bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tetrins: polypeptides that form bundled filaments in Tetrahymena
Authors: Honts Jerry E. , Williams Norman E. 
Published: April 2021

ABSTRACT
The cortex of the ciliated protozoan Tetrahymena contains a number of fibrous elements, including a network of filaments that pervades the feeding organelle of this organism. The cluster of polypeptides (79–89K; K=103MT) in Tetrahymena pyriformis GL-C that constitute these filaments has been purified by in vitro assembly after solubilization in 1.0 M KI. Four distinct sets of these polypeptides, designated ‘tetrins’, have been shown to be distinguishable from each other by immunochemical and biochemical criteria. The smallest filaments reassembled in vitro were 3–4 nm in diameter and these fine filaments were seen to be bundled together into thicker strands of varying diameters, similar to those within the cell. The thicker filament bundles were clearly distinguishable from intermediate filaments, but fine filaments in these bundles were superficially similar to the 2–5 nm filaments described as microtubule-associated proteins in other organisms. The ultrastructure of the tetrin filaments localized within the feeding organelle reveals a substantial presence of these filaments apart from microtubules. In addition, circular dichroism measurements indicate a relatively low a-helical content for these filaments and suggest that the tetrins may be substantially different from other fine filament proteins such as the tektins and giardins.
Changes in the rate of oxygen consumption in synchronous cultures of the fission yeast Schizosaccharomyces Pombe
Authors: Novak B. , Mitchisonf J. M. 
Published: April 2021

ABSTRACT
Oxygen consumption was measured with an oxygen electrode in synchronous cultures of S. pombe. There were changes during the cell cycle in the rate of oxygen uptake, which are most clearly shown as oscillations in acceleration curves (rate of the rate of uptake). Under various conditions of selection and induction synchrony the acceleration curves are similar to those found earlier for CO2 production. As with CO2 production, the oscillations continued after a block to the DNA-division cycle. There were, however, two differences between oxygen uptake and CO2 production. The oxygen oscillations were more marked and also were out of phase by half a cycle. The respiratory coefficient therefore changes through the cycle.
Adaptation to non-ammoniagenic medium and selective substrate feeding lead to enhanced yields in animal cell cultures
Authors: Hassell T. , Butler M. 
Published: April 2021

ABSTRACT
Methods for the adaptation of three animal cell lines to media in which glutamine is replaced with either glutamate or 2-oxoglutarate are described. The cell Unes differ in their rate of adaptation. The consequences of the adaptation of the McCoy cell line to a glutamate-based medium was measured in terms of: cell yield (increased by 17%), ammonia accumulation (reduced by 70%), glucose consumption (decreased by &gt;70%) and lactate accumulation (decreased by &gt;75%).
The value of such adaptation and concomitant changes in energy metabolism lies in the potential for increased cell yields. Batch feeding of adapted cells in a microcarrier culture with a cocktail of glucose and amino acids resulted in increases in cell yields of 80% compared to unfed controls.
Effect of temperature on the assembly of tight junctions and on the mobility of lipids in membranes of ht29 cells
Authors: Cohen E. , Ophir I. , Henis Y. I. , Bacher A. , Shaul Y. Ben 
Published: April 2021

ABSTRACT
In the human colon adenocarcinoma cell line HT29, tight junctions can be induced by treatment with appropriate proteases or salt solutions. The temperature dependence of induced tight junction formation is characterized by a marked sigmoidal behavior. The different methods of induction used in this study were characterized by threshold temperatures ranging from 15 to 32°C. Fluorescence photobleaching recovery measurements of the lateral diffusion of a fluorescent phospholipid probe in the cellular plasma membrane gave no evidence for a phase transition or for alteration in the organization of membrane lipids in lateral domains in the temperature range between 0 and 37°C. Moreover, dynamic parameters of the probe in the plasma membrane did not change substantially on mild treatment with trypsin. Thus, the temperature dependence of tight junction formation is not dictated by the bulk properties of the cytoplasmic membrane lipids. The observed temperature dependence suggests that the assembly of tight junctions is a cooperative process, which may involve conformational rearrangement in a protein precursor subsequent to its proteolytic activation.
Gene expression pattern of chicken erythrocyte nuclei in heterokaryons
Authors: Bergman Mathias , Ringertz Nils 
Published: April 2021

ABSTRACT
Expression of erythro-specific chick genes was studied in heterokaryons prepared by fusing chick erythrocytes (CE) with rat myoblasts. In this type of heterokaryon the inactive erythrocyte nucleus takes up nuclear proteins of myoblast origin and undergoes transcriptional reactivation. In order to study the stability of the genetic programming of the reactivated CE nucleus, chick gene expression was examined by analysis of RNA from the heterokaryons. Probes for several erythro- and chick-specific genes were used. The heterokaryons showed strong expression of the chick histone H5 and adult β-globin genes, while other genes, e.g. the transcription factor Eryf1 gene, normally expressed during erythroid differentiation, were not transcribed. Although the CE used were of the definitive lineage, the heterokaryons showed activation of the chick embryonic β-globin gene, i.e. a gene normally expressed only in CE of the primitive lineage.
We conclude that the reactivation of the mature CE nucleus in a rat cytoplasm resulted in a more immature erythroid gene expression pattern. The activation of the embryonic β-globin gene indicated a switch of the lineage-specific gene expression pattern. This switch occurred in the absence of DNA replication. The strong expression of the globin and H5 genes in heterokaryons, in the absence of expression of the regulatory factor Eryf1, suggested the existence of Eryf1-independent regulatory mechanisms for erythroid gene expression in these cells.
Peroxisomes induced in Candida Boidinii by methanol, oleic acid and d-alanine vary in metabolic function but share common integral membrane proteins
Authors: Goodman Joel M. , Trapp Steven B. , Hwang Harold , Veenhuis Marten 
Published: April 2021

ABSTRACT
Peroxisomes massively proliferate in the methylotrophic yeast Candida boidinii when cultured on methanol as the only carbon and energy source. These organelles contain enzymes that catalyze the initial reactions of methanol utilization. The membranes contain abundant proteins of unknown function; their apparent molecular masses are 20, 31, 32 and 47×10 3M r and are termed PMP20, PMPs31-32 and PMP47. Recently, we reported that peroxisomes in this yeast are also induced by oleic acid and D-alanine as carbon sources, and that these peroxisomes contain increased concentrations of the enzymes of fatty acid β-oxidation or D-amino acid oxidase, respectively. Tliis report extends these findings and further compares the enzyme composition from peroxisomes induced by methanol, oleic acid and D-alanine. The patterns of matrix proteins represented on SDS-polyacrylamide gels from peroxisomes induced by oleic acid or D-alanine were found to be very different from those of peroxisomes induced by methanol. In order to differentiate between membrane proteins that have specific functions in pathways of substrate utilization from those with more generalized functions, peroxisomal membranes from cultures grown on methanol, oleic acid or D-alanine were purified. Analysis of these fractions demonstrated that while PMP20 is found only in peroxisomes induced by methanol, the PMPs31-32 and PMP47 were the abundant peroxisomal membrane proteins (PMP) regardless of inducing substrate. The data strongly suggest that the function of PMP20 is related to methanol metabolism. In contrast, the functions of PMPs31-32 and PMP47 are ‘substrate-nonspecific’. We speculate that they may relate to the structure, assembly or general function of the organelle.
Antibody markers of basal cells in complex epithelia
Authors: Purkis P. E. , Steel J. B. , Mackenzie I. C. , Nathrath W. B. J. , Leigh I. M. , Lane E. B. 
Published: April 2021

ABSTRACT
In the course of immunohistochemical studies it has become apparent that there is a distinct phenotype of keratin expression that is shared by basal epithelial cells in a variety of different tissues. A basal cell can be defined as a cell in contact with a basal lamina but with no free luminal surface; this distinguishes it from a simple epithelial cell, which has a free luminal surface as well as basal lamina contact, and from stratifying suprabasal kératinocytes, which have neither basal lamina contact nor free luminal surface. All basal cells, whether they are in glandular ductal or secretory epithelia, or in stratified squamous epithelia, express the keratin pair K5 and K14. In this paper we describe monoclonal and polyclonal antibodies that are monospecific for both keratins 14 and 5 or are specific for denaturationsensitive epitopes unique to basal cells, including five new monoclonal antibodies: LL001 and LL002 (to keratin 14), 2.1.D7 (to keratins 5, 6 and 8), and LH6 and LH8 (conformation-specific basal cell markers). These antibodies have been used to monitor the distribution of the basal cell phenotype and to demonstrate the expression of keratins 5 and 14 in this cell type, in both stratified epithelia and mixed epithelial glands. The consistent association of this keratin pair with basal cells suggests a possible specific function for these keratin in reinforcing epithelia under physical stress, whilst expression of these keratins may conflict with the differentiated functions of most simple epithelial cells.
Characteristics of cells that give rise to the central nervous system
Authors: Temple Sally 
Published: April 2021

ABSTRACT
Neural induction by the axial mesoderm designates a population of embryonic ectoderm cells to give rise to the central nervous system (CNS). The cells of the neural rudiment are overtly similar and are distributed in a single cell layer that folds up to become the neural tube. The nuclei of the neural tube cells undergo a ‘to and fro’ migration in synchrony with their cell cycles, and the mitotic phase occurs at the border of the neural tube lumen that comprises the early ventricular system (Sauer, 1935). As development proceeds, neurons and glioblasts migrate away from this ventricular zone and begin to form the mature CNS. Different classes of CNS cells arise on well-defined time-schedules (see Jacobson, 1978, for a review) and the precise timing of cell differentiation is likely to be important in generating CNS cytoarchitecture and appropriate cell–cell interactions.
A centrosomal antigen localized on intermediate filaments and mitotic spindle poles
Authors: Buendia Brigitte , Antony Claude , Verde Fulvia , Bornens Michel , Karsenti Eric 
Published: April 2021

ABSTRACT
A monoclonal antibody (CTR2611) raised against centrosomes isolated from human lymphocytes (KE37) stains the pericentriolar material and intermediate filaments in the same cells. In MDCK cells, where most of the microtubules do not originate from the pericentriolar region during interphase, the antigen is distributed along intermediate filaments. At the onset of mitosis, a large fraction of the CTR2611 antigen associates with the minus-end domain of the microtubules of the mitotic spindle but not with the pericentriolar region itself. Treatment of mitotic MDCK cells with taxol leads to the assembly of many microtubule asters in the cytoplasm at the expense of the mitotic spindle. The CTR2611 antigen is present in the center of each of these asters. Similar asters can also be produced in vitro by adding taxol to concentrated Xenopus egg mitotic cytoplasm. Again, the antigen is found close to the center of the asters. These results suggest that CTR2611 antigen is associated with a material involved in microtubule nucleation or microtubule minus-end stabilization. The monoclonal antibody recognizes a 74×103Mr polypeptide and other polypeptides at 120×103Mrand 170×103Mr. The 74×103Mr polypeptide is found in all species examined so far, suggesting that it contains a highly conserved epitope.
Subpopulations of chondrocytes from different zones of pig articular cartilage: Isolation, growth and proteoglycan synthesis in culture
Authors: Siczkowski Martin , Watt Fiona M. 
Published: April 2021

ABSTRACT
Articular cartilage varies in ultrastructure and composition with distance from the articular surface. We have cultured chondrocytes from different zones of pig articular cartilage and investigated whether there are intrinsic differences in their behaviour that might account for the variation observed in intact tissue. On isolation, cells from the upper third of the cartilage were smaller than those of the lower third, but this difference was not maintained in culture. Upper zone cells attached and spread more slowly than lower zone cells; morphological differences between the two populations could be seen for several weeks. The growth rates of the two populations were similar, but upper zone cells reached a lower confluent density. Levels of protein synthesis were similar for both populations, but upper zone cells deposited less proteoglycan in the cell layer. On isolation, the percentage of upper zone cells that stained positive with MZ15, a monoclonal antibody to keratan sulphate, was smaller than the percentage of lower zone cells, but this difference was lost after several days in culture. Nevertheless, the keratan sulphate content of proteoglycan synthesised by lower zone chondrocytes at high density was greater than of that synthesised by upper zone cells. The proportion of nonaggregating proteoglycan was greater in upper than lower zone cartilage and this difference was also observed in long-term cultures. Proteoglycans were further characterised by composite and polyacrylamide gel electrophoresis and by immunoblotting; differences detected in cartilage extracts were not, however, maintained in culture; instead, the small proteoglycans synthesised by both upper and lower zone cells varied with plating density. Finally, alkaline phosphatase, a marker of hypertrophic, calcifying cartilage, was only expressed in lower zone cultures. We conclude that some of the observed heterogeneity of articular cartilage reflects intrinsic differences between the cells of different zones, whereas some may reflect the response of chondrocytes to different environmental conditions.
Modulation of native chondroitin sulphate structure in tissue development and in disease
Authors: Caterson Bruce , Mahmoodian Fatemeh , Sorrell J. Michael , Hardingham Tim E. , Bayliss Michael T. , Carney Stephen L. , Ratcliffe Anthony , Muir Helen 
Published: April 2021

ABSTRACT
Chondroitin sulphate proteoglycans are synthesised by different tissues and cell types, and the chondroitin sulphate chains are variably sulphated. Three monoclonal antibodies 3B3, 7D4 and 6C3 that recognise different native chondroitin sulphate epitopes have been used to investigate changes in structure during embryonic tissue development in the chick and in the response of mature canine articular cartilage during experimental osteoarthritis. Strong focal expression of the epitopes was seen during development of chick bursa, which was different for the three epitopes and which changed during 5 days of development. In embryonic chick limb, although chondroitin sulphate is present throughout the cartilage, the 3B3 epitope, which is at the non-reducing terminus of chains, was only expressed on chondroitin sulphate within one region of the sub-articular cartilage. In mature canine articular cartilage the expression of this epitope on proteoglycans was very low, but when determined 3 or 6 months after induction of experimental osteoarthritis the level was greatly increased in all joints tested (23/23). The abundance of the other two native chondroitin sulphate epitopes was also increased in this experimental disease. The results show that expression of the chondroitin sulphate epitopes detected by the monoclonal antibodies changes during cellular differentiation and development and suggests that it is closely controlled by the cells synthesising chondroitin sulphate chains.
A vibrating electrode analysis of extracellular ion currents in Acetabularia acetabulum
Authors: O’shea Paul , Goodwin Brian , Ridge Irene 
Published: April 2021

ABSTRACT
An investigation of extracellular ionic currents in Acetabularia acetabulum is presented. Utilising the vibrating electrode technique it is shown that there are large (up to 380μAcm-2) light-dependent and small (up to lOμAcm-2) light-independent extracellular ionic currents around Acetabularia. The current density was greatest at the rhizoid and diminished towards the developing apex where there was no measurable current.
Ion-replacement and ion-transport inhibitor studies indicated that Cl-was the main constituent of the light-dependent and light-independent currents. Calcium ions were found to contribute about 5–15% of the light-independent current and &lt;1% of the light-dependent current, as deduced from cobalt inhibition studies. Possible mechanisms responsible for these phenomena are discussed briefly.
The three-dimensional arrangement of chromosomes at meiotic metaphase I in normal and interchange heterozygotes of Briza humilis
Authors: Moss Janet M. , Murray Brian G. 
Published: April 2021

ABSTRACT
Pollen mother cells at metaphase I have been reconstructed from serial sections in normal and interchange heterozygotes of Briza humilis. The pollen mother cells have an irregular shape with a prominent projection from the tangential face into the anther loculus. The seven bivalents of the normal plant are usually arranged with one bivalent in a central position surrounded by a ring of the remaining six or as a ring of all seven bivalents. The centrahperipheral distribution of quadrivalents is different in two different interchange plants; in a sector analysis, where cells are divided into fourquarters relative to the tangential face of the pollen mother cell, the two plants also show differences in quadrivalent distribution, indicating that individual chromosomes occupy different positions in the cell. The relevance of these results to the positioning of quadrivalents in lateral squashes of meiotic metaphase I are discussed.
Broad spectrum pan-cadherin antibodies, reactive with the C-terminal 24 amino acid residues of N-cadherin
Authors: Geiger Benjamin , Volberg Tova , Ginsberg Dorit , Bitzur Sigal , Sabanay Ilana , Hynes Richard O. 
Published: April 2021

ABSTRACT
We describe here the preparation and application of antibodies directed against a synthetic, 24 amino acid long, peptide corresponding to the conserved cytoplasmic C terminus of N-cadherin. We demonstrate here that the antibodies to the synthetic peptide react extensively with all known members of the cadherin family and, in addition, recognize novel cadherins in a variety of cells and tissues, suggesting that these antibodies indeed exhibit pan-cadherin reactivity. By Western blot screening of chicken tissues at least 4 different immunoreactive bands were resolved, commonly disclosing 2–3 distinct bands within the same tissue. The pan-cadherin antibodies also displayed a broad interspecies cross reactivity, recognizing cadherins in man, bovine, canine, avian, amphibian and teleost cells. This property renders these antibodies excellent reagents for the cloning and identification of novel cadherins. Immunocytochemical labelling with the pan-cadherin antibodies, at the light- and electron-microscope levels, revealed an extensive reactivity with intercellular adherens junctions in cardiac muscle and in various epithelia. We thus propose that the pan-cadherin antibodies may be used as ubiquitous cadherin probes and serve as markers for adherens junctions.
Subcellular distribution of hepatic alanine:glyoxylate aminotransferase in various mammalian species
Authors: Danpure Christopher J. , Guttridge Keith M. , Fryer Patricia , Jennings Patricia R. , Allsop Jennifer , Purdue P. Edward 
Published: April 2021

ABSTRACT
The subcellular distribution of alanine:glyoxylate aminotransferase 1 (AGT1) enzyme activity and immunoreactive protein has been determined in the livers of a variety of mammalian species (marmoset, baboon, cat, rabbit, pig, sheep) using the techniques of post-embedding protein A-gold immunoelectron microscopy and isopycnic density gradient centrifugation. In baboon and rabbit livers, AGT1 was exclusively peroxisomal. Morphometric analysis of the distribution of immunoreactive AGT1 protein in cat liver showed that 91–92% was located in the mitochondria with 8–9% in the peroxisomes. In marmoset liver, 59% of AGT1 was found in the mitochondrial matrix and 41% in the peroxisomal matrix. The results from pig and sheep were ambiguous, because of the low levels of expression of AGT1. The implications of these data in terms of the metabolic roles of AGT1 (gluconeogenesis and glyoxylate detoxification) and in terms of the evolutionary acquisition and loss of functional mitochondrial and peroxisomal targeting sequences are discussed.
Kinetochore fiber formation in dividing generative cells of Tradescantia Kinetochore reorientation associated with the transition between lateral microtubule interactions and end-on kinetochore fibers
Authors: Liu Bo , Palevitz Barry A. 
Published: April 2021

ABSTRACT
Division of the generative cell of Tradescantia virginiana is unusual in that a typical bipolar spindle is not present Instead, the cell contains an axial system of microtubule (Mt) bundles, with kineto-chores distributed along the length and depth of the cell. Kinetochore fibers appear to be derived from and remain attached to the Mt bundles. Localizations with both anti-tubulin and CREST serum were performed in order to probe this relationship further. Pairs of CREST-positive, fluorescent dots presumed to be kinetochores are initially oriented transverse to the cell axis and appear to be associated with the Mt bundles via latéral interactions. Adjacent pairs are often joined to the same bundles, like rungs on a ladder. Lateral interactions are then converted intoor replaced by end-on kinetochore fibers similar in morphology to those seen in other cells. This conversion is accompanied by a realignment of the kinetochore pairs along the long axis of the cell. In addition, the center-to-center spacing between filial kinetochores doubles. Interconnections between kinetochore fibers and surrounding Mts appear to be maintained during the transition. These results may provide a general insight into the manner in which kinetochores interact with the division apparatus in eukaryotes.