bluuebunny/crossref_metadata_2025_split huggingface dataset:
Biologic activity of anti‐thyrotropin anti‐idiotypic antibody
Authors: Farid Nadir R. , Brioñes‐Urbina Rosario , Nazrul‐Islam M. 
Published: December 2004

AbstractWe raised an antihuman thyrotropin anti‐idiotypic antibody and showed that it was active at the thyrotropin receptor. Thus this antibody inhibited 125I b‐TSH binding to thyroid plasma membranes, stimulated adenylate cyclase activity through a guanyl nucleotide‐dependent mechanism, increased radioiodide entry rate into isolated porcine thyroid follicular cells, and induced such cultured cells to organize into follicles. All these parameters are typical of thyrotropin action. This work raises the possibility that thyroid stimulating antibodies that cause the hyperthyroidism of Graves disease may be, at least in some patients, anti‐thyrotropin anti‐idiotypic antibodies. It also offers a novel method whereby antireceptor antibodies used in the isolation and characterization of the receptor may be raised from ligands.
A basement membrane‐associated glycoprotein from skeletal muscle
Authors: Marton Linda S. G. , Arnason Barry G. W. 
Published: December 2004

AbstractWe have isolated a major glycoprotein that appears to be associated with rat skeletal muscle basement membrane. We determined that the glycoprotein was part of the muscle cell surface complex when we found it to be enriched in preparations of muscle ghosts. We isolate the glycoprotein from homogenized muscle preextracted with 4 M and 8 M urea. It elutes as a major component in the presence of 8 M urea/50 mM 2‐mercaptoethanol. Its apparent molecular weight on sodium dodecyl sulfate gels is 130,000. Amino acid analysis indicates that it is not a collagen but that it does contain small amounts of hydroxyproline and hydroxylysine. There may be collagenous domains in the glycoprotein molecule, for it is cleaved into three fragments by purified bacterial collagenase. Immunoperoxidase staining confirms that the 130,000‐dalton protein is localized at the surface of adult skeletal muscle cells. It is probably a general basement membrane‐associated glycoprotein because we found material immunologically cross‐reactive with the muscle glycoprotein in basement membrane regions of kidney, liver, brain, and small intestine. We have shown the glycoprotein to be distinct from fibronectin, laminin, and types I, III, IV, and V collagens in enzyme‐linked immunosorbent assays.
Biochemical characterization of transformation‐specific proteins of acute avian leukemia and sarcoma viruses
Authors: Moelling K. , Owada M. K. , Greiser‐Wilke I. , Bunte T. , Donner P. 
Published: December 2004

AbstractThe biological and biochemical properties of the transformation‐specific proteins of three avian oncornaviruses with different oncogenic potentials were compared, namely the gag‐myc protein of the avian myelocytomatosis virus MC29, the gag‐erb A protein of the avian erythroblastosis virus AEV, and the gag‐fps protein of Fujinami sarcoma virus FSV. These oncogenes were analyzed in transformed fibroblasts that expressed only the transforming proteins but showed no virus replication. Monoclonal antibodies against the viral structural protein p19, which is the N‐terminus of the proteins, were used for indirect immunofluorescence, for immunoprecipitation of the proteins from subcellular fractions, and for immunoaffinity column chromatography. With this last method a 3000‐fold purification of the proteins was obtained. By indirect immunofluorescence it was shown that the gag‐myc protein was located in the nucleus, and bound to DNA after purification. The gag‐erb A protein was not nuclear but probably located in the cytoplasm and did not bind to DNA after purification. Neither of the two proteins exhibited protein kinase activity. In contrast, the gag‐fps protein did not bind to DNA but showed protein kinase activity after purification. It was not located in the nucleus either.
Binding of isolated 3T3 surface membranes to growing 3T3 cells and their effect on cell growth
Authors: Lieberman Michael A. , Keller‐McGandy Christine E. , Woolsey Thomas A. , Glaser Luis 
Published: December 2004

AbstractWe have quantitated by autoradiography the binding of [125I]labeled 3T3 plasma membrane fragments to 3T3 cells growing on the surface of plastic dishes; ie, the same conditions in which these membranes specifically arrest the growth of 3T3 cells early in the G1 phase of the cell cycle. We have been able to demonstrate that binding of membranes to cells is coincidental with the expression of the growth inhibitory activity of protein(s) present in the membrane fragments. Treatments that reduce binding (heat denaturation of the membranes or culture in the presence of high scrum) also reduce growth inhibitory activity. [125I]labeled membranes bound to cells are located primarily on the cell surface (as determined by electron microscope autoradiography) and are exchangeable with unlabeled membranes. We conclude that binding of membranes to cells is necessary but may not be sufficient for the expression of the growth inhibitory activity of these membranes. This approach provides information not only on the average level of binding of membranes to cells, but also provides a quantitative assessment of the variation of the level of membrane to cell binding between different cells in the population.
Characteristics of plasma membrane isolated from a mouse T lymphoma line: comparison after nitrogen cavitation, shearing, detergent treatment, and microvesiculation
Authors: Culvenor Janetta G. , Mandel Thomas E. , Whitelaw Alison , Ferber Ernst 
Published: December 2004

AbstractPlasma membrane was isolated from the mouse T lymphoma cell line WEHI‐22 using four different methods of cell disruption followed by centrifugal fractionation. Disruption by nitrogen cavitation or by shearing with a cell pump produced plasma membrane vesicles of similar buoyant density (1.10 g/ml) and morphological appearance. Few C‐type virus particles were present. Cell disruption with 2% Tween‐40 produced membrane vesicles of similar morphology but lower density (1.09 g/ml). All of the above preparations resulted in vesicles with aggregated intramembranous particles after freeze fracture. Microvesiculation with a sublytic concentration of a lysophosphatidylcholine analog (ET‐12‐H) (0.0032% w/v) produced small membrane vesicles which could be isolated without differential centrifugation. However, these had a slightly higher density than vesicles prepared by cavitation or shearing and were co ntaminated by virus particles. Unlike the other preparations, vesicles prepared with ET‐I2‐H had dispersed intramembranous particles. The enzyme γ‐glutamyl transferase was enriched from 20‐ to 45‐fold in the membrane preparations and proved a suitable plasma membrane marker for these cells whose 5′‐nucleotidase content is very low.
Transformation of MMC‐E epithelial cells by acute 3611‐MSV: inhibition of collagen synthesis and induction of novel polypeptides
Authors: Keski‐Oja Jorma , Rapp Ulf R. , Vaheri Antti 
Published: December 2004

AbstractMouse embryo epithelial cells MMC‐E were transformed by novel fibrosarcoma‐inducing murine sarcoma virus 3611 ‐MSV. The cells were analyzed for the production and deposition of pericellular glycoproteins by immunofluorescence and by radioactive metabolic and cell surface labeling techniques followed by analysis in polyacrylamide gels and fluorography. The pericellular fibronectin matrix was lost, but unlike in virus‐transformed fibroblastic cells, the production of fibronectin was not affected. The major differences detected were decrease in collagen production and initiation of synthesis of two major glycoproteins with Mr 58,000 and 60,000. Cell surface carbohydrate labeling indicated that after 3611‐MSV transformation the cells expressed Mr 100,000 and 68,000 polypeptides. The present and previous results show that viral transformation of epithelial cells induces different transformed phenotypes that are associated with distinct alterations in pericellular glycoproteins.
The fate of the N‐formyl‐chemotactic peptide receptor in stimulated human granulocytes: subcellular fractionation studies
Authors: Jesaitis Algirdas J. , Naemura Joseph R. , Painter Richard G. , Schmitt Manfred , Sklar Larry A. , Cochrane Charles G. 
Published: December 2004

AbstractExperiments were performed to examine how human granulocytes, stimulated by N‐formyl‐chemotactic peptides, process the N‐formyl peptide receptor. One percent of the surface N‐formyl‐chemotactic peptide receptors of purified human granulocytes were covalently, specifically, and radioactively labeled at 4°C using the photochemically reactive N‐formyl‐chemotactic hexapeptide CHO‐Nle‐Leu‐Phe‐Nle‐[l25I] Tyr‐N°(6‐(4′‐azido‐2′‐nitrophenyl‐amino)hexanoyl)‐Lys. After incubation in the presence of 500 nM of N‐formyl‐Met‐Leu‐Phe at 37°C, the cells were lysed and fractionated by isopycnic surcrose density gradient sedimentation. Receptor‐associated radioactivity cosedimented with plasma membrane in fractions from cells kept at 4°C or incubated at 37°C for 2 min or less. Fractionation of cells incubated at 37°C for longer times revealed that the radioactivity sedi‐mented to lower densities coincident with Golgi markers and the site of noncovalently bound and internalized formyl‐chemotactic peptide. To follow the redistribution of unoccupied receptors, human granulocytes were stimulated with 500 nM N‐formyl‐Met‐Leu‐Phe at 37°C for 5 min, washed, lysed by N2 cavitation, and fractionated by rate zonal sucrose density gradient sedimentation. Compared to unstimulated controls the specific binding of N‐formyl‐Met‐Leu‐[3H]Phe decreased 76% ± 9% in plasma membrane fractions. N‐formyl‐Met‐Leu‐[3H]Phe‐binding activity associated with an intracellular pool cosedimenting with specific granules remained unchanged. Approximately 20% of the activity lost in the plasma membrane could be accounted for by a redistribution of specific N‐formyl‐Met‐Leu‐Phe binding to fractions enriched in azurophil granules. We conclude that the receptor is the carrier in the internalization of the N‐formyl‐chemotactic peptides to a Golgi‐enriched fraction and hypothesize that after a short residency in this fraction, the receptor may dissociate from the ligand and pass onto a fraction consedimenting with dense granules.
Photoaffinity labeling of the N‐formyl peptide receptor of human polymorphonuclear leukocytes
Authors: Painter Richard G. , Schmitt Manfred , Jesaitis Algirdas J. , Sklar Larry A. , Preissner Klaus , Cochrane Charles G. 
Published: December 2004

AbstractQuantitative analysis of ligand‐occupied receptor interactions with elements of the cytoskeleton and with intracellular compartments requires a sensitive and simple method of identifying the receptor‐ligand complex in living cells. Toward this goal, we have prepared a photoactivatable arylazide derivative of the chemotactic peptide N‐formyl‐Nle‐Leu‐Phe‐Nle‐Tyr‐Lys, which can be radiolabeled to high specific activity with 125I. This derivative was biologically active as judged by its ability to elicit superoxide anion production by human PMNL at nanomolar concentrations (ED50 ∼ 0.7 nM). When incubated at 0°C with whole PMNL, radioactive ligand became specifically and saturably associated with a 60‐70,000‐dalton species (as assessed by SDS‐PAGE) after exposure to UV light. Addition of 10‐100‐fold excess of unlabeled parent or unlabeled azidopeptide derivative completely blocked uptake into this species. Approximately 20‐40% of the available surface receptor‐binding sites were covalently labeled under these conditions. Subcellular fractionation of the labeled cells on sucrose gradients after homogenization showed that the labeled species was primarily associated with plasma membrane‐rich fractions. The labeled receptor could be completely solubilized with Triton X‐100 in a form which eluted as a single species with a Stoke's radius of less than 50 Å on Sepharose 4B columns. In addition, the solubilized receptor‐ligand complex bound specifically to wheat germ agglutinin, indicating that it is probably a glycoprotein. The ability to label the receptor in living PMNL with a high efficiency should facilitate the study of receptor dynamics and receptor physiochemical properties in this system.
Receptor‐bound thrombin is not internalized through coated pits in mouse embryo cells
Authors: Bergmann John S. , Carney Darrell H. 
Published: December 2004

AbstractThe localization of thrombin receptors on mouse embryo (ME) cells was examined using electron microscope (EM) immunocytological techniques. ME cells were fixed with formaldehyde, prior to thrombin binding, and thrombin visualized on cell surfaces using affinity‐purified antithrombin rabbit antibody and colloidal gold labeled anti‐rabbit IgG. Colloidal gold particles were found in clusters on the surface of cells incubated with thrombin. There were approximately seven particles per cluster observed in thin sections with cluster diameters ranging from 70 to 200 nm. These clusters were not observed on cells incubated without thrombin. The total number of particles present on cells incubated with and without thrombin indicate that the colloidal gold labeling is approximately 98% specific for thrombin. Only four colloidal gold particles out of approximately 1,200 were associated with coated pits. Thus the thrombin receptor clusters do not appear to associate with coated membrane regions. To determine whether receptor‐bound thrombin was internalized by receptor‐mediated endocytosis, ME cells were incubated with 125I‐thrombin and examined using EM autoradiography and the trypsin sensitivity of 125I‐thrombin which was associated with the cells. In two types of experiments, where thrombin was incubated with cells at 4°C and the temperature increased to 37°C and where initial incubation was at 37°C, the receptor‐directed specific internalization proceeded at approximately the same rate as nonspecific internalization. These studies indicate that thrombin that binds to its receptors on ME cells is not rapidly internalized by receptor‐mediated endocytosis.
Organization and expression of hepatitis B sequences cloned from hepatocellular carcinoma tissue DNA
Authors: Dejean Anne , Carloni Guido , Bréchot Christian , Tiollais Pierre , Wain‐Hobson Simon 
Published: December 2004

AbstractWe have constructed a phage λ library of liver DNA fragments from West African patient who died of liver failure due to advanced hepatocellular carcinoma. Four hepatitis B virus (HBV) DNA‐carrying recombinants have been isolated, one clone (λÍ22) being analyzed in greatest detail. It contains approximately 3.8 kb of HBV DNA without detectable deletions or rearrangements. One site of integration lies close to the nick in free viral DNA. The restriction map of the HBV sequences is close to those published for the ay subtype. Coconvection of mouse Ltk−cells with λÍ22 and cloned: thymidine kinase gene results in the expression of gene S and the excretion of hepatitis B surface antigen (HBsAg) particles into the culture supernatant.
DNA methylation, retroviruses, and embryogenesis
Authors: Jaenisch Rudolf , Harbers Klaus , Jähner Detlev , Stewart Colin , Stuhlmann Heidi 
Published: December 2004

AbstractBy exposing preimplantation embryos to Moloney leukemia virus (M‐MuLV), we have previously derived substrains of mice designated as Mov‐1‐Mov‐13 which genetically transmit the virus from one generation to the next. In some of the substrains the inserted viral genome becomes activated at specific stages of embryogenesis and the available evidence suggests that these viral genomes are developmentally regulated. To investigate the effect of cellular differentiation on virus expression, M‐MuLV was introduced either into preimplantation or postimplantation mouse embryos or into embryonal carcinoma (EC) cells. Whereas preimplantation embryos or EC cells are not permissive for virus expression, efficient replication occurred in postimplantation embryos or in differentiated cell lines. The viral genomes introduced into early embryonal cells were highly methylated and noninfcctious when analyzed in the adult. In contrast, viral genomes introduced into postimplantation embryos or into differentiated cells remained unmethylated and were infectious in a transfection assay. These results demonstrate an efficient de novo methylation activity which appears to be involved in repression of genes introduced into pluripotent embryonal cells and which is not observed in cells of the postimplantation embryo or in differentiated cells in tissue culture.
Cholera toxin B‐subunit protects mammalian cells from ricin and abrin toxicity
Authors: Delfini Carlo , Sargiacomo Massimo , Amici Carla , Oberholtzer Goffredo , Tomasi Maurizio 
Published: December 2004

AbstractThe glycoproteins ricin and abrin intoxicate cells by inhibiting protein synthesis. Pretreatment of HeLa cells with cholera toxin partially protects them from ricin and abrin activity. The involvement in this phenomenon of the various effects of cholera toxin, namely, redistribution of membrane receptors elicited from protomer B and increasing cyclic AMP concentrations induced by protomer A, were studied. Substances able to enhance cyclic AMP concentrations do not affect ricin and abrin activity, while protomer B alone protects cells. In addition, the effects of several lectins on ricin or abrin toxicity were examined. Almost complete prevention of ricin or abrin activity was obtained using concanavalin A (Con A) and wheat germ agglutinin (WGA). Conversely, neither succinyl Con A nor Ulexeuropeus agglutinin (UEA) affected the cellular response. Both protomer B of cholera toxin and Con A did not alter the binding of ricin or abrin; they seem to protect cells by altering membrane structure.
Influence of growth conditions on the composition of the plasma membrane from yeast and on kinetic properties of two membrane functions
Authors: Stadtlander Klaus , Rade Sabine , Ahlers Jan 
Published: December 2004

AbstractThe influence of different growth conditions on the phospholipid composition and on two membrane functions, the Mg‐ATPase and the purine transport system, was investigated. Addition of cholinechloride to the growth medium led to a certain rise in the amount of phosphatidylcholine, whereas supplementation with ethanolamine resulted in a considerably higher portion of phosphatidylethanolamine. When yeast cells were cultured at lower temperatures we found more short‐chain fatty acids with a higher content of monounsaturated chains as compared to higher growth temperatures. Addition of paraquat, a herbicide which enhances lipid peroxidation by free radicals, reduced the amount of unsaturated fatty acids without influencing their chain length.The altered membrane composition had no influence on the basic mechanism of interaction between ATPase, MgATP, and free Mg2+ ions. However, several kinetic constants such as Km, Vmax, Ka, and especially Ki were influenced to some extent. Whereas the affinity of the purine transport system to its substrate was not significantly changed by the growth conditions, an effect on Vnlax could be seen. Lower growth temperatures clearly led to higher maximal uptake velocities. The presence of paraquat during growth resulted in a considerable decrease of Vmax.
Lipolysis induction in adipocytes by a protein from tumor cells
Authors: Kitada Shinichi , Hays Esther F. , Mead James F. , Zabin Irving 
Published: December 2004

AbstractExtracts of thymic lymphoma that are obtained from AKR mice and are kept in the cold for at least several days can induce lipolytic activity in rat adipocyte suspensions. Freshly prepared extracts have low activity but contain a low molecular weight material of less than 10,000 daltons that aggregates on standing in the cold and becomes active. Treatment of aged extracts with trypsin causes a loss in activity indicating that the active material is a protein. It has been obtained in partially purified form, is relatively heat stable, and is not a lipase.Activity was also demonstrated in AKRXDBA/2 lymphoma (induced by AKR SL3‐3 virus) and in transplanted lymphomas from a Friend‐virus‐induced erythroleukemia cell line in DBA/2 mice, but was not detected in normal thymus, spleen, liver, or other tissues. The partially purified material produced a massive fat mobilization when injected into normal mice.
Ionic regulation of MEL cell commitment
Authors: Levenson Robert , Macara Ian , Cantley Lewis , Housman David 
Published: December 2004

AbstractA key event in the initiation of the dimethyl sulfoxide (DMSO)‐induced program of murine erythroleukemia (MEL) cell differentiation is a rise in the level of cytoplasmic calcium ions. Our interest in the present study is whether other inducers of the terminal erythroid differentiation program also act via a calcium‐dependent pathway. Inhibition of calcium transport has been found to prevent the induction of MEL cell commitment by DMSO, butyric acid (BA), or hypoxanthine (HX). Enhancement of the calcium flux rate with A23187 or elevation of cytoplasmic calcium levels with FCCP stimulates the kinetics of commitment in response to all three inducers. These results suggest that of the inducers we have tested (DMSO, BA, and HX), all three act to initiate commitment via a common mechanism which involves modulation of cytoplasmic calcium levels.
Development of tyrosine aminotransferase in perinatal rat liver: Changes in functional messenger RNA and the role of inducing hormones
Authors: Perry Stephanie T. , Rothrock Robin , Isham Kenneth R. , Lee Kai‐Lin , Kenney Francis T. 
Published: December 2004

AbstractExpression of the hepatic enzyme tyrosine aminotransferase was analyzed in the perinatal period of development in the rat, when this expression undergoes significant changes associated with hepatocyte differentiation. In late prenatal liver both enzyme and functional mRNA gene products are present at levels 10‐ to 15‐fold below those in the fully differentiated adult liver. This low level of expression in fetal liver is refractory to induction by glucocorticoids, but both gene products are increased to a limited extent by cyclic AMP. This induction by cyclic AMP (cAMP) does not confer glucocorticoid‐responsiveness on expression. By 3 hr after birth both functional mRNA and enzyme levels are significantly increased, an increase which continues until a peak is reached at 12 hr that is appreciably above the adult levels. Both gene products then decline until adult levels are reached by 24 hr. The postnatal shift in aminotransferase expression is accompanied by acquisition of the capacity to respond to glucocorticoids. Treatment of newborns with an antiglucocorticoid steroid or with glucose suppresses the postnatal overshoot of expression, but neither treatment affects the increase from fetal to adult levels of expression. The results indicate that prior to birth, expression of the aminotransferase gene is partially repressed, a repression that is lifted essentially immediately upon birth. The hormones capable of inducing aminotransferase synthesis have no apparent necessary role in this process.