bluuebunny/crossref_metadata_2025_split huggingface dataset:
Variation in cytoplasmic microtubule organization and spindle length between the two forms of the dimorphic fungus Candida albicans
Authors: Barton Richard , Gull Keith 
Published: April 2021

ABSTRACT
Candida albicans is a dimorphic fungus capable of growing as a budding yeast and as a filamentous hypha. We have used the technique of immunofluorescence to study the changes in the microtubule cytoskeleton during the cell cycle in both growth forms. This approach has revealed the presence of an extensive system of microtubules, including cytoplasmic microtubules and a rod-like intranuclear spindle. We have provided a complete description of the arrangement of cytoplasmic and spindle microtubules at each phase of the yeast cell cycle. A novel and characteristic feature of the yeast phase of Candida is the presence of an array of short microtubules at the neck of the doublet cell. This neck-associated array (NAA), is apparently organized independently of the main microtubuleorganizing centre, the spindle pole bodies, at late anaphase. Analysis of microtubule patterns in the hyphal state reveals that the general arrangements of microtubules are similar to those seen in the yeast phase. These patterns suggest a role for the cytoplasmic microtubules in the nuclear migration that occurs during hyphal growth. A major finding is that the mitotic spindle in hyphae is considerably longer (12–20μm) than the spindle in yeast cells (7–8 μm). This may reflect the role of the hyphal mitotic spindle not only in nuclear division but also in the positioning of the daughter nuclei at the centres of hyphal compartments.
Expression pattern of two related cystic fibrosis-associated calcium-binding proteins in normal and abnormal tissues
Authors: Wilkinson Maureen M. , Busuttil A. , Hayward Caroline , Brock D. J. H. , Dorin Julia R. , Heyningen Veronica Van 
Published: April 2021

ABSTRACT
This paper reports further study of the identity and function of a protein shown to be elevated in serum from cystic fibrosis (CF) patients and clinically normal heterozygotes. Monoclonal antibodies, specifically recognizing the tentatively named cystic fibrosis antigen (CFAg), were produced. Immunoaffinity purification of CFAg from several sources revealed two components: 11×103 and 14×103Mr proteins. cDNA clones corresponding to each protein have been isolated. Data-base comparisons of the deduced amino acid sequences suggest that both genes encode related but distinct calcium-binding proteins. We propose the name calgranulin A and B, for the 11×103 and 14×103Mr components, respectively. It is clear from the assignment of the calgranulin genes to chromosome 1 that neither is the product of the mutant CF gene, which maps to chromosome 7.
We have used the monoclonal antibodies to study the tissue distribution of the two proteins in a wideranging immunohistological survey. Where possible the pattern of expression was confirmed by RNA blot analysis. Strong calgranulin expression in granulocytes was confirmed. In addition to myeloid cells, a restricted subset of normal stratified squamous epithelia were found to be calgranulin-positive. These included tongue, oesophagus and buccal cells, the last of which has been shown to have altered calmodulin activity in CF patients. Using indirect alkaline phosphatase staining, tissue sections of lung, pancreas and skin (normally considered sites where the CF defect is expressed) were not calgranulin-positive. However, by indirect immunofluorescence, nasal polyp sections showed weak patchy calgranulin expression in some epithelial cells, and stronger, higher frequency expression when such cells were briefly cultured.
A number of hyperproliferative, neoplastic or frankly malignant epithelia were found to express the two proteins. Calgranulin expression is a good marker for ‘reactive’ epithelium in skin and for squamous cell carcinomas of skin, lung and buccal tissues. The calgranulin-positive permanent cell line from a buccal squamous cell carcinoma may prove a suitable tool for unravelling the calgranu-lin-CF relationship.
Dictyostelium discoideum mutant Synag 7 with altered g-protein–adenylate cyclase interaction
Authors: Snaar-Jagalska B. Ewa , Haastert Peter J. M. Van 
Published: April 2021

ABSTRACT
Previous results have shown that Dictyostelium discoideum mutant synag 7 is defective in the regulation of adenylate cyclase by receptor agonists in vivo and by GTPγS in vitro; the guanine nucleotide activation of adenylate cyclase is restored by the high-speed supernatant from wild-type cells.
Here we report that in synag 7 membranes: (1) cyclic AMP receptors had normal levels and were regulated by guanine nucleotides as in wild-type; (2) GTP binding and high-affinity GTPase were reduced but still stimulated by cyclic AMP; (3) the supernatant from wild-type cells restored GTP binding to membranes of this mutant, and partly restored high-affinity GTPase activity; (4) the supernatant of synag 7 was ineffective in these reconstitutions and did not influence GTP binding and GTPase activities in mutant or wild-type membranes.
These results suggest that the defect in mutant synag 7 is located between G-protein and adenylate cyclase, and not between receptor and G-protein. A factor in the supernatant is absent in synag 7 and appears to be essential for normal GTP binding, GTPase and activation of adenylate cyclase. This soluble heat-labile factor may represent a new molecule required for receptor-and G-protein-mediated activation of adenylate cyclase.
MSH inhibits growth in a line of amelanotic hamster melanoma cells and induces increases in cyclic AMP levels and tyrosinase activity without inducing melanogenesis
Authors: Slominski Andrzej , Moellmann Gisela , Kuklinska Elizabeth 
Published: April 2021

ABSTRACTIn Bomirski Ab amelanotic hamster melanoma cells, L-tyrosine and/or L-dopa induce increases in tyrosinase activity as well as synthesis of melanosomes and melanin. L-tyrosine also modifies melanocyte-stimulating hormone (MSH) binding. In this paper we show that in the Bomirski amelanotic melanoma system MSH and agents that raise inUa-cellular cyclic AMP induce dendrite formation, inhibit cell growth, and cause substantial increases in tyrosinase activity without inducing melanin synthesis. Tyrosinase activity is detected only in broken cell preparations, or cytochemically in fixed cells. In the continued absence of mature melanosomes, the induced enzyme remains in elements of the trans-Golgi reticulum. Comparative measurements of cyclic AMP in amelanotic and tyrosine-induced melanotic cells show similar basal levels. L-tyrosine and L-dopa have little or no effect, whereas MSH may cause a 1000 % peak increase in cyclic AMP levels both in amelanotic and melanotic cells. None of these agents influences cyclic GMP or inositol trisphosphate (InsP3) levels. Ln agreement with the InsP3 assays, phorbol ester (TPA) has no effect on melanization, tyrosinase activity or cell prolfleration. In conclusion, in the Bomirski amelanotic melanoma, MSH induces only partial cell differentiation associated with raised levels of cyclic AMP. Induction of melanosome synthesis and melanization by L-tyrosine or L-dopa appear to follow pathways unrelated to cyclic AMP, cyclic GMP or InsP3.
Microtubule orientation during stomatai differentiation in grasses
Authors: Cho Soon-ok , Wick Susan M. 
Published: April 2021

ABSTRACT
The changing orientation of microtubules (MTs) during formation of the stomatai complex in grasses was observed by immunofluorescence microscopy, beginning with the asymmetrical division of the cell that gives rise to the guard cell mother cell, i.e. the guard cell grandmother cell. The asymmetrically placed preprophase band (PPB) of guard cell grandmother cells and hair cell mother cells is always laid down parallel to the distal end wall even when this wall is oblique to the long axis of the cell. The first step in formation of the PPB of a subsidiary cell mother cell appears to be establishment of an incomplete band of MTs. Whereas the mature PPB forms a curved line in a face view of a subsidiary cell mother cell, in this early stage MTs form fan-shaped arrays that focus on two points along the edge of the subsidiary cell mother cell. Replacement of the transversely oriented interphase microtubule band of the guard cell mother cell with the longitudinally oriented PPB involves several distinctive stages: (1) appearance of MTs directed toward the centre of the periclinal surface along the entire length of the lateral walls. (2) Appearance of another set of MTs along the entire width of both end walls, likewise focused toward the centre of the periclinal surface. Together these two groups of MTs form a cross with broadened tips in face view of the leaf. (3) Disappearance of the first set of MTs, and formation of an increasingly narrow band from the latter at the site of future cytokinesis. Although the anaphase spindles of guard cell grandmother cells, hair cell mother cells and guard cell mother cells are usually diagonally oriented relative to the site occupied previously by the PPB, the line connecting the centres of the spindle poles that are established at prophase is perpendicular to the persisting PPBs. Unlike the situation in certain other hair cells, MTs in leaf hair cells are transversely oriented even when the cells are highly elongated.
The glycoprotein of VSV accumulates in a distal Golgi compartment in the presence of CCCP
Authors: Burkhardt Janis K. , Hester Susan , Argon Yair 
Published: April 2021

ABSTRACT
The post-translational modifications of the G protein of vesicular stomatitis virus, described in the preceding paper, indicate that its transport is arrested by carbonylcyanide m-chlorophenylhydra-zone (CCCP) in or near the trans-Golgi. Immuno-fluorescence microscopy of BHK-21 cells infected with vesicular stomatitis virus and treated with CCCP shows an accumulation of G protein in the Golgi area. In the same cells, the morphology of wheat germ agglutinin (WGA)-staining structures in the perinuclear region is aberrant. Using anti-BiP antibody, there is no obvious change in the structure of the endoplasmic reticulum. Electron microscopy reveals that the aberrant structures in the perinuclear region result from dilation of Golgi cistemae and accumulation of large vacuoles near the Golgi stack. The appearance of these aberrant structures is dose-dependent and they disappear after the protonophore is removed. The vast majority of the vacuoles accumulate on the trans side of the Golgi stack. A small fraction of them contain the marker enzyme thiamine pyrophosphatase (TPPase). By immunoelectron microscopy, most of the vacuoles contain G protein. We conclude that most of the Golgi-associated vacuoles are derived from a distal Golgi transport compartment, possibly the trans-Golgi reticulum, and that CCCP reversibly inhibits the transport of newly synthesized G protein through this distal compartment.
Injection of Xenopus eggs before activation, achieved by control of extracellular factors, improves plasmid dna replication after activation
Authors: Wangh Lawrence J. 
Published: April 2021

ABSTRACT
Injection of molecular probes into unfertilized Xenopus eggs requires suppression of activation. But the unfertilized egg is poised for activity, and pricking, like sperm penetration, triggers the start of the first cell cycle. Methods of suppressing activation generally rely on introduction of drugs into the cell, but some of these techniques are irreversible. I report here that injection without activation can also be accomplished by simply limiting extracellular free Ca2+ to 1–2 μM. The site of injection heals, but the cortex does not contract. Gentle modification of the vitelline envelope, which causes it to become tougher, improves the rate of healing to about 100%. Healed eggs are stable for hours and can be activated when needed. Injection of a plasmid derived from type 1 bovine papilloma virus revealed that replication occurs only after activation, but preloading the DNA markedly increased the efficiency of first-round replication. DNA interaction with the unactivated egg cytoplasm may therefore be required for efficient replication of exogenous DNA. The new procedures described here are likely to be of general utility.
Nucleoside diphosphokinase, an enzyme with step changes in activity during the cell cycle of the fission yeast Schizosaccharomyces pombe II. dissociation of the steps from the DNA-division cycle after induction synchronization
Authors: Creanor J. , Mitchison J. M. 
Published: April 2021

ABSTRACT
Synchrony was induced in cultures of the mitotic mutant cdc2.33 of Schizosaccharomyces pombe by shifting up an asynchronous culture to the restrictive temperature for a period of 3–5-4–5h and then shifting down to the permissive temperature. The resulting synchronous divisions had short cycle times, down to 50% of the normal cycle. The oscillatory control of nucleoside diphosphokinase activity was also synchronized by the shift-down and the activity rose in a step pattern. Unlike the situation in the normal cycle, this step pattern was dissociated from the shortened cell cycle and had a longer period and different phase relations. It may be that the normal entrainment or coupling between the cell cycle and the activity control fails if the cell cycle is too short. The period of the activity control (equal to the protein doubling time at the restrictive temperature) appears to be temperature-compensated.
Lithium ions induce prestalk-associated gene expression and inhibit prespore gene expression in Dictyostelium discoideum
Authors: Peters Dorien J. M. , Campagne Michiel M. Van Lookeren , Haastert Peter J. M. Van , Spek Wouter , Schaap Pauline 
Published: April 2021

ABSTRACT
We investigated the effect of Li+ on two types of cyclic AMP-regulated gene expression and on basal and cyclic AMP-stimulated inositol 1,4,5-trisphos-phate (Ins(1,4,5)P3) levels. Li+ effectively inhibits cyclic AMP-induced prespore gene expression, half-maximal inhibition occurring at about 2mM-LiCl. In contrast, Li+ (1–3 mM) promotes the cyclic AMP-induced increase of cysteine proteinase-2 mRNA levels, and induces the expression of this prestalk-associated gene in the absence of cyclic AMP stimuli. At concentrations exceeding 4–5 mM, LiCl inhibits cysteine proteinase-2 gene expression. LiCl reduces basal Ins(1,4,5)P3 levels and decreases the cyclic AMP-induced accumulation of Ins(1,4,5)P3; both effects occur half-maximally at 2–3 mM-LiCl. These results indicate that the induction of the cysteine proteinase-2 gene by Li+ is not due to elevated levels of Ins(1,4,5)P3. It is, however, possible that inhibition of prespore gene expression by Li+ is caused by Li+-induced reduction of basal and/or stimulated Ins(1,4,5)P3 levels.
Evidence for a M
r 88 000 glycoprotein with a transmembrane association to a unique flagellum attachment region in Trypanosoma brucei
Authors: Woods Angela , Baines Anthony J. , Gull Keith 
Published: April 2021

ABSTRACT
We have examined the relationship of externally accessible proteins associated with the internal cytoskeleton of procyclic Trypanosoma brucei. Two approaches were taken. First, externally disposed glycoproteins were identified with lectins and examined for their persistence and location in isolated cytoskeletons. Second, proteins containing tyrosine residues available for chemical modification on the outer surface were identified in isolated cytoskeletons and probed for glycosylation. The procyclic form of T. brucei that was employed does not express the variable surface glycoprotein. The lectin concanavalin A (ConA) bound to the outer surface of T. brucei in two discrete locations; one a narrow line close to the flagellum attachment zone on the cell body, the other at the distal tip of the flagellum itself. Of these, only the cell body labelling was detected when isolated cytoskeletons were probed with fluorescein isothiocyanate-labelled ConA. When cytoskeletons were prepared from cells labelled with gold-conjugated ConA, a narrow line of label was detected parallel to the flagellum attachment zone but was distinct from it. Only one cytoskeletal protein, of Mr 88 000, could be labelled at the cell surface by the 125l/iodogen procedure. This protein could be precipitated from SDS-solubilized cytoskeletons with ConA-agarose. These data indicate the existence of a previously undetected cytoskeletal structure, situated in the cell body, close to the point of flagellum attachment, which has a transmembrane association with an external Mr88000 glycoprotein.
Infection of algae-free Paramecium bursaria with symbiotic Chlorella sp. isolated from green paramecia: II. A timed study
Authors: Meier Renate , Wiessner Wolfgang 
Published: April 2021

ABSTRACT
Algae-free Paramecium bursaria was exposed to cells of Chlorella sp. for 30 s (pulse) and then incubated in algae-free medium for periods between 0 and 15 min. During this chase the fate of the vacuoles formed during the exposure to algae was followed in order to reveal the moment of perialgal vacuole (PV) formation. PVs are characterized by always enclosing an individual algal cell and thus differ from digestive vacuoles (DVs). PVs did not appear immediately after the pulse, but were found only in cells chased for at least 3 min. In those ciliates the algae-containing vacuoles were more than 3 min old and located in the middle part of the cell. These results showed that PVs were not formed directly at the cytopharynx, but many algae were at first enclosed together in large DVs. After the release from the cytopharynx DVs undergo a sequence of fusion events during their cyclosis: fusion with acidosomes apparently occurs at the cell’s posterior end, not later than 2 min, and fusion with lysosomes in the middle region of the cell at the earliest at about 7 min, after the pinching off of a DV from the cytopharynx. Thus, PVs appeared to develop from condensing DVs after acidosomal but before lysosomal fusion. As the first step, part of the DV enclosing an individual algal cell must detach from the large vacuole. Further steps and the implications of the mechanism of PV formation resulting in the re-establishment of endosymbionts in P. bursaria are discussed.
A comparison of the biological activities of the cell-adhesive proteins vitronectin and fibronectin
Authors: Underwood P. A. , Bennett F. A. 
Published: April 2021

ABSTRACT
The effects of vitronectin and fibronectin upon the attachment and growth of bovine corneal endothelial cells (BCE) and BHK-21 cells were compared. Similar dose-response curves for cell attachment to the substratum were obtained for both molecules and both cell types, although BCE cells exhibited a slight preference for vitronectin, and BHK cells for fibronectin. When, however, cells were plated in medium containing bovine serum stripped of fibronectin, they attached and grew normally, whereas in medium containing serum stripped of vitronectin, cells either failed to attach (BHK-21) or attached but exhibited poor cell spreading and growth. This dependence of cells upon vitronectin, rather than fibronectin, in serum for cell attachment, was shown to be due to a failure of fibronectin to coat the substratum in the presence of other serum proteins. Vitronectin was able to coat the substratum efficiently in the presence of other serum proteins. Although dependent upon vitronectin for adhesion to the substratum, bovine endothelial cells were unable to synthesize endogenous vitronectin.
Ultrastructure of Fanconi anemia fibroblasts
Authors: Willingale-Theune J. , Schweiger M. , Hirsch-Kauffmann M. , Meek A. E. , Paulin-Levasseur M. , Traub P. 
Published: April 2021

ABSTRACT
Employing indirect immunofluorescence and conventional electron microscopy, gross nuclear aberrations were observed in cultured interphase fibroblasts derived from a patient suffering from Fanconi’s anemia (FA). Such aberrations were predominantly expressed in cells at high passages between 28 and 34. The structure of the nuclei appeared compound in nature, often consisting of two to three nuclear fragments connected to each other by thin nuclear bridges containing chromatin and nuclear lamin material. In other cases, the nuclei appeared lobed or budded but the cells did not contain distinct nuclear fragments. Chromatin was conspicuously absent from some nuclear lobes, revealing empty, cage-like structures comprising nuclear lamin material. Micronuclei were often abundant in the perinuclear cytoplasm but in some instances they appeared to be composed of chromatin lacking a delineating nuclear lamin matrix. Residual cytoskeletons examined by whole-mount electron microscopy revealed a network of inter mediate filaments (IFs) within FA fibroblasts forming a bridge between the plasma membrane and the nucleus or its major fragments. In addition, there were thinner, 3–4 nm filaments connecting individual IFs with the surface of the nucleus. Micronuclei that were not connected to the main nuclear body, but which were delineated by a distinct lamina and possessed nuclear pores, did not appear to be anchored to the IF network. Multinuclearity, nuclear fragmentation, irregular chromatin distribution and inter-nuclear chromatin/lamin bridges might result from a failure in the redistribution of chromatin to sister nuclei, incomplete cytokinesis and proliferation of nuclear envelope material. These phenomena point to precocious aging of FA fibroblasts and may occur as a consequence of spontaneous damage to the sister chromatids or through the action of DNA-toxic agents.
Cellular localization of the serh surface antigen in Tetrahymena thermophila
Authors: Bolivar Ignacio , Guiard-Maffia Jacqueline 
Published: April 2021

ABSTRACT
We have purified the SerH surface antigen of T. thermophila by a novel and simple procedure and produced specific antisera against it. By the use of various immunochemical techniques, we have investigated the intracellular distribution of the antigen and shown that SerH is not only abundant in the cortex but also in the digestive apparatus of the ciliate. In each of these two localizations, SerH occupies a variety of compartments: in the cortex it can be found in the surface coat, the exocytotic mucocysts, the endocytotic parasomal sacs and as an integral protein of the membrane; in the digestive apparatus, SerH is found around ingested bacteria, in the cytoplasm surrounding the cytopharynx and the forming food vacuoles, and, seemingly, as a membrane-associated protein in young food vacuoles. Pulse-chase experiments have shown that feeding dramatically increases the global turnover of SerH. Besides these localizations, SerH is principally found in clumps around dense intracytoplasmic spheres, which could be mucocyst precursors. Indirect evidence is presented that SerH is routed to the peripheral or extracellular compartments via the mucocysts. The antigen is absent from alveolar, nuclear or mitochondrial membranes. We propose that SerH covers any membrane in contact or future contact with the extracellular medium.