bluuebunny/crossref_metadata_2025_split huggingface dataset:
Formation of protease nexin‐thrombin complexes on the platelet surface
Authors: Gronke Robert S. , Curry Thomas K. , Baker Joffre B. 
Published: December 2004

AbstractWe have recently described a platelet factor that is similar to the fibroblast thrombin inhibitor protease nexin I (PNI) [12]. The present manuscript shows that this platelet form of PN (PNp) does not complex [125I]‐thrombin that has been blocked at its active site, consistent with the conclusion that it is a thrombin inhibitor. When platelets are incubated with [125I]‐thrombin, PNp‐[125MI]‐thrombin complexers accumulate both in the medium and on the platelet surface. In the case of fibroblasts, PNI‐[125I]‐thrombin Complexes that form in solution bind to the cells as a consequence of a receptor‐mediated clearance process [Low et al, Proc Natl Acad Sci USA 78:2340, 1981]. We show here that the PNp‐[125I]‐thrombin complexes that accumulate in platelet‐binding incubation medium do not bind to platelets. Thus, the platelet‐associated complexes must form by [125I]‐thrombin binding to PNp that is associated with the platelet surface. Pretreatment of platelets with heparin markedly increases the number of PNp‐[125I]‐thrombin complexes that form on platelets. The basis for this increase in unclear. This effect seems incompatible with a heparinlike factor acting as the surface binding site for PNp.
Growth‐promoting effects of esterolytically inactive thrombin on macrophages
Authors: Bar‐Shavit Rachel , Kahn Arnold J. , Mann Kenneth G. , Wilner George D. 
Published: December 2004

AbstractIt has been recognized for many years that α‐thrombin, like other better known mitogens (eg, PDGF, EOF, etc) is capable of initiating proliferation in quiescent cells belonging to the fibroblast family. However, unlike these other peptides, thrombin is a serine protease whose function as a growth stimulator for fibroblasts is intimately linked to its estefolytic activity. Thus, while native α‐thrombin is capable of evoking DNA synthesis in GoG1‐arrested cells, neither enzymatically inactive thrombin (eg, iPR2P‐α‐thrombin) nor partially degraded thrombin (eg, γ‐thrombin) shares in this capability. Data from our laboratory have shown that thrombin is chemotactic for peripheral blood monocytes and for cells belonging to the monocyte/macrophage family and that this activity is not dependent upon thrombin's enzymatic properties. Our recent findings demonstrate that thrombin also serves as a growth factor for these cells, and this mitogenic capability is independent of esterolytic function and resides in the same region of the molecule as that responsible for chemotaxis. Additionally, by means of techniques such as computer modeling and peptide synthesis, we have now been able to delineate a distinct mitogenic subsite within this chemotactic thrombin sequence. Thus, the sequence in the thrombin B chain that mediates chemotaxis represents a true cell interactive exosite additionally capable of stimulating growth and possibly other biological functions in cells of macrophage/monocyte lineage.
Transforming growth factors and control of neoplastic cell growth
Authors: Keski‐Oja Jorma , Leof Edward B. , Lyons Russette M. , Coffey Robert J. , Moses Harold L. 
Published: December 2004

AbstractTransforming growth factors (TGFs) are peptides that affect the growth and phenotypic of cultured cells and bring about in nonmalignant fibroblastic cells phenotypic properties that resemble those of malignant cells. Two types of TGFs have been well characterized. One of these, TGFβ, is related to epidermal growth factor (EGF) and binds to the EGF receptor, whereas the other. TGFβ, is not structurally or functionally related to TGFβ or EGF and mediates its effects via distinct receptors.TGFβ is produced by a variety of normal and malignant cells. Depending upon the assay system employed, TGFβ has both growth‐inhibitory and growth‐stimulating properties. Many of the mitogenic effects of TGFβ are probably an indirect result of the activation of certain growth factor genes in the target cell. The ubiquitous nature of the TGFβ receptor and the production of TGFβ in a latent form by most cultured cells suggests that the differing cellular responses to TGFβ are regulated either by events involved in the activation of the factor or by postreceptor mechanisms. The combined effects of TGFβ with other growth factors or inhibitors evidently play a central role in the control of normal and malignant cellular growth as well as in cell differentiation and morphogenesis. Since transforming growth factor as a concept has partially proven misleading and insufficient, there is a need to find a new nomenclature for these regulators of cellular growth and differentiation.
The role of ATP in the cytostructure of the hepatocytes
Authors: Katz Joseph , Wals P. A. 
Published: December 2004

AbstractWe have previously described the preparation of hepatocytes from which the plasm membrane was removed by digitonin treatment. Such “nude” cells were found to be very stable in sucrose media containing above 50 mM NaCl or KC1, but they disintegrate near instantly in salt‐free media, liberating nuclei, mitochondria, and other organelles. We show here that disintegration occurs at a physiologic pH and in the presence of oxygen. Disintegration was blocked by rotenone, oligomycin, KCN, and carboxyatractyloside, establishing that oxidative phosphorylation and ATP generation is essential for disintegration to occur. The addition of ATP, GTP, ITP, or ADP (but not AMP) in the presence of the inhibitors, induced breakdown.Taxol, an inhibitor of tubulin depolymerization and phalloidin, a drug that stabilizes actin fibers, prevented disintegration in salt‐free media. The effect of these drugs was counteracted by the addition of ATP.Our results show that two conditions are essential to induce the disintegration of the nude cell: media of low ionic strength, and ATP generation. The ATP effect is likely to be of physiological significance, suggesting role for ATP generation in affecting polymerization of cytoskeletal elements.
Hyaluronate‐binding protein of simian virus 40‐transformed 3T3 cells: Membrane distribution and reconstitution into lipid vesicles
Authors: Chi‐Rosso Gloria , Toole Bryan P. 
Published: December 2004

AbstractHyaluronate‐binding protein (HASP) has been extracted in detergent from the membranes of simian virus 40‐transformed 3T3 (SV‐3T3) cells (Underhill et al, J Biol Chem 258:8086–8091, 1983). When SV‐3T3 cells were treated with trypsin prior to isolation and dissolution of the membranes, no hyaluronate‐binding activity could be detected. This indicates that all of the detectable HABP of SV‐3T3 cells is located on the external surface of the plasma membrane rather than on internal membranes, which would be inaccessible to the trypsin. The detergent‐extracted HABP from SV‐3T3 membranes was reconstituted into the membrane of lipid vesicles, which were formed by addition of exogenous phosphatidylcholine and cholic acid to the extracts followed by removal of detergent by dialysis against 0.02 M Tris pH 8.0 in the presence of protease inhibitors. Reconstitution was assessed by sedimentation in a discontinuous sucrose gradient and by gel filtration on Sepharose 4B in the presence and absence of detergent. The characteristics of binding of hyaluronate to the reconstituted HABP were then compared with those studied previously for the original membrane‐bound HABP and the detergent‐extracted HABP (Underhill et al, J Biol Chem 258:8086–8091, 1983). It was observed previously that binding of hyaluronate to HABP in the cell membranes was of higher affinity and specificity than to HABP in the detergent extracts of these membranes. It was found here that reconstitution of the extracted HABP into the membranes of lipid vesicles led to restoration of affinity of binding to the level observed in the original cell membranes. However, whereas chondroitin sulfate does not compete significantly for binding of hyaluronate to cell membrane‐bound HABP, partial competition was observed for the reconstituted HABP as well as for detergent‐extracted HABP. Thus, it is concluded that the high affinity of binding of hyaluronate to the plasma membrane of SV‐3T3 cells is in part dependent on insertion of the HABP in the membrane, but that other interactions, not duplicated in our reconstitution experiments, must be necessary for the specificity of the HABP.
Autostimulatory mechanisms in myeloid leukemogenesis
Authors: Schrader J. W. , Leslie K. B. , Ziltener H. J. , Schrader S. 
Published: December 2004

AbstractWEHI‐274 is a monocytic leukemia that arose in a BALB/c mouse infected with Abelson murine leukemia virus. A series of subclones were derived from early passages of this tumor. Three subsets of these leukemogenic subclones were identified. Two subsets demonstrated autostimulatory patterns of growth. This was due to the ectopic production of the T‐cell lymphokine the panspecific hemopoietin IL‐3 in one case and of the T‐cell lymphokine granulocyte‐macro‐phage colony‐stimulating factor (GM‐CSF) in the other. The third type of subclone did not secrete any autostimulatory growth factor. In the subclone producing IL‐3, one copy of IL‐3 gene was rearranged and abnormal IL‐3 RNA transcripts were present in the nucleus. Subclones producing GM‐CSF also contained abnormal GM‐CSF RNA transcripts, although no rearrangement of the GM‐CSF gene was detected. All three sets of subclones shared a common rearrangement of one c‐myb oncogene, suggesting that they share a common ancestor. These results suggest that initiation or progression of leukemogenic behavior in this abnormal clone occurred in three different ways, two of which involved autostimulation by the ectopic activation of T‐cell lymphokine genes.
Inhibition of epidermal growth factor‐stimulated DNA synthesis by a bovine sialoglycopeptide inhibitor occurs at an intracellular level
Authors: Bascom Charles C. , Sharifi Behrooz G. , Johnson Terry C. 
Published: December 2004

AbstractThe control of cell proliferation involves the complex interaction between growth factors and growth inhibitors. We have examined this interaction with the mitogen epidermal growth factor (EOF) and a recently purified 18 kD, pI 3, sialoglycopeptide that reversibly inhibits cellular metabolism of a variety of cells. The sialogly‐copeptide was a very potent inhibitor of EOF action; 0.22 nM of the inhibitor completely blocked the mitogenic effect of 1.60 nM of EGF. The sialoglycopeptide, however, did not affect the binding of EGF to 3T3 cells. Neither the mixed affinities (0.11–1.9 nM) of binding nor the total number of receptors (50,000 receptors/cell) for EGF were altered by the addition of the Sialoglycopeptide. In addition, competitive binding experiments demonstrated the specificity of inhibitor binding to 3T3 cells and also showed that EGF and the Sialoglycopeptide did not share the same receptor, suggesting that the inhibitor blocked EGF action at a postreceptor, intracellular event in the signal cascade. We further demonstrated that the Sialoglycopeptide had to be added within 2.5 hr after EGF to block effectively the stimulation of DNA synthesis by the growth factor, suggesting that the inhibitor blocked EGF stimulation at a relatively early step in the signal transduction mechanism.
Comparison of basement membrane matrix degradation by purified proteases and by metastatic tumor cells
Authors: Starkey Jean R. , Stanford David R. , Magnuson James A. , Hamner Steve , Robertson Nancy P. , Gasic Gabriel J. 
Published: December 2004

AbstractWe have examined the nature of biochemical degradation of an isolated basement membrane matrix (bovine lens capsule) using different methodologies. The first strategy was quantitation of the release of surface‐bound 125I and a second the documentation by SDS‐PAGE of the appearance of putative cleavage products and the loss of high‐molecular‐weight components from the matrix. Basement membrane matrix bands resolved on SDS‐PAGE were identified by their protease sensitivities as well as by Western immunoblots using monoclonal antibodies developed for this study. Radioiodinated components were found predominantly at positions on the gel equivalent to 160–200 kd and 400 kd proteins. Since these labeled moieties were sensitive to bacterial collagenase digestion and stained with anticollagen type IV antibodies, they were determined to represent various configurations of collagen type IV. Several other lower‐molecular‐weight bands also stained with the anticollagen IV antibodies. Monoclonal antibodies reactive with laminin exhibited a complex staining pattern on the gels, which included the expected 200 and 400 kd components. We confirmed that lens capsule basement membrane contained only a single heparan sulfate glycosaminoglycan species, and tumor cell‐induced glycosaminoglycan degradation within the basement membrane matrix was detected using cellulose acetate electrophoresis.Distinctive putative cleavage products were resolved on SDS‐PAGE gels from matrices subjected to digestion by a variety of purified proteases as well as by metastatic tumor cells or their conditioned media. Tumor cells of different histio‐types produced different characteristic cleavage patterns, suggestive of the existence of several pathways of matrix degradation. Overall, primary tumor cells exhibited a greater degradative activity towards the basement membrane matrix than did long‐term tissue culture‐passaged cells. The same tumor cell line could exhibit considerably different patterns of both protein and glycosaminoglycan degradation depending on recent culture history. The relevance of these biochemical studies to the pathogenesis of malignant neoplasms is shown by: (1) the evaluation of degradative activities of B16 tumor cell populations exhibiting enhanced lung‐colonizing phenotypes, and (2) the ability of a known antimetastatic moiety with antiproteasc activity (Haementeria leech species salivary gland extract) to protect matrix components from degradation by tumor cell‐conditioned medium.
Steroid hormone antagonists at the receptor level: A role for the heat‐shock protein MW 90,000 (hsp 90)
Authors: Baulieu Etienne‐Emile 
Published: December 2004

AbstractAntisteroid hormones compete for hormone binding at the receptor level and prevent the hormonal response. A new concept is proposed for explaining the antiglucocorticosteroid activity of RU 486 in the chick oviduct system. It is based on the ability of the antisteroid to stabilize the hetero‐oligomeric 8S‐form of the glucocorticosteroid receptor (GR), which involves the interaction of the 94k‐receptor and heat‐shock protein MW 90,000 (hsp 90). It is proposed that hsp 90 caps the DNA binding site of the receptor, and this prevents it from binding to the DNA of hormone regulatory elements (HRE) and increasing transcription of regulated genes. This paper reviews other antiglucocorticosteroid and antiestrogen systems with reference to this hypothesis and also describes a four‐step analysis of the molecular mechanism of antisteroid hormone action at the receptor level.
Ecto‐cyclic AMP‐receptor in goat epididymal intact spermatozoa and its change in activity during forward motility
Authors: Dey Chinmoy S. , Majumder Gopal C. 
Published: December 2004

AbstractGoat epididymal intact spermatozoa have been shown to possess on the external surface specific receptors that bind with high affinity to exogenous [8‐3H]cyclic AMP. The ecto‐cyclic AMP‐receptor activity was not due to contamination of broken or “leaky” cells, if any. The binding reaction of [3H]cyclic AMP with the receptors was extremely rapid. Uptake of the labeled cyclic AMP to the sperm cytosolic fraction was undetectable. There was little leakage of cyclic AMP‐receptors from intact spermatozoa during the binding assays. The binding reaction was proportional to cell concentration, specific and saturable at 250 nM cyclic AMP. The binding of the labelled cyclic nucleotide was nearly completely displaced at saturating concentrations (2.5 μM) of the unlabelled nucleotide. The ecto‐receptors showed high specificity for binding to cyclic AMP. The Kd of the binding sites was approximately 1.7 × 10‐8 M. The binding interaction was highly sensitive to treatment with proteolytic enzymes: trypsin, chymotrypsin, or pronase (125 μg/ml). Sonication caused a nearly 450% increase of the ecto‐receptor activity. The specific activity of the ecto‐cyclic AMP‐receptor was approximately twofold higher in the vigorously forwardly motile spermatozoa than in the “composite” cells, suggesting that the ecto‐receptors may have a role in modulating flagellar motility.
Role of receptor occupancy in the transition from responsive to unresponsive states in cultured breast tumor cells
Authors: Darbre Philippa D. , King Roger J. B. 
Published: December 2004

AbstractProgression from a steroid sensitive to insensitive state is characteristic of breast tumors, but little is known about the molecular mechanisms involved. Changes in steroid receptor can be associated with the progression. This paper reviews the cell culture data pertaining to loss of response and concludes that loss of receptor is a consequence rather than a cause of insensitivity. This view is based on evidence that loss of all response parameters occurs despite the presence of fully functional receptors as determined by transfection experiments. The postreceptor defect appears to be at the level of the hormone response element of the responsive genes arid may involve DNA methylation. The implications of the model for human breast cancer biology are discussed.
Identification and characterization of tyrosine kinase activity associated with mitochondrial outer membrane in sarcoma 180 cells
Authors: Piedimonte Giuseppe , Chamaret Solange , Dauguet Charles , Borghetti Angelo F. , Montagnier Luc 
Published: December 2004

AbstractTyrosine protein kinase activity has been detected in the mitochondrial fraction purified from sarcoma 180 tumor cells. Following hypotonic disruption of mitochondria, tyrosine kinase activity appeared to cosediment with monoamine oxidase, marker enzyme of mitochondrial outer membrane; meanwhile, serine and threonine kinases were found to be associated with the inner membrane and matrix of mitochondria. Mitochondrial tyrosine kinase(s) showed thermosensitivity and Mn 2+ dependence, useful properties for its characterization and separation from tyrosine kinases associated with other particulate fractions and from serine and threonine kinases associated with mitochondria. Following in vitro incubation of mitochondria with labelled ATP as substrate and analysis by PAGE, a complex pattern of phosphotyrosine containing proteins with a major band of 50–55 kilo‐daltons resulted.
Cytogenetic diversity in primary human tumors
Authors: Wolman Sandra R. , Camuto Patricia M. , Perle Mary Ann 
Published: December 2004

AbstractCytogenetic patterns from primary short‐term culture of breast cancer, renal carcinoma, and tumors of the central nervous system are presented to illustrate the range of karyotypic diversity of human solid tumors as well as their biologic differences in culture systems that support their growth. These studies have illustrated several major issues. (1) Results vary with the tissue of origin: primary cultures from breast are almost uniformly diploid, while renal tumors are near‐diploid, mosaic, and show clonal aberrations; and CNS tumors are heterogeneous: some diploid, some near‐diploid and some highly aneuploid. (2) Results after short‐term culture are selective, representing subpopulations from the heterogeneous cells that are detected on direct analysis of fresh tumors by cytogenetics or flow cytometry (FCM). It is not yet clear whether prognosis depends on the dominant population of the primary tumor or alternatively should be influenced by detection of small aneuploid subpopulations. (3) Evidence from all three tumor types supports the interpretation that cytogenetically normal diploid cells constitute part of some tumor populations, and may be better adapted to routine growth in culture than aneuploid subpopulations from the same primary tumors. These cells may also compose a major portion of the viable population of tumors in vivo and, therefore, could represent a useful model for studies of tumorigenesis and therapeutic regimens.
Isolation and visualization of Met‐72‐positive, metastatic variants present in B16 melanoma tumor masses
Authors: Parratto Nanette P. , Kimura Arthur K. 
Published: December 2004

AbstractMetastatic variants of the B16 melanoma displaying high experimental metastatic potential have been shown to express high levels of a 72,000‐dalton glycoprotein (Met‐72) on their cell surface (Kimura AK, Xiang J: J Nat Can Inst 76:1247–1253, 1986). Monoclonal antibodies (MoAb) directed against the Met‐72 determinant have been used in this study as immunohistochemical reagents on preparations of fresh B16 melanoma tumors and their metastases. These immunohistochemical analyses have utilized frozen sections, impression smears, and cytospin preparations of fresh tumors harvested at various time points during tumor growth, to view the presence and location of Met‐72‐positive metastatic variants within tumor masses. Biotinylated anti‐Met‐72 MoAbs were reacted with freshly dissociated tumor cells from a B16 melanoma ovarian metastasis. These cells were then reacted with fluorescein isothiocyanate (FITC)‐streptavidin and analyzed by flow cytometry. A discrete population of positively staining cells was detected and isolated by cell sorting techniques. Met‐72‐positivc cells were then cloned and reanalyzed after several weeks of in vitro expansion and found to have high experimental metastatic potential to ovaries. Frozen sections of subcutaneous tumors and their metastases were analyzed by immunoperoxidase techniques. A consistent finding in these studies has been that the few tumor cells which showed high intensity of Met‐72 staining were positioned perivascularly and at the invading front of B16 melanoma tumors.
Analysis of cell surface glycoprotein changes related to hematopoietic differentiation
Authors: Reading Christopher L. , Hickey Catherine M. , Yong Weiben 
Published: December 2004

AbstractA high‐resolution technique has been used to study differentiation‐related and leukemia‐associated glycoproteins. Cells are labeled with the membrane‐impermeable probe sulfo‐N‐hydroxysuccinimidyl‐biotin. Nonionic detergent extracts are subjected to affinity chromatography on a number of immobilized lectins and after polyacrylamide gel electrophoresis in sodium dodecyl sulfate (SDS‐PAGE) and western transfer, the biotin‐labeled glycoproteins are visualized by using avidin‐horseradish peroxidase and 4‐chloronaphthol. With the aid of the lectins concanavalin A, Dolichos biflours agglutinin, Lens culinaris hemagglutinin, peanut agglutinin, pokeweed mitogen, Ricinus communus agglutinin I, soybean agglutinin, Ulex europeus agglutinin I (UEA), and wheat germ agglutinin, each purifies different glycoprotein subsets from the same cell type. Mature cells of distinct hematopoietic lineages differ considerably in their cell surface glycoprotein patterns.This technique was used to analyze the glycoproteins of human leukemia cells before and after the induction of differentiation. K562 cells differentiated along different lineages after treatment with phorbol 12‐myristate 13‐acetate, sodium butyrate, dimethyl sulfoxide, or hemin. Limited specific alterations were observed with a number of lectins when K562 erythroleukemia cells were induced to differentiate. Among these, a number of bands were identified that were either lost or appeared after induction of differentiation with all four agents. In contrast, the glycoproteins bound by UEA were drastically diminished after induction of differentiation, and the remaining UEA‐bound glycoproteins bore little resemblance to those of the cells before treatment. This high‐resolution technique may be useful as a general method for the examination of cell surface glycoprotein differences. Once specific glycoprotein alterations are detected, lectin affinity chromatography and SDS‐PAGE allow purification of antigens for the production of monoclonal antibodies.