bluuebunny/crossref_metadata_2025_split huggingface dataset:
Immunochemical and ultrastructural mapping of the gelatin-binding and cellattachment regions of human plasma fibronectin with monoclonal antibodies
Authors: Hasty David L. , Courtney Harry S. , Simpson W. Andrew , Mcdonald John A. , Beachey Edwin H. 
Published: April 2021

ABSTRACT
Monoclonal antibodies against fibronectin were used to locate the gelatin-binding and cell-attachment regions of plasma fibronectin at an ultrastructural level. A total of 23 hybridomas were generated using mice immunized with either intact fibronectin or a 40000 Mr gelatin-binding fibronectin fragment. One of these antibodies (D9b) strongly inhibited the interaction of radio-labelled fibronectin with gelatin. Another antibody (IB10) inhibited the attachment of Chinese hamster ovary (CHO) cells to a fibronectin substratum by 99%. Both of these antibodies were purified by affinity chromatography on columns of fibronectin-Sepharose and were then incubated with soluble fibronectin to form antigen-antibody complexes. The complexes were separated from free antibody on a column of Sephadex G-200 and were prepared for electron-microscopic examination by spraying on mica discs and rotary shadowing with platinum. As determined by this method, the fibronectin molecules measured 124 ± l.7nm in length. Monoclonal antibody IB10 was visualized as a globular projection 40 ± l.4nm from one end of the fibronectin filament. Monoclonal antibody D9b, on the other hand, was visualized as a globular projection at or near one or both ends of the molecule. These data provide the first morphological localization of the gelatin-binding and cell-attachment regions of fibronectin and indicate that further studies using mono-clonal antibodies directed toward other epitopes should shed light not only on function but also on the tertiary and quaternary structure of the fibronectin molecule.
Localization of low abundance dna sequences in tissue sections by in situ hybridization
Authors: Lo Cecilia W. 
Published: April 2021

ABSTRACT
Specific DNA sequences were localized in the nuclei of paraffin-embedded mouse tissue sections with in situ hybridization using a biotinylated globin probe in conjunction with a streptavidin-alkaline phosphatase detection system. Globin inserts were clearly detected in the tissue sections of transgenic mice containing 1000, 120 or 5 copies of the exogenously introduced β-globin genes. In addition, specific hybridization signal was also obtained for the endogenous complement of ß-globin genes in the tissue sections of normal mice. These results demonstrate that this hybridization procedure is very sensitive and should be useful for characterizing the distribution of low abundance DNA sequences in cells and tissue sections.
Size uniformity of ribonucleoprotein matrix particles in loops of Pleurodeles waltlii lampbrush chromosomes visualized by electron microscopy
Authors: N’Da E. , Bonnanfant-Jaїs M. L. , Penrad-Mobayed M. , Angelier N. 
Published: April 2021

ABSTRACT
The different kinds of loops of lampbrush chromosomes were identified in phase contrast, then analysed by electron microscopy on thin sections. Examination at high magnification showed that the basic structure of the ribonucleoprotein (RNP) matrix of all kinds of loops is a 30 nm RNP particle. Furthermore, this study suggests that the morphological differences between the loops are due to the extent of aggregation of these particles.
The extracellular electrical current pattern and its variability in vitellogenic Drosophila follicles
Authors: Bohrmann Johannes , Dorn Alfred , Sander Klaus , Gutzeit Herwig 
Published: April 2021

ABSTRACT
We determined the extracellular electrical current pattern around Drosophila follicles at different developmental stages (7–14) with a vibrating probe. At most stages a characteristic pattern can be recognized: current leaves near the oocyte end of the follicle and enters at the nurse cells. Only at late vitellogenic stages was an inward-directed current located at the posterior pole of many follicles. Most striking was the observed heterogeneity both in current pattern and in current density between follicles of the same stage. Different media (changed osmolarity or pH, addition of cytoskeletal inhibitors or juvenile hormone) were tested for their effects on extrafollicular currents. The current density was consistently influenced by the osmolarity of the medium but not by the other parameters tested. Denuded nurse cells (follicular epithelium locally stripped off) show current influx, while an accidentally denuded oocyte produced no current. Our results show that individual follicles may be electrophysiologically different, though their uniform differentiation during vitellogenesis does not reflect such heterogeneity.
Transcriptive and replicative activity of the X chromosome in an autosomal segmental hyperploid in Drosophila and its significance
Authors: Ghosh Syamasri , Mukherjee A. S. 
Published: April 2021

ABSTRACT
In the present investigation the transcription and replication patterns have been examined in different segments of the X chromosome and in certain specific segments (88B—92A) of an autosomal segmental hyperploid in which an extra segment 88B–92A (3R) is translocated to the X chromosome in addition to the normal two doses. Transcriptive activity monitored by [3H]uridine-labelling of these autosomal hyperploids reveals an enhanced hyperactivity of the male X chromosome while the female X chromosomes show no change in their activity. [3H]thymid1ne autoradiograms reveal that while the labelling frequencies of most replicating sites are distinctly lowered in the autosomal hyperploid males, no change within sexes is resolvable with regard to labelling-intensity profile. Furthermore, the X-autosome labelling frequency relation shows a distinct deviation from linearity, suggesting multiple events that lead to a higher template form of the X chromosome. These findings lead us to suggest that the signals emanating from auto-some(s) do not interfere with the primary modulation inherent in the X chromosome, but act on a modulated organization of the same at a second step evoking higher activity in the male X chromosome. The results further reveal that the gene activity of the X chromosome remains unaffected by the pattern of pairing of the autosomal segments.
Membrane fusion events in the Ca2+/ionophore-induced acrosome reaction of ram spermatozoa
Authors: Fléchon J. E. , Harrison R. A. P. , Fléchon B. , Escaig J. 
Published: April 2021

ABSTRACT
An acrosome reaction was induced in ejaculated ram spermatozoa by treatment with calcium and the ionophore A23187. Samples were fixed at different times after initiation of induction, and the morphological changes within the head membranes that took place as exocytosis occurred were studied in freeze-fracture replicas.
Reacted acrosomes appeared in individual spermatozoa within the calcium/ionophore-treated population at different times after the start of treatment; the first cells had reacted by 10 min, whereas some took more than 40 min to react. No changes were observed in control populations.
An early effect of treatment (seen in most cells within 10 min) was the appearance of particle-free ‘clearings’ in the plasma membrane over the entire acrosomal region, with aggregation of intra-membranous particles between and around these ‘clearings’. At the same time, there was an increase in the number of large particles (⩾10 nm) within the plasma membrane over the ‘lunula’ of the equatorial segment and the anterior part of the post-acrosomal region.
Fusion of the plasma and outer acrosomal membranes began in a limited area at the border between the anterior and equatorial segments of the acrosome. It then spread, following arborescent pathways, sideways along this border and forwards towards the apex of the head. This labyrinthic propagation resulted in an ‘acrosomal cap’ increasingly fenestrated towards its posterior margin. Fusion propagation over the equatorial segment was inhibited, apparently as a result of the highly ordered structure of the membranes in this region.
Contacts of chick fibroblasts on glass: Results and limitations of quantitative interferometry
Authors: Bailey Juliet , Gingell David 
Published: April 2021

ABSTRACT
We have examined the contacts made by explanted chick heart and limb bud fibroblasts after 24–48 h on glass, using quantitative interference reflection microscopy (IRM). Contacts beneath very thin cytoplasmic lamellae were avoided because the images of such contacts depend on the thickness of the lamellae.
Plaque-like focal contacts, distinguished on the basis of shape and low irradiance (darkness), are intimate adhesions to the substratum. These images can be interpreted if it is assumed that microfllaments associated with the lower membrane increase the local cytoplasmic refractive index. The range of irradiances measured for focal contacts was found to be rather wide, and our modelling shows that the most likely explanation for this is that the images receive variable contributions from the adjacent cytoskeleton. For this reason it is particularly difficult to assign a characteristic thickness for these contacts from IRM data.
Close contacts, seen principally as ‘grey’ regions under migrating cells at the edges of the expiants, also show a wide range of irradiances. Unlike focal contacts, it is not necessary to postulate any involvement of the cytoskeleton in their images and they can be modelled as regions where an aqueous glycocalyx zone about 20–30 nm thick separates the membrane bilayer from the glass. Paler grey regions that also look like close contacts are apparently formed where the cell surface has lifted several tens of nanometres from the glass.
Developmental and mitotic behaviour of two novel groups of nuclear envelope antigens of Drosophila melanogaster
Authors: Frasch Manfred , Paddy Michael , Saumweber Harald 
Published: April 2021

ABSTRACT
Two novel groups of nuclear envelope antigens have been identified using monoclonal antibodies. On immunoblots the antigens correspond to distinct sets of polypeptides in the 175 ×103 molecular weight range. The antigens are enriched in a nuclear matrix-pore complex-lamina fraction of Drosophila tissue culture cells. We have studied the cellular distribution of these antigens throughout oogenesis and early embryo development.
Immunoblots show that one group of the 175 ×103Mr antigens is maternally transmitted to the embryo. This had already been observed for the 74/76× 103MrDrosophila lamins described previously, and we showed that a large proportion of the lamins is localized in the interior of the oocyte nucleus. We have also followed the fate of the high molecular weight antigens during mitosis. Each of the antigens uses a different pathway for its distribution to the daughter nuclei. These observations may give clues to the molecular mechanisms involved in the disassembly-reassembly process of the nuclear envelope.
Hyaluronic acid modulates proliferation of mouse dermal fibroblasts in culture
Authors: Yoneda Masahiko , Yamagata Masahito , Suzuki Sakaru , Kimata Koji 
Published: April 2021

ABSTRACT
When the concentration of hyaluronic acid was monitored in primary cultures of mouse skin dermal fibroblasts, there was an increase in hyaluronic acid proportional to the increase in cell number during the logarithmic growth phase. The concentration reached the maximum value 2 days before the cells became confluent, and then decreased gradually. Hyaluronic acid added at 1 mg ml−1 during the logarithmic phase either promoted or inhibited cell growth, depending on the density of cells at the time when hyaluronic acid was added. Hyaluronic acid (1 mgml−1) added to subconfluent or postconfluent cultures induced a transient DNA synthesis with a consequent increase (&gt;20%) in cell number. The effects appeared to be specific, since neither hyaluronic acid oligosaccharides nor some other types of glycosaminoglycan (chondroitin, chondroitin sulphates, heparan sulphates and heparin) had any similar effects. Dibutyryl adenosine 3′,5′-cyclic monophosphate (dbcAMP), at 1 mM, added to subconfluent or postconfluent cultures had promoting effects successively on hyaluronic acid synthesis and on cell growth. An increase in hyaluronic acid synthesis also occurred when dbcAMP was added to day 1 cultures in the logarithmic growth phase, but the effect on cell growth was reversed; there was an inhibition rather than a promotion. The pattern of cell density-dependent variation of the dbcAMP effect is quite similar to that observed with exogenously added hyaluronic acid. Therefore, we propose that hyaluronic acid added exogenously or supplied endogenously by increased synthesis may act as a modulator of mouse dermal fibroblast proliferation.
Hyaluronic acid-dependent change in the extracellular matrix of mouse dermal fibroblasts that is conducive to cell proliferation
Authors: Yoneda Masahiko , Shimizu Satoru , Nishi Yoshimi , Yamagata Masahito , Suzuki Sakaru , Kimata Koji 
Published: April 2021

ABSTRACT
Fluorescein isothiocyanate (FITC)-labelled hyaluronic acid, when incubated with subconfluent cultures of mouse dermal fibroblasts, was incorporated into the extracellular matrix. Deposition of the fluorescent label reached the maximum about 48 h after its addition. Hyaluronic acid decasaccharide, but not octasaccharide, inhibited the incorporation of the fluorescent label, suggesting that at least 10 sugar units in length are necessary for the incorporation of hyaluronic acid. A 2M-urea extract of the cell layer had the ability to bind [3H]hyaluronic acid. Again, the binding was inhibited by hyaluronic acid decasaccharide but not by octasaccharide, suggesting the presence in the urea extract of a hyaluronic acid-binding molecule that may participate in the incorporation of hyaluronic acid. A supramolecular aggregate prepared by rate-zonal sedimentation from the 2M-urea extract contained chondroitin sulphate proteoglycans capable of interacting with hyaluronic acid. Their core molecules were identical in size with those from a hyaluronic acid-binding chondroitin sulphate proteoglycan (PG-M) previously described in chick embryo fibroblasts.
Immunofluorescence analyses with anti-proteoheparan sulphate antibodies indicated that both exogenous addition of hyaluronic acid and enhanced synthesis of hyaluronic acid caused a preferential decline in the proteoheparan sulphate level in the extracellular matrix. Subsequent to this change, the cells began transient DNA synthesis. We suggest that hyaluronic aciddependent modulation of the level of proteoheparan sulphate in the extracellular matrix could be a causal event of cell proliferation.
The rescue of oral development of defective-micronucleate conjugants of Paramecium tetraurelia by normal gametic nuclei
Authors: Chau M. F. , Ng Stephen F. 
Published: April 2021

ABSTRACT
The present study further analyses the importance of postmeiotic divisional derivatives of the micronucleus in the development of the oral apparatus of Paramecium during sexual reproduction. Cell lines possessing defective micronuclei generated by laser microbeam irradiation of the micronucleus were employed. They exhibited anomalies in nuclear reorganization and stomatogenesis in the sexual cycle. During autogamy, in some cells the micronuclear cycle terminated shortly after meiosis, resulting in the loss of all postmeiotic micronuclear derivatives. Stomatogenesis became arrested at an early stage of assembly of the oral membranelles, but the old oral apparatus was resorbed as usual, leading to the production of astomatous cells at the end of the sexual cycle. Conjugation of these cell lines with normal micronucleates rescued both nucleogenesis and stomatogenesis in the defective-micronucleate conjugant, primarily as a result of transfer of the male gametic nucleus from the normal conjugant to the defective-micronucleate mate. These observations demonstrate the stomatogenic significance, in particular in the initiation of oral membranelle assembly, of the gametic nuclei during sexual reproduction. The present study also suggests the possibility of micronuclear activities in the early part of the sexual cycle affecting postzygotic nucleogenesis.
Partition of protein (mass) to sister cell pairs at mitosis: A re-evaluation
Authors: Sennerstam Roland 
Published: April 2021

ABSTRACT
Since the 1960s it has been thought that there is to some extent a difference in the partition of mass to daughter cells at mitosis. Recent studies using modern techniques give further support to such a phenomenon, which has become almost an axiom in cell biology. It has been suggested that such unequal distribution of metabolic constituents at mitosis contributes to the dispersion in cell generation times.
In the present work, PCC3 embryonal carcinoma (EC) cells were studied as undifferentiated G1 sister pairs by microspectrophotometry (MSP) following Feulgen-Naphthol Yellow staining (FNYS), in order to evaluate their protein content. Despite the considerable intraclonal intermitotic time heterogeneity found in undifferentiated PCC3 EC cells, it was concluded that the postmitotic difference in mass (protein) between sister cell pairs exerts a minimal influence upon the cell population mass variability, whereas it was deduced to have an influence upon variation in interphase time duration when comparing sister cell pairs. This offers a cell-physiological explanation to the randomly distributed difference repeatedly found between sister cell generation times. Furthermore, there was no correlation seen between the mass difference found between sister cell pairs postmitotically and the size of the mother cell.
Newt epidermal cell migration over collagen and fibronectin involves different mechanisms
Authors: Donaldson Donald J. , Mahan James T. , Smith Gerald N. 
Published: April 2021

ABSTRACT
Effects of the synthetic peptides, Arg-Gly-Asp-Ser (RGDS), the amino acid sequence representing the fibroblast attachment site in fibronectin, and Arg-Gly-Glu-Ser (RGES), on collagen- and fibronectin-mediated migration in newt epidermal cells were compared. When RGDS at 50 μg ml− 1 was included in the incubation medium of skin explants, migration in fibronectin-coated dishes was almost totally blocked. In type I collagencoated dishes, this concentration of RGDS also inhibited migration, but to a lesser degree than on fibronectin. With 250 μg ml− 1 of RGES in the medium, the reverse was true. Here, migration on collagen was practically non-existent, while migration on fibronectin was affected only moderately. Collagen-mediated migration was sensitive to RGDS even when the peptide was added after migration on the coated substratum was well underway.
At a coating concentration of 10 μg ml−1 CB3, a cyanogen bromide fragment of the collagen alpha 1(1) chain, which contains no RGD sequences, was as good a migration substratum as intact collagen applied at the same coating concentation. At lower concentrations intact collagen was somewhat better than equivalent concentrations of CB3. The presence of RGDS in the medium throughout an experiment inhibited migration in CB3-coated dishes in a manner similar to its effect in dishes coated with collagen. On both substrata there appeared to be a peptidesensitive and a peptide-insensitive component to migration. The inhibitory effect of RGES on CBS-mediated migration was also similar to its effect in collagen-coated dishes.
Monensin, an ionophore known to block secretion and endocytosis inhibited migration on fibronectin and collagen to a small, but statistically insignificant degree. A more pronounced, statistically significant effect was seen in CBScoated dishes. Electrophoretic analysis of the cell extract and the medium of cells migrating overnight on CB3 in the presence of [35S] methionine showed no evidence of fibronectin secretion by the migrating cells.
These results indicate that newt epidermal cells use different mechanisms as they migrate over fibronectin and collagen. The data could be explained by the existence of two classes of extracellular matrix receptors on epidermal cells or one class of receptor that binds to the active site(s) in fibronectin and collagen with different affinities. Our inability to detect fibronectin secretion by cells migrating on CB3 and the collagen-like sensitivity of CB3-mediated migration to RGDS suggests that some epidermal receptors involved in migration are capable of recognizing more than just the RGD sequence. The effect of monensin in CB3-coated dishes may be an indication that receptor recycling occurs during migration over some substrata.
The molecular biology of receptors. techniques and applications of receptor research
Authors: Hughes R. C. , Strosberg. A. D. 
Published: April 2021

ABSTRACT
The stated aim of this book is to present relatively briefly the main technical approaches being used for the characterization of cellular receptors involved in recognition of externally applied biologically active ligands. The emphasis is on the chemical isolation and characterization of receptors and there is little discussion of signal transmission and subsequent cell activation. The research topic is huge, is growing very rapidly and is a favoured target for many comprehensive treatments.
A gentle method for preparing cyto- and nucleo-skeletons and associated chromatin
Authors: Jackson D. A. , Yuan J. , Cook P. R. 
Published: April 2021

ABSTRACT
We describe a method for permeabilizing and extracting cells that preserves both structure and function whilst allowing the cell derivatives to be handled freely. Cells are encapsulated in microbeads of agarose; the coat of agarose, which is freely permeable to small molecules, forms a protective layer around fragile cell constituents. Cells are then permeabilized by the non-ionic detergent Triton X-100 or antibody and complement in a buffer whose ionic composition mimics that of the cytoplasm. The resulting structures have been characterized morphologically (by immunofluorescence and electron microscopy) and biochemically. Lysis with Triton removes both cell and nuclear membranes, and extracts most of the cytoplasm to leave chromatin surrounded by cytoskeleton; nucleus and cytoplasm then become accessible to triphosphates, enzymes and antibodies. Lysis with complement permeabilizes the cell membrane but leaves the nuclear membrane intact; triphosphates and restriction enzymes, but not antibodies, can then enter both nucleus and cytoplasm. Both types of lysis yield preparations whose chromatin template remains essentially intact, and which is replicated and transcribed at rates close to, or greater than, those found in vivo. Treatment of complement-lysed cells with Triton reduces the very efficient DNA synthesis, implying that the nuclear membrane is involved, directly or indirectly, in replication.