bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photosensitization to ultraviolet irradiation and selective killing of cells following uptake of pyrene-containing fatty acid
Authors: Fibach Eitan , Morand Olivier , Gatt Shimon 
Published: April 2021

ABSTRACT
Cells were incubated with 12-(l-pyrene)-dodecanoic acid (P12), a long-chain fatty acid to which a pyrene ring has been attached covalently. This acid was transported across the plasma membranes of cells and subsequently incorporated into their neutral lipids and phospholipids. Irradiation of these pyrene-containing cells for short periods (0·5–4 min) with ultraviolet light at 366 nm resulted in eventual cell death. Similar irradiation had no effect on cells that had not been exposed to Pl2. The time of the period of irradiation necessary for inducing the toxic process was related to the quantity of Pl2 incorporated, the latter being a function of the respective metabolic activity of the individual cell type. The degree of incorporation of P12 into a cell, and consequently its acquired sensitivity to killing by ultraviolet irradiation at 366 nm, was affected by the incubation temperature and addition of non-fluorescent fatty acid, albumin or other serum proteins. Different degrees of incorporation of P12 into various cell types were used for selective killing and elimination of cell populations by irradiation at 366 nm. The combined procedure of preincubation with P12 followed by ultraviolet irradiation thus permitted selection of cell types with a greater resistance to this procedure.
The cell cycle of symbiotic chlorella: iii. numbers of algae in green hydra digestive cells are regulated at digestive cell division
Authors: Mcauley P. J. 
Published: April 2021

ABSTRACT
Regression analysis of the relationship between the size of interphase and mitotic digestive cells of green hydra, and the numbers and total volume of the symbiotic Chlorella algae they contain showed a partial correlation only, suggesting that numbers of algae per cell are not regulated by limiting them to a specific proportion of the host cell, and that the variation observed in numbers of algae per cell is not due to variation in host cell size. After hydra were fed, which stimulates algae and digestive cells to divide at the same time, numbers of algae per cell were higher in prophase than in interphase cells, and numbers increased as mitosis proceeded. In excised regenerating peduncles algae divide before digestive cells, and at the onset of digestive cell division mitotic cells were found to contain almost twice the number of algae as before excision. Thus, almost all of the algal cell division necessary to maintain a constant population size was associated with digestive cell division. Analysis of variance in numbers of algae in telophase mother and daughter cells suggested that the proportion of algae dividing as a result of host cell mitosis was greater in digestive cells with few algae than in those with many algae. The fact that the mechanism controlling the proportion of algae dividing in host cells is expressed at host cell division and is manifested in the daughter cells may contribute to wide variation in numbers of algae per cell.
The cell cycle of symbiotic chlorella: IV. DNA content of algae slowly increases during host starvation of green hydra
Authors: Mcauley P. J. , Muscatine L. 
Published: April 2021

ABSTRACT
The distribution of DNA content of symbiotic Chlorella algae freshly isolated from green hydra was compared with that of cultured Chlorella of the NC64A strain, using flow cytometry. In non-logarithmic cultures of NC64A most cells had accumulated in G\ phase, while in logarithmic cultures a peak containing cells in S phase and mitosis could be distinguished from the larger peak. However, symbiotic algae showed a single broad peak in which there was no clear distinction between G1 and S phase/mitosis. When hydra were starved for a prolonged period, inhibiting host cell and algal division, the DNA content of the symbiotic algae slowly increased, and the number of daughter cells produced after a single feeding increased with the length of the preceding period of starvation. This suggests that symbiotic algae are able to cycle slowly through S phase, but unless the host is fed they cannot traverse into mitosis and complete the cell division cycle. No significant difference in cell size was found between algae producing either four or eight daughter cells after 1-day- or 22-day-starved hydra were fed, suggesting that algal cell size did not determine the number of daughter cells produced. Instead, this may be dependent upon the length of time the cell had spent in S phase prior to receiving the, as yet unknown, stimulus to enter into mitosis.
Proteins of the membrane skeleton in rat sertoli cells
Authors: Ziparo E. , Zani B. M. , Filippini A. , Stefanini M. , Marchesi V. T. 
Published: April 2021

ABSTRACT
Analogues of the α, β and γ subunits of human spectrin and erythroid protein 4.1 have been detected in rat Sertoli cell primary cultures. Immunofluorescence of permeabilized cells showed that erythroid type spectrin, protein 4.1 and actin co-distribute within the cells as filamentous structures. Fodrin-like molecules were distributed in a diffuse manner, mostly associated with the plasma membrane. Immunoprecipitation and immunoblotting experiments indicated that the polypeptides present in rat Sertoli cells are immunologically related and display molecular weights similar to their analogues in the human erythroid and non-erythroid membrane skeleton.
Electron-microscopic studies of the ca antigen, epitectin
Authors: Bramwell M. E. , Wiseman G. , Shotton D. M. 
Published: April 2021

ABSTRACT
Epitectin, the mucin-like glycoprotein defined by the monoclonal antibodies CAI, CA2 and CA3, has been examined by electron microscopy to determine its shape and size. It appears to be a single extended strand with a mean length of about 270 nm. The antibodies CAI and CA2 appear to bind preferentially to a terminal site on the epitectin molecule.
Cytochemical and biochemical evidence of cathepsin B in malignant, transformed and normal breast epithelial cells
Authors: Křepela E. , Bártek J. , Skalková D. , Vičar J. , Rasnick D. , Taylor-Papadimitriou J. , Hallowes R. C. 
Published: April 2021

ABSTRACT
Human breast cancer cell lines, as well as transformed mammary epithelial cells (HBL-100) and growth-stimulated normal breast epithelial cells showed positive cytochemical reaction with the proteinase substrate 2-(N-benzyloxycarbonyl-L-arginyl -L -arginylamido) - 4 -methoxynaphthalene, in the presence of 5-nitrosalicylaldehyde. The reaction product, small fluorescent granules, was distributed throughout the cytoplasm, in the perinuclear zone, in some cytoplasmic projections, and at the cell surface. Using a panel of various proteinase inhibitors, we found that the formation of the reaction product was an enzymic function of a cysteine proteinase.
Using the substrate 7-(N-benzyloxycarbonyl-L-arginyl-L-arginylamido)-4-methylcoumarin, we evaluated some biochemical properties of the cysteine proteinase, including pH-activity profile, pH stability, apparent relative molecular mass and sensitivity toward various proteinase inhibitors. We found that the proteinase from the studied breast epithelial cells exhibited characteristics of a mature form of cathepsin B.
Taken together, the cytochemical and biochemical data provide evidence that human breast epithelial cells of cancer origin, as well as in the transformed or growth-stimulated state express active cathepsin B and compartmentalize it into specific subcellular sites.
Chemotaxis towards pteridines during development of Dictyostelium
Authors: Tillinghast H. S. , Newell P. C. 
Published: April 2021

ABSTRACT
Following a previous study indicating a sensitivity to folate during the developmental phase of Dictyostelium discoideum, a series of pteridines were investigated for their ability to induce amoebal chemotaxis during development of this organism. Several compounds were found to resemble folate in their ability to induce chemotaxis of both vegetative amoebae and amoebae developing during the first few hours of starvation. One compound, L-monapterin, was distinct in showing chemotactic activity only during the developmental phase after approximately 12 h of starvation. Tests using the polymerization of cytoskeletal actin as an assay for a cellular response correlated with chemotaxis showed that 10 nM-L-monapterin was a potent inducer of this response and that responsiveness appeared only after 12 h of development. The timing of these events may be correlated with the formation of tips containing stalk cells that occurs in multicellular aggregates at approximately 12 h, and suggests a role for L-monapterin (or a naturally occurring, closely related pteridine) in cell sorting. The evolutionary significance of the roles of pteridines is discussed.
Tissue inhibitor of metalloproteinases (timp) regulates extracellular type i collagen degradation by chondrocytes and endothelial cells
Authors: Gavrilovic Jelena , Hembry Rosalind M. , Reynolds John J. , Murphy Gillian 
Published: April 2021

ABSTRACT
A specific antiserum to purified rabbit tissue inhibitor of metalloproteinases (TIMP) was raised in sheep, characterized and used to investigate the role of TIMP in a model system. Chondrocytes and endothelial cells cultured on 14C-labelled type I collagen films and stimulated to produce collagenase were unable to degrade the films unless the anti-TIMP antibody was added. The degradation induced was inhibited by a specific anti-rabbit collagenase antibody. It was concluded that TIMP is a major regulatory factor in cell-mediated collagen degradation.
Gland formation of human colon cancer cells combined with foetal rat mesenchyme in organ culture: an ultrastructural study
Authors: Fukamachi Hiroshi , Mizuno Takeo , Kim Young S. 
Published: April 2021

ABSTRACT
The morphogenetic potential of human colon cancer cells was examined by combining cells with foetal rat mesenchyme in organ culture. Out of four cell lines examined, LS174T cells formed glandular structures composed of a simple columnar or cuboidal epithelium with a lumen in the centre of the cell mass. Ultrastructurally, these gland-forming LS174T cells exhibited polarity, with nuclei located basally, microvilli projecting into the lumen, tight junctions at the cellcell junction facing the lumen, desmosomes at the subluminal region, and basal laminae at the epithelial-mesenchymal interface. Other cell lines did not form such glandular structures, while some cells could form microvilli, tight junctions or basal laminae, which were arranged randomly. It is concluded that it is not the existence but the ordered arrangement of these structures that is essential for gland formation by epithelial cells. The mechanism of gland formation is discussed with special reference to the arrangement of different structures.
Expression of C-myc during differentiation of the human teratocarcinoma cell line Tera-2
Authors: Schofield P. N. , Engstrom W. , Lee A. J. , Biddle C. , Graham C. F. 
Published: April 2021

ABSTRACT
The quantity of c-myc mRNA was measured during the retinoic-acid-induced differentiation of the pluripotent human teratoma cell line, Tera-2 cl. 13. As the cells were exposed to retinoic acid for longer periods of time the duration of the cell cycle progressively increased (measured by the rate of S phase entry) until the cells were effectively quiescent and expressed characteristic differentiation markers. Under these circumstances steady-state levels of c-myc expression increased by up to 1·6-fold with respect to rapidly growing undifferentiated cells. Southern blot analysis of the c-myc genes in Tera-2 indicated no major rearrangement or amplification in the cell line.
Leukotrienes stimulate initiation of DNA synthesis in cultured arterial smooth muscle cells
Authors: Palmberg Lena , Claesson Hans-Erik , Thyberg Johan 
Published: April 2021

ABSTRACT
The effects of leukotrienes on initiation of DNA synthesis in growth-arrested arterial smooth muscle cells cultivated in a defined, serum-free medium were studied. The results showed that LTB4, LTC4 and LTD4 were all stimulatory with a distinct effect already at 0·01 pM and a maximal effect at 10pM; in contrast, LTE4 lacked effect. 5S,12S-DHETE, an isomer of LTB4, was inactive in itself but blocked the effect of LTB4. Treatment of the cells with indomethacin or acetylsalicylic acid, two cyclooxygenase inhibitors, blocked induction of DNA synthesis by LTB4, indicating that the effect of this compound was mediated by a cyclooxygenase product. Up to 10 pM, the leukotrienes stimulated initiation of DNA synthesis with similar potency to platelet-derived growth factor (PDGF). The maximum labelling index obtained with PDGF was, however, about twice that obtained with the leukotrienes. At suboptimal concentrations of PDGF, the leukotrienes had an additive effect. The prereplicative lag phase was 16–20h with LTB4, 12–16 h with LTC4, and 8—12 h with PDGF. In metabolic experiments no signs of synthesis of leukotrienes were detected by cells stimulated with the calcium ionophore A23187, arachidonic acid, or LTA4 for 10–30 min, neither was any apparent degradation of LTB4 observed. On the other hand, LTC4 was transformed into LTD4 and LTE4. Taken together, the results indicate that leukotrienes are able to stimulate quiescent arterial smooth muscle cells to enter the cell cycle and to replicate their DNA. In vivo, stimulation of cell growth by leukotrienes could add to other established functions of these substances in tissue repair, inflammation, and atherogenesis.
Transfection and stable expression of a dominant selective marker Ecogpt in a cultured cell line of the fish, Carassius auratus
Authors: Isa K. , Shima A. 
Published: April 2021

ABSTRACT
The synthetic plasmid, pSV2-gpt, was transfected into the cultured fish cells (RBCF-1 line) using polycation and dimethyl sulphoxide. The maximum transfection frequency estimated by colony number in the selection medium was 585 trans-fectants/5× 10s treated cells per 50 ng plasmid DNA. The isolated transfectants expressed the xanthine guanine phosphoribosyltransferase (XGPRT) activity encoded by the plasmid DNA associated with the promoter of simian virus 40 (SV40). The resistance to mycophenolic acid and the XGPRT activity of every transfectant examined were stable, indicating the possibility that pSV2-gpt was integrated into the genomic DNA of the host fish cells. Our results, in addition to those already reported for mammalian and avian cell lines, indicate that the promoter in the early region of SV40 can function in cultured fish cells. This success in obtaining cultured fish cells with a dominant selective marker will provide a useful clue for somatic cell genetic studies of fish in the future.
Gradient perception by neutrophil leucocytes, continued
Authors: Lauffenburger Douglas , Farrell Brian , Tranquillo Robert , Kistler Amy , Zigmond Sally 
Published: April 2021

ABSTRACT
The mechanism by which neutrophil leucocytes exhibit chemotaxis continues to be the subject of debate. In recent articles in this journal (Vicker el al. 1986; Haston & Wilkinson, 1987) the question of whether neutrophils can perceive spatial attractant concentration gradients has been discussed. The purpose of this brief note is to give attention to some information that should help clarify some of the points raised by these articles.
Differential expression of the ed sequence-containing form of cellular fibronectin in embryonic and adult human tissues
Authors: Vartio Tapio , Laitinen Lusa , Närvänen Outi , Cutolo Maurizio , Thornell Lars-Erik , Zardi Luciano , Virtanen Ismo 
Published: April 2021

ABSTRACT
Monoclonal mouse hybridoma antibodies were obtained for secreted cellular fibronectin (cFn) from A8387 fibrosarcoma cells. One of them, 52-DH1 (DH), reacted exclusively with cFns but not with plasma Fns (pFns) in immunoblotting and solid-phase EIA. The DH antibody also recognized thermolysin cFn fragments and β-galacto-sidase-Fn fusion protein which contained the ED sequence specific to at least some forms of cFns. On the other hand, the DH antibody failed to recognize a fusion protein that was otherwise identical but lacked the ED sequence. Thus, the antigenic determinant for the DH antibody was located to the ED sequence. The DH antibody was then used to study the expression of ED sequence containing cFn (EcFn). For comparisons, another monoclonal antibody, 52BF12 (BF), recognizing equally well both pFns and cFns, was used. Immunoblotting of pFn fragments indicated that this antibody had the antigenic determinant at or close to the cell-binding site of Fn. EcFn wasrevealed by the DH antibody in embryonic and adult fibroblasts and in a variety of other cultured normal and malignant human cells. In embryonic tissues EcFn was abundant in developing basement membranes, as shown in foetal kidney and muscle, while in adult tissues it was confined only to endothelia of larger blood vessels. Furthermore, in embryonic tissues the capillaries showed bright EcFn-positivity not found any more in adult tissues. Human plasma contained a small quantity of EcFn, which may hence have an endothelial origin. EcFn was also prominent in the stroma of malignant tumours as well as in reactive benign conditions, such as granulation tissue and decidual cells. The results suggest that EcFn is a form of the protein which may have a particular role in developing and reactive tissues in embryos and adults.
F-actin distribution in polymorphonuclear leucocytes
Authors: Haston Wendy S. 
Published: April 2021

ABSTRACT
The polarization and amoeboid locomotion of neutrophil leucocytes is stimulated by chemotactic factors, which initiate waves of contraction in both adherent and non-adherent neutrophils. These cyclical contractile events have previously been analysed by time-lapse filming but the mechanisms involved in the coordination of the cytoskeleton during locomotion have not been elucidated, one reason being because of the problems involved in fixing motile cells. In this paper we show that improved fixation of motile neutrophils with low concentrations of glutaraldehyde followed by glycine quenching demonstrated significant differences in the pattern of staining with TRITC-phalloidin in neutrophils moving on different substrata. Previous film analysis had shown the basic features of locomotion to be similar on all substrata.
A prominent feature of leucocyte locomotion on two-dimensional substrata (e.g. protein-coated glass), on three-dimensional collagen gels or inmotile cells floating in suspension, is the wave of contraction that passes antero-posteriorly along the length of the cell. The organization of the cytoskeletal elements has not been demonstrated at contraction waves, but light fixation with glutaraldehyde followed by staining with TRITC-phalloidin demonstrated prominent bands of Factin in neutrophils inside collagen gels. These bands were not present in neutrophils either in suspension or moving on a two-dimensional substratum.
Although all motile neutrophils had brightly stained anterior lamellipodia, the cells moving on the two-dimensional substratum had very extensively ruffled leading lamellae stained very brightly with TRITC-phalloidin.
The reasons for the absence of consistent bands of F-actin at contraction waves are discussed.
Contact behaviour during the reassociation of dissociated epithelial cells in primary culture
Authors: Brown R. M. , Middleton C. A. 
Published: April 2021

ABSTRACT
The behaviour in culture of dissociated epithelial cells from chick embryo pigmented retina epithelium (PRE), corneal epithelium (CE) and epidermis has been studied using time-lapse cinematography. The analysis concentrated on the contact behaviour of 60 previously isolated cells of each type during a 24h period starting 3–5 h after the cells were plated out.
During the period analysed the number of isolated cells in cultures of all three types gradually decreased as they became incorporated into islands and sheets of cells. However, there were significant differences in behaviour between the cell types during the establishment of these sheets and islands. In PRE cell cultures, islands of cells developed because, throughout the period of analysis, collisions involving previously isolated cells almost invariably resulted in the development of a stable contact. Once having established contact with another cell these cells rarely broke away again to become reisolated. In contrast the contacts formed between colliding CE and epidermal cells were, at least initially, much less stable and cells of both these types were frequently seen to break away and become reisolated after colliding with other cells. Sheets and islands of cells eventually developed in these cultures because the frequency with which isolated cells become reisolated decreased with increasing time in culture.
The possible reasons underlying the different behaviour of PRE cells, when compared with that of CE and epidermal cells, are discussed. It is suggested that the decreasing tendency of isolated CE and epidermal cells to become reisolated may be related to the formation of desmosomes.
The cell cycle and its relationship to development in Acanthamoeba Castellanii
Authors: Stöhr Michael , Bommert Kurt , Schulze Ingrid , Jantzen Helga 
Published: April 2021

ABSTRACT
The cell cycle and the relationship between particular cell cycle phases and the differentiation of trophozoites into cysts were reinvestigated in Acanthamoeba castellanii using flow fluorometric measurements of nuclear DNA content and synthesis, and synchronization of cells by release from the stationary phase. The investigation was performed with cultures growing in non-defined medium (ND cells) showing a high degree of encystation in response to starvation, and with subcultures growing in chemically defined nutrient medium (D cells) exhibiting a very low encystation competence. In both cultures the cell cycle starts with a short S phase taking place simultaneously with cytokinesis, followed by a long G2 phase. A G1 phase seems to be either absent or very short. Synchronization experiments reveal that in ND cells encystation is initiated from a particular position of late G2. The high encystation competence of stationary phase ND cells seems to be due to arrest of cells at this particular cell cycle position. The lack of encystation competence of stationary phase D cells correlates with the loss of accumulation of cells at this particular stage of the cell cycle. This change of the property of cells is related to the growth condition and not to an irreversible loss of encystation competence of D cells.
Taxol-induced structures derived from cytoskeletal elements of the Nicotiana pollen tube
Authors: Tiezzi A. , Moscatelli A. , Milanesi C. , Ciampolini F. , Cresti M. 
Published: April 2021

ABSTRACT
Nicotians pollen tube extracts were treated with 20 μM-taxol and structures derived from the cytoskeleton were collected and observed in the electron microscope. We have identified three different groups of elements with characteristic size and morphology: wide filaments (WF) probably formed by assembled microtubules, thin filaments (TF) interacting with WF and debrislike material principally associated with TF. SDS-PAGE and Western blot analysis provide some preliminary evidence of the biochemical composition of the taxol-induced structures.