bluuebunny/crossref_metadata_2025_split huggingface dataset:
Actin in plants
Authors: Lloyd Clive 
Published: April 2021

ABSTRACT
It has been known for some time that actin exists in lower plants, the most familiar examples being provided by certain algae in which actin constitutes the cytoplasmic cables along which particles and organelles stream. The choice of material was an important part of determining the identity of the filaments because these giant filamentous cells were capable of being broken open to expose cytoplasmic strands, which could then be decorated with heavy meromyosin (HMM) (reviewed by Williamson, 1986).
Cell adhesion and phagocytosis promoted by monoclonal antibodies not directed against fibronectin receptors
Authors: Grinnell Frederick , Ho Chin-Han , Tuan Tai-Lan 
Published: April 2021

ABSTRACT
In this report we describe cell adhesion and phagocytosis promoted by two monoclonal antibodies that were selected for immunofluorescence staining of non-permeabilized baby hamster kidney (BHK) cells. Anti-BHKl staining was heaviest along cell margins, whereas anti-BHK2 staining was continuous along cell margins. Neither antibody stained elongated plaque structures such as were observed when cells were reacted with antibodies to fibronectin (FN) receptors. The monoclonal antibodies functioned as adhesion ligands in four different assays: attachment to culture dishes, spreading, binding of latex beads and phagocytosis. Anti-BHKl and anti-BHK2 promoted attachment to culture dishes similarly, but anti-BHK2 was more effective at promoting cell spreading. Antibody-promoted cell spreading was inhibited by the peptides Ser-Asp-Gly-Arg and Gly-Arg-Gly-Asp-Ser-Pro but not by other, related, peptides tested. The monoclonal antibodies also promoted binding of latex beads, and the bead binding sites were motile, on the basis of their ‘capping’ response. Nevertheless, anti-BHK2 beads were phagocytosed by cells 5-to 20-fold more efficiently than anti-BHKl beads. The binding sites for anti-BHKl and anti-BHK2 were characterized by immunoprecipitation experiments. Anti-BHKl binding sites contained 50K (K= 103Mr) and 88K components under non-reducing conditions that migrated as a 51/53K doublet and a 93K component under reducing conditions. On the other hand, anti-BHK2 binding sites contained 88K and 110K components under non-reducing conditions that shifted to apparent 107K and 128K values when measured under reducing conditions.
Secretion of adhesive material during encystment of Phytophthora cinnamomi zoospores, characterized by immunogold labelling with monoclonal antibodies to components of peripheral vesicles
Authors: Gubler Frank , Hardham Adrienne R. 
Published: April 2021

ABSTRACT
During encystment, zoospores of the dieback fungus Phytophthora cinnamomi attach themselves to the plant root surface by secretion of adhesive material. Previous workers have proposed, on the basis of ultrastructural studies, that the adhesive material is released by rapid exocytosis of large vesicles that underlie the zoospore plasma membrane. In the present study a monoclonal antibody (Cpa-2) that binds to the adhesive material has been used to investigate the sites of storage of this material in the zoospores, and the timing and pattern of its secretion during encystment. Immunolabelling of thin sections of zoospores with Cpa-2 followed by gold-labelled secondary antibodies has revealed that the adhesive material is not stored in the large peripheral vesicles but in a population of small vesicles in the cell periphery. In studies of other Oomycete fungi, these small vesicles have usually been described as microbodies. Another monoclonal antibody (Lpv-1) does bind to the contents of the large peripheral vesicles. Double immunolabelling of zoospores and encysting cells with Cpa-2-Au10 and Lpv-1-Aui8, coupled with morphometric analysis, has shown that 85% of the adhesive material is secreted within the first minute following induction of encystment and that the large peripheral vesicles are not exocytosed during encystment but instead tend to migrate towards the centre of the cell. Immunoblot analysis with Cpa-2 shows the presence of several high molecular weight bands (Mr&gt; 300 000) which also react with the lectin, soybean agglutinin. These high molecular weight components are susceptible to digestion with Pronase. Lpv-1 also reacts with high molecular weight bands but of different mobility from those recognized by Cpa-2. Concanavalin A binds to bands corresponding to those labelled by Lpv-1. We conclude that adhesion of cysts to plant roots involves the secretion of high molecular weight glycoproteins by rapid exocytosis of small peripheral vesicles and that the material contained in the large peripheral vesicles is also glycoprotein in nature but is not secreted during encystment.
Introduction of a porcine growth hormone fusion gene into transgenic pigs promotes growth
Authors: Vize Peter D. , Michalska Anna E. , Ashman Rod , Lloyd B. , Stone B. A. , Quinn P. , Wells J. R. E. , Seamark R. F. 
Published: April 2021

ABSTRACT
Six transgenic pigs have been produced by microinjecting a human metallothionein promoter/porcine growth hormone gene construct into the pronuclei of fertilized eggs which were transferred to synchronized recipient sows. The resulting transgenic animals contained between 0·5 and 15 copies of the gene construct per cell, and at least one of the animals expressed the introduced gene and grew at an increased rate compared to both transgenic and non-transgenic littermates. Some of the transgenic animals that did not appear to grow at increased rates were found to contain rearranged gene sequences. Two of the transgenic pigs have been shown to pass on the introduced genes to their offspring.
Spectrin-like proteins in the paraflagellar rod structure of Trypanosoma brucei
Authors: Schneider André , Lutz Hans U. , Marugg Richard , Gehr Peter , Seebeck Thomas 
Published: April 2021

ABSTRACT
A polyclonal, monospecific rabbit antibody to human erythrocyte spectrins cross-reacted with two sets of proteins (a doublet of 180/200K and a triplet of 67–66–65K; K= 103Mr) in the parasitic protozoon Trypanosoma brucei brucei. Except for the 66K protein, the cross-reacting proteins are localized in the flagellum, on the basis of evidence from cell fractionation and immunofluorescence microscopy. Immunogold labelling and electron micrographs further revealed that the spectrin-like proteins are confined to the paraflagellar rod structure. The spectrin-like proteins with apparent molecular weights of 180 and 200 share homology with spectrin band 1, since V8-protease from Staphylococcus aureus generated similarly sized, antigenic peptides from these proteins. The results indicate homology between the cross-reacting proteins and human red cell spectrin.
A contractile cytoskeletal network ofParamecium:the infraciliary lattice
Authors: De Loubresse Nicole Garreau , Keryer Guy , Viguès Bernard , Belsson Janine 
Published: April 2021

ABSTRACTAmong the various cytoskeletal networks and structures that compose the highly organized cortex of Paramecium, the infraciliary lattice (ICL) is the innermost one and marks the cortical boundary. It is made up of filamentous bundles running around the proximal ends of basal bodies. Immunofluorescence studies, using two different antibodies specifically labelling the network, allowed us to describe the disorganization-reorganization cycle of the ICL during division, and observations by immunoelectron microscopy provided new information on its ultrastructure. A partial purification of large fragments of a contracted form of the network was obtained. Among the proteins from ICL-enriched fractions, two 23 to 24(×103)Mr polypeptides were shown to cross-react with a polyclonal antibody raised against 22 to 23(×103)Mr Ca2+-binding proteins from the microfibrillar ectoplasmic-endoplasmic boundary of Isotricba and to be selectively solubilized in the presence of EGTA.The possibility that the ICL may be a new example of a non-actin contractile system found in lower eukaryotes is discussed.
Formation of cell outgrowths by external force: A model study
Authors: Popov S. V. , Margolis L. B. 
Published: April 2021

ABSTRACT
Cell outgrowth formation by a force applied to the external membrane was investigated. This extrinsic force, which is generated in a special chamber by an alternating current (AC) electric field (EF) of high frequency, pulls the membrane outwards. The force arises due to the redistribution of ions beneath the cell surface and is applied to the thin (10–20 Å) undermembrane layer. This force is sufficient to generate cell-specific membrane protrusions of various types. The morphology of these protrusions in mouse embryo and human fibroblasts, and in mouse L cells, resembles that of the outgrowths that these cells form under normal physiological conditions. Ehrlich ascites tumour cells (which normally grow in suspension) in an AC EF form only thin short processes. Erythrocytes when subjected to EF treatment are not capable of producing processes at all. An aligned system of microfilaments was found in the outgrowths produced by mouse embryo fibroblasts. However, cytochalasin B, sodium azide + 2-deoxy-D-glucose, carbonyl-m-chlorphenylhydrazon + 2-deoxy-D-glucose, colcemid and incubation at 4°C were not able to prevent the generation of processes in an EF. It is proposed that the morphology of cell protrusions is determined by the structure of the domains in the plasma membrane, rather than by active cytoskeletal reorganization. The experimental system that we developed provides an opportunity for studying the mechanical linkages of cytoskeletal elements with the plasma membrane.
Foetal and cancer patient fibroblasts produce an autocrine migrationstimulating factor not made by normal adult cells
Authors: Schor Seth L. , Schor Ana M. , Grey Ann Marie , Rushton Graham 
Published: April 2021

ABSTRACT
We have previously reported that (1) the migration of foetal and adult fibroblasts into threedimensional collagen matrices is differentially affected by cell density, and (2) skin fibroblasts from cancer patients commonly display a foetal-like mode of migratory behaviour. Data presented here indicate that differences in the migration of these cell types are particularly apparent in cultures plated at high density (i.e. at cell confluence); under these conditions, foetal fibroblasts and the foetal-like fibroblasts of cancer patients migrate into the three-dimensional collagen matrix to a significantly greater extent than do normal adult cells. In this initial study concerned with the biochemical basis of these observations, we report that medium conditioned by either foetal or cancer patient fibroblasts stimulates the migration of confluent adult cells. This stimulation of migration is specific to confluent cells, as the migration of subconfluent adult fibroblasts is unaffected by these conditioned media. Gel filtration chromatography of foetal fibroblast-conditioned medium indicates that migration-stimulating activity is recovered in a single peak with an apparent molecular mass in the range of 50–60 (×103). The active migration stimulating factor (MSF) in both foetal and cancer patient fibroblast-conditioned media appears to be a protein stable at acid pH, but inactivated by heat, alkaline pH and reductive alkylation. MSF produced by foetal and cancer patient fibroblasts is presumably responsible for the characteristically elevated levels of migration displayed by these cells in confluent culture, thereby suggesting an autocrine mode of action for this factor. Stimulation of adult cell migration by MSF requires the presence of either serum or plateletpoor plasma and is not observed in serum-free medium. MSF does not appear to affect either the proliferation or morphology of normal adult cells under any of the culture conditions examined.
Fibroblasts from cancer patients display a mixture of both foetal and adult-like phenotypic characteristics
Authors: Schor Seth L. , Schor Ana M. , Rushton Graham 
Published: April 2021

ABSTRACT
We have previously reported that foetal and adult fibroblasts display distinctive migratory phenotypes when cultured on three-dimensional collagen gels. Both skin and tumour-derived fibroblasts from a significant proportion of patients with breast cancer were subsequently observed to display foetal-like migratory behaviour. In the accompanying paper concerned with the biochemical basis of these observations, we presented evidence that foetal fibroblasts and the foetal-like fibroblasts of cancer patients produce a soluble migration-stimulating factor (MSF) not made by normal adult cells. Data are presented here indicating that: (1) the spontaneous foetal to adult transition in migratory phenotype that foetal fibroblasts undergo after approximately 50–55 population doublings in vitro is correlated with a cessation of MSF production; (2) breast cancer patient fibroblasts do not undergo such a phenotypic transition and continue to produce MSF for their entire in vitro lifespan. These foetal-like cancer patient fibroblasts do, however, resemble normal adult cells by a number of other criteria, including population doubling potential, enhanced migration in the presence of serum compared to platelet-poor plasma, saturation cell density and morphology in confluent culture. These data indicate that the fibroblasts of breast cancer patients express a mixture of both foetal and adult phenotypic characteristics. Such a finding is consistent with published information indicating that foetal-to-adult transitions in various fibroblast phenotypic characteristics occur in a temporally disparate fashion during normal development, and further imply that cancer patient fibroblasts have undergone only certain of these transitions.
The structure and interactions of components of nuclear envelopes from Xenopus oocyte germinal vesicles observed by heavy metal shadowing
Authors: Stewart Murray , Whytock Sue 
Published: April 2021

ABSTRACT
We have examined the structure of the nuclear envelope of oocytes of Xenopus laevis by electron microscopy of metal-shadowed specimens. Material was prepared by either freeze-drying or a rapid protocol using air-drying after dehydration in ethanol followed by amyl acetate. These methods emphasized different aspects of the structure and enabled an integrated view of the arrangement of nuclear pore complexes, nuclear lamina and pore-connecting fibrils to be assembled. In specimens prepared by either airdrying or freeze-drying, the lamina meshwork beneath the nuclear face of the envelope was well preserved, but the fine structure of the nuclear pores was superior in freeze-dried preparations. Both methods also showed pore-connecting fibrils that were clearly not components of the lamina. By using stereo pairs, we established criteria for recognizing the cytoplasmic and nucleoplasmic faces of shadowed nuclear envelopes. These views also enabled us to identify the levels at which different fibrous components were attached to the pores. In particular, we were able to visualize the nuclear lamina fibres and poreconnecting fibrils simultaneously and show that they attach to the pore complexes at different levels. We supplemented this work by using a range of treatments to disrupt the nuclear envelope slightly and gained several insights into this structure as a result. Sometimes pore complexes and their connecting fibrils were stripped from the envelope. This enabled a clearer view of these connections to be obtained without the lamina present. Moreover, in some conditions, the nuclear pore complexes and fibrous lamina began to disintegrate, thereby showing some of the morphological components from which they were assembled.
Deficiency in immune complex uptake by chronic granulomatous disease neutrophils
Authors: Petty Howard R. , Franc Joseph W. , Boxer Laurence A. 
Published: April 2021

ABSTRACT
Receptor-mediated binding and endocytosis by normal and chronic granulomatous disease (CGD) polymorphonuclear (PMN) leucocytes have been investigated. Our results suggest that activation of the respiratory burst is a requisite for normal immune complex internalization. Cell-associated immune complexes were detected by fluorescence microscopy, electron microscopy and flow cytometric techniques. These measurements indicate that immune complex uptake is defective in CGD patients, but not in normal subjects. Antibody-dependent binding and complement-dependent binding and endocytosis were not affected. The functional association of the respiratory burst and antibody-dependent endo cytosis was further explored using rhodamine-labelled glucose oxidase: anti-glucose oxidase immune complexes. These complexes generate H2O2 in the presence of glucose. When treated with these complexes, CGD PMNs showed similar glucose-dose-dependent increases in both H2O2 production and cell-associated fluorescence. Therefore: (1) respiratory burst and immune complex uptake are coexisting deficiencies that may be a manifestation of a single defect; and (2) the respiratory burst may be one participant in immune complex endocytic triggering.
The role of intracellular Ca2+ during early sexual development in Dictyostelium discoideum: effects of laci3, lns(1,4,5)P3, TMB-8, chlortetracycline and A23187 on cell fusion
Authors: Lydan Michael A. , O’Day Danton H. 
Published: April 2021

ABSTRACT
The agents LaCl3, Ins(l,4,5)P3, TMB-8, chlortetracycline (CTC) and A23187 were used to study the requirement for internal calcium mobilization during gamete cell fusion in Dictyostelium discoideum. The inhibition of the influx of calcium (LaCl3) prevented cell fusion in a dose-dependent manner. At the intracellular level, Ins(l,4,5)P3, an endogenous regulator of calcium release from intracellular stores, stimulated cell fusion within one hour following its addition. Treatment with agents that prevent the release of calcium from intracellular stores (TMB-8, CTC) also inhibited cell fusion in a dose-dependent manner. However, the non-specific augmentation of cytosolic calcium levels through the use of the ionophore A23187 inhibited cell fusion, and the amount of inhibition was directly related to the drug concentration. Studies on cell morphology and growth plus results from reversibility experiments involving the ability to form macrocysts reveal that these effects are not due to non-specific drug toxicity. In total, these results suggest that the mobilization of calcium both from the extracellular environment and from intracellular stores is important and is probably regulated during gamete cell fusion in D. discoideum.
Insulin-like growth factors and the multiplication of Tera-2, A human teratoma-derived cell line
Authors: Biddle C. , Li C. H. , Schofield P. N. , Tate V. E. , Hopkins B. , Engstrom W. , Husklsson N. S. , Graham C. F. 
Published: April 2021

ABSTRACT
A human teratoma cell line (Tera-2) was grown in serum-free medium, and the population multiplication was stimulated by the addition of somato-medins/insulin-like growth factors (IGFs). Both IGF-I and IGF-II gave maximal stimulation when added daily at 10 ng ml-1. The IGFs did not substantially change the labelling index of the cells, and the IGFs appeared to exert their effect on population multiplication by increasing cell survival. Membranes isolated from Tera-2 cells displayed both type 1 and type 2 IGF receptors.
Endoplasmin is a reticuloplasmin
Authors: Koch G. L. E. , Macer D. R. J. , Wooding F. B. P. 
Published: April 2021

ABSTRACT
The location of endoplasmin in the endoplasmic reticulum was investigated by biochemical and immunoelectron microscopic analyses. The protein could be obtained in a soluble form by procedures that do not involve the use of any detergents. The soluble protein has the amino- and carboxy-terminal sequences of the intact molecule, showing that it has not been proteolysed. Application of the Triton X-114 phaseseparation test does not reveal significant hydrophobicity in the molecule. Immunogold labelling studies on cells with a dilated endoplasmic reticulum (ER) lumen show that endoplasmin is uniformly distributed throughout the lumen, with no evidence of a preferential association with the membrane. These studies clearly demonstrate that endoplasmin is a luminal protein of the ER, i.e. a reticuloplasmin, and not an integral membrane protein.
The ultrastructure and timing of events in the nuclear cycle of the fungus Entomophaga aulicae
Authors: Murrin Faye , Newcomb William , Heath I. Brent 
Published: April 2021

ABSTRACT
The ultrastructure of the mitotic nuclear division cycle of the fungus Entomophaga aulicae was studied from serial sections of hyphal tips and protoplasts. The extranuclear bar-shaped nucleus-associated organelle (NAO) remained associated with the persistent nuclear envelope throughout. Prior to spindle formation, a patch of intranuclear NAO-associated chromatin detached from the nuclear envelope to yield a chromatinfree zone containing fine filaments and a linear array of presumptive kinetochores. Early metaphase spindles less than 1 pm in length were characterized by a ‘fused’ metaphase plate consisting of kinetochore-associated chromatin and a full complement of at least 15 kinetochore microtubules per half-spindle, while most of the chromatin was remote from the intranuclear spindle. Analysis of the distribution of antiparallel spindle microtubules indicated that polar separation and concomitant spindle elongation through metaphase were not accompanied by intermicrotubule sliding. Anaphase exhibited extensive decondensation of the large patches of condensed chromatin characteristic of all other stages. In a logarithmically growing protoplast population all nuclei contained spindle microtubules, with metaphase occupying approximately 66% of the nuclear cycle time. The calculated genome size of 4-3 pg, and average DNA content per chromosome of 0-3 pg, are extremely high for fungi.
Differential Cytolocalization Of Prosomes In Axolotl During Oogenesis And Meiotic Maturation
Authors: Gautier J. , Pal J. K. , de Sa M.-F. Grossi , Beetschen J. C. , Scherrer K. 
Published: April 2021

ABSTRACT
The prosomes, a novel type of small RNA-protein complex previously characterized in avian and mammalian cells, were isolated from axolotl (Ambystoma mexicanutn) oocytes and identified by sedimentation analysis and protein composition. The prosomal nature of these particles was further ascertained by immunoblot analysis with anti-duck prosome monoclonal antibodies. By in vitro [3SS] methionine labelling, de novo synthesis of prosomal proteins could be detected neither during oogenesis nor meiotic maturation. The results obtained by both indirect immunofluorescence and immunoblot analyses demonstrated a dramatic change in the localization of prosomal antigens during oocyte development. They were initially detected in the oocyte cytoplasm, during oocyte growth. At the end of vitellogenesis (stages V-VI), they entered the nucleus (germinal vesicle) and were accumulated there to the highest concentration. During oocyte maturation, after nuclear envelope breakdown, prosomal antigens were found to be localized again in the cytoplasm, until fertilization. No specific localization of prosomal antigens in mature oocytes, unfertilized and fertilized eggs was observed within the oocyte cytoplasm in relation to the cytoplasmic rearrangements leading to grey crescent formation.