bluuebunny/crossref_metadata_2025_split huggingface dataset:
The extracellular matrix of human amniotic epithelium: Ultrastructure, composition and deposition
Authors: Aplin J. D. , Campbell S. , Allen T. D. 
Published: April 2021

ABSTRACT
Ultrastructural comparisons have been made between human amnion extracellular matrix in tissue and cell culture. Immunochemical analysis of matrix deposited by monolayers of cultured amnion epithelial cells has also been undertaken. The basal cell surfaces are highly invaginated with an associated basal lamina that is more electron dense at the distal tips of basal cell processes where hemidesmosomes are frequent. Immediately below the lamina densa is a zone rich in collagen bundles. In the underlying stroma two types of fibril predominate, one striated of 50 nm diameter and one of 18 nm diameter. The observations suggest that at gestational term the epithelial cells are still active in the production of matrix. Secretion appears to occur into invaginations in the basal cell surface where a loosely organized mixture of stromal-type and basal laminal-type aggregates is formed. In culture on plastic, cells also deposit a mixture of basal laminal (type IV collagen+ laminin) and stromal (collagens type I + III) components as well as fibronectin. However, segregation into a true basal lamina with underlying stroma does not occur in vitro, suggesting the need for an organized subcellular template to complete matrix morphogenesis. The in vitro and in vivo evidence suggest that the epithelium contributes to the subjacent dense collagenous zone as well as to the basal lamina.
Water ordering during the cell cycle: Nuclear magnetic resonance studies of the sea-urchin egg
Authors: Zimmerman S. , Zimmerman A. M. , Fullerton G.D. , Luduena R. F. , Cameron I. L. 
Published: April 2021

ABSTRACT
Nuclear magnetic resonance was used to measure spin-lattice water proton relaxation times (T1) during the first cell cycle in sea-urchin zygotes of packed Strongylocentrotus purpuratus. Following insemination there was a 90% increase in the T1 value. The increase in T1 at fertilization could be accounted for by the accumulation of extracellular fluid between the egg surface and the fertilization envelope. The T1 value then remained without change during the first cell cycle, except at metaphase when there was a significant 13% decrease. The lowered T1 values measured at metaphase were not related to a change in the water content of the packed cells, which remained fairly constant throughout the cell cycle. High hydrostatic pressure, low temperature and colchicine (agents that depolymerize mitotic apparatus microtubules) did not affect the T1 values in fertilized eggs. Treatment in vitro of a microtubule protein preparation with low temperature and colchicine resulted in an increased T1, which accompanied the depolymerization of microtubule protein. Since depolymerization of the microtubules associated with the mitotic apparatus by high pressure, colchicine or low temperature does not alter the T1 of water protons in the cell, it is proposed that the increased state of ordered water molecules at metaphase is maintained by non-microtubular factor(s) of the metaphase egg.
Characterization of rat mammary cell types in primary culture: Lectins and antisera to basement membrane and intermediate filament proteins as indicators of cellular heterogeneity
Authors: Warburton Michael J. , Ferns Sharon A. , Hughes Christine M. , Rudland Philip S. 
Published: April 2021

ABSTRACT
Three morphologically distinct major cell types were observed in primary cultures obtained from the mammary parenchyma of glands from virgin rats. These cell types consisted of small cuboidal epithelial cells, larger epithelioid cells and elongated cells. We have investigated the distribution of the basement membrane proteins laminin and type IV collagen, and the intermediate filament proteins vimentin and prekeratin, in these three cell types using immunofluorescence techniques. Antisera to the basement membrane proteins stain the large epithelioid cells and the elongated cells, but do not stain the small cuboidal cells. Polyclonal antiserum to keratin stains all the small cuboidal and large epithelioid cells, but only a small subpopulation of the elongated cells. However, a monoclonal antibody to keratin, LP34, stains only the large cuboidal and a proportion of the elongated cells. Vimentin antiserum fails to stain the small cuboidal cells but stains all the large epithelioid and elongated cells. In addition, peanut lectin, which binds only to ductal lining epithelial cells in the virgin rat mammary gland in vivo after their treatment with neuraminidase, binds to the small cuboidal cells after neuraminidase treatment but not to the other cell types. However, Griffonia simplicifolia agglutinin I, which specifically stains myoepithelial cells in vivo, binds to the large epithelioid and elongated cells but not to the small cuboidal cells. These results suggest that the small cuboidal cells are related to mammary ductal epithelial cells whereas the large epithelial and elongated cells have some characteristics of myoepithelial cells.
The behaviour in vitro of epidermal cells from normal and Pupoid foetus mutant mouse embryos
Authors: Anderson S. , Ede D. A. 
Published: April 2021

ABSTRACT
Pupoid foetus (pf/pf) is a recessive lethal mutation of the mouse causing epidermal hypertrophy and disorganization of peripheral sensory nerves and mesoderm.
The comparative behaviour of epidermal cells from normal and pupoid foetus mutant mouse embryos was studied in vitro. Epidermal explants from the snout region of 12-5-to 13-day embryos were grown in culture for periods of up to 2 weeks. Cultures from both phenotypes were filmed using time-lapse cinemicrography for up to 3 days following explantation.
Paths of individual cells-were traced as they migrated from the explant, and their rate of locomotion and directional persistence were calculated. Differences in these parameters between the two phenotypes were tested statistically. The overall morphology of the cultures, and the tendency of the cells to detach from the periphery of the cell mass were also compared.
The results show that, between 25 and 60 h after explantation, epidermal cells frompupoidfoetus embryos move consistently more slowly than normal cells, and follow a more erratic path. This situation is reversed, however, between 16 and 25 h.
This suggests that the pf mutation causes an alteration in epidermal cells that affects their locomotion, and which is maintained for a minimum of 3 days in the absence of other influencing factors.
The ultrastructure of synchronized hela cells
Authors: Erlandson R. A. , Harven E. DE 
Published: April 2021

ABSTRACT
Synchronous populations of mitotic HeLa cells were obtained by the controlled agitation method, and a detailed morphological study of the cells in all phases of the cell cycle was under-taken to correlate variations in cell structures to known coexisting biochemical events. Auto-radiographic techniques using tritiated thymidine (3H-TdR) were used to detect S1 cells, and colcemid was added to some G2 samples to prevent the cells from going into the next cycle, thus preventing contamination with G1 cells.
The approximate duration (in hours) of the 4 phases were as follows: M = 1·4, G1= 8–9, S = 7, G2 = 4, and the generation time (T) = 21 ± 2 h. Randomization of the cell populations became apparent in the G2 phase (contaminated with S and M cells) and was most likely a result of the genetic make-up of the individual (mixoploid) HeLa cells, nutritional factors (serum lots used), temperature shock, and handling effects. Polyribosomes shifted to monomeric ribosomes during late prophase, at which time nucleoli also break down. These changes are correlated with the drop in protein and RNA synthesis reported for mitotic mammalian cells. The Golgi apparatus persisted in a modified form throughout mitosis. The mid-body forms from the anaphase stem-body and may interfere with the separation of daughter cells. Our studies suggest that the mid-body goes to one of the daughter cells where remnants of this structure were seen in early G1 cells. Large numbers of polyribosomes and the presence of well-developed nucleoli (many attached to the nuclear envelope) characterized G1. These structures, which play a major role in protein and RNA synthesis, persist with slight variations throughout inter-phase. Dense fibrillar nuclear bodies were prominent in late G1 cells. Centrioles separate during G1, and replicate by orthogonal budding during the S phase. Reproducible labelling patterns which reflect the asynchronous multireplicon nature of DNA synthesis in mammalian cells were characteristic of the various stages of the 51 phase. Granular nuclear bodies, which were prominent in S and G2 cells, may correspond to the larger species of heterogeneous nuclear RNA found in HeLa cells. G2 cells were similar in appearance to S cells. As heterochromatin areas increased in late G2 and prophase, perichromatin granules (of unknown significance) became prominent. Mitochondria behaved as independent cell organelles throughout the cell cycle.
Hypertrophied RER, SER, and annulate lamellae, characterized the cytoplasm of colcemid-treated cells. The above changes are indicative of increased metabolic activity, and these structures may function in the production of colcemid-detoxifying enzymes in a manner analogous to that of drug-treated hepatocytes, such as those treated with phenobarbital.
An investigation of the molecular components of desmosomes in epithelial cells of five vertebrates
Authors: Suhrbier Andreas , Garrod David 
Published: April 2021

ABSTRACT
We have shown previously, by fluorescent antibody staining, that desmosomal antigens are widely distributed in the tissues of vertebrate animals. Furthermore, we have demonsuated mutual desmosome formation between cells derived from man, cow, dog, chicken and frog. In this paper we have studied the components of desmosomes in a tissue or a cell line from each of these animals by immunoblotting with antibodies raised against the desmosomal components isolated from bovine nasal epithelium. Blotting was carried out on bovine nasal epithelial desmosomal cores, desmosome-enriched fractions derived from chicken and frog epidermis, nuclear matrixintermediate filament scaffolds derived from Madin-Darby bovine and canine cells (MDBK and MDCK), and unextracted cultured human foreskin keratinocytes.
The results show that desmosomes from all these sources contain high molecular weight proteins (desmoplakins) of similar or identical molecular weights (250 000 and 215 000). Antibodies against the two lower molecular weight desmosomal proteins (83 000 and 75 000) always recognized one or two bands in very similar molecular weight regions of the gels. The desmosomal glycoproteins were found to be much more variable than the proteins: they vary between sources in molecular weight, heterogeneity and antibody cross-reactivity. For instance, antibody specific for a group of glycoprotein bands of 175 000, 169 000 and 164 000 (Mr;) in bovine nasal epithelium recognizes three bands of 245 000, 230 000 and 210 000 in MDCK cells but only a single band of 190 000 in keratinocytes. In mammals, the 175 000-164 000 glycoproteins and the desmosomal adhesion molecules, the desmocollins (Mr 130 000 and 115 000 in cow’s nose), are immunologically distinct. In chicken and frog, however, there are glycoproteins that react with both anti-175 000—164 000 and anti-desmocollin antibodies, but there are also distinct desmocollin bands. The significance of these results is discussed in relation to conservation of desmosomal components and adhesion mechanisms. It is suggested that adhesion may be performed by a well-conserved protein domain and that the variation between desmosomal glycoproteins from different sources may be due to differences in their carbohydrate composition.
Structure of landmark loop ribonucleoprotein matrices in Pleurodeles waltlii lampbrush chromosomes visualized by scanning electron microscopy
Authors: Bonnanfant-JaïS M. L. , N’DA E. , Penrad-Mobayed M. , Angelier N. 
Published: April 2021

ABSTRACT
Landmark loop ribonucleoprotein (RNP) matrices of Pleurodeles waltlii lampbrush chromosomes were systematically examined by scanning electron microscopy (SEM). The results, which corroborated similar studies by electron microscopy (EM), showed that RNP transcripts in normal loops, and RNP matrices in granular, globular and dense loops, are composed of one basic structure: an RNP particle with a diameter of 30 nm.
SEM observations also clarified the spatial arrangement of this particle in the RNP matrices of all the loop types examined.
The specific morphology of normal, granular, globular and dense loop RNP matrices depended on the degree of compaction of the transcription products; this compaction resulted both from the packaging of RNP transcripts and the progressive coiling of the loop axis.
Facultative heterochromatin in Locusta migratoria spermatogenesis: correlation between electron opacity and heteropycnosis
Authors: Friedländer Michael , Hauschteck-Jungen Elisabeth 
Published: April 2021

ABSTRACT
The unpaired X chromosome of Locusta migratoria males is facultatively heterochromatic in the spermatocytes and early spermatids, showing an alternating cycle of positive-negative-positive heteropycnosis. Discrimination between facultative heterochromatin and euchromatin was made using a modification of the Feulgen reaction. It was found that the differential stainability of the DNA of the X chromosome is correlated with the electron opacity of its chromatin. The corresponding differential stainability and electron opacity should reflect differences in protein content or in spatial rearrangement since the amount of DNA in the X chromosome that is transmitted by the spermatozoa to the next generation should remain constant.
Optimization of environment for high density vero cell culture: effect of dissolved oxygen and nutrient supply on cell growth and changes in metabolites
Authors: Nahapetian Ara T. , Thomas James N. , Thilly William G. 
Published: April 2021

ABSTRACT
This study was initiated for optimization of the environment of a technologically useful mammalian cell line for high density production. Cultures of Vero cells on microcarriers were perfused with 100%, 50%, 25% and 12-5% modified L15 media (galactose was replaced with 10 mM-fructose, with 4 HIM-glutamine and 5% foetal bovine serum) in phosphate-buffered saline at either 4 or 8 vol. day−1. Cell growth, pH, dissolved oxygen, and changes in the metabolites, lactate to pyruvate and lactate to ammonia indices, demonstrated that under the conditions used in the present study, perfusion of cultures with 50% L15 medium in PBS at 8 vol. day−1’ provided the optimum microenvironment for Vero cell growth. The highest cell density in the perfused cultures was 3×107 cells ml−1, which at these conditions was ten times higher than the maximum cell density (3×106 cells ml−1’) obtained in a batch culture. Nutrient supply and conditioning factors were the most probable growth-limiting factors in cultures that were perfused with 12·5% and 25% L15 media, while multilayering, limitation of available oxygen, and accumulation of metabolic endproducts in the cellular microenvironment were the most probable causes of a densitydependent inhibition of cell growth observed under the optimized and overfed (supply of 100% L15 medium at the rate of 8 vol. day−1’) culture conditions. Under the optimized environmental condition, the major source of energy was probably glutamine during the first week. However, significant utilization of fructose became evident at higher cell densities during the second week, when lactate production dramatically declined and reached an almost undetectable level, while respiration progressively assumed the predominant role in energy production. It is postulated that ‘available’ oxygen in the multicell-layered microenvironment of the optimized cultures was higher than in the overfed culture due to the greater utilization rate of oxygen for oxidation of excess nutrients in the overfed culture.
Organization of chromosomes in the mouse nucleus: Analysis by In situ hybridization
Authors: Katsumata Makoto , Lo Cecilia W. 
Published: April 2021

ABSTRACT
We used in situ hybridization with various biotinylated DNA probes to characterize the distribution of mouse chromosomes in the nucleus. This entailed an examination of plasmid-marked chromosomes from two strains of transgenic mice and also an examination of the distribution of centromeres and total mouse genomic DNA. Our results show that, regardless of the hybridization probes used or the tissue types examined, with sections of mouse tissues embedded in paraffin all chromosomal DNA appeared to be localized to the nuclear periphery. This was observed in tissues fixed with either crosslinking or non-crosslinking fixatives, and submitted to a variety of prehybridization treatments. Further experiments with non-embedded nuclei fractionated from mouse liver revealed a similar distribution of DNA at the telomeric end of chromosome 3, but for centromeric DNA and total mouse genomic DNA, hybridization signals were observed both in the interior and at the periphery of the nucleus. These observations preclude the exclusive localization of chromosomes to the nuclear periphery. However, they indicate that a subset of centromeres are likely to be associated with the nuclear membrane, and that there is such an association at the telomeric end of chromosome 3. Overall, these results are compatible with previous observations of other investigators showing regions of contact between chromosomes and the nuclear membrane.
Characterization of a novel nuclear envelope protein restricted to certain cell types
Authors: Lord Janet M. , Thick Jane A. , Bunce Christopher M. , Taylor Alexander M. R. , Gallimore Phillip H. , Mills Deryck , Brown Geoffrey 
Published: April 2021

ABSTRACT
The monoclonal antibody AGF2.3 identifies a nuclear envelope protein that is restricted to certain cell types. In particular, this antigen shows a reduced level of expression during haemopoietic cell maturation. In this study, we have examined the relationship of this protein to known nuclear envelope proteins that have a similar molecular mass. Antigen extraction and immunoelectron microscope studies revealed that the AGF2.3 protein is an integral membrane protein present at both the inner and outer aspects of the nuclear envelope. The protein is not associated with nuclear pores and therefore is distinct from pore complex proteins. The AGF2.3 protein does not have ATPase activity. Therefore, this protein is also distinct from a myosin heavy chain-like ATPase that is associated with the nuclear envelope. The AGF2.3 antibody identifies a novel nuclear envelope protein. Further studies of the biochemical nature of the AGF2.3 protein should provide insight into novel cellular processes at the nuclear envelope relating to the lineage or maturation status of cells.
Platelets contain a 21 ok microtubule-associated protein related to a similar protein in hela cells
Authors: Tablin Fern , Reeber Miriam J. , Nachmias Vivianne T. 
Published: April 2021

ABSTRACT
We have demonstrated the presence of a 210K (K= 103Mr) microtubule-associated protein (MAP) in blood platelets and have studied its relationship to tubulin and to the cytoskeleton, using a well-characterized polyclonal antibody for the analysis. When platelet lysates were enriched for tubulin by an assembly cycle at 37°C, the 210K MAP was also enriched, as detected by Western blotting, while the antigen was not detected in pellets from cold-treated samples that lacked stabilized tubulin. Immunofluorescence of resting platelets showed that the 210K antigen colocalized with the microtubule coil in ring-like structures. On the other hand, in preparations of platelet cytoskeletons, the 210K antigen was present in samples from platelets in which the coil was disassembled (cold-treated without taxol pretreatment) as well as from platelets in which the coil was preserved (at 37°C without taxol, or 4 °C with taxol pretreatment). In chilled platelets with disassembled microtubule coils, indirect immunofluorescence using antibodies to 210K or tubulin gave a diffuse signal throughout the platelet cytoplasm. However, immunofluorescence of the 210K antigen in both resting and cold-treated platelets displayed discrete or patchy staining as compared to the continuous staining with antitubulin. We conclude that 210K MAP is present in platelets, that it copurifies with tubulin and that it is localized along the microtubule coil. Our results also suggest that the 210K MAP may interact with some other element(s) of the cytoskeleton, and hence that it might serve as a linking protein.
Adhesion and locomotion of granulocytes under flow conditions
Authors: Doroszewski Jan , Kiwala Anna 
Published: April 2021

ABSTRACT
The aim of this study was to compare the strength of the surface adhesion of migrating human granulocytes and the main parameters of their locomotion under the influence of various external forces. The strength of adhesion of granulocytes moving in a quiescent medium was studied by detaching them gravitationally from the plane surface situated above them. In these conditions the force of adhesion is of the same order of magnitude as the gravitational force operating upon the cells. The locomotion characteristics of granulocytes migrating on a surface below them are similar to those observed during their movement on a surface above. When the granulocytes migrate with the medium flowing past them, they are not detached from the surface even by relatively great shearing forces (10 and 100 times greater in comparison with the gravitational force) and the locomotion parameters are only slightly modified. The results show that granulocytes are able to migrate in a similar manner when they are subjected to various external forces.
The effects of glycosylation inhibitors on the proliferation of a spontaneously transformed cell line (3T6) in vitro
Authors: Engstrom Wilhelm , Larsson Olle 
Published: April 2021

ABSTRACT
We have examined the effects of different inhibitors of glycosylation processing on the proliferation of a spontaneously transformed murine cell line (3T6) in vitro. It was found that whereas two compounds that specifically inhibit distal steps in the glycosylation chain (swainsonine and castanospermine) only exerted marginal inhibitory effects on cell multiplication, a proximal inhibitor (tunicamycin) efficiently decreased the rate of DNA synthesis in a dose-dependent fashion. This tunicamycin-induced inhibitory effect on cell proliferation was cell cycle-specific, in the sense that cells in G1 only were blocked in their cell cycle progression. Like others (Volpe & Goldberg, 1983), we found that tunicamycin inhibited the activity of 3-hydroxy-3-methylglutaryl coenzyme-A reductase (HMG-CoA), which constitutes the ratelimiting step in the biosynthesis of cholesterol and isoprenoid derivatives, by cata lysing the reduction of HMG-CoA to mevalonate, and it has been suggested that it plays a role in the control of cell proliferation and in tumour transformation. This raises the question as to whether tunicamycin exerts its inhibitory effects on cell proliferation via the isprene-synthetic pathway in addition to its effects on aspargine-linked glycosylation. By adding exogenous mevalonate, the rate-limiting step at which HMG-CoA reductase converts HMG-CoA to mevalonate can be bypassed. We found that addition of mevalonate partially reverses the effects of tunicamycin on cell proliferation. This suggests that tunicamycin exerts different effects, which taken together lead to a cessation of cell proliferation. One of these effects is likely to be mediated via the mevalonate-synthetic pathway.