bluuebunny/crossref_metadata_2025_split huggingface dataset:
The abnormal morphology of polyoma-transformed baby hamster kidney cells is due to a failure to respond to 70k spreading factor
Authors: Knox Peter , Griffiths Sheila 
Published: April 2021

ABSTRACT
The typical elongated bipolar morphology of baby hamster kidney (BHK) cells is not shown by polyoma-transformed BHK (Py-BHK) cells. Instead, the transformed line adheres poorly to tissue-culture plastic and cells have a more rounded morphology than the parent line. Plasma fibronectin is known to mediate the spreading of BHK cells, but when human serum is subjected to Sephacryl S-300 chromatography two peaks of spreading activity are eluted; the first is fibronectin and the second, which is quantitatively more significant, is a 70 K protein that is not related to fibronectin and stimulates spreading by a different mechanism. Py-BHK cells spread well in low concentrations of purified fibronectin but will not spread well in levels of serum that contain similar of greater concentrations of fibronectin. This is because fibronectin-mediated spreading of both BHK and Py-BHK cells occurs only in the presence of low concentrations of other proteins; albumin and other serum proteins inhibit fibronectin-mediated spreading. BHK cells spread under routine culture conditions in response to the 70 K factor rather than fibronectin. The altered morphology that results from viral transformation is due to a failure of the cells to respond to the 70 K spreading factor.
Biliary secretion of sodium fluorescein in primary monolayer cultures of adult rat hepatocytes and its stimulation by nicotinamide
Authors: Gebhardt Rolf , Jung Wilhelm 
Published: April 2021

ABSTRACT
Addition of sodium fluorescein to primary cultures of rat hepatocytes resulted in a rapid uptake of the dye by the hepatocytes and a subsequent accumulation in bile canaliculi-like structures. A similar distribution was obtained with fluorescein diacetate. Concentrations of Na-fluorescein accumulating within canaliculi varied over a wide range, often far exceeding that used in the medium. Ouabain strongly blocked cellular uptake, thus also impairing secretion of Na-fluorescein, whereas colchicine affected neither process. Taurolithocholate had virtually no influence on uptake, but markedly reduced the number of fluorescent canaliculi. Furthermore, fluorescent canaliculi could be discharged by addition of 1 M-sucrose in Hank’s buffer, without affecting viability of the cultured cells.
The percentage of canicular structures accumulating high amounts of Na-fluorescein markedly increased during cultivation for 7 days, concomitant with the progressive development of originally small and sporadic canaliculi into an anastomosing network of slender channels. This canalicular proliferation was strikingly reinforced by 20 mM-nicotinamide, resulting in an impressive network of canaliculi within 2–3 days. Nicotinamide also supported the secretion of Na-fluorescein, which could be stimulated further by addition of dehydrocholate.
These results suggest that cultured hepatocytes are able to re-create a functional biliary polarity at least with respect to the biliary secretion of Na-fluorescein.
In vitro proliferation and lifespan of bovine aorta endothelial cells: Response to conditioned media
Authors: W. Lincoln David , Whitney Ronald G. , Smith James R. 
Published: April 2021

ABSTRACT
The effect of conditioned medium on the growth rate of bovine aorta endothelial cells (CSC311) was examined. Media conditioned by several cell types (both immortal and normal) was found to increase the growth rate of CSC311 cells-The growth rate of CSC311 was increased even when the medium was conditioned by other CSC311 cells. The rate of growth of unstimulated CSC311 cells is 0·43 population doublings (p.d./day. Conditioned medium from several cell types gave a maximum stimulated growth rate of 1·3 p.d./day. In addition, we present evidence for an increase in the degree of stimulation by the growth-promoting activity found in conditioned medium with increasing in vitro age of CSC311 cells.
Mechanism of fc-mediated interaction of eosinophils with immobilized immune complexes: I. effects of inhibitors and activators of eosinophil function
Authors: Oliver Rhonda C. , Glauert Audrey M. , Thorne Kareen J. I. 
Published: April 2021

ABSTRACT
A protein of apparent molecular weight 55000, designated protein 3, becomes newly detectable on the eosinophil surface as a specific consequence of interaction with antigen-antibody complexes immobilized in agar layers. The effect of various agents upon this interaction has been determined by monitoring the appearance of this protein by lactoperoxidase-catalysed iodination. Other parameters that have been measured include: the attachment of eosinophils to the agar layers and their subsequent degranulation, as measured by the release of granule peroxidase, and the degree of spreading of the eosinophils, as assessed by electron microscopy.
Attachment of eosinophils to antibody-coated layers is inhibited by heat-aggregated immunoglobulin G (IgG), suggesting that this attachment is mediated via eosinophil Fc receptors. In addition, agents, such as the eosinophil chemotactic factor Ala-Gly-Ser-Glu, that enhance the expression of Fc receptors also enhance the appearance of protein 3, while agents, such as hydrocortisone, that inhibit the expression of Fc receptors reduce its appearance. It is concluded that the appearance of protein 3 parallels the expression of Fc receptors.
Attempts to block the Fc region of the bound antibody with staphylococcal protein A were not successful. These experiments indicated that the Fc region of bound IgG has different binding sites for protein A and for the Fc receptor.
The correlation between the appearance of protein 3 and subsequent degranulation of the eosinophils was confirmed by the use of agents, such as cytochalasin D and levamisole, that enhance both the appearance of protein 3 and degranulation. Conversely, hydrocortisone reduces the appearance of protein 3 and inhibits degranulation.
Protein 3 does not appear when eosinophils adhere to agar layers coated with concanavalin A instead of antibody and the eosinophils do not degranulate. Addition of the calcium ionophore A23187, while causing the release of granule peroxidase, does not elicit the appearance of protein 3. These observations provided additional evidence that the appearance of protein 3 is a specific consequence of the interaction of eosinophils with antibody-coated surfaces.
The fact that protein 3 appears at the eosinophil surface as a direct consequence of the interaction with antibody suggests that this protein is closely associated with the eosinophil Fc receptor. The enhancement of the appearance of protein 3 in the presence of cytochalasin D indicates that the movement and reorientation of both this protein and the Fc receptor are constrained by association with cytoplasmic microfilaments.
The mechanism of fc-mediated interaction of eosinophils with immobilized immune complexes ii. identification of two membrane proteins, modified by the interaction
Authors: Thorne Kareen J. I. , Free Jill , Franks David , Oliver Rhonda C. 
Published: April 2021

ABSTRACT
Human peripheral blood eosinophils attach to and flatten down onto antibody-coated surfaces and subsequently degranulate. An antibody-coated surface was prepared by treating a layer of agar, containing tetanus toxoid antigen and eosinophil chemotactic factor (EOF), with human anti-tetanus immunoglobin. Changes in eosinophil surface proteins during attachment to the antibody-coated agar layer were detected by lactoperoxidase catalysed iodination. Purified eosinophils were pre-treated with unlabelled iodide, lactoperoxidase and hydrogen peroxide to block pre-existing accessible tyrosine residues on the cell surface. They were then allowed to interact with the agar layer, and subsequently treated with lactoperoxidase and luI-labelled iodide to label newly accessible surface proteins. Separation of the radioactive proteins by sodium dodecyl sulphate/polyacrylamide gel electrophoresis revealed that, while incubation of the cells in suspension restored the major proteins to the cell surface, interaction with the antibody-coated agar layer caused the appearance of additional proteins of apparent molecular weight 55K, 30K, 28K and 18K.
The 55K, 28K and 18K proteins were greatly reduced when antibody was absent, but the 55K protein was distinguishable from immunoglobulin G (IgG) heavy chain, since it could be detected in low amounts even in the absence of antibody. It was found in purified plasma membranes and it could be separated from IgG heavy chain by iso-electric focusing. The possibility is discussed that this protein is either linked to the receptor for the Fc portion of IgG, or that it is itself the receptor.
The 18K protein required both antibody and ECF for maximum expression, but was seen in limited amounts with ECF alone. Possibly it is concerned with an ECF-mediated recognition of IgG. Unlike the 55K protein, it binds concanavalin A.
Plasma membranes were prepared from eosinophils by lysis in borate, followed by purification on a glass-bead column. Both the 55K and the 18K proteins were found to be major components of the eosinophil membrane.
An ultrastructural study of the interaction in vitro between Trypanosoma theileri and bovine leucocytes
Authors: Townsend Jackie , Duffus W. P. H. , Glauert Audrey M 
Published: April 2021

ABSTRACT
Bovine neutrophils, eosinophils and macrophages obtained from the mammary gland were cytotoxic to Trypanosoma theileri epimastigotes in vitro in the presence of specific antibody. A detailed ultrastructural study revealed that all types of effector cell phagocytosed T. theileri despite the relatively large size of this parasite (10–130μm).
Phagocytosis proceeded in the classical manner by envelopment of the trypanosome by long pseudopodia. With eosinophils and macrophages structural damage of the parasite was only observed following ingestion. There was evidence of inter-granule fusion in eosinophils prior to the discharge of granule contents into the parasitophorous vacuole; following degradation of the parasite in eosinophils some phagolysosomes opened to the exterior and released what appeared to be trypanosome debris. While eosinophils required less than 30 min to initiate serious damage to the parasite, macrophages required in excess of 2 h to produce similar damage. Conversely, neutrophils caused severe damage within 5 min.
An important feature of neutrophil-mediated cytotoxicity was the extensive structural damage to the parasite that was observed before closure of the phagosome. Initially this damage was observed at the end of the trypanosome that was in contact with the neutrophil. This finding suggests that neutrophil-mediated killing of T. theileri is a combination of both extracellular and intracellular mechanisms.
Structure and chemical composition of insoluble filamentous components of sperm flagellar microtubules
Authors: Linck R. W. , Langevin G. L. 
Published: April 2021

ABSTRACT
By progressive solvent extraction, we have obtained a series of subfragments of flagellar microtubules. Mild treatment gives rise to ribbons that contain longitudinally arranged protofilaments. Further extraction leaves a distinctive residue containing thinner ribbons, of three and eventually two protofilaments. Finally, filaments 2–3 nm in diameter and fibrous ribbons apparently containing 6 or more 2 nm subfibrils are found. This latter solvent-resistant material is consistently enriched in a characteristic set of polypeptides, which are found in flagella of several different species, including echinoderms and a mollusc. These polypeptides appear different from α- and β-tubulin on the basis of their solubilities, isoelectric points and electrophoretic mobilities in sodium dodecyl sulphate/polyacrylamide gels; these conclusions are reinforced by peptide mapping after limited proteolytic digestion, although the latter method reveals certain similarities between these unique flagellar proteins, tubulin, chicken gizzard desmin and rabbit actin. A remarkable feature of the protein in the final fraction is the high a-helical content: 71 % as measured by circular dichroism. We consider the possible origins of these filaments in the microtubule, in particular the possibility that microtubule protofilaments are heterogeneous in protein composition, and we discuss some of the implications of our findings.
Gene expression in Acetabularia: I. Calibration of wheat germ cell-free translation system proteins as internal references for two-dimensional electrophoresis
Authors: Shoeman Robert L. , Schweiger Hans-Georg 
Published: April 2021

ABSTRACT
Modification of existing two-dimensional techniques enables isoelectric focusing and sodium dodecyl sulphate polyacrylamide gel electrophoresis of complex mixtures of proteins to be completed within 8 h. The method was optimized to separate the protein components of a wheat germ cell-free translation system, providing a statistically proven resolution better than 0 03 of a pH unit for the isoelectric point and 1000 for Mr. Fourteen of the more than 300 proteins separated were characterized with respect to Mr and isoelectric point relative to standard proteins under the same conditions. Stained wheat germ proteins thus serve as internal standards for analysis of in vitro translation products.
Patterns of protein synthesis during the cell cycle of the fission yeast Schizosaccharomyces pombe
Authors: Creanor J. , Mitchison J. M. , Williams D. A. 
Published: April 2021

ABSTRACT
The rate of protein synthesis through the cell cycle of Schizosaccharomyces pombe has been determined from the incorporation of pulses of [3H]tryptophan in synchronous cultures prepared by selection in an elutriating rotor. This selection procedure caused minimal perturbations as judged by asynchronous control cultures, which had also been put through the rotor. The rate of synthesis showed a periodic pattern rather than a smooth exponential increase. There was a sharp increase in the rate at an ‘acceleration point’ at about 0-9 of the cycle. Model-fitting by a novel procedure suggests that the average single cell has an increasing rate of protein synthesis for the first 60% of the cycle and a constant rate for the remaining 40%.
The same pattern was shown in less extensive experiments with [3H]leucine and [3H]phenyl- alanine. It was also shown in a series of size mutants, which indicates that the pattern is not size-related, in contrast to earlier work on the rates of synthesis of messenger RNA. However, one large mutant (cdc z.M35r20) had a significantly earlier acceleration point.
Care was taken to justify the assumption that the rate of incorporation of tryptophan was a valid measure of the rate of protein synthesis. A tryptophan auxotroph was used to eliminate the problem of endogenous supply and the size of the metabolic pool was measured through the; cycle. This pool did not show cell-cycle related fluctuations. An operational model of the pools is presented.
Calcium-sequestering vesicles and contractile flagellar roots
Authors: Salisbury J. L. 
Published: April 2021

ABSTRACT
The intracellular localization of calcium during contraction of striated flagellar roots of the green alga Tetrasehnis subcordiformis was investigated using calcium pyroantimonate and calcium oxalate cytochemistry and energy-dispersive X-ray microanalysis.
Vesicles (0·25-0·50 μm diameter) located in the anterior-most region of the cell are calcium-sequestering organelles. These vesicles exhibit a consistent and reproducible localization of electron-opaque pyroantimonate and oxalate salts of calcium. Striated contractile flagellar roots (CFR) show a periodic pattern of calcium antimonate (Ca-Sb) deposits following ‘calcium shock’ stimulation of contraction of this organelle. When CFRs are in a fully extended state they do not show Ca-Sb deposits. Deposits of Ca-Sb precipitate are present throughout the cytosol when CFRs are stimulated to contract.
The implications of these findings with respect to the regulation of intracellular levels of ‘free ‘Ca2+ and to the mechanism of CFR contraction are discussed.
Glycoconjugates from high endothelial cells: I. Partial characterization of a sulphated glycoconjugate from the high endothelial cells of rat lymph nodes
Authors: Andrews P. , Milsom D. W. , Stoddart R. W. 
Published: April 2021

ABSTRACT
Rat lymph nodes secrete a sulphated macromolecule. This molecule was isolated by ion-exchange chromatography and partially characterized by gel-permeation chromatography, before and after chemical and enzymic modification, and electrophoresis on polyacrylamide gels, paper and glassfibre paper. The results obtained suggest that the label was not incorporated into a proteoglycan but entered a glycolipid that is non-covalently linked to a glycoprotein. A possible role for this complex is discussed.
Comparative study of extracellular fibrils on the ectodermal layer in gastrulae of five amphibian species
Authors: Nakatsuji Norio , Johnson Kurt E. 
Published: April 2021

ABSTRACT
Previous studies have shown the presence of a network of extracellular fibrils on the inner surface of the ectodermal layer of Ambystoma maculatum gastrulae. The alignment of the network along the blastopore-animal pole axis has suggested that the network of fibrils guides the migrating mesodermal cells in gastrulae by contact guidance. We have also shown that these fibrils can be deposited on substrata by explanted embryonic fragments and that substrata conditioned in this manner support directed cell migration. In this study, we found that the appearance of the fibrils in the embryos coincides with the start of cell migration towards the animal pole. Gastrulae of three urodele species examined (A. maculatum, A. mexicanum and Cynops pyrrhogaster) have similar dense networks of fibrils. Xenopus laevis gastrulae also have similar fibrils but fewer fibrils compared to urodele embryos. Rana pipiens gastrulae have very few extracellular fibrils. The scarcity of the fibrils in anuran species may be related to the differences in arrangement of mesodermal cells during migration.
Ultrastructural changes in keratinizing epithelium following trypsinization, epidermal detachment and apposition to mesenchymes
Authors: Jensen H. M. , Mottet N. K. 
Published: April 2021

ABSTRACT
The cellular effects of trypsinization, a commonly used method for separating epithelial from mesenchymal tissues, were examined with the electron microscope. Specimens were fixed after each step of the trypsinization process in 1 % OsO4 in double strength Tyrode solution and after 1–7 days of culture following reapposition of the epithelium to its own mesenchyme or collagen-rich 12-day embryonic quadriceps tendon. Controls consisted of specimens identically prepared from limb bud skin derived from the same site from s-day normal embryos to hatching. A second series of controls were 5-day skin explants cultured for 1-7 days in vitro following identical preparation except for the omission of trypsin.
Trypsin caused transient cytoplasmic protrusions (‘blebs’) on the deep aspect of the basal cells, cellular shrinkage and increase in lysosomes. The basal lamina was disrupted overlying the blebs and remained attached to the basal cells only between the blebs. Continuity of the basal lamina was restored within 24 h after the onset of cultunng and developed precociously thereafter, regardless of whether it was reapposed to its own collagen-poor mesenchyme or the collagen-rich quadriceps tendon. In the latter, focal excessive basal lamina formation was observed. Epithelial cell differentiation proceeded equally precociously in trypsinized and non-trypsinized cultures. Disruption of the basal lamina by trypsinization did not produce detectable alteration in the synthesis of tonofilaments, desmosomes, granular reticulum or corpuscula cnbriformia. Keratohyaline bodies were not found in any of the cultures and keratinized cells did not develop.
Natural variability in the length of thin and thick filaments in single fibres from a crab, Portunus Depurator
Authors: Franzini-Armstrong Clara 
Published: April 2021

ABSTRACT
The carpopodite flexor of the walking legs of the crab Portunus depurator contains fibres belonging to 3 groups. These are characterized by differences in the cross-striation spacing. Fibres having sarcomeres of approximately 4, 5 and 7 μm are here called short, medium and long sarcomere types, respectively.
Within individual fibres belonging to any of the groups the length of the A band is not constant. Up to 25 % length differences have been measured in A bands belonging even to the same fibril.
The bridge-free regions of the thick filaments are not always in the centre, so that the filaments are often asymmetric. Analogally, the L line, resulting from the alignment of the bridge-free regions of the thick filaments, may be asymmetrically placed in the Z band. The length of the bridge-free region in crab thick filaments is 60 nm, while the corresponding region in vertebrate thick filaments is 120 nm. This is discussed in terms of a possible model of the filament.
The length of the thin filaments is proportional to that of the thick filaments in the corresponding portion of the sarcomere. When two A bands of different length occur in adjacent positions along the fibril, the Z line is not a centre of symmetry.
The ratio of thin to thick filament number is variable in individual fibrils. In general, the ratio is higher in the medium sarcomere type fibres than in the short sarcomere type.
Stretched and shorter portions of single fibres of the medium type have been examined and the A-band length populations compared. From such a study it can be deduced that passive length changes occur in crab fibres by sliding of thin and thick filaments.