bluuebunny/crossref_metadata_2025_split huggingface dataset:
Relative daughter cell volume and position of the division furrow in Tetrahymena
Authors: Hjelm K. K. 
Published: April 2021

ABSTRACT
The relative daughter cell volume (RDCV) values for Tetrahymena pyrifomtis were determined at division on live cells. It was found that the anterior cell is generally larger than the posterior cell, and that the RDCV values are distributed in groups 5–6% apart. The RDCV value was found to be independent of predivision cell volume, indicating that the mother cell is divided into proportional volumes. The cells seem, however, not to assess volume directly but rather a parameter related to the cell volume. Furthermore, the RDCV value was found to increase during cell division, so that the final value is not reached until actual separation of daughter cells.
It is suggested that the division furrow is positioned so that the area of the cell surface lying between the old oral apparatus and the posterior pole of the cell is divided into equal parts. It is further suggested that several alternative values of the RDCV are possible, only one of which is expressed in each cell. The early division furrow is placed anteriorly to its final position, and its location is adjusted during cytokinesis.
Participation Of Concanavalin A Binding Sites In The Interaction Between Trypanosoma Cruzi And Macrophages
Authors: Meirelles M. N. L. , Martinez-Palomo A. , Souto-Padron T. , Souza W. De 
Published: April 2021

ABSTRACT
Untreated mouse peritoneal macrophages as well as macrophages treated with concanavalin A (ConA) were incubated in the presence of untreated or ConA-treated epimastigotes and trypo-mastigotes of Trypanosoma cruzi. Treatment of epimastigotes or trypomastigotes with ConA increased or decreased their uptake by macrophages, respectively. Treatment of the macrophages with ConA reduced by 70 % and increased by five times the ingestion of epimastigotes and trypomastigotes, respectively. These results are discussed in relation to previous studies on the mobility of ConA receptors in the membrane of the parasite. Using fluorescein- or ferritin-labelled ConA we observed that ConA binding sites located on the plasma membrane of macrophages are internalized during endocytosis of T. cruzi, and observed in association with the membrane of the endocytic vacuole. Vacuoles without parasites showed a uniform distribution of ConA binding sites, while these sites were distributed in patches in vacuoles containing parasites. These results, in association with others previously reported, suggest the involvement of glycoproteins and/or glycolipids localized on the cell surface of T. cruzi and macrophages during the T. cruzi-macrophage interaction.
Surface Membrane Regeneration In Deciliated Tetrahymena
Authors: Williams Norman E. 
Published: April 2021

ABSTRACT
The induced synthesis of identified surface membrane proteins has been demonstrated in deciliated Tetrahymena. Cells in the process of regenerating cilia were also studied using transmission electron microscopy in order to obtain information on the deployment of new membrane at the cell surface. The results obtained suggest a pattern of membrane flow that includes the ‘pellicular alveoli’, a subsurface membrane system characteristically present in ciliated protozoa. The results of 125I surface-marking experiments were consistent with the notion that new membrane is added initially in non-ciliated regions, then subsequently flows laterally to cover regenerating cilia.
Syncytioskeletons in choriocarcinoma in culture
Authors: Ockleford C. D. , Dearden L. , Badley R. A. 
Published: April 2021

ABSTRACT
Indirect immunofluorescence microscopy using anti-actin serum has been used to investigate the distribution of actin-containing polymers in BeWo cells. This cell line, derived from a human choriocarcinoma, contains tissue that, like its tissue of origin, is partly syncytial. The syncytial nature has been inferred from study of Nomarski optical sections and from transmission electron microscopy.
The multinucleated plaques of tissue possess a syncytioskeleton with a number of actin-containing features characteristic of cultured cells. These include stress fibres, cortical layers and ruffled membranes. Other actin-containing structures are more typical of the related non-pathological syncytiotrophoblast. These include a dense population of microvilli.
The overall organization of the actin syncytioskeletons bears no obvious relationship to the number or position of nuclei in the syncytium.
Indirect immunofluorescence microscopy has also been employed to localize the protein tubulin in BeWo cells. The microtubules do not appear to be spatially organized by a particular nucleus. Rather, there are numerous microtubule-organizing centres (MTOCs) that exist in the cytoplasm and do not have the expected numerical and positional relationship to nuclei.
From these data it appears that polymeric cytoskeletal elements in these syncytia are organized in a manner not immediately subordinate to syncytial nuclei.
Hela cells form focal contacts that are not fibronectin dependent
Authors: Morgan Jean , Garrod David 
Published: April 2021

ABSTRACT
HeLa cells cultured on glass substrata produce numerous prominent focal contacts, which reside at the termini of actin microfilament bundles. However, very few of the cells stain for fibronectin with specific anti-fibronectin antibody. Moreover, the cells form focal contacts in fibronectin-depleted medium, in the presence of high concentrations of anti-fibronectin immunoglobulin G and in the presence of monensin. No fibronectin synthesis can be detected by [35 S]methionine-labelling and immunoprecipitation. The possibility that HeLa cell focal contacts are independent of fibronectin in their formation is discussed in relation to the controversy about the relationship between fibronectin and focal contacts.
Scintillation and autoradiographic studies on 63Nickel uptake inPseudomonas tabaci
Authors: Al-Rabaee R. H. , Sigee D. C. 
Published: April 2021

ABSTRACTScintillation studies on the uptake of 63Ni2+ by Pseudomonas tabaci demonstrate an incorporation of approximately 2·5 nmol per 1010 bacterial cells, in medium containing 12 nmol (8·3 μCi) per ml. Over 80% of the incorporated Ni2+ is lost from the cells during washing, fixation and dehydration with ethanol. The remaining insoluble (bound) 63Ni2+ has the highest level in cells fixed in acetic acid/ethanol (O·4 nmol/1010 cells), with smaller amounts in paraformaldehyde- and glutaraldehyde-fixed cells. The radioactive level in aldehyde-fixed cells represents a total Ni2+ uptake of about10−18g or 104 atoms per cell.Light- and electron-microscope autoradiography corroborated the scintillation studies in demonstrating a higher retention of label by cells fixed in acetic acid/ethanol, possibly reflecting a higher retention of medium Mτ proteins with this type of fixation. High-resolution electron-microscope autoradiography involving gold latenβification with physical development demonstrated a clear localization of silver grains to the central nucleoid region (seen most clearly over the discrete nucleoid of aldehyde-fixed cells) and within this to the chromatin (seen most clearly over the condensed chromatin of acetic acid/ethanol-fixed cells). It is suggested that the incorporated
Neuromuscular junctions in the body wall muscles of the earthworm, Lumbricus terrestris linn
Authors: Mill P. J. , Knapp M. F. 
Published: April 2021

ABSTRACT
The fine structure of the neuromuscular junctions in the body wall muscles of the earthworm 13 described. The segmental nerves send branches into the muscle layers. Axons in the nerve branches contain numerous synaptic vesicles and contact is established between these axons and muscle fibres or muscle tails; the latter may extend for a considerable distance from the muscle fibre. The cleft between the axolemma and sarcolemma is 85–120 nm wide and contains basement membrane material. At intervals small aggregations of electron-dense material are attached to the axonal membrane and synaptic vesicles are associated with these. The sarcolemma bears rather larger masses of dense material and is also specialized extracellularly.
The rapid intermixing of cell surface antigens after formation of mouse human heterokaryons
Authors: Frye L. D. , Edidin M. 
Published: April 2021

ABSTRACT
Cells from established tissue culture lines of mouse (CIID) and human (VA-2) origin were fused together with Sendai virus, producing heterokaryons bearing both mouse and human surface antigens which were then followed by the indirect fluorescent antibody method. Within 40 min following fusion, total mixing of both parental antigens occurred in over 90 % of the heterokaryons.
Mouse H-2 (histocompatibility) and human surface antigens were visualized by successive treatment of the heterokaryons with a mixture of mouse alloantiserum and rabbit anti-VA-2 antiserum, followed by a mixture of fluorescein-labelled goat anti-mouse IgG and tetramethyl- rhodamine-labelled goat anti-rabbit IgG(Fc).
The CIID × VA-2 fusions were carried out in suspension and maintained at 37°C in a shaking water bath; aliquots were removed at various intervals and stained with the above reagents. The heterokaryon population was observed to change from an initial one (5-min post-fusion) of non-mosaics (unmixed cell surfaces of red and green fluorescence) to one of over 90 % mosaics (total intermixing of the 2 fluorochromes) by 40 min after fusion. Mouse-human hybrid lines, derived from similar fusions, gave fluorescence patterns identical to those of the mosaic heterokaryons.
Four possible mechanisms would yield such results: (i) a very rapid metabolic turnover of the antigens; (ii) integration of units into the membrane from a cytoplasmic precursor pool; (iii) movement, or ‘diffusion ‘of antigen in the plane of the membrane; or (iv) movement of existing antigen from one membrane site into the cytoplasm and its emergence at a new position on the membrane.
In an effort to distinguish among these possibilities, the following inhibitor treatments were carried out: (1) both short- and long-term (6-h pre-treatment) inhibition of protein synthesis by puromycin, cycloheximide, and chloramphenicol; (2) short-term inhibition of ATP formation by dinitrophenol (DNP) and NaF; (3) short- and long-term inhibition of glutamine- dependent pathways with the glutamine analogue 6-diazo-5-oxonorleucine; and (4) general metabolic suppression by lowered temperature.
The only treatment found effective in preventing the mosaicism was lowered temperature, from which resulted a sigmoidal curve for per cent mosaics versus incubation temperature. These results would be consistent with mechanisms iii and/or iv but appear to rule out i and ii. From the speed with which the antigen markers can be seen to propagate across the cell membrane, and from the fact that the treatment of parent cells with a variety of metabolic inhibitors does not inhibit antigen spreading, it appears that the cell surface of heterokaryons is not a rigid structure, but is ‘fluid’ enough to allow free ‘diffusion’ of surface antigens resulting in their intermingling within minutes after the initiation of fusion.
Observations on the fine structure and development of the spindle at mitosis and meiosis in a marine centric diatom (Lithodesmium undulatum): IV. the second meiotic division and conclusion
Authors: Manton Irene , Kowallik K. , Stosch H. A. Von 
Published: April 2021

ABSTRACT
The second meiotic division is shown to be of critical importance for interpretation of structures and events already seen at other divisions. The development of flagellar bases at interkinesis is demonstrated in relation to precursor material seen to accumulate near each pole at meiosis I. The name ‘paracentrosome’ is suggested for this material, which is used up in forming the flagellar bases and spindle precursor. The spindle at late prophase, metaphase and telophase II is shown to resemble those of other divisions except that it is consistently smaller; this fact is numerically demonstrated from serial sections of metaphase II cells. The greatly reduced size and unusual shape of the polar plates present in addition to flagellar bases at metaphase II suggest that these are in a sense equivalent structures with a mutually competitive relation to the paracentrosome.
Preliminary observations with the light microscope on the relatively large nuclei of oogonia during meiosis I have shown that the haploid chromosome number is not less than 19 nor more than 23 and that chromatid separation in relation to the kinetochores at anaphase I is normal; the bearing of these findings on interpretation of the spindle is discussed.
Comparisons with other organisms are carried out in a preliminary way and the investigation ends with a résumé of the more important externally visible events in male gametogenesis adjusted to a common time scale in the course of one day.
Specificity of pseudopodium induction by the action of cations on Amoeba proteus
Authors: Brewer J. E. , Bell L. G. E. 
Published: April 2021

ABSTRACT
Some substituted cholines, long-chain aliphatic substituted amines and simple inorganic salts have been tested at different concentrations for their ability to induce pseudopodia from Amoeba proteus. The ability of substituted amines to induce pseudopodia is inversely related to their ability to bind to acid polysaccharides. The reaction of compounds with the surface polysaccharide is probably not in itself the only requirement for pseudopodium induction. A mechanism is proposed in which the properties of the cell membrane are altered by the reaction of compounds with bulky cationic groups with the membrane lipid. The formation of new pseudopodia is not the direct result of a local reduction in the surface charge density or in surface potential.
Studies on the mechanism underlying the inhibition by puromycin of cell aggregation in vitro
Authors: Dunn M. J. , Owen E. , Kemp R. B. 
Published: April 2021

ABSTRACT
Cells dissociated with 0·25 % crude trypsin from the muscle tissue of 9-day-old chick embryos were employed to investigate the effect of puromycin on cellular metabolism. Parallel studies were also made, using the gyratory shaker, to confirm the effectiveness of puromycin in inhibiting cell aggregation and protein synthesis.
Puromycin when introduced at a concentration of 10μg/ml into a suspension of cells in Eagle’s MEM did not completely inhibit cell aggregation. Small aggregates were formed in the first 4 h of the experiment. Protein synthesis of the rotated cells, as measured by the incorporation of L-[α -14C]leucine into proteins, was arrested by 91 · 7% within 15 min of introducing puromycin into a cell suspension. The antibiotic retained its inhibitory effect on protein synthesis for the 24-h period of rotation.
Puromycin inhibited the cellular oxygen uptake and carbon dioxide evolution of the rotated cells by 40 % within 4 h of its introduction. However, treated cells were still respiring, though at a much reduced rate, at the end of the 24-h experimental period. The release of radioactive carbon dioxide by puromycin-treated cells was also inhibited by 40% at the 4-h stage but after 8 h no further14CO2 was evolved. The presence of the antibiotic markedly inhibited the uptake of glucose by trypsin-dissociated cells.
The level of glycogen and lactate in cells suspended in Eagle’s MEM was reduced very considerably over a 24-h period. The presence of puromycin accelerated glycogen utilization over the first 6 h of rotation but at 24 h there was a difference of only 0 · 6 % between the glycogen content of treated cells and controls. At 24 h 11·3 % less lactate remained in the puromycin-treated cells than in the controls.
The ATP/ADP ratio of trypsin-dissociated cells decreased from an initial value of 2 · 59 to 1 · 45 after rotation for 24 h. In the presence of puromycin the ATP/ADP ratio was 0 · 62 at 4 h and had further declined to 0 · 48 by 24 h.
The effects of puromycin on the aggregation, protein synthesis and cellular metabolism of trypsin-dissociated cells are discussed in relation to cellular adhesive mechanisms.
Axonal microtubules of crayfish and spiny lobster nerve cords are decorated with a heat-stable protein of high molecular weight
Authors: Warren Robert H. 
Published: April 2021

ABSTRACT
Axons of crayfish and spiny lobster ventral nerve cords contain large numbers of microtubules that are decorated with fine filaments. These microtubules can be stabilized in permeabilized axons using buffers that contain either polyethylene glycol or glycerol/dimethyl sulphoxide. In the former, the stabilized microtubules retain their filaments and their normal spacing; in the latter, the filaments are stripped off and the bare microtubules collapse onto one another. This observation has been used as the basis for a method of identifying some of the proteins that make up the filaments. Axons are first permeabilized and stabilized in either buffer and then treated with a microtubuledepolymerizing buffer. The axons treated first with polyethylene glycol release tubulin and significant quantities of microtubule-associated proteins (MAPs), while the axons pre-treated with glycerol release tubulin and only traces of associated proteins. One of the proteins released in largest quantity along with tubulin from polyethylene glycol-treated axons is a high molecular weight, heatstable MAP that co-electrophoreses with MAP-2 from mammalian brain. This same protein copurifies with tubulin that is obtained from crayfish nerve cords by two cycles of polymerization and depolymerization. It is concluded that this protein is a component of the filaments that decorate the axonal microtubules of the crayfish and spiny lobster.
Possible translocation of a gene for thymidylate kinase from the chloropast to the nuclear genome during evolution
Authors: Groot Egon J. De , Schweiger Hans-Georg 
Published: April 2021

ABSTRACT
On the basis of the fact that in Acetabularia three out of four enzymes that are involved in deoxyribonucleotide metabolism are translated on 70 S ribosomes, while a fourth one is synthesized on 80 S ribosomes, the suggestion was made that translation on 80 S ribosomes might reflect an evolutionarily more recent situation while translation on 70 S ribosomes might be of more ancient origin. This hypothesis prompted experiments aimed at defining the site of translation of thymidylate kinase in a species closely related to Acetabularia but long ago separated from it: Batophora oerstedii. It was demonstrated that in this species, in contrast to a number of Acetabul·ariae, thymidylate kinase is translated on 70 S ribosomes. A possible, appealing interpretation of this finding is that during evolution the coding site for thymidylate kinase has been translocated from the chloropast to the nuclear genome.
X-ray analysis of Lymnaea stagnalis muscle fibres does not suggest that the sarcolemma is permeable to lanthanum ions
Authors: Swales L. S. , Gardner D. R. 
Published: April 2021

ABSTRACT
The cross-striated muscle from the heart ventricle and the smooth penis retractor muscle of the freshwater snail Lymnaea stagnalis have been investigated by X-ray microanalysis to establish whether lanthanum can cross the plasma membrane, as has been reported by other investigators. Tissues were incubated in 1 mM ionic lanthanum before fixation in phosphate- or cacodylate-buffered fixative. X-ray mapping for emissions in the lanthanum energy range indicates a concentration of emissions that coincided only with the network of sub-surface transverse tubules formed by the invagination of the plasma membrane and with the plasma membrane/extracellular space interface. X-ray energy spectra were collected from various cell compartments; peak-to-background ratios were obtained and analysed statistically. Cacodylate buffer is less effective than phosphate buffer in precipitating lanthanum, but no evidence to suggest the redistribution of lanthanum in cacodylate-buffered preparations was found. Lanthanum is precipitated only in the sub-surface transverse tubules and at the plasma membrane/extracellular space interface in both heart ventricle muscle and penis retractor muscle, fixed in either phosphate or cacodylate buffer. There was no evidence of lanthanum precipitation in the background cytoplasm or on any cytoplasmic organelle. These results confirm our hypothesis that lanthanum does not cross the plasma membranes in these molluscan tissues.
Surface charge of insect haemocytes, examined using cell electrophoresis and cationized ferritin-binding
Authors: Takle Garry , Lackie Ann M. 
Published: April 2021

ABSTRACT
Differences in the negative surface charge of haemocytes from Periplaneta americana and Schistocerca gregaria have been revealed using cell electrophoresis and cationized ferritin-binding. Although haemocyte populations from both insect species exhibit ranges of negative surface charge, both techniques show that Schistocerca haemocytes are significantly more negative than Periplaneta haemocytes. The results may help to explain why Schistocerca haemocytes adhere poorly to negative substrata, both in vitro and in vivo, and suggest that an electrostatic mechanism may be involved, at least in part, in adhesion of insect haemocytes to substrata.
Further ultracytochemical analysis of rat adenohypophyseal cells: Detection of two distinct enzyme activities within a single cell
Authors: Khokhlov S. Ye. , Nevorotin A.F. 
Published: April 2021

ABSTRACT
In an effort to ascertain whether a lysosomal enzyme, aryl sulphatase (ArSase), might share the same cell and, or, the same intracellular structure(s) with a histochemical Golgi apparatus marker, thiamine pyrophosphatase (TPPase), in rat pituitary mammotrophs and somatotrophs a technique for a selective demonstration of both enzyme activities within a single specimen has been developed. The technique is based on the selective dissolution of TPPase-related precipitates with 50% sulphuric acid in an ultrathin section of a pituitary specimen processed consecutively for ArSase and TPPase. The analysis of pairs of micrographs displaying the same structures before and after treatment with sulphuric acid has shown that TPPase-related precipitates are located mainly in the trans-Golgi lamellae while ArSase-related precipitates (resistant to sulphuric acid) could be found in both GERL and its derivatives (lysosomes, immature secretion granules) and in the TPPase-reactive trans-Golgi pole in both cell types studied. When seen within the same dictyosome each enzyme activity resided generally within an individual Golgi lamella. Direct continuity between ArSase- and TPPase-related precipitates was also occasionally encountered. The results indicate that ArSase and TPPase activities can share the trans-cisternae of the Golgi apparatus in mammotrophs and somatotrophs of rat pituitary.
A new vacuum-operated stress-providing instrument that applies static or variable duration cyclic tension or compression to cells in vitro
Authors: Banes Albert J. , Gilbert Jerome , Taylor Duane , Monbureau Olivier 
Published: April 2021

ABSTRACT
An instrument providing cyclic stress to cells cultured in vitro has been developed. The unit uses a vacuum to deform a plastic Petri dish yielding 0·13% compression to cells on the inner surface, measured by strain gauge recordings. A regimen of 25 s stress and 5 min relaxation induced no significant change in synthesis of a 45×103Mr protein that comigrates with actin, whereas a 52× 103Mr protein that comigrated with tubulin decreased from 12·7 ± 0·451% of the total protein synthesized in control, static cells to 8·53 ± 0·182% in stressed cells. The unit may have a broad application in monitoring biochemical changes in response to stress in cells such as muscle, lung, tendon, ligament and bone that are normally subjected to tension or compression.