bluuebunny/crossref_metadata_2025_split huggingface dataset:
Organization of actin cytoskeleton during early endothelial regeneration in vitro
Authors: Gabbiani Giulio , Gabbiani Françoise , Heimark Ronald L. , Schwartz Stephen M. 
Published: April 2021

ABSTRACT
The pattern of early cell movement after an experimental ‘wound’ and the organization of actin in stationary and moving cultured endothelial cells have been studied by means of: (1) time-lapse photography; (2) indirect immunofluorescence using anti-actin antibodies with and without pretreatment with the actin destabilizing factor present in human plasma; and (3) differential centrifugation and densitometric analysis of stained sodium dodecylsulphate/polyacrylamide gels in order to evaluate the total and relative amounts of G and F-actin. Up to 5 h after a single scratch, movement consists of a coordinate spreading and translocation of a band of about 10 cells from the wound edge. Compared to stationary cells, moving endothelial cells show: (1) no significant changes in the intensity and distribution of immunofluorescent staining with anti-actin antibodies, but an increased sensitivity of cytoplasmic actin, including stress fibres, to the actin-destabilizing factor purified from human plasma; and (2) no significant change in the total amount of actin, but a decreased relative amount of F-actin and a corresponding increased relative amount of G-actin. We conclude that endothelial cell movement in vitro is accompanied by a rapid change in the state of actin organization characterized by an overall decrease in cytoplasmic F-actin.
Three-Dimensional Geometry Of Motile Hamster Spermatozoa
Authors: Woolley D. M. , Osborn I. W. 
Published: April 2021

ABSTRACT
Micrographs were made of free-swimming hamster spermatozoa using a high intensity xenon flash and two-colour darkground illumination - conditions that permit three-dimensional reconstruction of the instantaneous shape of the flagellum. From the waveforms observed, we constructed an account of the three-dimensional kinematics of this flagellum. We found that near-planar bends grew on the proximal 25% of the flagellum to reach a mean angle of 1·7 rad. Principal bends achieved a greater angle than reverse bends. As bends propagated they maintained their near-planarity and their angle, but decreased in radius of curvature. However, the plane of the more distal bends tended to become displaced, as though a predominantly clockwise torsion of the axoneme was developing in the interbend segment. This gave rise to a complex shape resembling a sinistral helix of reducing pitch and eccentricity. There are clear indications that not all cycles of bending lead to the same degree of three-dimensionality.
Organization Of Extracellular Matrix By Chick Embryonic Corneal Epithelial Cells In Culture And The Role Of Fibronectin In Adhesion
Authors: Mattey D. L. , Garrod D. R. 
Published: April 2021

ABSTRACT
Corneal epithelial cells from IS-day chick embryos produce an extensive extracellular matrix when cultured for up to 7 days on plastic, glass, and gelatin-coated substrata. lmmunofluorescence studies revealed the presence of a fibrillar fibronectin matrix that became more extensive with time in culture. When cells were cultured in fibronectin-depleted medium little or no fibronectin was evident in the first 24 h, although the cells attached and spread normally when compared with controls. Considerably more fibronectin was associated with the cells after 48 h. Incubation of cells with [35S]methionine, followed by immunoprecipitation of cell extracts by specific anti-fibronectin antibody, confirmed that the cells synthesize fibronectin.
Cells cultured in fibronectin-coated substrata were able to reorganize the fibronectin into fibrillar form as well as to endocytose fibronectin. It is suggested that cells ‘comb’ fibronectin from the substratum and organize it into fibrils.
Interference reflection microscopy revealed no simple correlation between the distribution of fibronectin and focal contacts. However, some focal contacts seemed to lack fibronectin. In the presence of anti-fibronectin immunoglobulin G cells initially attached but failed to spread, and subsequently detached from glass and fibronectin-coated substrata. However, they attached and spread on collagen substrata. The results suggest that fibronectin is unnecessary for initial cell attachment but may be important in maintaining cell adhesion and spreading on certain substrata. However, it is not necessary for attachment and spreading on collagen. Cells on collagen may attach and spread directly on the substratum via specific collagen receptors or by using some other type of attachment factor(s).
Electron microscopy revealed a densely staining fibrillar matrix between the basal cell layer and substratum as well as in the intercellular spaces between cells. Components of this matrix and the cell surface were strongly stained by ruthenium red, which indicates the presence of acidic groups such as glycosaminoglycans.
Sperm chemotaxis in siphonophores: II. calcium-dependent asymmetrical movement of spermatozoa induced by the attractant
Authors: Cosson Marie Paule , Carré Danièle , Cosson Jacky 
Published: April 2021

ABSTRACT
Spermatozoa from siphonophores have been shown to be attracted towards an extracellular structure, the cupule, which covers the predetermined site of fertilization of the egg.
Observations on sperm behaviour during the chemotactic response show that spermatozoa describe trajectories of large diameter (700-1000 µm) while far from the cupule, and of smaller diameter (200µm) in the cupule area. The transition between the two types of swimming occurs progressively when spermatozoa cross a 3 mm wide area around the cupule. After a few minutes 99 % of the spermatozoa keep swimming around the attractant source, following circular paths 150-200 µm in diameter.
In the absence of the attractant, comparable modifications of sperm trajectories are observed in the presence of the ionophore A23187 and high calcium concentrations. In the presence of 10−2M calcium ions, A23187-treated spermatozoa describe trajectories 200 µm in diameter, which increase up to 800 µm at lower calcium concentrations (10−6M).
In the absence of calcium ions, spermatozoa swim across the cupule area without modification of their trajectories and no sperm accumulation can be detected. This requirement of the chemotactic response for calcium ions is observed either with fresh cupules stuck on the eggs, with cupules separated from the eggs, or with cupule extracts. Moreover, a soluble component fractionated from the cupule induces, when diluted in sea water, a reduction in the size of the sperm trajectories and this also requires calcium ions.
The present data show that the chemotactic response of siphonophore sperm, which requires millimolar concentrations of calcium ions, occurs through a non-transient induction of increased asymmetry of the flagellar waveform. It is proposed that the natural attractant operates to produce an increase in the intraaxonemal calcium concentration.
Appearance of specific antigenic proteins in the maturing sexual organs of Sinapis flowers
Authors: Jacqmard A. , Lyndon R. F. , Salmon J. 
Published: April 2021

ABSTRACT
Three proteins specific to the flowering state were found in Sinapis by immunological techniques. Two of these are specific to the stamen and one to the pistil. By the use of a histoimmunofluorescence technique their localization in the developing flower primordia and in the apex was examined during the transition to flowering. These proteins are not detected in the apex at evocation. They all appear at a relatively late stage of stamen or pistil maturation. The stamen proteins are localized in both the intine and exine layers of pollen grains in stamens 2-3 mm long; at anthesis they are essentially in the exine. The pistil protein is found in the stigma and in the transmitting tissue of the style. All these proteins contain sugar residues. A possible implication of these proteins in the process of male-female recognition is discussed.
Control of cellular differentiation by temperature in the cellular slime mould Dictyostelium discoideum
Authors: Maeda Mineko 
Published: April 2021

ABSTRACT
The effects of low temperature on morphogenesis and cellular differentiation of Dictyostelium discoideum were examined. During incubation at 5 °C, the vegetative and preaggregation cells never developed, but cell masses at the aggregation or slug stage developed to form hemispherical, or dumbbell-shaped multicellular structures. By staining with FITC-antispore IgG, the structures formed after 10 days of incubation of tipped aggregates at 5 °C were found to be composed of 90% spores, 5% prespore cells and 5% non-stained cells. Since only 20% of the total cells constituting the tipped aggregate had been prespore cells at the beginning of incubation, this showed that spore differentiation proceeded even at low temperature, while stalk differentiation was completely inhibited. Similar results were obtained when the cells were incubated at 3 °C. However, at 0°C, morphogenesis and cellular differentiation did not occur, although most of the prespore cells at the late culmination stage differentiated incompletely into spores. Possible reasons for the high proportion of spores being induced by low temperature are discussed.
Mechanical stretching increases the number of epithelial cells synthesizing dna in culture
Authors: Brunette D. M. 
Published: April 2021

ABSTRACT
The influence of mechanical stretching on epithelial (E) cells was examined by culturing E cells derived from the epithelial cell rests of Malassez on a flexible plastic substrate and stretching the substrate by means of an orthodontic screw. A significant increase in the number of E cells synthesizing DNA was observed after just 30 min of stretching. In 17 experiments the ratio of cells labelled with tritiated thymidine in cultures stretched for 2h to the number of labelled cells in unstretched controls was 1·92 ± 0·34. An increase in labelling as a result of stretching was found for E cells cultured at either high or low cell-population densities but the effect was most pronounced for E cells cultured at higher concentrations of foetal bovine serum. Morphometric analysis of electron micrographs of stretched and unstretched cultures indicated that the stretched cultures had a higher volume fraction of filamentous structures and more desmosomes per unit length of cell membrane than unstretched cultures. The behaviour of E cells in response to stretching in vitro appears to be similar to the response of the epithelial rests in vivo when the latter are exposed to tension as a result of forces produced by orthodontic techniques.
Macromolecular glucosamine-containing component of the surface of cultivated mouse cells
Authors: Onodera K. , Sheinin Rose 
Published: April 2021

ABSTRACT
It has been demonstrated that a glucosamine-containing macromolecular component of the cell surface of 3T3 mouse cells, and SV4O-transformed cells, is released from cells by treatment with trypsin under conditions in which the plasma membrane remains functionally intact. This was shown by the fact that the treated cells could be cloned with high plating efficiency and remained impermeable to the vital stain, erythrocin. A method for specifically marking this surface component has been devised based on the finding that in 3T3 cells growing synchronously after subculture by trypsin maximum incorporation of glucosamine into this material occurs 12 − 13 h thereafter. Of the total radioactive glucosamine incorporated into macro molecular cell constituents, over 80 % was recovered in surface component.
Studies on the biosynthesis of surface component revealed that this was periodic during a cycle of cell duplication, with an increased rate of formation immediately after cell division. It was found that the surface component of 3T3 cells differed from that of SV40-transformed cells.
Control of flagellum number in naegleria : temperature shock induction of multiflagellate cells
Authors: Dingle A. D. 
Published: April 2021

ABSTRACT
This paper describes the production of supernumerary flagella by flagellates of Naegleria gniberi exposed to sublethal temperature shocks during the amoeba-to-flagellate transformation. When transformed at any constant temperature below 34°C, cells of N. gniberi strain NB-1 may develop from 1 to 4 flagella, but biflagellate cells predominate and the average number of flagella per cell in these populations is approximately 2 ·2. Populations exposed to a 38 °C temperature shock during transformation develop about twice as many flagella as controls (average number of flagella per cell is approximately 4·5). The individual response of cells is extremely heterogeneous: some develop no more than the normal 2 flagella, whereas others develop as many as 18. At least half the cells produce 5 or more flagella, as opposed to fewer than 1 % with 5 or more flagella in control populations. Multiflagellate cells and populations are normal in appearance, apart from the excess flagella and resulting disorientation of the normal swimming pattern. The supernumerary flagella, their basal bodies and the rhizoplast (which is also occasionally doubled) are indistinguishable from those of normal cells. Maximal production of flagella occurs over the narrow temperature range from 37 · 5 to 38 ·5 °C and is related to the duration of exposure to a given temperature: optimal flagellum induction is obtained following a 45 · 50 min exposure to a 38 · 2 °C temperature shock. After approximately 1 h the flagellates revert to amoebae, losing both normal and supernumerary flagella. Populations of these amoebae followed through 2 more cycles of retransformation and reversion developed the normal number of flagella (2 · 2). Clones isolated from multiflagellate populations were identical to normal populations, developing approximately 2 · 1 flagella per flagellate at normal temper atures and 4 ·5 flagella per flagellate when temperature shocked again.
The effect of 2-phenyl ethanol on the dna synthesis cycle of Schizosaccharomyces pombe
Authors: Bostock C. J. 
Published: April 2021

ABSTRACT
The effect of different concentrations of 2-phenyl ethanol (PE) on growth and DNA synthesis of Schizosaccharomyces pombe is described. 0·3 % PE inhibits the entry of cells into 5 phase, but allows a doubling in the number of cells in the culture. The effect of 0·2 % PE on random and synchronous cultures of S. pombe shows that, in the continued presence of the inhibitor, the S phase is moved to a different point in the cell cycle. Cells continue to grow in the presence of 0· 2 % PE with a G1 phase occupying a significant portion of the cell cycle. This differs from normal growth when the G1 phase is absent.
The competitive effects of serum proteins on cell adhesion
Authors: Curtis A. S. G. , Forrester J. V. 
Published: April 2021

ABSTRACT
Binding curves for the adsorption of plasma fibronectin, alpha-l-antitrypsin, alpha-2-macroglobulin, ceruloplasmin, transferrin and bovine serum albumin to plain and to hydroxylated polystyrene surfaces were measured. These curves were correlated with the adhesion of BHK cells and leucocytes to these adsorbed protein surfaces in protein-free culture media. Hydroxylated polystyrene adsorbed less of alpha-l-antitrypsin, alpha-2-macroglobulin and albumin than the plain polystyrene. On the other hand the hydroxylated surfaces bound more fibronectin than the plain polystyrene surfaces. Hydroxylated polystyrene surfaces were also more adhesive for both BHK cells and leucocytes than plain polystyrene: a result confirming earlier work. The competition of fibronectin for adsorption to plain polystyrene with alpha-l-antitrypsin, alpha-2-macroglobulin and ceruloplasmin was measured and correlated with effects on cell adhesion. The results suggest that the low adhesiveness of BHK cells and leucocytes on plain polystyrene in sera-containing media is due both to the low binding of fibronectin and to the binding of serum albumin, alpha-l-antitrypsin and alpha-2-macroglobulin. The relative unimportance of fibronectin in adhesion to these surfaces is shown by the finding that cell attachment will not occur to polystyrene surfaces that have bound high levels of the antiadhesive proteins in the presence of fibronectin, even though attachment will occur in the absence of fibronectin provided that the antiadhesive proteins are lacking.
An immunoelectron microscopic study on the distribution of a cell surface-associated adhesive glycoprotein synthesized by rat ascites hepatoma cells
Authors: Hattori Ryuichi , Ishimaru Yasuji , Kurano Ryoichi , Hayashi Hideo 
Published: April 2021

ABSTRACT
As previously described, a cell surface-associated adhesive factor (AF) was separated from differentiated rat ascites hepatoma AH136B cells (forming cell islands in vivo) and highly purified by chromatography. AF synthesis by the cells was investigated by means of ultrastructural immunoperoxidase cytochemistry. Its synthesis and localization in vivo were observed in the perinuclear spaces, the rough endoplasmic reticulum, the Golgi apparatus, the smooth-membranous vesicles, and the contact region of basolateral cell surfaces of the cells in the islands, and also in the intercellular spaces. No AF synthesis was detectable in the nucleus, the free ribosomes, the mitochondria or the apical non-contacting cell surfaces.
Similar features of AF synthesis and localization were also induced by dissociated AH136B cells in vitro. Upon adhesion of such recovered cells, AF was also localized at the contact surface of the adjacent cells, but not at the non-contacting free surface.
Incomplete contact site a glycoprotein in hl220, a modb mutant of Dictyostelium discoideum
Authors: Gerisch G. , Weinhart U. , Bertholdt G. , Claviez M. , Stadler J. 
Published: April 2021

ABSTRACT
HL220, a modB mutant that lacks a modification of certain membrane proteins of Dictyostelium discoideum, has been shown to aggregate and to form EDTA-stable intercellular contacts typical of aggregating wild-type cells. A developmentally regulated glycoprotein of 80×103 apparent molecular weight has been identified as a target site of adhesion-blocking Fab and thought to be involved in EDTA-stable cell contact formation (Müller & Gerisch, 1978). In the HL220 mutant this glycoprotein is no longer recognized by a modB-specific antibody. Therefore, it has been suggested that the 80×103Mr glycoprotein, or a modification on it, is not required for the EDTA-stable cell contact of aggregating cells.
We show that HL220 synthesizes an equivalent of the 80x lfPMr glycoprotein with an apparent molecular weight of 68×103. The mutant product reacted with certain monoclonal antibodies highly specific for the 80×103Mr glycoprotein in the wild type, and was developmentally regulated like the 80×103MT glycoprotein. These results indicate that the 68×103Mr protein of the mutant lacks a modification, most likely an oligosaccharide residue, the absence of which causes the substantial shift of the apparent molecular weight from 80×103 to 68×103. Monoclonal antibodies that did not react with proteins of the mutant could be classified according to their reactions with different sub-sets of wild-type proteins. These results indicate that the proteins that reacted with either one or the other antibody were not modified by a uniform structure. The modification rather varies from one sub-set of cross-reacting proteins to another,-suggesting differences between the glycosyl residues of the partially cross-reacting proteins.
HL220 cells showed strongly reduced EDTA-stable’contact formation under our conditions. EDTA-sensitive intercellular adhesion was undetectable in the mutant, whereas adhesion of the cells to the substratum appeared to be strengthened.The rear ends of the cells, in particular, were tightly attached to glass or Teflon surfaces.
The mutant cells were capable of responding chemotactically. Propagated excitation waves like those known to be based on periodic cyclic AMP production and relay were clearly seen. Extracellular phosphodiesterase induction by cyclic AMP and phosphodiesterase inhibitor production were normal. These results indicate that the generation of chemotactic signals and the cellular responses to cyclic AMP are not severely affected by the mutation.
Enzymic ribonucleoside reduction at the non-phosphorylated level in Acetabularia
Authors: Groot Egon J. De , Schweiger Hans-Georg 
Published: April 2021

ABSTRACT
The occurrence of an enzyme that catalyses the conversion of cytidine into deoxycytidine was demonstrated in homogenates of Acetabularia. Cytidine was identified as the substrate by comparing cytidine, cytidine 5’-monophosphate, cytidine S’-diphosphate and cytidine 5’-triphos-phate as potential substrates. Experiments with ATP analogues whose inhibitory effect on kinase reactions is well established, supplied evidence that the nucleoside is reduced without a phosphorylation step before the reduction. Further evidence in this line came from incubations with cytidine in the presence of phosphatase and from trap-type experiments in which the effects of excess non-labelled cytidine 5’-phosphate and deoxycytidine, respectively, on the formation of deoxycytidine phosphates from cytidine were studied.
A mutant of Chlamydomonas reinhardtii that lacks the flagellar outer dynein arm but can swim
Authors: Kamiya Ritsu , Okamoto Mitsumasa 
Published: April 2021

ABSTRACT
A new type of Chlamydomonas mutant, which lacks the outer dynein arm but can swim, was isolated. Sodium dodecyl sulphate/polyacrylamide gel electrophoresis showed that four of the ten high-molecular-weight bands of dynein present in the wild-type axoneme are missing or diminished in the mutant axoneme. The mutant has a swimming rate of about 35 μm/s and a flagellar beat frequency of about 25 Hz, both of which are about 1 /2·5 to 1 /3 of those of the wild type. The mutant flagella beat with an asymmetric, cilia-type pattern, similar to the forward-swimming mode of the flagellar beating pattern of the wild type. However, unlike wild-type flagella, the mutant flagella never beat with a symmetrical waveform: when the cells were stimulated by intense light, the mutant transiently stopped beating its flagella, whereas the wild-type cell transiently swam backwards with the two flagella beating with a symmetrical waveform.
Both wild-type and mutant cells could be demembranated by Nonidet P40 and their swimming reactivated by addition of Mg-ATP in the virtual absence of Ca2+. Double reciprocal plots of the beat frequency against ATP concentrations showed a linear relationship for both strains, yielding maximal frequencies of 44 Hz (wild type) and 23 Hz (mutant). The mutant axonemes can be reactivated only when the Ca2+ concentration is lower than 10-6 M: at pCa 4, the wild-type axonemes beat with a symmetrical waveform, but the mutant axonemes showed no movement. These findings indicate that the outer dynein arm is dispensable for flagellar beating of the asymmetric waveform (forward-swimming mode), but not for beating of the symmetrical waveform (backward-swimming mode), and thus suggest the importance of the outer dynein arm in the switching of flagellar waveforms.