bluuebunny/crossref_metadata_2025_split huggingface dataset:
Down‐regulation of gonadotropin and β‐adrenergic receptors by hormones and cyclic AMP
Authors: Fishman Peter H. , Rebois R. Victor , Zaremba Terrye 
Published: December 2004

AbstractLoss of gonadotropin receptors in murine Leydig tumor cells and of β‐adrenergic receptors in rat glioma C6 cells occurred following exposure of the cells to human chorionic gonadotropin and isoproterenol, respectively. Down‐regulation of receptors was mimicked in part by other agents that elevated cyclic AMP levels in the cells such as cholera toxin and dibutyryl cyclic AMP. Whereas agonist‐mediated receptor loss was rapid and almost total, down‐regulation by cyclic AMP was slower and less extensive. Down‐regulation of receptors did not appear to be accompanied by loss of the regulatory and catalytic components of adenylate cyclase. Hormone‐mediated down‐regulation was preceded by desensitization of hormone‐stimulated adenylate cyclase. In contrast, there was no evidence that cyclic AMP caused desensitization. Finally, loss of receptors induced either by agonists or cyclic AMP required protein synthesis as cycloheximide inhibited down‐regulation. We conclude that down‐regulation of receptors in these cells is a complex process involving both cyclic AMP‐independent and ‐dependent events.
Immunopurification, characterization, and nature of membrane association of human melanoma‐associated oncofetal antigen gp87 defined by monoclonal antibody 140.240
Authors: Liao Shuen‐Kuei , Kwong Pak C. , Khosravi Mohammed J. 
Published: December 2004

AbstractA melanoma‐associated oncofetal antigen, gp87 (a p97‐like molecule), defined by the monoclonal antibody (MoAb) 140.240 has been purified to homogeneity from the spent medium of cultured melanoma cells by a two‐step immunoadsorbent procedure. The first immunoadsorbent step using glutaraldehyde‐insolubilized MoAb 140.240 (ascites fluid) resulted in a 13‐fold enrichment with 93% recovery in the bound material. In the second immunoadsorbent step constructed by the purified IgG2a of MoAb 140.240 (culture fluid) coupled to CNBr‐activated Sepharose 4B the bound material from the first step was further purified resulting in a 330‐fold purification with 90% recovery. SDS‐polyacrylamide gel electrophoretic analysis of the final purified material revealed a single band migrating as a polypeptide with an approximate molecular weight of 87 Kd, consistent with the size of the molecule immunoprecipitated by MoAb 140.240 from lysates of radiolabelled melanoma cells. Preliminary amino acid analysis indicates a particularly high proportion of phenylalaninc in gp87. We have also compared gp87 with two well defined antigens, HLA‐A,B,C (integral membrane protein) and “94K” melanoma/carcinoma–associated antigen (peripheral membrane protein) with respect to antigen extractability from melanoma cells using phosphate‐buffered saline, 0.1 M urea, 3 M NaCl, or nonionic detergent (NP‐40). The results showed that whereas 94K antigen was extractable by each of the four different solutions, gp87, similar to HLA‐A,B,C antigens, could only be extracted with NP‐40, strongly suggesting that gp87 is an integral melanoma cell component.
Matrix influence on the tumor cell stimulation of fibroblast collagenase production
Authors: Biswas Chitra 
Published: December 2004

AbstractCocultures of rabbit fibroblasts and mouse B‐16 melanoma cells produce increased levels of collagenase against type I collagen. This stimulatory effect was also found when fibroblasts were cultured in conditioned media from tumor cells. However, the level of the stimulatory factor in conditioned media was influenced by matrix deposited by fibroblasts. Thus, conditioned media collected from mono‐layers of B‐16 plated on fibroblast matrix consistently showed high levels of the factor activity. The influence of the matrix on the level of the factor was not removed by treating the fibroblast matrix with collagenase or chondroitinase ABC and was not reproduced by collagen‐coated dishes.
Activation of type I collagen genes in cultured scleroderma fibroblasts
Authors: Vuorio Tuula , Mäkelä Jyrki K. , Vuorio Eero 
Published: December 2004

AbstractFibroblasts cultured from affected skin areas of five patients with cutaneous scleroderma were found to produce increased amounts of collagen when compared with nonaffected control cells. Total RNA was isolated from the cultures and analyzed for its level of proα1(I)collagen mRNA by hybridization of RNA blots with a cloned cDNA probe. The levels of proα1(I)collagen mRNAs relative to total RNA were two‐ to sixfold higher in the samples from affected cells, accounting for the increased synthesis of type I collagen. Cytoplasmic dot hybridizations were performed to measure the cellular content of proα1(I)collagen mRNA: up to ninefold increases in the level of this mRNA per cell were found. Upon subculturing, scleroderma fibroblasts were found to reduce gradually the increased synthesis of collagen to the level of non‐affected controls by the tenth passage. The levels of type I collagen mRNAs were also reduced, but more slowly. The results suggest that in scleroderma fibroblasts the genes for type I collagen are activated at procollagen mRNA level or that they are more stable and that the activating factors are lost during prolonged cell culture because cells from affected areas lose their activated state.
Evidence for p15 cleavage site in myc‐specific proteins of avian MC29 and OK10 viruses
Authors: Sovová Vlasta , Trávníček Miloslav , Hložánek Ivo , Černá Hana , Alitalo Kari , Vaheri Antti 
Published: December 2004

AbstractMyc‐related proteins were precipitated from MC29 virus‐transformed cells (PR‐2) and from OK10 virus‐transformed cells (9C) by anti‐gag and anti‐myc sera. Immunoprecipitates were cleaved with the avian retroviral protease p15 and the cleavage products analyzed in SDS‐PAGE. Cleavage fragments of p110gag‐myc (product of MC29 virus) and p58myc (product of OK10 virus) showed the presence of a p15 cleavage site within the myc‐specific region. The site is missing in deletion mutants of MC29 virus.
Phosphorylation of a tropomyosin‐like (30 KD) protein during platelet activation
Authors: Bourguignon Lilly Y. W. , Field Seth , Bourguignon G. J. 
Published: December 2004

AbstractIn this study, we have used the tumor promoter 12‐o‐tetradecanoylphorbol‐13‐acetate (TPA), as well as its biologically inactive analogue 4α‐phorbol 12, 13‐didecanoate (4α‐PDD), to investigate platelet protein phosphorylation and its possible correlation with platelet activation. Our data show that TPA, but not 4α‐PDD, induces a preferential phosphorylation of a 30,000 dalton (30 KD) protein. This phosphoprotein is found to be physically associated with an actomyosin‐containing platelet cytoskeleton complex. Further analysis using both standard two‐dimensional gel electrophoresis and one‐dimensional urea‐SDS gel electrophoresis reveals that this 30 KD protein has several tropomyosin‐like properties. Most importantly, the degree of TPA‐induced phosphorylation of the 30 KD protein is directly proportional to the extent of platelet granule release and the shape change of the platelet, as well as to the degree of aggregation. We speculate that this phosphorylated tropomyosinlike protein may play a pivotal role in the regulation of actomyosin‐mediated platelet contractility, which has been previously implicated in a variety of platelet functions.
Molecular shape and self‐association of vinculin and metavinculin
Authors: Molony Leslie , Burridge Keith 
Published: December 2004

AbstractVinculin, a 130,000‐dalton protein localized to adhesion plaques, and metavinculin, a 150,‐000 dalton protein closely related to vinculin, have been studied using rotary shadowing and electron microscopy. Both proteins have globular head regions attached to rod‐shaped tail domains. Vinculin and metavinculin also both form complexes consisting of four to six individual molecules. These multimers are formed by head‐to‐head as well as tail‐to‐tail interactions.Talin, another protein which has been localized to adhesion plaques and binds to both vinculin and metavinculin, has also been investigated using shadowing techniques. Talin is an elongated, flexible molecule in high ionic strength buffers, as shown here by rotary shadowing and negative stain electron microscopy.
Vascular endothelial cells in cell‐mediated immunity: Adoptive transfer with in vitro conditioned cells is genetically restricted at the endothelial cell barrier
Authors: Standage Blayne A. , Vetto R. Mark , Jones Rich , Burger Denis R. 
Published: December 2004

AbstractDelayed‐type hypersensitivity (DTH) is a cell‐mediated immune response that can be adoptively transferred in rats when greater than 2 × 108 cells from peritoneal exudate, lymph nodes, or spleen are used. We have shown that by using an in vitro conditioning step with antigen, transfer can be subsequently carried out with as few as 2 × 107 spleen cells. The magnitude of DTH was reflected in ear swelling after intradermal injection of antigen [tuberculin or keyhole limpet hemocyanin (KLH)] and confirmed histologically. The transfer was antigen specific, requiring the sensitizing antigen in both the in vitro conditioning step and in the ear test challenge. Adoptive transfer with conditioned cells was genetically restricted by alleles of the RT‐1 region [major histocompatibility complex (MHC) of the rat]. Brown Norway strain (n haplotype) immune cells would not transfer DTH to Lewis (1 haplotype), ACI (a haplotype), or Buffalo (b haplotype) rats, whereas each strain would transfer DTH to syngeneic recipients. Moreover, this pattern of restriction held for all strains when tested in reciprocal fashion. In additional experiments, F1 to parental bone marrow chimeras were constructed so that bone‐marrow‐derived cells and non‐bone‐marrow‐derived cells were of different RT‐1 haplotypes. When these chimeras were used as recipients, transfer of DTH was only observed when immune donor cells and recipient non‐bone‐marrow‐derived cells were syngeneic. These results point to the critical role of non‐bone‐marrow‐derived cells (endothelial cells) in the DTH reaction.
Design and characterization of peptides with amphiphilic β‐strand structures
Authors: Osterman David G. , Kaiser E. T. 
Published: December 2004

AbstractTo extend our studies on peptides and proteins with amphiphilic secondary structures, a series of peptides designed to form amphiphilic β‐strand structures was designed, synthesized, and characterized by circular dichroism and infrared spectroscopy. Amphiphilic β‐strand conformations may be likely to appear in a variety of surface‐active proteins, including apolipoprotein B and fibronectin. In a β‐strand conformation, the synthetic peptides will possess a hydrophobia face‐composed of valine side chains and a hydrophilic face composed of alternating acidic (glutamic acid) and basic (ornithine or lysine) residues. The peptides studied had a variety of chain lengths (5, 9, and 13 residues), and had the amino groups either free or protected with the trifluoroacetyl group. While the peptides did not possess a high potential for β‐sheet formation based on the Chou Fasman parameters, they possessed significant β‐sheet content, with up to 90% β‐sheet calculated for the 13‐residue protected peptide. The driving force for β‐sheet formation is the potential amphiphilicity of this conformation. The β‐strand conformation of the 13‐residue unprotected peptide was stable in 50% trifluoroethanol, 6 M guanidine hydrochloride, and octanol. The peptides are strongly sell‐associating in water, which would reduce the unfavorable contacts of the hydrophobic residues with water. It is clear that small peptides can be designed to form stable β‐strand conformations.
Cellular redistribution of β‐adrenergic receptors in a human astrocytoma cell line: A comparison with the epidermal growth factor receptor in murine fibroblasts
Authors: Wakshull E. , Hertel C. , O'Keefe E. J. , Perkins J. P. 
Published: December 2004

AbstractThe redistribution of β‐adrenergic receptors (β‐AR) during agonist‐induced desensitization has been compared to the process of receptor‐mediated endocytosis of epidermal growth factor (EGF) in human astrocytoma cells (1321N1). [125I]EGF exhibited saturable binding to high affinity (KD = 1–2 nM) receptor sites on intact 1321Nl cells. [125I]EGF was found to internalize rapidly using an acid wash technique to remove surface bound hormone. Sucrose density gradient fractionation following exposure to EGF revealed a redistribution of EGF binding sites from high density (heavy peak) to low density (light peak) regions of the gradient. The light peak binding probably represents EGF in internalized vesicles formed during endocytosis. Low temperature (4 °C) or the presence of the lectin concanavalin A (con A) inhibited this ligand‐induced movement of EGF receptors. When cells were incubated simultaneously with EGF and the β‐AR agonist isoproterenol, both receptors were found to co‐migrate in the low density regions of sucrose gradients. No evidence of heterologous ligand‐induced receptor endocytosis was found. These results suggest that the EGF receptors and β‐AR are processed in parallel by 1321N1 cells.
Wound fluid angiogenesis factor stimulates the directed migration of capillary endothelial cells
Authors: Banda Michael J. , Dwyer Karyn S. , Beckmann Alice 
Published: December 2004

AbstractDuring wound healing, new capillaries grow into the wound site. An angiogenesis factor isolated from wound fluid stimulates the movement of capillary endothelial cells in a filter migration assay. Experiments were carried out to determine whether the movement seen in the assay was chemokinetic or chemotactic. Capillary endothelial cells were plated onto a collagen‐coated coverslip and inverted over a visualization apparatus. Cells exposed to a constant concentration of wound fluid angiogenesis factor (WAF) were more mobile than cells not exposed to WAF, and this movement was chemokinetic. When exposed to a gradient of WAF, the cells translocated toward the higher concentration; this directional movement was chemotactic. Cells in a gradient of WAF morphologically aligned with the gradient. These data support the idea that wound healing angiogenesis is regulated by the chemotaxis of capillary endothelial cells.
Antibodies specific for the carboxy‐terminal region of the major surface glycoprotein of simian rotavirus (SA11) and human rotavirus (Wa)
Authors: Streckert Hans‐Jürgen , Grunert Barbara , Werchau Hermann 
Published: December 2004

AbstractAntibodies specific for the major outer capsid protein (VP7) of the simian rotavirus SA11 were obtained by immunization of rabbits with a synthetic peptide, Ser‐Ala‐Ala‐Phe‐Tyr‐Tyr‐Arg‐Val, corresponding to the eight carboxy‐terminal amino acids of the viral protein predicted from the nucleotide sequence of the gene segment 9 of the SA11 genome. As the carboxy‐terminal region of the VP7 of human rotavirus Wa has an identical sequence, cross‐reactivity of the raised antibodies was observed with this strain.
Treatment of a fatal transplantable erythroleukemia by procedures that lower endogenous erythropoietin
Authors: Hossain Azhar , Kim Jung‐Kon , Hankins W. David 
Published: December 2004

AbstractThe in vitro growth of primary erythroleukemia cells has been examined in the presence and absence of the hormone erythropoietin (EPO). Although these leukemic cells had previously been considered to be hormone‐independent, addition of EPO was found to be essential for maximum growth in culture. Erythroid colonies that grew in the presence of EPO were leukemogenic when returned to mice. Influence of EPO on the in vivo growth of leukemic cells was indicated by our findings that (1) administration of the hormone caused a more severe leukemia and rapid death, and (2) transfusion of red blood cells, which lowers endogenous EPO, led to decreased spleen size and increased survival of leukemic mice. We suggest from our results that hormone‐associated therapy might be efficacious in the treatment of this and, perhaps, other leukemias.
Human restriction fragment length polymorphisms and cancer risk assessment
Authors: Krontiris Theodore G. , DiMartino Nancy A. , Colb Mark , Mitcheson H. David , Parkinson David R. 
Published: December 2004

AbstractThe polymorphic restriction fragments of the human Ha‐ras locus, produced by the variable tandem repetition (VTR) of a short consensus sequence, fall into three classes based on allelic frequencies. Alleles of the “rare” class (individual frequencies < 0.5%) have been detected only in white blood cell and tumor DNA of cancer patients. This phenomenon is independent of ethnic origin. No significant association of rare alleles with cancer patients has been demonstrated at an independent tandem repeat locus, VTR4.1. The results suggest that the Ha‐ras restriction fragment length polymorphism is useful in cancer risk assessment.
Properties of catalase activity in vegetative and sporulating cells of yeast Saccharomyces cerevisiae
Authors: Ota Akihiro 
Published: December 2004

AbstractProperties of catalase activities have been examined in the intact cells of early stationary phase and cells 3 hr after transfer to sporulation medium in Saccharomyces cerevisiae. The catalase activities of the two cells had a broad optimal pH from 6 to 8. Catalase activity in the intact cells increased throughout a 4‐hr period of the observation following transfer to sporulation medium. Almost all the catalase activity in vegetative cells was lost by the treatment at 60°C for 10 min. Catalase activities of both cells were inhibited by KCN, NaN3, o‐phenanthroline, and PCMB. The catalase activity of the vegetative cells was slightly more inhibited and inactivated than that of the sporulating cells by the inhibitors and by the treatment with HCl or NaOH.
The thyroid “microsomal” antigen is an epitope on the thyrotropin receptor
Authors: Islam Nazrul , Tuppal Raj , Hawe Beverley S. , Briones‐Urbina Rosario , Farid Nadir R. 
Published: December 2004

AbstractAntimicrosomal antibodies are present in the sera of most patients with autoimmune thyroiditis, and Graves' disease. It has, in general, been difficult to separate antimicrosomal activity from that directed against the thyrotropin (TSH) receptor in Graves' IgG preparations. The “microsomal” antigen has been localized to the endoplasmic reticulum and microfollicular aspect of thyrocytes; its structure is however unknown. In an attempt to identify the thyroid microsomal antigen, we studied the interaction of Hashimoto's IgG with high microsomal antibody titre and negative for thyroglobulin with purified thyroid plasma and light microsomal membranes. We allowed Hashimoto's, Graves', and control IgGs to bind to protein blots of thyroid plasma membranes resolved on SDS‐PAGE under nonreducing conditions. All seven Hashimoto's IgG at a concentration of 2 mg/ml interacted with an M ∼︁ 197,000 polypeptide corresponding to the TSH holoreceptor. By contrast to Graves' IgG (which were positive at 1 mg/ml), however, this binding was not blocked by pretreatment of the protein blots with TSH. Normal IgGs showed no binding at concentrations of up to 2 mg/ml.Both Hashimoto's and Graves' IgG interacted with TSH‐affinity column‐purified receptor preparations.Two of the Hashimoto's IgGs induced adenylate cyclase activation in thyroid plasma membranes, three inhibited TSH‐stimulated enzyme activation, and two were without effect. Two classes of autoantibodies, other than TSH receptor directed, were encountered; one class raised to antigens common to all seven patients and another class unique to individual patients, eg, Mr 210,000 and Mr 20,000 polypeptides.We propose that the TSH receptor has multiple epitopes (functional domains), and the one to which antimicrosomal antibody bind is likely to be spatially separated from that with which Graves' IgG and TSH interact. Differences in affinity or number of sites allows for the demonstration of Graves' IgG against a background of antimicrosomal antibody.
Number of receptor sites from Scatchard and Klotz graphs: Complementary approaches
Authors: Faguet Guy B. 
Published: December 2004

AbstractEstimates of number of receptor sites and evaluation of the complexity of the binding process require collection of a spectrum of binding measurements and selection of a theoretical model to fit the experimental data. The appropriateness of the measurements and of the model can be visually judged on graphic displays of the model‐data fitting curves in Scatchard and semilogarithmic coordinates. This approach is helpful for detecting the two types of errors most frequently found in reports of binding studies: (1) underestimating the number of binding sites, and (2) failure to recognize the complexity of the binding process. While the former is readily recognizable on semilogarithmic but not on Scatchard plots of the model fitting the data, the latter might not be apparent on either plot. Collection of extensive measurements over a wide range of ligand concentrations with graphic display of the model‐data fitting curves in Scatchard and semilogarithmic coordinates should be used to recognize and prevent both errors.
Phenotypic characterization of Ewing sarcoma cell lines with monoclonal antibodies
Authors: Lipinski Marc , Braham Karim , Philip Irène , Wiels Joëlle , Philip Thierry , Dellagi Koussay , Goridis Christo , Lenoir Gilbert M. , Tursz Thomas 
Published: December 2004

AbstractThe histogenesis of Ewing sarcoma, the second most frequent bone tumor in humans, remains controversial. Four Ewing cell lines were analyzed by immunological methods. A panel of antibodies directed to T, B, and myelomonocytic markers gave negative results. Surface antigens recognized on Ewing cells were found to be related to the neuroectoderm lineage. Ganglioside GD2, a marker of neuroectodermal tissues and tumors, was present on all lines. These were also stained by the mouse monoclonal antibody HNK‐1, which detects a carbohydrate epitope present on several glycoconjugates of the nervous system, including two glycoproteins, the myelin‐associated glycoprotein and the neural cell‐adhesion molecule (N‐CAM), and an acidic glycolipid of the peripheral nervous system. The P61 monoclonal antibody, which reacts with a peptide moiety of N‐CAM, and a rabbit antiserum, raised to purified mouse N‐CAM and not recognizing the HNK‐1‐defined epitope, were also reactive. By contrast, all antibodies specific for hematopoietic cell surface antigens were totally negative. Besides these antigenic features, Ewing sarcoma cells are characterized by a specific t(11:22)(q24;q12) translocation also observed in neuroepithelioma, a neuroectodermal tumor, suggesting a possible evolutionary related origin. The recent finding that the human N‐CAM gene is located at the vicinity of the breakpoint on chromosome 11 indicates that it might be involved in genetic rearrangements occurring in this region.
Association of tyrosine protein kinase activity with mitochondria in human fibroblasts
Authors: Piedimonte Giuseppe , Silvotti Lucia , Borghetti Angelo F. , Chamaret Solange , Montagnier Luc 
Published: December 2004

AbstractA tyrosine protein kinase activity has been detected in the mitochondrial fraction purified from human fibroblasts. By enzymatic and sedimentation analysis this activity appeared to be localized in the mitochondrial outer membrane. Mitochondrial tyrosine phosphorylation was strictly dependent on the presence of Mn2+ ions. An inverse relationship between cell proliferation and mitochondrial protein phosphorylation on tyrosine residues has been found: a marked increase in the mitochondrial tyrosine kinase activity occurred when a significant reduction in the growth rate followed serum step‐down. In mitochondria purified from resting cells, a protein band with apparent molecular weight of 50 kd appeared to be phosphorylated on tyrosine.