bluuebunny/crossref_metadata_2025_split huggingface dataset:
Phosphatases and differentiation of the golgi apparatus
Authors: Dauwalder Marianne , Whaley W. G. , Kephart Joyce E. 
Published: April 2021

ABSTRACT
Cytochemical techniques for the electron microscopic localization of inosine diphosphatase, thiamine pyrophosphatase, and acid phosphatase have been applied to the developing root tip of Zea mays. Following formaldehyde fixation the Golgi apparatus of most of the cells showed reaction specificity for IDPase and TPPase. Following glutaraldehyde fixation marked localization of IDPase reactivity in the Golgi apparatus was limited to the root cap, the epidermis, and the phloem. A parallelism was apparent between the sequential morphological development of the apparatus for the secretion of a polysaccharide product, the fairly direct incorporation of tritiated glucose into the apparatus to become a component of this product and the development of the enzyme reactivity.
Acid phosphatase, generally accepted as a lysosomal marker, was found in association with the Golgi apparatus in only a few cell types near the apex of the root. The localization was usually in a single cisterna at the face of the apparatus toward which the production of secretory vesicles builds up and associated regions of what may be smooth endoplasmic reticulum. Since the cell types involved were limited regions of the cap and epidermis and some initial cells, no functional correlates of the reactivity were apparent. Despite the presence of this lysosomal marker, no structures clearly identifiable as ‘lysosomes ‘were found and the lack of reaction specificity in the vacuoles did not allow them to be so defined.
Division and dna synthesis in the kinetoplast of Crithidia Fasciculata
Authors: Anderson W. , Hill G. C. 
Published: April 2021

ABSTRACT
In Critliidia fascicuJata division of the kinetoplast occurs prior to karyokinesis. Kinetoplast division involves the lateral replication of the nucleoid, and the subsequent constriction and ‘pinching off’ of the nucleoid and mitochondrial components. Two subunits are produced.
DNA synthesis in the kinetoplast and the nucleus is overlapping but asynchronous. Experiments for short labelling times indicate that the kinetoplast S period either precedes, succeeds or is simultaneous with the nuclear period of DNA synthesis. The kinetoplast divides in a manner in which some radioactivity is transmitted to each unit.
Compartimentage des activités enzymatiques dans le spermatozoïde de certains mollusques gastéropodes: I. localisation des déshydrogenases
Authors: Personne P. , Anderson W. 
Published: April 2021

ABSTRACT
Les activités succinate tétrazolium réductasique et NADH2 tétrazolium réductasique one été mises én évidence á l’aide de la cytochimie ultrastructurale dans les spermatozoides de quelques Gastériopodes Pulmonés, Testacelle et Escatgot. Ces activités enzymatiques se localisent dans un espace fort restreint du derivd mitochondrial, l’hélice secondaire, qui correspond ácequi subsists de la matrice des mitochondries originelles. La ‘métamorphose’ mitochondriale a abouti á uneségregation des activites déshydrogénasiques dans une portion spécialisée du dérivé mitochondrial, le compartiment matriciel.

SUMMARY
By electron-microscope cytochemistry, succinate- and NADH2-tetrazolium reductase activities have been demonstrated in spermatozoa of the pulmonate gastropods, Testacella and Helix. Enzyme reaction product is restricted to the mitochondrial compartment named the secondary helix; this compartment is derived from the matrix of typical mitochondria. ‘Mitochondrial metamorphosis’ during spermiogenesis accomplishes the segregation of dehydrogenases to this matrical compartment.
Changes in thrombocyte ultra-structure during clot retraction*
Authors: Shepro D. , Belamarich F. A. , Merk F. B. , Chao F. C. 
Published: April 2021

ABSTRACT
The contraction of the entire thrombocyte appears to be a primary factor in the retracting mechanism of dogfish (Musteltis canis) in vitro blood clots. Microtubules probably account for the condensation and lobation of the nucleus, and the impetus for cytoplasmic contraction appears to be dependent upon the grouping of microfibres of dimensions difficult to measure. These microfibres show a striking resemblance to materials stored within adjacent vesicles. A second type of fibre (60 A in diameter) extends from the bases of pseudopods into the adjacent matrix. There also appears to be partial engulfment of an extracellular amorphous material by the plasma membrane. The ultrastructure of the thrombocyte during clot retraction shows some striking similarities to the mammalian platelet under similar conditions, and leads one to believe a phylogenetic relationship exists between these haemostatic cells.
Non-nucleolar transcription complexes of rat liver as revealed by spreading isolated nuclei
Authors: Harper Francis , Puvion-Dutilleul Francine 
Published: April 2021

ABSTRACT
Miller’s technique was applied to isolated nuclei of rat liver. Both the usual nucleolar and non-nucleolar transcription complexes were visualized. In addition, an unusual type of putative non-ribosomal transcription unit was revealed. It was characterized by a high density of the lateral ribonucleoprotein (RNP) fibrils. Although these particular units exhibited a regular increase of fibril lengths, the length of the transcript-covered deoxyribonucleoprotein (DNP) fibres and the morphological aspect of the RNP fibrils distinguished them from the nucleolar ‘Christmas-tree’ -like figures. The linear and granular configuration of the transcripts and the absence of terminal knobs made them similar to non-nucleolar nascent RNP fibrils.
High-voltage electron microscopy reveals new components in the axonemes and centroplast of the centrohelidian Raphidiophrys ambigua
Authors: Riedek Conly L. 
Published: April 2021

ABSTRACT
A high-voltage electron microscope was used to study the structure of the centroplast and axonemes in the ccntrohclidian Heliozoan Raphidiophrys ambigua. In Raphidiophrys the microtubules (Mrs) of each axonemc are arranged so that they describe the apices of an array of hexagonally shaped prisms and all axonemes originate from a centroplast located near the centre of the cell. The centroplast was found to consist of 3 components: (1) a tripartite central disk, (2) a sphere of electron-opaque material, approximately 0·75μm in diameter, which immediately surrounds the central disk, and (3) a slightly less electron-opaque centroplast shell, approximately 2–3 μm in diameter, which consists primarily of hitherto undcscribed components associated with the proximal 1–2μm of each axonemal base. The new axonemal components described in this study include: (1) a 20-nm rod positioned in the centre of each hexagonal prism of Mts comprising the axonemal pattern, and (2) an electron-opaque linkage material which connects each Mt of the axonemal pattern to its 4 nearest neighbours. Both of these structures are associated with the base of each axoneme within the centroplast shell, both form crossbridges with axonemal Mts, and both terminate at the periphery of the centroplast shell once the complete axonemal Mt pattern is established. It is suggested that these structures are involved in forming and maintaining the Mt pattern seen in the axopodia of Raphidiophrys.
Characterization of a cv-1 cell cycle ii. the role of cell-substrate attachment
Authors: Gershey Edward L. , D’Alisa Rose M. 
Published: April 2021

ABSTRACT
The availability of synchronous cultures of untransformed CV-1 cells has allowed analysis of the role of cell-substrate attachment in cell cycle progression as well as the ability of serum and SV40 infection to override the requirement for cell-substrate attachment. Attachment to a solid substrate is required for progression through G1. Prevention of attachment results in cell cycle arrest 30 min after cytokinesis. Serum is required for attachment, but increasing the serum concentration from 2 to 20% does not enhance cell attachment, nor obviate its need for cell cycle progression. SV40 infection does not overcome the requirement of serum for attachment nor the need of attachment for normal cycling.
Inhibition of fibronectin-mediated adhesion of hamster fibroblasts to substratum: effects of tunicamycin and some cell surface modifying reagents
Authors: Butters Terry D. , Devalia Vinod , Aplin John D. , Hughes R. Colin 
Published: April 2021

ABSTRACT
Using baby hamster kidney (BHK) fibroblasts we have studied the effect of tunicamycin, a specific inhibitor of protein glycosylation, on the ability of trypsinized cells to attach and spread onto fibronectin. Tunicamycin inhibited mannose incorporation into total acid-precipitable glycoproteins by at least 95 % while glucosamine and leucine incorporation were less or hardly inhibited. Hydrolysis and analysis of [3H]glucosamine-labelled glycoproteins showed that radioactivity incorporated into cells exposed to tunicamycin was present predominantly as galactosamine, presumably present in O-glycosidically linked glycan chains whose assembly is insensitive to the drug.
Treated cells exhibit reduced amounts of surface-associated fibronectin and adhere relatively poorly to plastic or collagen surfaces pre-coated with plasma or BHK cell-derived fibronectins at the minimum concentrations required to induce nearly quantitative attachment and spreading of untreated cells. Drug-treated cells do adhere and spread into a bipolar configuration on surfaces saturated with fibronectin. Cells treated with tunicamycin and then grown in the absence of the drug revert to a more normal behaviour, indicating that under certain conditions the effects of the drug are reversible.
Fibronectin-mediated spreading of trypsinized BHK cells is also inhibited by pre-treatment of cells with several non-penetrating reagents reactive with cell surface amino groups, namely pyridoxal phosphate, trinitrobenzene sulphonate and fluorescein 5-isothiocyanate. Analysis of surface substitution indicates a strong correlation between the extent of amino group substitution and inability of treated cells to interact with a fibronectin lattice.
While the extent of attachment under these conditions is normal, cells pretreated with a specific non-penetrating thiol reagent, p-chloromercuribenzenesulphonate fail to attach to fibronectin-coated culture dishes in a dose-dependent fashion, indicating that a biochemical distinction can be made between the processes of attachment and spreading.
We conclude that both N-glycosidically linked carbohydrate moieties of BHK cell surface glycoproteins and primary amine groups present in surface proteins or lipid head groups play a role in interactions of cells with fibronectin, leading to the formation and maintenance of a stable well-spread morphology. Both N-linked glycans and surface sulphydryl groups appear to be required for an attachment process which precedes spreading.
Calcium requirement for the secretion of peroxidases by plant cell suspensions
Authors: Sticher Liliane , Penel Claude , Greppin Hubert 
Published: April 2021

ABSTRACT
Spinach (Spinacia oleracca, L.) cells in liquid culture release peroxidases. This release is reduced by EGTA and promoted by calcium ions. In a medium deprived of calcium the rate of peroxidase release is low, but immediately after addition of 1 mM calcium there is a sudden increase of the extracellular peroxidase activity. Extracellular calcium apparently penetrates into the cultured cells rather freely and, as a consequence, the rate of peroxidase secretion by these cells is directly correlated with the concentration of calcium in the medium. Magnesium, at twice the concentration used for calcium, has no effect on the release of peroxidases. Cells treated with Na azide, Na hydrogenarsenate or fluphenazine secrete less peroxidase upon addition of calcium.
Specific rosette formation between fibroblasts and erythrocytes
Authors: Rosen Steven D. , Singer Mark S. , Glabe Charles G. , Grabel Laura B. 
Published: April 2021

ABSTRACT
Fibroblast-like cells (BHK-21, Swiss 3T3, SV40 3T3, L929) will form rosettes by binding to erythrocytes of specific types. The specificity of binding varies with the cell line. Monolayer cultures of spread baby hamster kidney (BHK) cells also bind erythrocytes with the same specificity exhibited by suspended cells. Our studies have concentrated on rosette formation between trypsinized-ox (TOx) erythrocytes and BHK cells. Extensive protease treatment of the BHK cells reduces their ability to bind TOx erythrocytes in a dose- and time-dependent manner, suggesting the involvement of protein in the binding site. Simple saccharides, and glycopeptides isolated from ox erythrocyte ghosts, do not inhibit rosetting. However, neutral glycosphingolipids from ox erythrocyte ghosts inhibit BHK-TOx rosetting, whereas neutral glycosphingolipids from non-rosettirig rabbit erythrocytes have no effect on rosetting. Furthermore, incorporation of ox glycolipids into guinea-pig erythrocytes causes these non-rosetting erythrocytes to adhere to BHK cells. These experiments suggest that specific glycolipids of the ox erythrocyte act as receptors for binding sites on the cell surface of BHK cells. These cellspecific binding sites may play a role in cell-surface events involving carbohydrate recognition.
Endoplasmic reticulum membrane isolated from small-intestinal epithelial cells: enzyme and protein components
Authors: Fujita Michiya , Ohta Hidehiko , Uezato Tadayoshi 
Published: April 2021

ABSTRACT
Endoplasmic reticulum membrane-rich fraction was obtained by subfractionation of the light microsomes from mouse jejunal mucosal epithelial cells. It was marked by high glucose-6-phosphatase, NADPH-cytochrome c reductase, and NADH-cytochrome c reductase activities and low Na+,K+-ATPase activity. The enrichment of Na+,K+-ATPase was 180-fold higher in the basolateral membranes than in the endoplasmic reticulum membrane-rich fraction relative to glucose-6-phosphatase. The protein peak that was phosphorylated in a Na-dependent manner was prominent in the basolateral membranes while it was a minor peak in the endoplasmic reticulum membrane-rich fraction. Under the electron microscope the fraction was seen to be composed of homogeneous small vesicles with thin smooth membranes.
Fibronectin, intercellular junctions and the sorting-out of chick embryonic tissue cells in monolayer
Authors: Nicol A. , Garrod D. R. 
Published: April 2021

ABSTRACTA hierarchy of relative cohesiveness in monolayer of four different embryonic chick tissues was determined in a previous study. The hierarchy is: corneal epithelium ≏ liver parenchyma &gt; pigmented epithelium &gt; limb bud mesenchyme. The purpose of this paper is to describe the correlation between these adhesive relationships and, firstly, the amount of the adhesive glycoprotein, fibronectin, associated with the cells and, secondly, the morphology of their intercellular contacts. Fluorescent antibody staining of the cells with anti-fibronectin antibody showed that limb bud mesenchyme cells, the most weakly cohesive, had much more fibronectin than the other cell types. Thus there was a negative correlation between the amount of fibro-nectin and cellular cohesiveness. Analysis of intercellular contacts by electron microscopy showed that the most strongly cohesive cell types, corneal epithelium and liver parenchyma, were also those that possessed desmosomes.
The analysis of malignancy by cell fusion IX.* Re-examination and clarification of the cytogenetic problem
Authors: Evans E. P. , Burtenshaw M. D. , Brown B. B. , Hennion R. , Harris H. 
Published: April 2021

ABSTRACT
Previous experiments with crosses between malignant and diploid mouse cells had shown that the reappearance of malignancy in hybrids in which it was initially suppressed was associated in some cases with the elimination of the chromosomes 4 derived from the diploid parent cell. In others, however, this did not appear to be so. In the present study, we have re-examined the role of the diploid chromosomes 4 in the suppression of malignancy using natural polymorphisms of the centromeric heterochromatin to identify the parental origin of the chromosomes 4 in the hybrid cells. We now find that the diploid chromosomes 4 are indeed involved in the suppression of malignancy in all the tumours that we have examined, which include a carcinoma, a melanoma, a sarcoma and a lymphoma. In all crosses between these malignant tumour cells and diploid fibroblasts, there is selective pressure in vivo against the chromosomes 4 derived from the diploid cell and in favour of the chromosomes 4 derived from the malignant cell. This indicates that the chromosomes 4 in all these tumours are in some way functionally different from the chromosomes 4 of the diploid fibroblast. Reappearance of malignancy in hybrids in which it was initially suppressed may result from a reduction in the number of diploid chromosomes 4, an increase in the number of malignant chromosomes 4, or both. The gene on the diploid chromosome 4 responsible for the suppression of malignancy acts in a dose-dependent manner.
Nucleolar fusion in wheat
Authors: Jordan E. G. , Martini G. , Bennett M. D. , Flavell R. B. 
Published: April 2021

ABSTRACT
Two pairs of major nucleoli form in cells of the wheat variety Chinese Spring and these frequently fuse during the cell cycle. The volume of the nucleolus formed at the organizer on chromosome iB is approximately twice the volume of the nucleolus formed at the organizer on chromosome 6B. The volumes of fused nucleoli are distributed around the additive means expected if the nucleoli of the two different sizes fused in all possible combinations. Thus nucleolar volume but not the surface area is additive on fusion.
Four nucleoli can fuse to produce nuclei with nine different nucleolar patterns. All nine were found but the frequencies of the different fusion classes were different in different genotypes. The frequencies in euploid Chinese Spring and tetrasomie 3B showed small deviations from those expected if fusion between different nucleoli occurred with equal frequency, but in the aneuploids DT 5BL and DT sAL the fusion of heterologous nucleoli from chromosome 1B and 6B organizers occurred with a much higher frequency. It is suggested that the pattern of nucleolar fusion is determined in part by the position of the organizers in the nucleus, and their positions are altered in these ditelosomic stocks.
Association between tension and orientation of periodontal ligament fibroblasts and exogenous collagen fibres in collagen gels in vitro
Authors: Bellows C. G. , Melcher A. H. , Aubin J. E. 
Published: April 2021

ABSTRACT
The relationship between the development of tension in sheets of fibroblasts and the orientation of these cells and collagen fibres in collagen gels was examined. Cell-containing, three-dimensional collagen gels were established in agarose-coated Epon dies measuring 10 mm × 4 mm × 4 mm, to which pieces of demineralized tooth and bone had been attached at opposite ends. Contraction of the gel into an opaque structure suspended between the two particles occurred over 24 h and resulted in concave upper and lateral surfaces and a flat to slightly concave lower surface. Initial orientation of the fibres along the tooth-bone axis was followed by similar orientation of the cells. Gels cast without cells exhibited no change in dimensions. Release of the tooth particle after 12 or 24 h of incubation led to shortening of the contracted gels 5 min following release. This shortening was significantly greater (P &lt; 0·001) than that of uncontracted or slightly contracted gels (1 h and 3 h incubation). Gels attached at one end only compacted around the site of attachment but did not show orientation of cells or fibres. Gels containing colcemid or cytochalasin D were only slightly compacted and did not develop tension. Collagen fibres, but not cell in colcemid-containing gels, showed some alignment; neither were aligned in the presence of cytochalasin D. These data suggest that both microtubules and microfilaments are necessary for alignment of cells and the establishment of tension between two points of attachment in collagen gels. Furthermore, they lend support to our previously advanced hypothesis that the development of tension between two points can result in the orientation of the cells along an axis connecting the points of attachment. This could provide a mechanism for the development of oriented fibre systems in vivo.
The mononuclear cell population in rat leg muscle: its contribution to the lysosomal enzyme activities of whole muscle extracts
Authors: Etherington David J. , Wardale R. John 
Published: April 2021

ABSTRACT
The mononuclear cell fraction of rat hind-limb muscle was obtained by digestion with clostridial collagenase in the presence of calcium ions, filtration through nylon screens and washing to remove the enzyme. Final traces of contaminant myofibrillar debris were separated by isopycnic centrifugation in a Percoll density gradient. Whole muscle, Washed cells and Percoll-fractionated cells were extracted in the presence of non-ionic detergent and the supernatants assayed for the lysosomal enzymes cathepsins B + L, 2V-acetyl-β-glucosaminidase, β-glucuronidase and protein. The enzyme levels were highest in the muscle from young rats, but the percentage of recovered activity in the mononuclear cell fraction was little altered by the age of the animal. The values obtained were: cathepsin B + L, 2·4–4·o%; N-acetylβ-glucuronidase, 4·3-7·6%; and β-glucuronidase, 6·3-10·3%. Because of unavoidable losses in preparation these are minimal values and the actual levels of activity from the mononuclear cell fraction in muscle would be higher. The specific activity values of the cell lysates were raised after isopycnic centrifugation and were nearly constant over the age range 65–180 days. Substantially higher specific activity values were obtained for the cells from rats of 38 days. When grown in culture the mononuclear cell fractions were seen to contain mainly fibroblasts and myoblasts with only few leucocytes. The cultures reached confluence by the second week, at which time numerous myotubes had formed. In addition there were groups of large, circular cells with a prominent centrosphere. The origin of these latter cells is uncertain.
It was concluded that although total lysosomal enzyme activity was higher in young rats there was little effect of age on the distribution of activity between muscle fibres and mononuclear cells in the muscle.
The effect of surface microvilli on the water permeability of single toad oocytes
Authors: Dick Elizabeth G. , Dick D. A. T. , Bradbury S. 
Published: April 2021

ABSTRACT
The water permeability of isolated toad ovarian oocytes was found from their rate of shrinkage in hypertonic Ringer’s solution. Apparent membrane permeability coefficients, (k), calculated on the assumption that the cell surface was smooth, rose from about 20 μm s−1 in small cells 200 μm in diameter, to 35 μm s−1 in cells 800 μm in diameter and then fell to 5 μm s−1 in large cells of 2000 μm diameter.
The factor (f) by which microvilh extend the oocyte surface area beyond that of a smooth sphere was estimated from an analysis of electron micrographs of the cell surface. The value of f rose from 2 × at 200 μm diameter, to 11 × at 800 μm diameter and then fell to 5 × at 2000 μm diameter. The correlation coefficient between k and f was 0 474 (0 005 &gt; P &gt; 0·001). Corrected permeability coefficients, (k’), calculated so as to take account of the effects of the microvilh, (k’ = k/f), declined with increasing oocyte size, from 5 μm s−1 in small cells (200 μm) to 1 μm s−1 in large cells (2000 μm).
The correlation between k and f indicates resistance to water flow by the cell membrane, while the decrease in k’ as the cell grows suggests that diffusion in the cytoplasm may also be sufficiently slow to affect water flow out of the cell. It may be calculated that a surface membrane permeability coefficient in the range from 2 to 30 μm s−1 combined with an internal diffusion coefficient in the range from 6 × 10−8 to 10−6 cm2 s−1 could account for the effects found.