bluuebunny/crossref_metadata_2025_split huggingface dataset:
Growth in cell length in the fission yeast Schizosaccharomyces pombe
Authors: Mitchison J. M. , Nurse P. 
Published: April 2021

ABSTRACT
The cylindrical cells of Schizosaccharomyces pombe grow in length by extension at the ends and not the middle. At the beginning of the cell cycle, growth is restricted to the ‘old end’, which existed in the prev10us cycle. Later on, the ‘new end’, formed from the septum, starts to grow at a point in the cycle that we have called NETO (‘new end take-off’). Fluorescence microscopy on cells stained with Calcofluor has been used to study NETO in size mutants, in blocked cdc mutants and with different growth temperatures and media. In wild-type cells (strain 972) NETO happens at 0·34 of the cycle with a cell length of 9·5μm. With size mutants that are smaller at division, NETO takes place at the same size (9·0–9·5 μm) but this is not achieved until later in the cycle. Another control operates in larger size mutants since NETO occurs at the same stage of the cycle (about 0·32) as in wild type but at a larger cell size. This control is probably a requirement to have completed an event in early G2, since most cdc mutant cells blocked before this point in the cycle do not show NETO whereas most of those blocked in late G2 do show it. We conclude that NETO only happens if: (1) the cell length is greater than a critical value of 9·0–9·5μm; and (2) the cell has traversed the first 0·3–0·35 of the cycle and passed early G2.
NETO is delayed in poor media, in which cell size is also reduced. Temperature has little effect on NETO under steady-state conditions, but there is a transient delay for some hours after a temperature shift. NETO is later in another wild-type strain, 132.
Time-lapse photomicrography was used to follow the rates of length growth in single cells. Wildtype cells showed two linear segments during the first 75% of the cycle. There was a rate-change point (RCP), coincident with NETO, where the rate of total length extension increased by 35%. This increase was not due simply to the start of new-end growth, since old-end growth slowed down in some cells at the RCP. Cdc11.123 is a mutant in which septation and division is blocked at 35 °C but nuclear division continues. The constant-length stage, which occupies the last 25% of the cycle in wild-type cells, also occurs in this mutant at 35°C, so end growth stops and restarts even though there is no septation. In cdc2.33, a mitotic mutant, there is a linear pattern with an RCP in cells held at 35 °C. The RCP is therefore a per10dic event that can take place even though the DNA division cycle is blocked.
Pollen-wall proteins: Electron-microscopiclocalization of acid phosphatase in the intine of Crocus vernus
Authors: Knox R.B. , Heslop-Harrison J. 
Published: April 2021

ABSTRACT
Acid phosphatase has been localized in the wall of the pollen grain of Crocus vernus Wulf at the electron-microscope level by a method using 2-naphthyl thiol phosphate as substrate in a simultaneous coupling reaction with fast blue BBN at pH 50, the product being given electron opacity by osmication.
Activity was found to be concentrated mainly in the intine, and to be associated with ribbon-like or filamentous inclusions believed to be proteinaceous on the basis of other criteria. Some activity was also detectable in the interstices of the exine. The observations confirm the general interpretation of the distribution of wall-held enzyme based upon light-microscopic cytochemistry, and provide the resolution necessary to establish unambiguously that they are associated with protein layers inserted during intine growth.
Mitosis in the fission yeast Schizosaccharomyces pombe as revealed by freeze-substitution electron microscopy
Authors: Tanaka Kenji , Kanbe Toshio 
Published: April 2021

ABSTRACT
Nuclear division in Schizosaccharomyces pombe has been studied in transmission electron micrographs of sections of cells fixed by a method of freeze-substitution. We have found cytoplasmic microtubules in the vicinity of the spindle pole bodies and two kinds of microtubules, short discontinuous ones and long, parallel ones in the intranuclear mitotic spindle. For most of the time taken by nuclear division the spindle pole bodies face each other squarely across the nuclear space but early in mitosis they briefly appear twisted out of alignment with each other, thereby imparting a sigmoidal shape to the bundle of spindle microtubules extending between them. This configuration is interpreted as indicating active participation of the spindle in the initial elongation of the dividing nucleus. It is proposed that mitosis is accompanied by the shortening of chromosomal microtubules simultaneously with the elongation of the central pole-to-pole bundle of microtubules of the intranuclear spindle. Daughter nuclei are separated by the sliding apart of interdigitating microtubules of the spindle at telophase. Some of the latter bear dense knobs at their ends.
Monensin and tunicamycin-induced inhibition of HT29 cell spreading and growth
Authors: El-Battari A. , Muller J. M. , Fantini J. , Bellot F. , Tirard A. , Ducret F. , Marvaldi J. 
Published: April 2021

ABSTRACT
HT29 cells originating from a human colon adenocarcinoma, spread very rapidly after seeding on their own extracellular matrix (ECM). Preincubation of cells with the inhibitor of protein glycosylation tunicamycin (TM) or with the ionophore monensin substantially suppressed cell spreading in serum-free medium without affecting cell adhesion to ECM. Addition of the drugs after cell attachment and spreading inhibited cell growth. TM-treated cells remained viable after 6 days of exposure to 2μgml−1 ′ of TM and resumed their normal growth rate and shape after removing the drug from the medium. On the contrary, monensin inhibition of cell growth was not reversible: after 3 days, cells detached from the ECM and were unable to exclude Trypan Blue. At the ultrastructural level, a swollen Golgi apparatus with numerous vacuoles was observed after treatment for 2h in either TM or monensin-preincubated cells. These results suggest that TM and monensin interfere with the insertion and, or, function of one or more cell surface glycoproteins, possibly interacting with cytoskeleton and involved in cell spreading and growth.
Calcium-transport function of the chick embryonic chorioallantoic membrane : I. in vivo and in vitro characterization
Authors: Tuan Rocky S. , Carson Monica J. , Jozefiak Judith A. , Knowles Kathy A. , Shotwell Barbara A. 
Published: April 2021

ABSTRACT
During chick embryonic development, the chorioallantoic membrane (CAM) is responsible for the mobilization of shell calcium into the embryonic circulation. The calcium-transport function of the CAM was studied here by measuring CAM calcium uptake in vivo and in vitro. The in vivo technique involved the use of an uptake chamber constructed on top of the CAM in situ. The in vitro methods included two systems: CAM tissue disks and cell-free microsomal membranes isolated from the CAM. Analyses using these three assays show that calcium uptake by the CAM exhibited characteristics indicative of active transport, such as temperature dependence, satura-bility, energetic requirement and ion specificity. The data also show that calcium-uptake activities of the CAM increase as a function of embryonic age in a manner coincident with the increased accumulation of calcium by the developing embryo in ovo.
Calcium-transport function of the chick embryonic chorioallantoic membrane ii. functional involvement of calcium-binding protein, Ca2+ -atpase and carbonic anhydrase
Authors: Tuan Rocky S. , Carson Monica J. , Jozefiak Judith A. , Knowles Kathy A. , Shotwell Barbara A. 
Published: April 2021

ABSTRACT
This study aimed to investigate the mechanism of active calcium transport in the chick embryonic chorioallantoic membrane (CAM) by assessing the functional involvement of three previously identified, putative components of the transport pathway. These components are a calcium-binding protein (CaBP), Ca2+-activated ATPase and carbonic anhydrase. Using specific reagents, including antibodies and enzyme inhibitors in vivo and in vitro in CAM calcium uptake assays, it was shown that these biochemically identified components were all functionally involved. The results of these studies also indicate that active calcium uptake by the CAM requires the presence of the CaBP on the cell surface in a laterally mobile manner, while carbonic anhydrase appeared to be a cytosolic component. We further analysed the subcellular location of the calcium-uptake activity by gel filtration and density-gradient fractionation of cell-free microsomes of the CAM and the results suggest that this activity is associated with the plasma membrane.
Spontaneous and induced dome formation by two clonal cell populations derived from a human adenocarcinoma cell line, ht29
Authors: Fantini J. , Abadie B. , Tirard A. , Remy L. , Ripert J. P. , Battari A. El , Marvaldi J. 
Published: April 2021

ABSTRACT
The replacement of glucose by galactose in the culture medium resulted in partial structural and functional enterocytic differentiation of HT29 cells. In order to characterize populations of homogeneously differentiated HT29 cells we have selected two clonal cell lines HT29-D4 and HT29-D9 with the following functional and structural characteristics when grown in a galactose-containing medium: (1) the two clonal cell populations were permanently morphologically differentiated as shown by the presence of mature junctional complexes and a well-organized brush border (especially for HT29-D4 cells); (2) HT29-D4 and HT29-D9 cells were able to form domes early in confluency, which indicated a functional state of differentiation; (3) the process of differentiation was fully reversible when glucose was added to the culture medium.
The induction of domes was investigated in these two cell populations and we demonstrated for the first time that proteolytic enzymes are potent inducers of dome formation. The architecture of domes either obtained spontaneously or induced by proteolytic enzymes was not maintained in the presence of ouabain (a specific inhibitor of the Na+/K+-ATPase).
In conclusion, HT29-D4 and HT29-D9 cells can be maintained permanently in a differentiated state in a glucose-free medium and were able to form domes at confluency. The observation that proteolytic enzymes were able to induce dome formation can help in the comprehension of the mechanism involved in the establishment of the differentiated state.
Alignment of fibroblasts on grooved surfaces described by a simple geometric transformation
Authors: Dunn G. A. , Brown A. F. 
Published: April 2021

ABSTRACT
The response of chick heart fibroblasts to grooved substrata was studied using microfabricated grooves and new measures of shape and alignment derived from the moments of cell shapes. Cell shape and alignment were measured on 23 different sets of regular, parallel grooves, which ranged in width from 1·65 to 8·96μm, and in repeat spacing from 3·0 to 32·0 μm. The grooves were of constant depth, 0·69 μ. Digitized video images were analysed to extract the zero-, first- and second-order moments of the cell shapes, from which were calculated three measures of cell shape, and three measures of cell alignment.
Regression analyses of the measures against parameters of the substratum such as groove width, repeat spacing and the ridge width between grooves show that ridge width is the main parameter affecting cell alignment (alignment being inversely proportional to ridge width), although groove width has a small additional effect. All the differences in cell shape between the different grooves can be summarized to a very good approximation as simple geometrical stretch transformations of the shapes of cells on planar surfaces. Our principal measure of cell alignment, paraxial elongation, is a measure of the necessary transformation. This finding has the interesting biological implication that the shape and orientation adopted by cells, in response to the grooves, are not governed by independent cellular mechanisms.
Intermediate filament proteins in classic and variant types of small cell lung carcinoma cell lines: A biochemical and immunochemical analysis using a panel of monoclonal and polyclonal antibodies
Authors: Broers J. L. V. , Carney D. N. , Rot M. Klein , Schaart G. , Lane E. B. , Vooijs G. P. , Ramaekers F. C. S. 
Published: April 2021

ABSTRACT
The intermediate filament protein (IFP) characteristics of a panel of lung cancer cell lines including adenocarcinoma (two cell lines) and small cell lung cancer (SCLC, three classic and three variant cell lines) were examined using one- and two-dimensional gel electrophoretic techniques, immunocytochemical techniques and immunoblotting assays. A panel of 28 monoclonal and polyclonal antibodies to the five different types of IFP were used. The results of our studies indicate that these human lung adenocarcinoma, classic SCLC and variant SCLC cell lines can be differentiated on the basis of their pattern of IFP.
The main conclusions from this study can be summarized as follows. (1) The two adenocarcinoma cell lines contain cytokeratins 7, 8, 18, and sometimes 19, next to vimentin intermediate filament (IF). (2) The three classic-type SCLC cell lines contain only cytokeratin IFs but not vimentin IF or neurofilaments (NFs). Cytokeratin polypeptides 7, 8, 18 and 19 could be detected. (3) All three variant-type SCLC cell lines do not contain detectable amounts of cytokeratins. In contrast, two out of three variant SCLC cell lines contain neurofilament proteins. All three varianttype SCLC cell lines contain vimentin IF. (4) Using immunoblotting assays with monoclonal and polyclonal antibodies to defined NF proteins the presence of the 68×103Mr and the 160×103Mr NF polypeptide could be demonstrated in two variant SCLC cell lines.
As patients with SCLC-variant phenotype have a poorer prognosis after cytotoxic therapy than patients with‘pure’ SCLC, the use of antibodies to IFP in staining fresh lung tumours, especially anaplastic ones, may differentiate the two subtypes of SCLC. Such a distinction would have a major impact on therapy selections and may be of prognostic importance.
Development of a three-dimensional extracellular matrix synthesized by human diploid fibroblasts in vitro
Authors: Qwarnström Eva E. , Page Roy C. 
Published: April 2021

ABSTRACT
Development and maturation of an extracellular matrix, synthesized by human gingival fibroblasts, have been studied microscopically. Pairs of demineralized, fibronectin-coated slices of human tooth root, 300 μm thick, were placed on confluent cell layers, defining a 0·5 mm wide space. The cultures were grown under standard conditions with ascorbic acid (50μgml−1) added daily. At various times up to 13 weeks, the cultures were fixed and the samples prepared for light and electron microscopy.
Cells from the monolayer became attached to, and migrated up, the vertical root surface and, during the time studied, completely filled the space between the root slices with an extracellular matrix. A close association was seen between the cell membrane and collagen fibres in the demineralized surface initially. A thin layer of fibrillar material was deposited between the cell and the vertical surface, and eventually an extracellular matrix surrounding the cells and attaching to the root surface was present. Samples fixed in the presence of Ruthenium Red showed intense staining of the fibrillar material, indicating the presence of anionic molecules. Additional cells migrated onto the newly synthesized matrix and up the root surface. Growth of the fibrillar networks on either side, horizontally and vertically, continued and, eventually, an extracellular matrix attaching to the vertical surfaces completely filled the previously empty space. Immunocytochemical staining showed that the matrix contained hyaluronic acid, chondroitin sulphate, dermatan sulphate and fibronectin at this time. Collagen fibres were observed at 6 weeks, and at later times collagen types I, III and V were the primary matrix components.
The fibroblasts attaching to the root slice and those present at the edge of the matrix had an elongated, polar form. The cells within the matrix frequently showed a stellate appearance with numerous extended processes, in contact with fibrillar material or collagen fibres. Fibroblast processes were at later times seen to enclose bundles of collagen fibres and to mediate cell-to-cell contact, occasionally via desmosome-like structures.
The structure and composition of the matrix and the appearance and apparent behaviour of the cells were similar to that observed in the healing wound. This system thus could provide a model for studying various aspects of regeneration of extracellular matrix.
Intra- and extracellular distribution of an endogenous lectin during erythropoiesis
Authors: Harrison F. Lynne , Catt James W. 
Published: April 2021

ABSTRACT
An endogenous β-galactoside-specific lectin has previously been isolated from rabbit bone marrow. The quantification of extracted lectin now indicates that approximately 75% of the lectin is intracellular in marrow. Indirect immunofluorescence studies show the extracellular lectin is associated with the erythroblast cell surface and is also found in some acellular areas of the marrow stroma. At enucleation, lectin surrounds the extruded nucleus while some residual lectin is observed in the cytoplasm of circulating reticulocytes and erythrocytes.
Structurally related Bacillus thuringiensis δ-endotoxins display major differences in insecticidal activity in vivo and in vitro
Authors: Knowles Barbara H. , Francis Philippa H. , Ellar David J. 
Published: April 2021

ABSTRACT
Many strains within the 22 serotypes of Bacillus thuringiensis produce crystal δ-endotoxins with slight differences in their insecticidal toxicity spectrum in vivo. Since the basis of this specificity is unknown, we chose to compare the activity of δ-endotoxins from three strains: B. thuringiensis var. kurstaki HD-1, var. aizawai HD-249 and var. thuringiensis HD-350, both in vivo and on insect cell lines in vitro. Immunoblotting with antisera to activated var. kurstaki Pl lepidopteran toxin revealed antigenic cross-reaction with the 130×103Mr toxin of var. aizawai, and with polypeptides of 130 and 138(×103)Mr from var. thuringiensis. In addition, crystals from var. kurstaki and var. aizawai contained an antigenically related 63xlO3Afr protein that did not cross-react with antisera to the 130× 103Mr component.
Bioassays on Pieris brassicae larvae (Lepidoptera) and Aedes aegypti larvae (Diptera) indicated that the 130×103Mr protein of var. kurstaki, and the 138 plus 130(×103)Mr components of var. thuringiensis killed only P. brassicae, while the 130×103.Mr protein of var. aizawai and the 63×103Mr proteins of var. aizawai and var. kurstaki were toxic to both P. brassicae and A. aegypti.
Activation of the 130 and 138 (×103)Mr proteins of the three varieties of B. thuringiensis with insect gut proteases yielded active products of 50— 60 (× 103)Mr. Assay of these products on a range of lepidopteran and dipteran cell lines revealed very different toxicity spectra: var. kurstaki killed only one lepidopteran line, var. thuringiensis killed two lepidopteran lines, while var. aizawai was cytolytic to all of the lepidopteran and most of the dipteran cell lines tested, reflecting its broader spectrum in vivo.
Thus we have shown that antigenic cross-reaction of B. thuringiensis δ-endotoxins does not necessarily imply a similar toxicity spectrum in vivo or in vitro.
Microinjection of immaturin rejuvenates sexual activity of old Paramecium
Authors: Haga Nobuyuki , Karino Setsuko 
Published: April 2021

ABSTRACT
The sexual activity of aged Paramecium that underwent about 700 fissions after conjugation was remarkably decreased. Microinjection of a soluble cytoplasmic fraction prepared from young immature cells (about 20 fissions after conjugation) restored the sexual activity of the aged cells to that of presenescent mature cells. The factor responsible for the recovery of the sexual activity’ was shown to have the same characteristics as immaturin in terms of molecular size and net charge. Rejuvenation of sexual activity lasted up to 20 fissions after microinjection. However, cell division rate or fertility after self-conjugation was not increased by the microinjection. Our finding indicates that the decrease in sexual activity caused by aging was not due to defects in the genes for mating substances but to a decrease in the activity of a soluble protein responsible for the expression of mating activity. This is the first description of the restoration of a senescent defect by microinjection of young cytoplasmic components into Paramecium.
The mobility of intramembrane particles in non-haemolysed human erythrocytes: Factors affecting acridine-orange-induced particle aggregation
Authors: Lelkes Gábor , Fodor Ildikó , Lelkes György , Hollán Susan R. 
Published: April 2021

ABSTRACT
It has previously been shown that reversible intramembrane particle aggregation can be induced in non-haemolysed human erythrocytes. This phenomenon, which can be induced by the cationic dye Acridine Orange, has been further investigated using different experimental conditions that are expected to influence the rate of aggregation of the particles.
In addition to the concentration of the dye, the rate of aggregation was also found to be dependent on the extracellular and intracellular pH, as well as on the type of buffer used. While lowering the pH of the Acridine Orange solutions resulted in decreased particle clustering, low intracellular pH increased and elevated intracellular pH decreased particle aggregation. Furthermore, at a given dye concentration and a given pH, Acridine Orange caused more intense aggregation in Tris-buffered saline than in isotonic phosphate buffer or phosphate-buffered saline. Under appropriate conditions Acridine Orange caused significant particle aggregation at concentrations as low as 0·25 mH within 30 s. During this period only discocyte-stomatocyte transformation occurred; neither agglutination nor vésiculation of the erythrocytes could be detected.
Treatment of the erythrocytes with Diamide (Serva), which cross-links spectrin via disulphide bridges and thereby reduces lateral diffusion of integral membrane proteins over large distances, had no inhibitory effect on Acridine-Orange-induced particle aggregation. Heating the erythrocytes to 50 °C, at which temperature denaturation of spectrin and fragmentation of the erythrocytes occur, and subsequently incubating them in Acridine Orange at room temperature, caused an almost maximal rate of particle aggregation within 10—30 s, without haemolysis.
The possible mechanism and significance of the particle aggregation phenomenon are discussed.
Substrate hydroxylation and cell adhesion
Authors: Curtis A. S. G. , Forrester J. V. , Clark P. 
Published: April 2021

ABSTRACT
Adhesion of BHK cells to a variety of polymer surfaces carrying measured densities of hydroxyl and carboxyl groups was studied. The effects on cell adhesion of blocking hydroxyl groups by acetylation and carboxyl groups with diazomethane were measured. Hydroxyl groups were required for cell adhesion, though the very high surface densities of these groups diminished cell adhesion. The optimal surface density of OH groups for BHK adhesion was 2000 per 1× 10−11 cm2. Carboxyl groups slightly inhibit cell adhesion, since blocking of these groups by methylation increased adhesion. The role of oxidizing systems of cellular origin in conditioning of the substrate, in serum-free conditions, was demonstrated for leucocytes and BHK cells, in particular by the result that oxidizable substrates such as phytane and poly(l,2-butadiene) could be made suitable for cell adhesion by contact with cells.