bluuebunny/crossref_metadata_2025_split huggingface dataset:
Desmoplakin expression and organization at human umbilical vein endothelial cell-to-cell junctions
Authors: Valiron Odile , Chevrier Véronique , Usson Yves , Breviario Ferruccio , Job Didier , Dejana Elisabetta 
Published: April 2021

ABSTRACT
Desmoplakin is an intracellular component of desmosomes which plays a role in the anchorage of intermediate filaments to these structures. We report here that, despite the absence of desmosomes, cultured endothelial cells from human umbilical vein express desmoplakin I and II both at mRNA and protein level. Desmoplakin I/II are found only in the detergent insoluble fraction suggesting that most of the protein is linked to the cytoskeleton. Desmoplakin I/II could be detected by western blot only in long confluent cells even if desmoplakin mRNA levels are unchanged by cell confluency. This suggests that desmoplakin might be stabilized at protein level by its association with junctional components. Immunofluorescence confocal microscopy showed that desmoplakin codistributes with VE-cadherin and plakoglobin along the lateral cell membrane. In contrast, desmoplakin localization was distinct from that of PECAM, an endothelial specific junctional protein localized outside adherence junctions. Endothelial cells do not have keratins but they express vimentin. In confluent cells vimentin forms peripheral filaments which attach to the cell membrane in areas at desmoplakin localization. These data suggest that desmoplakin may participate in the molecular organization of interendothelial junctions by interacting with VE-cadherin and promoting vimentin anchorage. This new type of intercellular junction seems to correspond to the ‘complexus adhaerentes’ described in vivo in lymphatic endothelium.
Dot-like focal contacts in adherent eosinophils, their redistribution into peripheral belts, and correlated effects on cell migration and protected zone formation
Authors: Tourkin Andre , Bonner Michael , Mantrova Ekaterina , LeRoy E. Carwile , Hoffman Stanley 
Published: April 2021

ABSTRACT
We have examined the organization of F-actin and focal contacts in eosinophils and the functional consequences correlated with their redistribution. In activated eosinophils adherent to laminin, F-actin is localized in large, uniformly distributed, dot-like structures. Colocalized with the F-actin are a variety of typical components of focal contacts including: the α6 and β1 integrins subunits (which mediate eosinophil adhesion to laminin), vinculin, talin, pp125FAK, paxillin, and tyrosine phosphorylated proteins, but not the β2 integrin subunit which is not involved in eosinophil adhesion to laminin. In unactivated eosinophils on laminin (which do not adhere well) and in activated eosinophils on non-adhesive surfaces (human serum albumin, tenascin, or a mixture of tenascin and laminin), dot-like accumulations of F-actin do not form.
When activated eosinophils are incubated on laminin in the presence of low concentrations of 1,1’-ethylidenebis(L-tryptophan), a remarkable rearrangement occurs. Both conventional and confocal microscopy suggest that the dotlike structures rearrange from a uniform distribution into thick, peripheral belts surrounding each cell with few dotlike structures internal to the belt. Functional consequences occur as a result of this rearrangement of focal contacts and the cytoskeleton. The belt of focal contacts acts as a size-dependent permeability barrier; fluorescent 8 kDa polyethylene glycol does not label the substrate underneath the cells whereas 3.5 kDa polyethylene glycol labels the substrate uniformly. The formation of belts of focal contacts also blocks the ability of eosinophils to migrate on laminin in response to a chemotactic gradient. While the mechanism of 1,1’-ethylidenebis(L-tryptophan) action remains to be determined, experiments indicate that the function of 1,1’-ethylidenebis(L-tryptophan) is distinct from the function of drugs that alter tyrosine kinase and serine/threonine kinase activities. Our observations reveal a novel mechanism for regulating cell behavior in invasive cells in which the rearrangement of focal contacts and the associated cytoskeleton may control cell migration and the sequestration of secreted cytotoxic and degradatory molecules. We propose that 1,1’-ethylidenebis(L-tryptophan) may mimic the function of an endogenous regulator of eosinophil morphology and behavior.
A different approach to tumour suppression: The Alexandra Kefalides Memorial Lecture
Authors: Harris Henry , Rawlins Joy , Sharps Jane 
Published: April 2021

ABSTRACT
When tumour cells are fused with normal ones, malignancy is suppressed. It has been shown that this suppression is associated with the imposition on the hybrid cell of the terminal differentiation programme of the normal parent cell. We report here the consequences of imposing the synthesis of keratin 1 and keratin 10, markers of terminal differentiation in the epidermal keratinocyte, on malignant cells of keratinocyte and non-keratinocyte lineage. We find that there is extreme selection in vivo against cells making keratin 1: tumours arising from inocula of such cells are invariably produced by the selective overgrowth of cells in which keratin 1 synthesis has been drastically reduced, usually to trace levels. No such selection operates against keratin 10. It is possible that if substantial synthesis of keratin 1 could be induced in malignant cells in a clinical context, some therapeutic benefit might accrue.
Epigenetic control of mammalian centromere protein binding: Does DNA methylation have a role?
Authors: Mitchell Arthur R. , Jeppesen Peter , Nicol Linda , Morrison Harris , Kipling David 
Published: April 2021

ABSTRACT
Chromosome 1 of the inbred mouse strain DBA/2 has a polymorphism associated with the minor satellite DNA at its centromere. The more terminal block of satellite DNA sequences on this chromosome acts as the centromere as shown by the binding of CREST ACA serum, anti-CENP-B and anti-CENP-E polyclonal sera. Demethylation of the minor satellite DNA sequences accomplished by growing cells in the presence of the drug 5-aza-2’-deoxycytidine results in a redistribution of the CENP-B protein. This protein now binds to an enlarged area on the more terminal block and in addition it now binds to the more internal block of minor satellite DNA sequences on chromosome 1. The binding of the CENP-E protein does not appear to be affected by demethylation of the minor satellite sequences. We present a model to explain these observations. This model may also indicate the mechanism by which the CENP-B protein recognises specific sites within the arrays of minor satellite DNA on mouse chromosomes.
N-tropomodulin: A novel isoform of tropomodulin identified as the major binding protein to brain tropomyosin
Authors: Watakabe Akiya , Kobayashi Ryuji , Helfman David M. 
Published: April 2021

ABSTRACT
We have identified and characterized two proteins in rat brain that bind to the neuron-specific tropomyosin isoform, TMBr3. The two proteins were identified by blot overlay assay, in which the proteins immobilized on the membrane were probed by epitope-tagged TMBr3, followed by detection with anti-epitope antibody. We have purified these proteins using a TMBr3 affinity column. Peptide sequencing as well as immunoblotting showed that one of the two proteins is identical to tropomodulin, a tropomyosin-binding protein originally identified in erythrocytes. The cDNA for the other protein was cloned from an adult rat brain cDNA library using degenerate oligonucleotides that we designed based on the peptide sequences. Sequence analysis of the cDNA clone revealed this protein to be a novel isoform of tropomodulin which is the product of a distinct gene, and is herein referred to as N-tropo-modulin. Recombinant N-tropomodulin bound to TMBr3 as well as to other low molecular mass tropomyosins (TM5a or TM5), but not to high molecular mass tropomyosins (TM2 or TMBr1). Northern blotting and RNase protection assays as well as immunoblotting showed that N-tropo-modulin is expressed predominantly in brain. Furthermore, RNase protection assays revealed no alternatively spliced regions within the coding sequence. Developmentally, N-tropomodulin was detected in rat brain as early as embryonic day 14 and reaches the adult level before birth. Immunofluorescence of primary frontal cortex cell cultures showed that N-tropomodulin is specifically expressed in neurons. The neuron-specific expression of N-tropomod-ulin strongly suggests specialized roles of this TM-binding protein in neurons.
C-Met signalling in an HGF/SF-insensitive variant MDCK cell line with constitutive motile/invasive behaviour
Authors: Webb C. P. , Lane K. , Dawson A. P. , Woude G. F. Vande , Warn R. M. 
Published: April 2021

ABSTRACT
The Met protein is a receptor tyrosine kinase for hepatocyte growth factor/scatter factor (HGF/SF), a multifunctional growth factor with mitogenic, motogenic and morphogenic properties. A morphologically altered variant of the MDCK cell line, MDCK-1, spontaneously exhibits a number of features associated with a partial HGF/SF-Met induced phenotype (less adhesive colonies in culture, enhanced invasion and motility, nascent tubule formation), but paradoxically does not respond to HGF/SF treatment. Although the overall cell surface expression and distribution of Met were found to be similar in parental MDCK cells and the MDCK-1 cell line, p145met autophosphorylation (± HGF/SF) was significantly reduced in MDCK-1 cells in vitro and in vivo when compared with parental MDCK cells. In contrast, EGF induced cell proliferation and EGF receptor autophosphorylation to similar levels in both cell lines. The basal levels of protein tyrosine phosphorylation were higher in MDCK-1 cells when compared with parental MDCK cells, including that of two prominent proteins with molecular masses of ∼185 kDa and 220 kDa. Moreover, both p185 and p220 are present and tyrosine phosphorylated in Met immunoprecipitates from MDCK-1 cells (±HGF/SF), but not parental MDCK cells. In addition, Met immunocomplexes from MDCK-1 cells exhibited an approximately 3-fold increased tyrosine kinase activity in vitro when compared with MDCK cells, correlating with the higher basal levels of total phosphotyrosine. Treatment of MDCK-1 cells with the tyrosine kinase inhibitor herbimycin A reverted the cell phenotype to a more MDCK-like morphology in culture, with a concomitant reduction in the tyrosine phosphorylation predominantly of p220. Taken together these data suggest that aberrations in Met activity and associated signalling render MDCK-1 cells insensitive to HGF/SF, and may also mediate alterations in MDCK-1 cell behaviour.
Patch-clamp capacitance analysis of the effects of α-SNAP on exocytosis in adrenal chromaffin cells
Authors: Kibble A.Victoria , Barnard Richard J. O. , Burgoyne Robert D. 
Published: April 2021

ABSTRACT
We have examined the effect of α-SNAP on exocytosis in adrenal chromaffin cells by direct assay of exocytosis using patch-clamp capacitance analysis. Cells were recorded using the whole cell patch-clamp configuration and the cells dialysed with control pipette solution or with a pipette solution containing α-SNAP or the deletion mutant α-SNAP(41-295). The deletion mutant was found to be unable to bind to syntaxin allowing a test of the requirement for syntaxin-binding for any effect of α-SNAP on exocytosis. Following cell dialysis for 10 minutes, cells were depo-larised five times at 2 minute intervals. At each depolari-sation step cells dialysed with α-SNAP showed a significant increase in both the initial rate and extent of exocytosis which was seen as a rise in membrane capacitance. This increase in exocytosis was not observed with α-SNAP(41-295) which instead produced some inhibition of the extent but had no effect on the initial rate of exocytosis. These results show directly that α-SNAP has a specific and marked stimulatory effect on exocytosis in chromaffin cells.
On the existence of a guanine nucleotide trap, the role of adenosine kinase and a possible cause of excessive purine production in mammalian cells
Authors: Green H. , Ishii K. 
Published: April 2021

ABSTRACT
It is usually assumed, in part from studies of bacteria, that there is free interconversion of adenosine 5′-monophosphate (AMP) and guanosine s′-monophosphate (GMP), and that the balance between the 2 nucleotides is maintained exactly by allosteric controls on the activity of the enzymes involved in the interconversion. However, there are good reasons for believing that in most mammalian cells the conversion of GMP to AMP is not an effective process. Furthermore, the activity of certain other enzymes of the purine scavenger pathways will tend to induce imbalance between AMP and GMP. This imbalance will be compensated, but the compensation mechanism will involve increased production and excretion of purines. It is suggested that the operation of this mechanism in the human would result in gout.
An ultrastructural study of the membranes of keratinizing wool follicle cells
Authors: Orwin D.F.G. , Thomson R.W. 
Published: April 2021

ABSTRACT
Measurements of the widths of apposed plasma membranes and of the spaces between them were made at different stages of differentiation of keratinizing and hardening cells of the wool follicle. In contrast to findings in the hair follicle, no changes were detected for apposed cortex, cortex/fibre cuticle and fibre cuticle/fibre cuticle cells until keratinization had taken place. The trilaminar appearance of the plasma membranes was then lost and the intercellular material decreased in width.
However, the inner root sheath cells developed a ‘membrane complex’ in enlarged inter-cellular spaces prior to hardening. Desmosomes are apparently retained in the hardened ‘membrane complexes’. A band of cytoplasmic material was also formed adjacent to the inner lamellae of the plasma membranes immediately before hardening of the cells.
The presence of gap and tight junctions in differentiating cell lines of the wool follicle was noted.
Real and reflected images of cells in profile: I. a method for the study of cell movement and adhesion
Authors: Hlinka J. , Sanders F. K. 
Published: April 2021

ABSTRACT
A new way of illuminating and photographing cells in profile has been developed, showing at the same time their images reflected in a glass substrate. Through its use in cinemicrography, the kinematics of cells and their adhesions can be observed with certainty, thus permitting a better understanding of their mode of locomotion.
Ribosome crystals in necrotizing cells from the posterior necrotic zone of the developing chick limb
Authors: Mottet N. K. , Hammar S. P. 
Published: April 2021

ABSTRACT
Ribosome and ‘protein crystals’ were observed in electron micrographs of degenerating cells from the posterior necrotic zone (PNZ) of developing chick limbs, stages 22 through 24.
Ribosome crystals were made up of basic units of 4 ribosomes arranged in a square tetramer. They were monomorphic with the surface lattice being of the p4 plane group. The 1-ribosome thick sheets of crystals were often seen stacked upon one another forming a 3-dimensional P422 configuration. The percentage of crystallized ribosomes within degenerating PNZ cells is nearly directly proportional to the degree of degeneration of the cell. Crystals identical to this have been observed in numerous types of embryonic chick cells subjected to hypothermia.
The ‘protein crystals’ were composed of straight filamentous structures separated by a distance of 20–30 nm. They were always closely associated with the ribosome crystals. These crystals are similar to those seen in cells treated with high doses of vinblastine and vincristine. The pathogenesis of the ribosome and protein crystals occurring in degenerating PNZ cells is unknown. They are not associated in any way with hypothermia or vinblastine-vincristine treatment.
Intermediate cells of the pancreas: I. ultrastructural characterization
Authors: Melmed R. N. , Benitez Carol J. , Holt S. J. 
Published: April 2021

ABSTRACT
The normal existence of cells in the pancreas with a structure intermediate between those of exocrine and endocrine cell types has long been a matter of dispute. The present study shows that, based upon morphological criteria, such intermediate cells are present in both the endocrine and exocrine tissues of the normal pancreas of the rat, guinea-pig, rhesus monkey, goat, chicken and frog. There is a tendency for intermediate cells to occur most frequently in the frog, where exocrine and endocrine cells are intermingled, and least frequently in higher species such as the rat, guinea-pig, monkey and goat where the endocrine cells are localized in discrete islets. Their occurrence in the chick appears to lie between these 2 extremes. The existence of intermediate cell types has been attributed to a ‘transformation’ of one form of specialized cell in the pancreas into another in response to a metabolic demand. However, the widespread occurrence of inter mediate cells in the normal pancreas suggests that they represent, ab initio, a distinct category of cell, the existence of which poses interesting questions concerning the genetic control of their specialized functions and of developmental processes in the pancreas. Moreover, intermediate cells, such as acinar cells containing endocrine β-granules might serve as a source of insulin additional or alternative to that provided by cells that are wholly endocrine in character.
Absence of centrioles in the first and second meiotic spindles of mouse oocytes
Authors: Szollosi D. , Calarco Patricia , Donahue R. P. 
Published: April 2021

ABSTRACT
Centrioles are present in oogonia and oocytes of hamsters, mice, rats, gerbils and man up to the pachytene stage. In subsequent meiotic stages, centrioles are absent. At the time of germinal vesicle breakdown in the mouse several foci composed of electron-dense fibrillar material from which microtubules radiate appear near the nucleus. These fibrillar aggregates, referred to as microtubule foci, form small asters and collectively perform the role of the spindle pole during the two meiotic divisions. There are multiple centres at each pole and their number may vary. Thus, centrioles are not obligatory organelles of the spindle apparatus.
The classes of kappa in Paramecium aurelia
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Authors: Preer L. B. , Jurand A. , Preer J. R. , Rudman B. M. 
Published: April 2021

ABSTRACT
Kappas (bacterial symbionts containing R bodies) have been studied in 16 strains of Para mecium aurelia, syngens 2 and 4. All produce toxins capable of killing sensitive paramecia. The first major class, the 51 group (consisting of the kappas of strains 51, 116, and 298), has R bodies which, when the pH is lowered below 6·5, unwind reversibly from the inside to form a tight tube; the outside end of the R-body ribbon forms an acute angle; no sheath surrounds the R body. The phage-like structures of the 51 group are helical; no capsomere-like structures are present; isolated R bodies do not have any killing activity. The second major class, the 7 group (strains 7, 576, BI 166-1, 249, 1041, 310, 1039), has R bodies which unwind irreversibly from the outside to form a loose twisted ribbon whose outside tip is blunt, irregular or finger-like; a single membraneous sheath covers the R body. Phage-like structures in the 7 group are spherical; capsomere-like structures are present; isolated R bodies show killing activity. The third major class, the 562 group (strains 562, 517, 511), is similar to the 7 group except that there is no sheath, no capsomeres, and free R bodies are almost or completely inactive. The phage-like structures are spherical, and unlike those of the 7 group, do not stick to the R bodies. In addition to these 3 major classes there are 3 strains which show important differences from the major classes and also differ among themselves. 1038 is like 7 in all respects except that the phage-like structures are helical and isolated R bodies are not very active. 51ml, presumably a mutant of 51, has spherical phage-like structures and 7 type-R bodies which are inactive when isolated. 570 is the only known mate-killer with R bodies; it has spherical phage-like structures.
It is noted that strain 1039 of the 7 group has very few phage-like structures, virtually all of which are empty. Since free 1039 R bodies are highly active, it is likely that intact phage-like structures are not essential for the toxic action on sensitives. The spherical and helical phage-like structures are probably very closely related because 51, which has helical structures, apparently gave rise to 51ml, which has spherical structures. Likewise the kappa symbionts of 1038 with helical phage-like structures are virtually identical to the kappas of the 7 group with spherical phage-like structures. The presence of phage-like structures in all strains with R bodies suggests that R bodies may be a product of phage activity. Strain 570, a mate-killer whose symbionts contain R bodies, provides a link between kappas and mus, the mate-killer symbionts. The symbionts of 570 are the only ones containing R bodies which are non-toxic when encountered by sensitives in the medium in which the paramecia are cultured.
Evidence that the synchronized production of new basal bodies is not associated with dna synthesis in Stentor coeruleus
Authors: Younger K. B. , Banerjee S. , Kelleher J. K. , Winston M. , Margulis Lynn 
Published: April 2021

ABSTRACT
Stentors were induced to produce synchronously thousands of new ciliated oral membranellar band basal bodies in less than 3 h. DNA synthesis does not accompany this process, as determined by [3H]thymidine incorporation into isolated bands and by sensitivity to DNA synthesis inhibitors (mitomycin C, ethidium bromide, cytosine arabinoside and hydroxyurea). Yet DNA could be detected in the cortex and the band at basal body sites by autoradiography. Since [3H]thymidine incorporation into membranellar band was eliminated in concentrations of ethidium bromide that had no effect on basal body formation, the previous reports of ciliate kinetosomal (basal body) DNA are interpreted as due to mitochondrial contamination. Specific cortical patterns of DNA that could have been easily misinterpreted as basal body-related were especially apparent in autoradiographs using [3H]actinomycin D as a ‘stain’.
In no experiment involving induced basal body regeneration could evidence be found for a correlation between new basal body production and DNA synthesis; RNA and protein synthesis correlated with basal body and cilia regeneration were, however, easily detected by the same techniques. We concluded that there is no evidence that basal body DNA synthesis is required for new basal body production.