the hybrids formed by the fusion of the tumour cells with L cell derivatives. None of the tumours produced by the injection of either the sarcoma/fibroblast or carcinoma/fibroblast hybrids were composed of cells containing chromosome complements corresponding to the sum of the 2 parental chromosome sets; all the tumours were formed by selective overgrowth of cells from which some chromosomes had been eliminated. These results indicate that the malignancy of the tumour cells can be suppressed by diploid fibroblasts as well as by the L cell derivatives, but that the rapid chromosome losses characteristic of hybrids between these tumour cells and diploid fibroblasts generate malignant segregants with much greater frequency. In the range of material examined in the present experiments malignancy thus behaves as if it were a recessive character.
Perinuclear dense bodies: Characterization as DNA-containing structures using enzyme-linked gold granules
Authors: Berger Sigrid , Schweiger Hans-Georg 
Published: April 2021

ABSTRACT
Cytoplasmic structures of the Acetabularia cell that appear close to the nucleus during the vegetative phase of the life cycle have been characterized cytochemically. The results obtained by using RNase and DNase linked to gold granules indicate that RNA and also DNA occur in these cytoplasmic structures.
Cell proliferation in Allium cepa L. meristems under 8-hydroxyquinoline, a chelating agent that affects DNA and RNA polymerases
Authors: Ferrero M. L. , Torre C. De La 
Published: April 2021

ABSTRACT
8-Hydroxyquinoline (HQ) chelates Mg2+ and Mn2+ and, secondarily, affects the activities of DNA and RNA polymerases. The in vivo effect of HQ has been estimated in Allium cepa L. meristems growing under new growth kinetics in the presence of this agent. HQ (at both 5 × 10−5 M and 10−4M) depressed incorporation of [3H]uridine much more effectively than that of [3H]-thymidine. Cycle kinetics in meristems behaved as if they were independent of the rates of synthesis or accumulation of RNA since, under HQ, cycle time was only moderately modified and the new cycle kinetics achieved could be explained by the new rates of [3H] thymidine incorporation. Lengthened S periods were partially compensated for by shortened G2 phases, suggesting that, in these cells, both the growth cycle and its coupling with the DNA-division cycle were not disturbed by a decreased amount of RNA.
Finally, the nucleolar cycle during mitosis, but not the interphase nucleolus, was modified under the new rates of RNA synthesis.
Clonal analysis of expression of epithelial antigens in cultures of normal human breast
Authors: Edwards Paul A. W. , Brooks Isobel M. , Bunnage Hilary J. , Foster A. Virginia , Ellison Morag L. , O’Hare Michael J. 
Published: April 2021

ABSTRACT
Cells from normal human breast epithelium were cloned in monolayer culture and the clones were stained with monoclonal antibodies. Tissue was from reduction mammoplasty operations. Cloning efficiences were 5-30%.
Two types of clone were identified: 10 to 30% were of relatively spread cells whose boundaries were often difficult to see by phase-contrast microscopy but where they were visible they appeared as dark lines. The edges of the clones usually appeared to be under tension. These clones were stained by two monoclonal antibodies, LICR-LON-M8 and M24, that stain luminal epithelial cells in the intact tissue, but not myoepithelial or stromal cells. Within a clone the cells showed a full range of antigenic phenotypes. This was confirmed for clones grown from single cells that had been isolated manually. The second type of clone was more compact with little evidence of tension at the edges, and cell boundaries were clearly visible and bright under phase contrast. These clones were not stained by antibodies M8 or M24. Both types of clone stained with a third monoclonal antibody that is specific for luminal epithelial cells in the intact tissue, LICR-LON-M18, but the distribution of staining was different in the different types of clone.
The simplest interpretation of the two types of clone is that luminal epithelial cells give rise to the spread type of clone while the myoepithelial cells give rise to the more abundant and vigorous compact clones. Alternatively, the compact clones may be from luminal epithelial cells that have lost differentiated characteristics.
Significance of a common epitope of plant and animal endomembranes
Authors: Bolwell G. Paul 
Published: April 2021

ABSTRACT
A rat monoclonal antibody that was raised against a common epitope on bean (Phaseolus vulgaris) endomembranes has been shown to cross-react with microsomal polypeptides from a number of plant and animal species. Immunoblotting has shown that the epitope is present on a large subset of polypeptides on microsomes of five animal species. The antigenic site appears to be accessible on intact bean membranes since it is readily digested by trypsin. The epitope is probably not derived post-translationally since the same Mr range is immunoprecipitated from polypeptides newly synthesized in vivo and in vitro. The polypeptides in bean appear to be regulated independently, one of Mr 58000, in particular, was highly induced by treatment of suspension cultures with fungal elicitor.
Preincubation of membranes enriched with endoplasmic reticulum and Golgi apparatus with the antibody blocks transfer of radioactivity from one compartment to the other in vitro. The common antigenic site could possibly be concerned in recognition or some fusion event during membrane trafficking within the cell.
Transplantation studies to investigate mesoderm-ectoderm adhesive cell interactions during gastrulation
Authors: Johnson Kurt E. 
Published: April 2021

ABSTRACT
Experiments involving transplantation of the roof of the blastocoel in Rana pipiens embryos reveal that the inner surface of the roof of the blastocoel must be coated with a fibrous extracellular matrix (F-ECM) to serve as a substratum for mesodermal cell migration. When the roof of the blastocoel is inverted the original outer surface, now projecting toward the blastocoel, does not become coated with F-ECM and does not support mesodermal cell migration. When the roof of the blastocoel is removed from a normal embryo and transplanted into an interspecific arrested hybrid embryo known to be deficient in F-ECM synthesis, the grafted ectodermal fragment does not become coated with F-ECM and does not support normal mesodermal cell migration. When a hybrid graft is placed in a normal embryo, the grafted ectodermal fragment becomes coated with F-ECM and supports mesodermal cell migration. In normal control embryos migrating mesodermal cells are polarized due to formation of lamellipodia on their leading but not their trailing edges. These cells are arranged in overlapping layers. The leading cells form lamellipodia on the roof of the blastocoel and trailing cells form lamellipodia on one another.
Kinetics and differentiation of marrow stromal cells in diffusion chambers in vivo
Authors: Bab I. , Ashton B. A. , Gazit D. , Marx G. , Williamson M. C. , Owen M. E. 
Published: April 2021

ABSTRACT
Rabbit marrow cells inoculated into diffusion chambers (107 cells/chamber) were implanted intraperitoneally into athymic mouse hosts and cultured in vivo for 20 days. A connective tissue consisting of bone, cartilage and fibrous tissues is formed by the stromal fibroblastic cells of marrow within the chambers. Cell kinetics and tissue differentiation have been studied using histo-morphometric and biochemical analyses. Haemopoietic cell numbers decrease to less than 0·05% of the initial inoculum during the 20-day period. At 3 days an average of 15 stromal fibroblastic cells only are identifiable within the chambers. After 3 days there is a high rate of stromal cell proliferation with a doubling time of 14·5 h during the period from 3 to 8 days and an increase in the total stromal cell population by more than six orders of magnitude from 3 to 20 days. Thirteen to fourteen population doublings occur before expression of the first observable differentiation parameter, alkaline phosphatase activity. The data demonstrate that the mixture of connective tissues formed within the chamber is generated by a small number of cells with high capacity for proliferation and differentiation. This is consistent with the current hypothesis that stromal stem cells are present in bone marrow.
Evidence for the existence in the nuclei of friend cells of a new type of ribonucleoprotein network
Authors: Yancheva Nina , Markov Dimiter , Djondjurov Lalio 
Published: April 2021

ABSTRACT
We have isolated fragments of a novel nuclear structure exhibiting the morphological and biochemical characteristics of a ribonucleoprotein network. Under transmission electron microscopy it is visualized as irregularly interconnected branches assembled by tightly packed particles with sizes between 100Å and 300Å. RNA extracted from this structure shows a complex pattern: as well as ribosomal 28S and 18S RNA, small amounts of heterogeneous nuclear RNA and small nuclear RNA are also present. The protein composition of the network indicates a strong domination of ribosomal polypeptides. This fact, considered together with the sedimentation characteristics of the prevailing type of particles isolated directly from the network, supports the conclusion that ribosomal particles are the representative particulate elements. Further electrophoretic analysis of the protein has pointed out that it also contains a significant number of acidic polypeptides. Control experiments have suggested that the site of origin of the network fragments studied is not nucleolar: the fragments are released during extraction, most probably from the nuclear periphery. It is not yet clear whether this structure is localized only at the nuclear periphery or represents an extensive structure, occupying the entire volume of the nucleus. It is speculated that the network is involved in the extranucleolar transport and maturation of ribosomes.
Widespread occurrence of anti-troponin T crossreactive components in non-muscle cells
Authors: Lim Soo-Siang , Hering Gordon E. , Borisy Gary G. 
Published: April 2021

ABSTRACT
Using a monoclonal antibody generated against striated muscle troponin T, we previously noted the presence of crossreactive components in smooth muscle and non-muscle cells. Since the presence of troponin T in tissues other than striated muscle is controversial, we sought to establish the nature of the crossreaction and to determine the extent of its occurrence. For this study, indirect immunofluorescence microscopy and immunoblot analyses were performed. Crossreactive material was found in diverse cells from the animal, plant and fungal kingdoms. On the basis of morphological distributions, both microtubule-associated and non-microtubule-associated components were revealed. Microtubule-associated components of animal cell lines included a 35×103Mr protein, similar in electrophoretic mobility to skeletal troponin T (37×103Mr). Reactive components of comparable mobility were observed in immunoblots of brain and cerebellar homogenates. Filamentous staining was observed in a variety of mammalian cells in culture and in cells of vertebrate tissues. Chick cerebellar tissue showed reactions in the neurites of the molecular layer and granule cell bodies. In the plant kingdom, examination of the onion root-tip cells indicated an association of crossreactive components with interphase cortical microtubules, preprophase bands, the mitotic spindle and phragmoplast microtubules. In the fungal kingdom, both interphase and mitotic spindle microtubules in a cellular slime mould were reactive. Nonmicrotubule-associated components were observed in the centrosphere regions of mitotic seaurchin eggs, in mitotic and interphase plasmodia of Physarum polycephalum, and in trichocysts and basal bodies of Paramecium tetraurelia. In all systems examined, the troponin T crossreactive components were located in regions or on structures of possible Ca2+ or calmodulin activity, suggesting a possible functional similarity to troponin T.
Splitting and internalization of the desmosomes of cultured kidney epithelial cells by reduction in calcium concentration
Authors: Mattey D. L. , Garrod D. R. 
Published: April 2021

ABSTRACT
Desmosome assembly may be induced in simple epithelial (MDBK and MDCK) cells maintained in low calcium medium (LCM: [Ca2+] &lt;0·05mM) by raising [Ca2+] to that of standard culture medium (SM: [Ca2+] = l·8mM). Here it is shown that if cells in SM are simply returned to LCM, their desmosomes split in the intercellular region within 15 min and the desmosomal halves are internalized within 30 min. This is the first time that desmosome splitting has been shown to occur in response to a reduction in [Ca2+] rather than Ca2+ chelation. Fluorescent antibody staining shows that the desmosomal glycoproteins as well as the plaque constituents are internalized, although a pool of the glycoproteins known as desmocollins remains at the cell surface, apparently unassociated with other desmosomal components. Desmosomal halves that have been recently internalized in response to LCM treatment do not return to the cell surface to participate in new desmosome formation. MDCK cells are able to form new desmosomes rapidly (15—30 min) while old desmosomes continue to be internalized.
The desmosomes of MDBK cells remain sensitive to splitting and internalization in response to reduction in [Ca2+] for up to 14 days of culture in SM. In contrast, the desmosomes of MDCK cells become resistant to reduction in [Ca2+], as well as Ca2+ chelation by EGTA, after 4–5 days in SM. When treated with LCM or EGTA, MDCK cells with ‘stabilized’ desmosomes partially separate but remain attached to each other at some points. Regions of attachment stain brightly with anti-demosomal antibodies and are characterized by ‘giant’ desmosomes, up to 4/tm long, roughly 20 times larger than those formed in cells in SM. These giant desmosomes may form by lateral fusion of small desmosomes.
Ascorbate induced changes in glycosaminoglycan synthesis and distribution of normal and sv40-transformed fibroblasts
Authors: Edward Michael 
Published: April 2021

ABSTRACT
The effect of ascorbate on the glycosaminoglycans synthesized by normal and simian virus 40(SV40)-transformed human skin fibroblasts was examined. Cells were incubated in the presence or absence of ascorbate, and radiolabelled with [3H]glucosamine and [35S]sulphate for 48 h, 3 days after reaching confluence. Glycosaminoglycans were analysed in the medium, a collagenase extract, and in the trypsin/cell-associated fraction. Hyaluronic acid was the main 3H-labelled glycosaminoglycan in all but the collagenase extracts, and showed a large decrease in normal fibroblast cultures, but a significant increase in SV40-transformed fibroblast cultures following feeding with ascorbate. Incorporation of [3H]glucosamine into sulphated glycosaminoglycans was reduced in normal fibroblast cultures but increased slightly in SV40-transformed cultures following ascorbate supplementation. [35S]sulphate incorporation remained essentially unaltered in both cell cultures. Ascorbate stimulated the deposition of glycosaminoglycans into the insoluble matrix of normal fibroblasts while reducing the deposition in SV40-transformed fibroblast cultures. The observed changes may in part be related to ascorbate-induced deposition of collagen in normal fibroblast cultures and the inability of the transformed fibroblast cells to deposit an extensive extracellular matrix, in addition to possible changes in the specific activity of the UDP-iV-acetyl- [3H]hexosamine pool.
Calcium-induced desmosome formation in cultured kidney epithelial cells
Authors: Mattey D. L. , Garrod D. R. 
Published: April 2021

ABSTRACT
Previous work has shown that cultured kératinocytes do not form desmosomes at low [Ca2+] (&lt;0·l mM) but may be induced to do so by raising [Ca2+] to physiological levels (l·8–2mM). Here, fluorescent antibody staining with specific anti-desmosomal antibodies and electron microscopy have been used to determine whether Ca2+-induced desmosome formation also occurs in simple epithelial cells.
Both Madin-Darby canine and bovine kidney cells (MDCK and MDBK) exhibit Ca2+-induced desmosome formation, but there are significant differences between them. MDCK cells resemble kératinocytes in showing showing rapid desmosome formation characterized by the simultaneous appearance of four desmosomal antigens at the cell periphery within 15–20 min of raising the [Ca2+]. In contrast MDBK cells take between 7 and 8 h to form desmosomes after Ca2+ switching, and this is characterized by slow appearance of two desmosomal antigens, the 175–164 (×103)Mr glycoprotein and desmoplakin, at the cell periphery.
Differences in the pattern of staining for desmosomal antigens between the two cell types in low and high [Ca2+] are described and discussed in relation to desmosome formation and internalization. Triton X-100 extractability of desmosomal antigen staining is also considered. While most is non-extractable, staining for the glycoproteins known as desmocollins is completely extractable from MDCK cells in low [Ca2+], but that which reaches the cell periphery after Ca2+ switching becomes non-extractable. Although neither cell type forms desmosomes in low [Ca2+], both possess zonulae adhaerentes, suggesting a difference in Ca2+ requirement for formation of these two junctions.
Endoplasmic reticulum contains a common, abundant calcium-binding glycoprotein, endoplasmin
Authors: Koch G. , Smith M. , Macer D. , Webster P. , Mortara R. 
Published: April 2021

ABSTRACT
The most abundant protein in microsomal membrane preparations from mammalian cells has been identified as a 100 × 103Mr concanavalin A-binding glycoprotein. The glycosyl moiety of the glycoprotein is completely sensitive to endoglycosidase H, suggesting a predominantly endoplasmic reticulum localization in the cell. Using a monospecific antibody it was shown by binding and immunofluorescence studies that the glycoprotein is intracellular. Immunoelectron microscopy showed that the glycoprotein was at least 100 times more concentrated in the endoplasmic reticulum than in any other cellular organelle. It was found to be substantially overexpressed in cells and tissues rich in endoplasmic reticulum. Since it is the major common protein component associated with the endoplasmic reticulum we refer to it as endoplasmin. Calcium-binding studies show that endoplasmin is a major calcium-binding protein in cells, suggesting that at least one of its roles might be in the calcium-storage function of the endoplasmic reticulum. The amino-terminal sequence of endoplasmin is identical to that of a 100 × 103Mr stress-related protein.
The lack of attachment of transformed embryonic lung epithelial cells to collagen I is corrected by fibronectin and FXIII
Authors: Paye M. , Lapière CH. M. 
Published: April 2021

ABSTRACT
PER cells, a transformed pulmonary epithelial cell line that adhered to a large extent to a fibronectin substratum, were found to be attachment-deficient to collagen I. Although fibronectin can bind to collagen I monomers and polymers, the addition of exogenous fibronectin in the attachment medium induced the adhesion of these cells to collagen I polymers but not to monomers. By adding the transglutaminase of blood coagulation, FXIII, in the presence of fibronectin, the attachment of PER cells to collagen I monomers could be recovered while the minimal concentration of fibronectin needed to promote their adhesion to polymers was lowered. These studies indicate that FXIII enhances the fibronectin-mediated attachment of PER cells to collagen I.
Differential expression of murine macrophage surface glycoprotein antigens in intracellular membranes
Authors: Smith Michael J. , Koch Gordon L. E. 
Published: April 2021

ABSTRACT
A monoclonal antibody recognizing a novel murine macrophage glycoprotein antigen (MAG) was prepared by the hybridoma technique. Using live and permeabilized macrophages to estimate surface and total MAG, respectively, it was found that at least 50% of the total antigen was intracellular. In contrast, another macrophage surface glycoprotein antigen, Mac-1, was undetectable in the intracellular pool. Immunofluorescence studies confirmed the existence of a substantial intracellular pool of MAG antigen. Similar results were obtained with a panel of cultured tumour cell lines. In one such cell line, it was shown that surface MAG existed in a distinct punctate pattern indicative of microdomains, whereas surface Mac-1 antigen gave a uniform distribution. The possible role of the surface microdomains in the differential expression of the two surface glycoproteins in intracellular membranes is discussed.