bluuebunny/crossref_metadata_2025_split huggingface dataset:
Membrane changes associated with mucus production by intestinal goblet cells
Authors: Swift J. G. , Mukherjee T. M. 
Published: April 2021

ABSTRACT
Changes in the structural organization of membranes of mucous bodies and the plasma membrane that occur during mucus production in goblet cells of rat rectum have been studied by thin-section and freeze-fracture techniques.
Immature mucous bodies are bounded by a trilaminar membrane and fracture faces of the membrane have randomly distributed intramembrane particles. During maturation, mucous bodies become packed tightly together and changes in the structure of their membranes include (1) fusion of apposing membranes of adjacent bodies to form a pentalaminar structure, (2) a reduction in the density of particles on membrane fracture faces, and (3) exclusion of particles from regions of membrane apposition. Some trilaminar membranes of mucous bodies fuse with the lumenal plasma membrane to form a pentalaminar structure. Sites of apposition between mucous body membranes and the lumenal plasma membrane are seen as particle-cleared bulges on fracture faces of the plasma membrane.
Our results indicate that membrane reorganization associated with mucous production in goblet cells includes a reduction and redistribution of some membrane proteins and that membrane fusion occurs between portions of membranes from which proteins have been displaced.
Mobility of concanavalin a receptors and distribution of cytoplasmic actin in odontogenic epithelial and mesenchymal cells
Authors: Prime S. S. , Toh B. H. 
Published: April 2021

ABSTRACT
The distribution of concanavalin A (Con A) surface receptors and cytoplasmic actin in the same cell was studied in monolayer cultures of 2 odontogenic epithelial cells of different developmental age and in ecto-mesenchymal cells derived from the same tooth germ. Con A receptors were demonstrated by fluorescein-isothiocyanate-labelled Con A (FITC-Con A) and cytoplasmic actin by a specific anti-actin autoantibody (AAA) traced with a rhodamine-labelled goat anti-human globulin (R-AHG). All 3 cell types, incubated with FITC-Con A at 37 °C for increasing time periods, showed progressive changes in staining patterns from clusters, caps to perinuclear globules. Capping was seen in the majority of immature epithelial cells at 120–180 min, in cells of more mature epithelium at 180-240 min and in ecto-mesenchymal cells at 240–360 min. Binding of FITC-Con A to cell surfaces resulted in sequential changes in AAA staining from filamentous to an aggregated or diffuse pattern, co-capping of aggregated or diffusely stained areas with those capped by FITC-Con A, presence of aggregated or diffusely stained areas in sites similar to the perinuclear globules stained by FITC-Con A, to final re-emergence of filamentous staining. Prior treatment of cells with cytochalasin B or colchicine promoted capping in epithelial but not in ecto-mesenchymal cells while presence of cither drug throughout the staining procedure inhibited capping. The results show that Con A receptors are more mobile in epithelial compared to ecto-mesenchymal cells and in immature epithelial cells compared to their more mature counterparts, and that binding and mobility of Con A receptors on the cell surface is associated with redistribution of cytoplasmic actin. The cytochalasin B and colchicine experiments suggest that both microfilaments and microtubules may have synergistic roles in the opposing functions of receptor anchorage and mobility, and that the relative receptor immobility of ectomesenchymal compared to epithelial cells may be attributed to firmer receptor anchorage to the cytoskeleton.
Oxygen uptake during the cell cycle of the fission yeast Schizosaccharomyces pombe
Authors: Creanor James 
Published: April 2021

ABSTRACT
Oxygen uptake was measured in synchronous cultures of the fission yeast Schizosaccharomyces pombe. The rate of oxygen uptake was found to increase in a step-wise manner at the beginning of the cycle and again in the middle of the cycle. The increases in rate were such that overall, oxygen uptake doubled in rate once per cell cycle.
Addition of inhibitors of DNA synthesis or nuclear division to a synchronous culture did not affect the uptake of oxygen. In an induced synchronous culture, in which DNA synthesis, cell division, and nuclear division, but not ‘growth’ were synchronized, oxygen uptake increased continuously in rate and did not show the step-wise rises which were shown in the selection-synchronized culture.
These results were compared with previous measurements of oxygen uptake in yeast and an explanation is suggested for the many different patterns which have been reported.
Interaction of leukocytes with vascular cells in culture
Authors: Beesley Julian E. , Pearson Jeremy D. , Carleton J. Susan , Hutchings Amanda , Gordon John L. 
Published: April 2021

ABSTRACT
The nature, kinetics and cofactor requirements of leukocyte adhesion to cultured vascular cells have been investigated in vitro, using a model system in which leukocyte suspensions are in continuous motion over the cultured cells. Adhesion is assessed by histological examination or by using 51Cr-labelled leukocytes.
Leukocytes adhere preferentially to endothelial cell monolayers rather than to smooth muscle cells, adventitial fibroblasts or serum-coated glass. Arterial and venous endothelium are equally good substrates for leukocyte adhesion, and lymphocytes and granulocytes at the same suspension density adhere to endothelial cells in similar numbers. Adherence is greatest during the first 10 min, and is inversely related to flow rate. Numbers of leukocytes adhering to the cell monolayer are proportional to the initial concentration of leukocytes in suspension, although only 2–10% of the leukocytes adhere. Leukocytes that have adhered to the cell monolayer spread over the cells and then migrate, apparently through intercellular junctions. Adhesion requires Ca2+ or Mg2+ ions, but not plasma protein cofactors. Fewer leukocytes adhere to endothelial cells grown for 48 h in rapidly stirred medium than to cells grown under conventional, static conditions.
Cell differentiation during fruiting body formation in Polysphondylium Pallidum
Authors: O’Day Danton H. 
Published: April 2021

ABSTRACT
The spatial pattern of cellular differentiation was studied during fruiting body formation in Polysphondylium pallidum using 3 different staining methods: Calcofluor fluorescence (cellulose accumulation), neutral red (prestalk cells) and immunofluorescence (prespore cells). Neutral-red staining revealed the existence of a clear prestalk region which becomes evident during aggregation and continues throughout culmination. Immunofluorescent staining demonstrated that cells in the prestalk region gradually lose their presporeness (fluorescence) as they are transformed into differentiated stalk cells. Calcofluor staining revealed that stalk cell differentiation begins during the mid-aggregation phase and that the mode of formation of the main stalk and the side branches differs slightly in morphology. Calcofluor staining also demonstrated the development, during aggregation, of a thick cellulosic girdle with lateral tubular extensions which surround the aggregation streams. The above results are discussed in terms of our present knowledge about differentiation and morphogenesis in cellular slime moulds.
Tumorigenicity of cells transformed by simian virus 40 and of hybrids between such cells and normal diploid cells
Authors: Gee C. J. , Harris H. 
Published: April 2021

ABSTRACT
A number of newly isolated clonal cell lines derived from diploid mouse embryo cells transformed by SV40 were examined in vitro and in vivo. Although these lines showed the properties that define transformation in vitro, they were not tumorigenic for many passages after their initial isolation.
Cells from tumours eventually produced by the SV40-transformed cells were fused with diploid mouse embryo cells. The hybrids formed were initially non-tumorigenic. This indicates that a normal diploid cell can suppress the malignant phenotype of a tumorigenic SV4O-transformed cell. The hybrid cells did, however, express the SV40 T antigen and they had a clearly transformed phenotype in vitro. It thus appears that neither the transformed phenotype nor the expression of the SV40 T antigen are enough to endow a cell with the ability to grow progressively in vivo.
The relationship between the transformed phenotype and tumorigenicity was further studied by fusing malignant mouse melanoma cells with non-tumorigenic SV4o-transformed cells. The hybrids expressed the transformed phenotype in vitro but were unable to form tumours in vivo. The changes that occur in cells after transformation by SV40 do not apparently affect the ability of these cells to suppress the malignant phenotype of tumour cells.
Specificity of the immaturitysubstances in Paramecium
Authors: Miwa Isoji 
Published: April 2021

ABSTRACT
Cytoplasm of Paramecium caudatum syngen 3 in the period of sexual immaturity was effective in inducing immaturity when injected into mating-reactive cells of other syngens of P. caudatum. When immature cytoplasm of P. caudatum was injected into mature cells of P. multimicronucleatum, immaturity was also induced in the latter cells. When cytoplasm of P. bursaria in the immaturity period was injected into mature cells of the same species, the latter became immature. But immature cytoplasm of P. caudatum was ineffective when injected into mature cells of P. bursaria. When immature cytoplasm of P. bursaria was injected into mature cells of P. caudatum, no difference from the control was observed. These results suggest that a difference in specificity of the immaturity substances exists between paramecia of the ‘aurelia’ group and those of the ‘bursaria’ group.
The sorting out of embryonic cells in monolayer, the differential adhesion hypothesis and the non-specificity of cell adhesion
Authors: Nicol A. , Garrod D. R. 
Published: April 2021

ABSTRACT
It has been reported previously that sorting out of chick embryonic liver parenchyma and limb bud mesenchymal cells would take place in monolayer culture. The distribution of cell types obtained (liver formed the internal, discontinuous phase) was interpreted in terms of the differential adhesion hypothesis. It was suggested that, in monolayer, liver cells were more cohesive than limb bud cells. In this paper we set out to extend the previous observations with 2 particular questions in mind: (i) Is sorting out in monolayer a general phenomenon occurring between a wider range of cell types ? (ii) Can evidence be provided for or against the interpretation of results in terms of the differential adhesion hypothesis ?
Sorting-out experiments were conducted on circular hydrophilic islands, on an otherwise hydrophobic substratum. Under these conditions, sorting-out in monolayer was obtained with binary combinations of 4 chick embryonic tissue types: liver parenchyma, limb bud mesenchyme, pigmented epithelium of the eye and corneal epithelium. With every combination but one, the cells of one type surrounded the cells of the other type, generating what we have called a ‘circle-within-a-circle’ configuration. With the remaining combination, liver parenchyma and corneal epithelium, only localized sorting was obtained. The ‘circle-within-a-circle’ configuration is consistent with an interpretation in terms of the differential adhesion hypothesis, according to which the distribution of cells is determined by the relative strengths of cohesions between their lateral surfaces.
In direct support of this is the finding from plating the different cell types at sub-confluent density on hydrophilic substrata that limb bud is the cell type having the weakest lateral cohesion in monolayer. Limb bud surrounded the other 3 tissues on hydrophilic islands. A hierarchy of lateral cohesiveness between the 4 cell types has been constructed. It is unlikely that the results can be explained in terms of specific cohesion. When plated together at subconfluent density, the 3 epithelial cell types aggregate together to form mixed monolayered islands, suggesting that they share common adhesive mechanisms.
Cell surface lipids and adhesion IV. The effects of trypsin on lipid turnover by the plasmalemma
Authors: Curtis A. S. G. , Hill Oya 
Published: April 2021

ABSTRACT
Trypsin treatment of intact cells or isolated plasmalemmae from embryonic chick neural retinae leads to an accumulation of lysophospholipids in the plasmalemmae. Trypsin was used at activities commonly used in cell disaggregation techniques. This accumulation appears to result from the decrease in acyltransferase activity in the plasmalemma produced by enzyme treatment. Plasmalemmal CoA ligase activity is not affected by trypsin treatment. Trypsiniza-tion has little effect on plasmalemmal phospholipase A2 activity. These results are discussed in relation to (a) the effects of trypsinization on cell adhesion, and (b) the theory that cells cannot adhere to lecithins because of their fluidity or surface-free-energy values. We propose that the effects of trypsinization on adhesion may in large part be due to the effects of the enzyme on plasmalemmal enzymes of the lipid turnover system rather than to effects on other plasmalemmal proteins. Similarly the inability of cells to adhere to lecithin substrates is simply explained as being due to the lysolecithin that contacting cells release from these substrates.
Interaction of lectins with proteins of the endoplasmic reticulum and golgi system of rat liver
Authors: Winqvist L. , Eriksson L. C. , Dallner G. 
Published: April 2021

ABSTRACT
The interaction of glycoproteins of rough and smooth microsomal and Golgi membranes with Sepharose-bound lectins has been studied. One of these lectins was a crude preparation from wheat germ lipase which was found to bind primarily to N-acetyl neuraminic acid. Rough microsomes, smooth microsomes and Golgi membranes contain glycoproteins which bind to Concanavalin A (Con A specific for mannose residues) in decreasing amounts in the order indicated (rough, smooth and Golgi) and to wheat germ agglutinin (WGA, glucosaminespecific) and to the crude lipase preparation in increasing amounts in the order indicated. The small amount of binding of rough microsomes and Golgi membranes to Crotalaria (galactosespecific) increases substantially after neuraminidase treatment. Three submicrosomal particle preparations enriched either in AMPase or in NADH- or NADPH-oxidizing electron-transport enzymes contain glycoproteins which bind Con A and wheat germ agglutinin. The latter binding is sensitive to neuraminidase treatment. Two other submicrosomal particle preparations, both enriched in glucose-6-phosphatase activity, bind preferentially to WGA. This binding is, however, not sensitive to neuraminidase. Prolonged incubation with Ervilia lectin (mannose-specific) inhibits NADH-ferricyanide reductase activity, while the electrontransport chain involving cytochrome b5 is also inhibited by Crotalaria, indicating that both the flavoprotein and the cytochrome b5 are glycoproteins whose oligosaccharide chains have terminal mannose or galactose residues.
Rectal papillae in Musca domestica: The cuticle and lateral membranes
Authors: Flower N. E. , Walker G. D. 
Published: April 2021

ABSTRACT
The role of specialized regions of insect rectal papillae in the regulation of water and ion uptake is well documented. Although the apparatus for active uptake of water or ions is located in various cell membranes, the absorbed molecules must first pass through the cuticle which lines the rectal epithelium. Most cuticle (e.g. abdominal) has been shown to be permeable only to molecules soluble in wax, and to be impermeable to water and ions. Obviously if such cuticle lined the rectum, absorption of water and ions would be severely restricted. The present freeze-fracture and lanthanum tracer study was undertaken to investigate in more detail both the morphological features of the rectal papillae cuticle which could be responsible for its anomalous permeability and the various cell membranes involved in this transport.
It has been suggested from permeability studies that the anomalous permeability of rectal papillae cuticle could be due to the lack of a complete wax layer over the surface of the rectal cuticle. The present study strongly supports this suggestion. Thus, the freeze-fracture micrographs have shown that a surface layer of the cuticle reacts during fracturing like a lipid bilayer. However, in rectal papilla cuticle this surface bilayer is interrupted at each epicuticular depression by areas of different fracturing behaviour. These discontinuities in the surface bilayer probably allow the rectal contents to contact directly the true cuticular matrix. They could, therefore, explain the ease with which water and ions penetrate the rectal cuticle and so gain access to the underlying epithelial cells. Although similar discontinuities are present on some of the rectal cuticle surface external to the rectal papillae, they appear to be filled in by plugs of lipid-like material.
The lateral plasma membranes of the rectal papillae cells are generally considered to be the main site of active transport. The present lanthanum tracer and freeze-fracture study has shown that the lateral plasma membranes contain 3 distinct differentiations. Septate junctions are present at the apical and basal surfaces of the epithelial layer; a further membrane differentiation is found adjacent to the septate junctions; and thirdly, an array of short, variable length, non-anastomosing linear structures covers most of the lateral plasma membrane surface. These latter structures, unlike known types of cell junctions do not show equivalent arrays in apposing membranes even when the lateral plasma membranes of adjacent cells are closely apposed. The possible function of these structures is discussed.
Location of radioactively labelled extracellular fluid indicators in nervous tissue by autoradiography
Authors: Brown D. A. , Stumpf W. E. , Roth L. J. 
Published: April 2021

ABSTRACT
The location of three radioactively labelled extracellular-space indicators ([3H]methoxyinulin, [3H]-D-mannitol and sodium [MS]sulphate) in the superior cervical sympathetic and nodose ganglia of cats was studied using an autoradiographic technique. The technique was designed to eliminate movement of soluble, diffusible substances in tissues after excision, and to provide high autoradiographic resolution. Ganglia were rapidly excised after administration of the radioactive compounds in vivo, and frozen in liquid propane. Frozen sections were cut at – 60 °C at a thickness of 0·7–0·8 μ. The frozen sections were freeze-dried, dry-mounted on dried, photographic emulsion-coated microscope slides, and exposed at – 15 °C until development.
The highest densities of silver grains in the autoradiographs were associated with regions of the tissue containing the greatest amounts of connective tissue. Lowest densities occurred beneath neurons and myelinated nerve fibres. The silver grain density beneath neuron peri-karya was between 10% and 15% of that associated with plasma. Attempts were made to determine the source of these subneuronal silver grains. The results suggested that they could not be ascribed to the following: background; chemographs and pressure artefacts; spread of radiation from radioactive material outside the perikarya; and in vitro translocation of radio-active material into the neurons or into the emulsion beneath the neurons. It was concluded that the subneuronal grains reflected a small amount of intraneuronal penetration of the compounds in vivo. There was very little difference between inulin, mannitol and sulphate with regard to the proportion of intracellular activity. Except for this small amount of intracellular radioactivity, the findings accord with the view that inulin, mannitol and sulphate are confined predominantly to the extracellular fluid.
Changes in the cytochemical properties of erythrocyte nuclei reactivated by cell fusion
Authors: Bolund L. , Ringertz N. R. , Harris H. 
Published: April 2021

ABSTRACT
When the nucleus of a chick erythrocyte is introduced into the cytoplasm of a HeLa cell it resumes the synthesis of RNA and DNA. This reactivation of the red cell nucleus is associated with an increase in volume and with changes in nuclear composition. These changes have now been studied by quantitative cytochemical techniques. During the process of reactivation the dry mass of the erythrocyte nucleus shows a marked increase which takes place largely before the replication of the DNA begins. Within 24 h of cell fusion, some erythrocyte nuclei already contain an increased amount of DNA, and 48 h after fusion many of them contain twice the normal diploid amount, thus indicating that they have replicated their DNA completely. The physical properties of the nuclear deoxyribonucleoprotein complex also change. The ability of the nuclear chromatin to bind acridine orange increases 4- to 5-fold well before the synthesis of DNA begins; and changes in the melting profile of the deoxyribonucleoprotein suggest that its structure is loosened. This view is also supported by the observation that the reactivity of the erythrocyte nuclei to the Feulgen stain is altered during the early stages of reactivation.
Preprophase microtubule bands in some abnormal mitotic cells of wheat
Authors: Pickett-Heaps J. D. 
Published: April 2021

ABSTRACTCaffeine treatment of growing wheat tissues was used to form binucleate or polyploid cells; preprophase microtubules in subsequent division cycles in these and some other abnormal cells were then examined. In root tips, binucleate cells or those with greatly enlarged nuclei usually contained one transverse preprophase band of microtubules; sometimes this was slightly asymmetrical or skew, and less commonly two bands were seen. In coleoptile vascular bundles, there were generally two or more bands in the greatly elongated cells, these sometimes appearing in different planes. During formation of the stomatai complexes, preprophase microtubules were almost invariably found where expected, preceding abnormal development both in untreated and also in caffeine-treated material, regardless of the number, disposition or size of nuclei. This occurred even when wall stumps, formed during a previous abortive division, indicated that that previous division was also asymmetrical. It is concluded that the position(s) of preprophase band(s) of microtubules is not particularly influenced by the nucleus or nuclei, being more susceptible to external morphogenetic influences which can persist for some considerable time. Particularly in the case of stomatai complexes, a cell wall seems necessary to seal off or otherwise fulfil the tendency towards asymmetrical division.