bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of hnk-1 monoclonal antibody on the substratum attachment and survival of neural crest and sclerotome cells in culture
Authors: Sanders E. J. , Cheung E. 
Published: April 2021

ABSTRACT
The sclerotome portion of the differentiating embryonic chick somite becomes infiltrated by neural crest cells prior to its dispersal towards the embryonic axis. This means that sclerotome cells explanted into culture for the purpose of examining their interactions in vitro are contaminated with a proportion of neural crest cells. The purpose of this study was to explore the neural crest cell adhesion epitope recognized by the HNK-1 monoclonal antibody and ways in which this antibody can be used to eliminate neural crest cells from mixed culture by selective cytotoxicity. Immunofluorescence technique, under the conditions used here, indicated that the antibody appeared to stain all the mesenchymal (i.e. neural crest) cells emigrating from pieces of embryonic neural tube in culture. Examination of the effects of HNK-1 suggests that the antibody interacts with substratum-binding sites on the neural crest cell surface. On fibronectin-coated substrata the antibody tended to inhibit neurite outgrowth but left the cells relatively well spread, while on laminin substrata the effect was to discourage both neurite extension and cell spreading, causing cell retraction. These results suggest that the cell surface epitope recognized by HNK-1 influences neurite outgrowth, neurite adhesiveness or both. Failure of cell spreading on laminin suggests interaction with the laminin binding sites on the cell body. Elimination of the crest cells from mixed culture with sclerotome was achieved by culturing the cells in the presence of HNK-1 antibody and complement during the period required for complete cell outgrowth from the sclerotome explant. This treatment resulted in cultures that, on further incubation, were entirely HNK-1 negative and that failed to show either the presence of neurite-bearing cells or of cells reacting positively to anti-neurofilament monoclonal antibody. We thus appear to have succeeded in removing the crest cells from the mixed population.
Initiation of the cortical reaction in hamster and sheep oocytes in response to inositol trisphosphate
Authors: Cran D. G. , Moor R. M. , Irvine R. F. 
Published: April 2021

ABSTRACT
Microinjection of inositol 1,4,5–trisphosphate into sheep and hamster oocytes induces secretion of cortical granules in a dose-dependent manner. In the sheep, this effect is strongly pH-dependent with minimal exocytosis taking place at pH 6·8 but a full cortical reaction occurring at pH 8·0. Exocytosis in the hamster is also affected by the pH of the external medium but to a lesser extent. Injection of GTPγS also induces exocytosis in both species but is more effective in the hamster. It is suggested that inositol metabolism stimulated by sperm-egg interaction with a GTP-binding protein may be part of the mechanism leading to cortical granule exocytosis and that this may be modulated by the external pH.
Identification of renin in resident alveolar macrophages and monocytes: HPLC and immunohistochemical study
Authors: Dezsö Balázs , Nielsen Arne Hoj , Poulsen Knud 
Published: April 2021

ABSTRACT
Normal, unstimulated alveolar macrophages (AM) and monocytes (Mo) from both mice and rats have been shown to exhibit an angiotensin-I-forming enzyme. This protease has a similar or identical molecular weight to plasma renin as judged by HPLC analysis. In addition, the enzyme activity could be almost completely inhibited by a specific antibody to pure mouse submaxillary gland renin. This indicates that the angiotensin-I-generating protease in AM and Mo is identical to true renin. These results are in accordance with those of immunocytochemical studies, since the cells sharing immunoreactive renin are macrophages and monocytes. The low percentage of renin positive cells may indicate a functionally different and probably distinct subpopulation of AM and Mo.
The presence of renin and angiotensins and angiotensin-I-converting enzyme in normal macrophages and monocytes seems to be common. Hence, the data presented raise the possibility that an intracellular renin-angiotensin system may infact exist in a certain subpopulation(s) of normal macrophages and monocytes.
Immunochemical and biochemical comparisons between embryonic chick bone marrow and epiphyseal cartilage chondroitin/dermatan sulphate proteoglycans
Authors: Sorrell J. Michael , Mahmoodian Fatemeh , Caterson Bruce 
Published: April 2021

ABSTRACT
Chrondroitin sulphate proteoglycans obtained from embryonic chick bone marrow and epiphyseal cartilage were compared using immunochemical and biochemical analyses. Proteoglycans from each tissue, separated on CsCl density gradients, under dissociative conditions, into high (1·6 gml−1), medium (l·5gml−1) and low (l·4gml−1) buoyant density fractions, were immunochemically analysed, using a panel of monoclonal antibodies that specifically recognize chondroitin 4-/dermatan sulphates, chondroitin 6-sulphate, keratan sulphate, the hyaluronate binding region present on connective tissue proteoglycans, and link protein. The same antibodies were used in Western blot analyses to detect intact proteoglycan monomers and core proteins that had been fractionated by agarose-poly-acrylamide and by sodium dodecyl sulphate-poly-acrylamide gel electrophoresis. Specific differences between marrow and cartilage proteoglycans were detected. In CsCl gradients, marrow proteoglycans displayed a higher degree of heterogeneity in terms of buoyant densities and hexuronate distribution.
Keratan sulphate chains were constituents of the majority of ‘large’ proteoglycans in the marrow; however, a portion of the large proteoglycans in marrow middle buoyant density fraction either lacked keratan sulphate chains or were substituted with a form different from that found on cartilage proteoglycans. Marrow lacked ‘small’ chondroitin/dermatan sulphate proteoglycans that were present in cartilage and contained a more heterogeneous population of proteoglycans, particularly in the lower buoyant density fractions. Both marrow and cartilage were similar in that they contained, as their major components, large, aggregating proteoglycans and link proteins that were immunochemically and biochemically identical. The significance of these differences between marrow and cartilage proteoglycans remains to be determined, but they may, in part, be responsible for imparting unique characteristics to the haematopoietic extracellular matrices.
The cytoskeletal elements of human retinal pigment epithelium: in vitro and in vivo
Authors: Mckechnle Nicol M. , Boulton Mike , Robey Helen L. , Savage Felicity J. , Grierson Ian 
Published: April 2021

ABSTRACT
The cytoskeletal elements of normal (in situ) and cultured human retinal pigment epithelium (RPE) were studied by a variety of immunocytochemical techniques. Primary antibodies to vimentin and cytokeratins were used. Positive immunoreactivity for vimentin was obtained with in situ and cultured material. The pattern of reactivity obtained with antisera and monoclonals to cytokeratins was more complex. Cytokeratin immunoreactivity could be demonstrated in situ and in cultured cells. The pattern of cytokeratin expression was similar to that of simple or glandular epithelia. A monoclonal antibody that specifically recognizes cytokeratin 18 identified a population of cultured RPE cells that had particularly well-defined filamentous networks within their cytoplasm. Freshly isolated RPE was cytokeratin 18 negative by immunofluorescence, but upon culture cytokeratin 18 positive cells were identifiable. Cytokeratin 18 positive cells were identified in all RPE cultures (other than early primaries), regardless of passage number, age or sex of the donor. In post-confluent cultures cytokeratin 18 cells were identified growing over cytokeratin 18 negative cells, suggesting an association of cytokeratin 18 immunoreactivity with cell proliferation. Immunofluorescence studies of retinal scar tissue from two individuals revealed the presence of numerous cytokeratin 18 positive cells. These findings indicate that RPE cells can be identified by their cytokeratin immunoreactivity and that the overt expression of cytokeratin 18 may be associated with proliferation of human RPE both in vitro and in vivo.
Ki-67 detects a nuclear matrix-associated proliferation-related antigen: II. Localization in mitotic cells and association with chromosomes
Authors: Verheijen R. , Kuijpers H. J. H. , Driel R. van , Beck J. L. M. , Dierendonck J. H. van , Brakenhoff G. J. , Ramaekers F. C. S. 
Published: April 2021

ABSTRACT
In interphase cells the proliferation-associated antigen recognized by monoclonal antibody Ki-67 is almost exclusively located in the nucleoli. When cells at several stages of mitosis were examined for the localization of the Ki-67 antigen, a striking redistribution could be observed. During prophase the distinct nucleolar Ki-67 fluorescence changed to a bright irregular meshwork throughout the nucleoplasm. At metaphase the antigen appeared to be distributed in a reticulate structure surrounding the condensed chromosomes, while at late telophase a punctated staining of the entire nucleoplasm was observed, which preceded the typical nucleolar localization pattern in each of the two daughter cells. Immunolabelling with Ki-67 of metaphase chromosome spreads revealed a circumferential staining of the individual chromosomes.
The Ki-67 antigen is preserved in nuclear matrix preparations obtained after in situ fractionation of interphase cells. When mitotic cells were exposed to such treatments, the obtained fluorescence data suggested that the antigen may be part of the chromosome scaffold.
Quantification of the Ki-67 fluorescence signal using flow cytometry revealed the highest staining intensities in mitotic cells. Furthermore, it was shown that nutritionally deprived cells became negative for Ki-67.
Intermediate filament collapse is an AtP-dependent and actin-dependent process
Authors: Hollenbeck P. J. , Bershadsky A. D. , Pletjushkina O. Y. , Tint I. S. , Vasiliev J. M. 
Published: April 2021

ABSTRACT
In this study, we have investigated the properties of intermediate filament rearrangements using experimentally induced collapse of vimentin intermediate filaments in mouse fibroblasts. In these cells, depolymerizing microtubules by colchicine or vinblastine treatment at 37 °C results in a two-stage collapse of intermediate filaments. First, the vimentin filaments aggregate into large cables; then, the cables coil into a dense mass surrounding the nucleus. By using inhibitors of oxidative phosphorylation along with glucose deprivation to lower intracellular ATP levels by 95 %, we have found that both stages of intermediate filament collapse require ATP. However, once collapse has occurred, only the second stage can be reversed in the absence of microtubules by lowering ATP levels. An additional difference between the two stages of collapse was revealed by treating cells with cytochalasin D: the formation of intermediate filament cables still occurs after disruption of the actin filament system by cytochalasin, but the subsequent coiling of cables to form a perinuclear mass is strongly inhibited by these conditions, and can be reversed by applying cytochalasin to cells in which intermediate filaments have already undergone complete collapse. We propose that the formation of vimentin cables involves a phosphorylation event, while the coiling of cables into a perinuclear mass relies on interaction of intermediate filaments with a component of the actin cortex.
Modulation of melanoma cell adhesion to basement membrane components by retinoic acid
Authors: Edward Michael , Gold Jean A. , Mackie Rona M. 
Published: April 2021

ABSTRACT
The effect of retinoic acid pretreatment on metastatic B16 melanoma cell adhesion in serum-free medium to tissue culture plastic precoated with fibronectin, laminin/nidogen, type I and type IV collagen was examined. Both control cells grown to subconfluence and cells treated with 10−6 M-retinoic acid adhered and spread rapidly on fibronectin (&gt;75% following 1 h of incubation) but adhered poorly to type I collagen (&lt;15%). Control cells adhered to laminin/nidogen (&gt;35%), type IV collagen (&gt;58%) and type IV collagen plus laminin/nidogen (&gt;80%), while retinoic acid-treated cells showed a reduced ability to attach and spread on these substrata, the number of adherent cells being reduced by 61% on laminin/nidogen, by 19% on type IV collagen, and by 41% on type IV collagen plus laminin/nidogen following Ih of incubation. The minimum concentration of retinoic acid required to yield an effective reduction in adhesion was 10−7M for type IV collagen and 10−10M for laminin/nidogen. Melanoma cells harvested at low density showed a reduced adhesion to laminin/nidogen and type IV collagen compared to that of subconfluent control cultures, but also showed a reduced adhesion to fibronectin. The effect of retinoic acid on cell adhesion was not, however, due to reduced cell density, as the cells were seeded so that control and retinoic acid-treated cultures were of a similar density when harvested.
An immunocytochemical study of the proliferating cell nuclear matrix antigen p125/6.5 during rat spermatogenesis
Authors: Hadjiolova K. V. , Martinova Y. S. , Yankulov K. Y. , Davidov V. , Kancheva L. S. , Hadjiolov A. A. 
Published: April 2021

ABSTRACT
In previous studies of proliferating mammalian cells a pl25/6.5 nuclear matrix antigen displaying a marked increase in mitotic cells has been identified. This antigen was investigated by immunocytochemistry of cryosections of testes at different stages of postnatal development: newborn, 20 days after birth and sexually mature rats. In Sertoli cells, the distribution of the p 125/6.5 antigen parallels [3H]thymidine incorporation: present in newborn and absent in sexually mature testes. The pl25/6.5 antigen is present also in some prespermatogonia of the newborn rat testis, which do not incorporate [3H]thymidine. At later stages of development, the pl25/6.5 antigen is present also in first meiotic prophase spermatocytes displaying an extrachromosomal nucleoplasmic distribution, while absent in spermatids and spermatozoa. These results show that the pl25/6.5 antigen increases not only during mitosis, but also during meiosis. They suggest further that this antigen is characteristic of both proliferating cells and cells (prespermatogonia) committed to proliferation.
Ontogenetic expression of the murine erythrocyte glycophorins
Authors: Dolci Elizabeth D. , Palade George E. 
Published: April 2021

ABSTRACT
The major sialoglycoproteins or glycophorins of the murine erythrocyte membrane, gp2 (AÇ44000) and gp3 (Mr 29 000), are expressed as identical or closely related antigens by the three erythroid cell lines that succeed each other in normal mouse development. The embryonic forms of gp2 and gp3 differ from the adult forms by their mobility on SDS-PAGE. The apparent Mr values are increased by 1000–2000 for gp2 and 500 for gp3. An increase in the microheterogeneity of both embryonic and fetal forms of gp2 is also detected. Variations in glycosylation account in part for the apparent differences in Mr. Sizing of O-glycosidically linked oligosaccharide chains reveals that fetal glycophorins contain predominantly trisaccharide units while their adult counterparts are mostly tetrasaccharides. The kinetics of gp2 and gp3 biosynthesis in fetal liver are comparable to those established for the splenic erythroblasts of adult anemic mice. Like their adult counterparts, fetal glycophorins incorporate [3H] palmitate and [3H]galactose. The results indicate that, in murine ontogeny, distinct but antigenically related sialoglycoproteins are produced at each erythropoietic stage.
Development of the quadripolar meiotic apparatus in Funaria spore mother cells: analysis by means of anti-microtubule drug treatments
Authors: Busby C. H. , Gunning B. E. S. 
Published: April 2021

ABSTRACT
Microtubule-dependent processes in Funaria hygrometrica spore mother cells (SMCs) were analysed by monitoring the effects of colchicine and oryzalin on pre-meiotic and meiotic events. The techniques used were electron microscopy, immunofluorescence microscopy of microtubules (MTs) and continuous video recording of events in treated and recovering live cells sampled at various stages of sporogenesis. Inferences drawn from previous work that the SMC plastids serve as MT-organizing centres were confirmed in so far as MT recovery in MT-depleted cells starts at the tips of the plastids. The MTs that emanate from these regions are required for positioning the plastids in the tetrahedral conformation, which defines the meiotic poles, for positioning lipid droplets in clusters at these poles and for positioning and holding the nucleus in the tetrahedral cage. If released, the nucleus can be moved by a non-MT system. Other phenomena not controlled by MTs are plastid elongation, maintenance of the tetrahedral conformation when the MTs are absent (during divisions or as a result of drug treatment) and (probably) development of the organelle band that spans the cell between divisions I and II.
In cells treated during division, when there is no nuclear envelope, the pattern of MT recovery is different: the plastids are inactive as microtubuleorganizing centres (MTOCs) but MTs reappear among the chromosomes. Spindles capable of transporting chromosomes regenerate. However, the importance of interactions between nucleus and plastids is highlighted by cases in which treatment has resulted in: (1) movement of the nucleus out of the quadripolar plastid cage; and (2) loss of the MTs at plastid tips that normally contribute to the spindle poles; in such cases quadripolarity is lost even though functional spindles return. Plastid MTOC activity returns when the nuclear envelope is in place, i.e. in interkinesis and after telophase II.
Distribution of a thiophosphorylated spindle midzone antigen during spindle reactivation in vitro
Authors: Wordeman Linda , Masuda H. , Cande W. Z. 
Published: April 2021

ABSTRACT
Mitotic spindles isolated from the diatom Stephano-pyxis furris will elongate in vitro in the presence of ATP with a concurrent decrease in the width of the zone of microtubule overlap. A spindle-associated phosphoprotein that co-localizes with the zone of microtubule overlap in isolated spindles serves as a convenient marker for midzone-associated proteins other than microtubules. We have used a monoclonal antibody that labels this protein when it is artificially thiophosphorylated and studied its redistribution during spindle reactivation in vitro. As the spindle elongates midzone label accumulates in a successively narrower and brighter ring at the spindle midpoint with increasing time in ATP. Biotinylated bovine microtubule segments polymerized onto the ends of the diatom microtubules increase the overall width of the zone of microtubule overlap and serve as a marker for the boundary of the original diatom overlap zone. During elongation in ATP, the biotinylated segments move into the area marked by the monoclonal antibody, which does not decrease in width until the spindle has elongated to the point at which the zone of microtubule overlap delineated by the newly polymerized microtubules is smaller than the original overlap zone. We use these results to develop a model to explain the behaviour of nonmicrotubule midzone-associated proteins during spindle elongation.
Immunochemical localization of amiloride-sensitive sodium channels in sodium-transporting epithelia
Authors: Tousson Albert , Alley Charles D. , Sorscher Eric J. , Brinkley B. R. , Benos Dale J. 
Published: April 2021

ABSTRACT
The localization of amiloride-sensitive Na+ channels in Na+-transporting epithelia was examined using antibodies made against amiloride-binding Na+ channel protein purified from bovine kidney. The distribution of the channel protein was determined in thick frozen sections at the light-microscopic level using indirect immunofluorescence, and at the electron-microscopic level using immunogold labelling. In the cells of both the intact bovine collecting tubule and A6 confluent monolayers, only the luminal or apical-facing surface membranes showed staining. Sodium channel proein was characteristically localized on microvillar domains of the apical μlasma membrane. Little or no basolateral membrane staining was evident. Channel protein was also absent from subapical vesicles and tight junctions, and was not found in bovine renal proximal tubules, cultured human secretory sweat coils, non-epithelial Chinese hamster ovary (CHO) cells or human skin fibroblasts.
Trypsinization of intact A6 monolayers prior to cell fixation abolished specific staining with antibody. Pretreatment with amiloride protected against this loss of staining. Thus, our probes are specific for amiloride-binding Na+ channel protein, and this channel protein is largely or comμletely confined to the apical membrane of Na+-transporting epithelia. The level and distribution of specific immunostaining in A6 cells was unchanged by aldosterone treatment, although channel activity, as measured by short-circuit current, increased threefold. This result demonstrates that Na+ channel protein is ever present at the cell surface and exists in both an active and an inactive form. We find no evidence that stimulation of Na+ uptake by aldosterone involves recruitment of new channels from a cytoμlasmic pool.
Patterns of expression of keratin 17 in human epithelia: dependency on cell position
Authors: Troyanovsky S. M. , Guelstein V. I. , Tchipysheva T. A. , Krutovskikh V. A. , Bannikov G. A. 
Published: April 2021

ABSTRACT
By immunomorphology, using keratin 17-specific monoclonal antibody, it has been shown that this keratin is expressed only in the basal cells of a group of complex epithelia: glandular epithelium with myoepithelial component, transitional and pseudostratified epithelia. Immunolocalization of keratin 17 provides evidence that the expression of this keratin strongly depends on the cell position within epithelial structures. The topographical character of the keratin expression suggests that these proteins may be implicated in the generation of spatial organization of epithelial tissues.
Parameciumtrichocysts isolated with their membranes are stable in the presence of millimolar Ca2+
Authors: Lima Oscar , Gulik-Krzywicki Tadeusz , Sperling Linda 
Published: April 2021

ABSTRACTWe have developed a simple and rapid procedure for the isolation of a pure fraction of Paramecium trichocysts (mature secretory vesicles) with their membranes. Since in wild-type Paramecium cells essentially all trichocysts are docked at pre-formed cortical sites, trichocysts were isolated from cells in which functional trichocysts remain free in the cytoplasm owing to a mutation, tam6, that affects the docking site. Examination of the preparations by freeze-fracture electron microscopy confirms the presence of the membranes. The distribution of particles in the membranes of the isolated trichocysts and in the membranes of wild-type trichocysts in situ are nearly identical and this argues against any rearrangement of the membranes during the isolation procedure. Although the trichocyst matrix undergoes a dramatic structural transition in the, presence of Ca2+ and water (matrix expansion), the isolated vesicles with intact membranes are perfectly stable in the presence of millimolar free Caz+. This result supports a chronology in which the first step in exocytosis is membrane fusion, the swelling of vesicle contents occurring only afterwards, once the contents come into contact with the water and Ca2+ of the external medium. The role of swelling would then be to help disperse, propel or otherwise empty the contents of the vesicle outside the cell.