bluuebunny/crossref_metadata_2025_split huggingface dataset:
Biological activities of laminin
Authors: Kleinman Hynda K. , Cannon Frances B. , Laurie Gordon W. , Hassell John R. , Aumailley Monique , Terranova Victor P. , Martin George R. , DuBois‐Dalcq Monique 
Published: December 2004

AbstractLaminin is a multifunctional protein with diverse biological activities. Like fibronectin, it can influence cell adhesion, growth, morphology, differentiation, migration, and agglutination as well as the assembly of the extracellular matrix. Laminin primarily affects cells of epithelial origin, and the response varies depending on the cell. Because most differentiated cells are difficult to maintain in culture, laminin may be an important supplement in studies on cell differentiation in vitro.
Anti‐idiotypic antibody identifies the cellular receptor of reovirus type 3
Authors: Gaulton Glen , Co Man Sung , Greene Mark I. 
Published: December 2004

AbstractThe binding and subsequent infectivity of reovirus to target cells are mediated by interaction with specific cell surface viral receptors. To gain a more detailed understanding of the biochemistry of the reovirus receptor and the cellular consequences of viral attachment, we have studied the binding of type 3 reovirus (Dearing strain) in a quantitative manner utilizing an antiidiotypic antibody probe. A syngeneic monoclonal antiidiotypic antibody (87.92.6) was prepared by immunization with hybridoma cells which secrete an antireovirus hemagglutinin‐specific antibody. This antiidiotypic antibody was previously shown to specifically recognize the cell surface receptor for reovirus type 3. In this report, we demonstrate that antiidiotype mimicked reovirus tropism in binding to murine thymomas; antiidiotype inhibited the binding of reovirus to specific targets, but not the binding of anti‐H‐2; and cross linking of receptor‐bound antiidiotype by antiimmunoglobulin induced patching, but not capping of reovirus receptors. Utilizing radiolabeled antiidiotype, we next quantitate the number of reovirus receptors on Rl.l and YAC thymoma cells and, finally, report on the preliminary identification of the reovirus receptor as a 67,000‐Da membrane glycoprotein.
Receptors for insulin and epidermal growth factor: Interaction with organomercurial agarose
Authors: Aglio Linda S. , Maturo Joseph M. , Hollenberg Morley D. 
Published: December 2004

AbstractThe receptor for both insulin and epidermal growth factor (EGF) from human placental membranes, after crosslink labeling with 125I‐labeled insulin and EGF, can be adsorbed to an organomercurial‐agarose derivative (Affi‐Gel 501) and can be recovered from the gel by elution with dithiothreitol (DTT). Pretreatment of crosslink‐labeled membranes with N‐ethylmaleimide (NEM) blocks the ability of the receptor to react with the organomercurial column. NEM also abolishes the protein kinase activity of both receptors. Under appropriate conditions, insulin can promote the reaction of the insulin receptor with the organomercurial‐agarose derivative. For both the insulin and EGF receptors, our results provide an avenue for the isolation of the sulfhydryl‐containing receptor domains that may play a role in the control of receptor function.
Structure of the murine anion exchange protein
Authors: Kopito Ron R. , Lodish Harvey F. 
Published: December 2004

AbstractA full‐length clone encoding the mouse erythrocyte anion exchange protein band 3, has been isolated from a cDNA library using an antibody against the mature erythrocyte protein. The complete nucleotide sequence has been determined. Substantial homology is evident between the deduced murine amino acid sequence and published sequences of fragments of human band 3 protein. The amino‐terminal 420 and the carboxy‐terminal 32 residues constitute polar, soluble domains, while the intervening 475 amino acids are likely to be intimately associated with the lipid bilayer. Hydrophobic analysis of this sequence, together with structural studies on the human protein, suggests the possibility of at least 12 membrane spans, predicting that both the amino‐ and carboxy‐termini are intracellular.
The design, synthesis, and characterization of tight‐binding inhibitors of calmodulin
Authors: DeGrado William F. , Prendergast Frank G. , Wolfe Henry R. , Cox Jos A. 
Published: December 2004

AbstractBased on a consideration of the probable structure of calmodulin and sonic natural peptides known to interact with it, two calmodulin‐binding peptides were designed. These peptides bind to calmodulin in helical conformations and are capable of forming electrostatic and hydrophobic interactions with calmodulin. Their dissocation constants for binding (⩽ 210 and 400 pM) place them as the tightest‐binding inhibitors of calmodulin thus far reported. The study of the interactions of these and similar peptides with calmodulin will provide valuable insights into the mechanisms whereby calmodulin binds to target enzymes, and it also serves as an excellent model system for exploring the physical chemistry of protein‐protein interaction.
Analysis of stable and unstable viral forms in SV40‐infected human keratinocytes
Authors: Naimski Piotr , Steinberg Mark L. 
Published: December 2004

AbstractWe analyzed the slate of the genomic DNA of the papovavirus SV40 in human keratinocytes as viral‐infected cells gradually acquired a transformed phenotype over time. Initially, the vast majority of the viral DNA is maintained either in a full‐length supercoiled form or as truncated subgenomic fragments with little evidence of integration. However, analyses of clonal populations revealed great heterogeneity and instability of the viral DNA, and we were able to isolate one clonal subpopulation in which integrated forms of the virus appeared to predominate. Similarly, uncloned populations eventually ceased production of the “free” viral DNA after several years in culture and instead came to display tandemly repeated SV40 copies at a single host integration site. Interestingly, Bgl II digestion of host DNA generated restriction fragments containing the integrated SV40 DNA, which were of differing sizes in cultures at the 144th vs the 163rd serial passage suggesting modification or rearrangement of sequences at or near the integration site. Host sequences flanking the integrated viral DNA at the 163rd serial passage have been isolated on restriction fragments generated by Eco RI, Bam HI, and Hpa II digestion. These analyses suggest that the integrated virus is linearized near the Bgl I site and contains a large deletion in the SV40 early region at one of the viral‐host junctions.
Inhibition of ornithine decarboxylase activity and cell growth by diamines: A comparison between the effects of two homologs, 1,3‐diaminopropane and 1,4‐diaminobutane (putrescine)
Authors: Linden Margareta , Oredsson Stina M. , Anehus Siw , Heby Olle 
Published: December 2004

AbstractThe ornithine decarboxylase (ODC) activity of Ehrlich ascites tumor cells was almost completely inhibited by treatment with either putrescine (10 mM) or 1,3‐diaminopropane (5 mM). 1,3‐Diaminopropane treatment eradicated the cellular content of putrescine and reduced that of spermidine and spermine. Putrescine treatment caused a dramatic increase in cellular putrescine content and a temporary decrease in spermidine and spermine content. Despite the fact that 1,3‐diamino‐propane and putrescine inhibited the ODC activity more effectively than did α‐difluoromethylornithine (DFMO), an enzyme‐activated irreversible inhibitor of ODC, they were considerably less antiproliferative in action. However, as compared to DFMO the diamines were less effective in reducing the total polyamine (putrescine + spermidine + spermine) content of the cells.
Posttranslational phosphorylation of specific chromosomal proteins and transcription of hnRNA genes in isolated nuclei: Retention of in vivo sensitivity to 5,6‐dichloro‐1‐β‐D‐ribofuranosylbenzimidazole (DRB)
Authors: Holst Mikael , Egyházi Endre 
Published: December 2004

AbstractThe rapidly turning over phosphorylation of specific nuclear nonhistone proteins, especially 42‐, 33‐, and 30‐kDa polypeptides, and its relation to the transcriptional activity of hnRNA genes was investigated in isolated nuclei from salivary gland cells of Chironomus tentans. Incubation conditions promoting the phosphorylation of nonhistone proteins as well as the transcriptional activity of RNA polymerase II were established. The pattern of 32P incorporation into the nonhistone proteins found in isolated nuclei resembled that obtained in experiments with intact cells, and the endogenous RNA polymerase II retained its ability to reinitiate the transcription under in vitro assay conditions. In addition, the in vivo sensitivity of the phosphorylation of 42‐, 33‐, and 30‐kDa polypeptides, like the sensitivity of the initiation of hnRNA transcription to 5,6‐dichloro‐1‐β‐D‐ribofuranosylbenzimidazole (DRB), were preserved in the nuclear preparation. The experimental data taken together provide further support for the idea that the activation of hnRNA genes is causally related to the phosphorylation of specific nonhistone proteins.
The leucine binding proteins of Escherichia coli as models for studying the relationships between protein structure and function
Authors: Antonucci Tammy K. , Landick Robert , Oxender Dale L. 
Published: December 2004

AbstractThe genes encoding the leucine binding proteins in E coli have been cloned and their DNA sequences have been determined. One of the binding proteins (LIV‐BP) binds leucine, isoleucine, valine, threonine, and alanine, whereas the oilier (LS‐BP) binds only the D‐ and L‐isomers of leucine. These proteins bind their solutes as they enter the periplasm, then interact with three membrane components, livH, livG, and livM, to achieve the translocation of the solute across the bacterial cell membrane. Another feature of the binding proteins is that they must be secreted into the periplasmic space where they carry out their function. The amino acid sequence of the two binding proteins is 80% homologous, indicating that they arc the products of an ancestral gene duplication. Because of these characteristics of the leucine binding proteins, we are using them as models for studying the relationships between protein structure and function.
Suramin binds to platelet‐derived growth factor and inhibits its biological activity
Authors: Hosang Markus 
Published: December 2004

AbstractThe polyanion suramin was recently found to inhibit binding of 125I‐PDGF (platelet‐derived growth factor) to Balb/e 3T3 cell membranes. Cultured Swiss 3T3 cells were used to investigate the mode of action of suramin and to monitor its effect on the biological activity of PDGF. Evidence is presented that suramin inhibits cellular binding of PDGF by binding to PDGF itself, thereby preventing it from binding to its cell surface receptor: First, while suramin inhibited I‐PDGF binding with a hail maximum inhibition concentration of ∼60 μM or 90 μg/ml in a simultaneous competition assay, it was inactive in a sequential radioreciptor assay, in which an inhibitor is expected to be active if it interacts with the receptor (even with relatively low affinity) but to be inactive if it interacts with PDGF. Second, suramin prevented immunoprecipitation of 125I‐PDGF in a dose‐dependent manner, with a half maximum effective concentration of ∼50 μM. Furthermore, suramin efficiently dissociated 125I‐PDGF bound to its cell surface receptor, whereas unlabeled PDGF even in large excess was virtually inactive. This is also in line with the proposed direct interaction between PDGF and suramin, since such an interaction can he envisaged to induce a conformational change in the PDGF‐receptor complex, resulting in an increased off‐rate of the complex. Reduced 125I‐PDGF binding in the presence of suramin correlated directly with a suramin dose‐dependent inhibition of PDGF‐induced incorporation of 3H‐thymidine into quiescent Swiss 3T3 cells and of the proliferation of these cells.These observations suggest that suramin, by complexing with PDGF, renders this mitogen unable to bind to its physiological receptor and, thereby, prevents PDGF‐initiated biological activities.
Quantitative relationship between initiation of hepatocarcinogenesis and induction of altered cell islands
Authors: Kaufmann William K. , Mackenzie Susan A. , Rahija Richard J. , Kaufman David G. 
Published: December 2004

AbstractWe have quantified the initiation of hepatocytic neoplasms and the induction of altered cell islands in regenerating livers of rats given a single treatment with one of three carcinogens before or during the peak of DNA synthesis after partial hepatectomy. For up to 20 wk after treating livers during the peak of DNA synthesis with methyl(acetoxymethy1)nitrosamine (DMN‐Ac), hepatocytic neoplasms were not seen. Thereafter, in rats fed the liver tumor promoter, phenobar‐bital, neoplasms emerged continuously so that by 60 wk after initiation, livers held an average of 5.5 neoplasms. Islands of cellular alteration, identified by their abnormal retention of glycogen on fasting, also appeared to emerge continuously between 20 and 60 wk after initiation. By 60 wk, promoted livers contained about 10,000 islands. In DMN‐Ac‐initiated, phenobarbital‐promoted livers, neoplasms and islands maintained a constant numerical relationship over time with about 1,450 islands emerging for every neoplasm that emerged. This ratio of islands to neoplasms differed according to the type of carcinogen used to initiate hepatocar‐cinogenesis and depending on whether promotion with phenobarbital was included. In livers initiated with DMN‐Ac but not promoted with phenobarbital, the ratio of islands to neoplasms was about 7,750: 1. In livers initiated by treatment with (±)‐7α,8β‐dihydroxy‐9β,10β‐epoxy‐7,8,9,10‐tetrahydrobenzo[a]pyrene at the peak of DNA synthesis and then promoted with phenobarbital, the ratio of islands to neoplasms was 7,200: 1. In livers exposed to gamma rays at the peak of DNA synthesis in regenerating livers and promoted, no neoplasms were seen in our sample although islands could be enumerated. Evaluation of another group of rats irradiated during the prereplicative phase of regeneration revealed two neoplasms in nine treated livers and a ratio of islands to neoplasms of greater than 12,000: 1. Thus, when comparing livers treated once with carcinogen and then promoted, this ratio of islands to neoplasms differed considerably according to the carcinogen being tested. These results suggest that the induction of glycogen‐retaining hepatocyte islands may not be a quantitative measure of the initiation of hepatocarcinogenesis.
Urokinase‐type and tissue‐type plasminogen activators have different distributions in cultured bovine capillary endothelial cells
Authors: Moscatelli David 
Published: December 2004

AbstractThe cell extracts and conditioned medium from cultured bovine capillary endothelial (BCE) cells were examined to determine the types of plasminogen activator (PA) present in each of these two fractions. The fractions were first analyzed by fibrin autography after sodium dodecyl sulfate (SDS)‐polyacrylamide gel electrophoresis. The cell extracts contained two species of PA of Mr 48,000 and 28,000. Multiple forms of PA were detected in the conditioned medium: variable amounts of the Mr 48,000 and 28,000 forms and a broad band of activity with Mr in the range of 67,000–93,000. The major fraction of the Mr 48,000 form was in the cell extract. Treatment of the cells with 12‐0‐tetradecanoyl phorbol‐13‐acetate or with a preparation containing angiogenic activity resulted in a proportionate increase in the levels of all forms. The Mr 48,000 form was demonstrated to be a urokinase‐like PA, since it was immunoprecipitated with antibodies to urokinase. When conditioned medium or cell extracts from biosynthetically labelled BCE cells were incubated with antiserum to urokinase, the Mr 48,000 form was immunoprecipitated only from the cell extract. The Mr 67,000–93,000 forms were demonstrated to be tissue‐type PAs, since they were immunoprecipitated with antibodies to tissue PA. When the same conditioned medium or cell extracts were incubated with antiserum to tissue‐type PA, the Mr 67,000–93,000 forms were immunoprecipitated only from the conditioned medium. Therefore, BCE cells are able to produce both tissue‐type PA, which is primarily secreted, and urokinase‐type PA, which remains primarily cell associated.
Monitoring of individual human exposure to aflatoxins (AF) and N‐nitrosamines (NNO) by immunoassays
Authors: Wild C. P. , Umbenhauer D. , Chapot B. , Montesano R. 
Published: December 2004

AbstractHighly sensitive immunoassays have been used to quantitate aflatoxins (AF) and N‐nitrosamines (NNO) in human body fluids and tissues, respectively. This approach was taken in order to quantitate environmental exposure to these agents at an individual level to facilitate the investigation of their role in the etiology of human cancer. In order to analyse AF in human urine, an immunopurification step has been developed by using AF‐specific antibody bound to AH‐Sepharose 4B gel in a small (4‐ml gel volume) affinity column prior to enzyme‐linked immunosorbent assay (ELISA). The ELISA can be used to quantitate aflatoxin B1 (AFB1) over the range 0.01 ng/ml to 10 ng/ml and the assay system has been validated by using human urine samples spiked with AFB1 over this concentration range. In addition, 29 urine samples from the Philippines have been analysed and found to contain a range of levels from zero to 4.25 ng/ml AFB1 equivalent with a mean of 0.875 ng/ml. This compared with a mean of 0.066 ng/ml AFB1 equivalent in samples from France.Radioimmunoassay of O6‐methyldeoxyguanosine (O6‐medG) has been performed on human oesophageal and cardiac stomach mucosal DNA from tissue samples obtained during surgery in Linxian County, People's Republic of China, an area of high risk for both oesophageal and stomach cancer. Using the methodology described and having 1 mg of hydrolyzed DNA allows the detection of approximately 25 fmol O6medG per mg DNA. Of the 37 tissue samples analyzed from Linxian County, 17 samples had levels of O6‐medG ranging from 15 to 50 fmol/mg DNA, ten showed higher levels up to 160 fmol/mg DNA, and the remaining ten samples were below the limit of detection. For comparison, 12 tissue samples were obtained from hospitals in Europe and all showed levels below 45 fmol O6‐medG/mg DNA with seven below the limit of detection. All tissue samples from Linxian county showed normal levels of O6‐alkylguanine DNA alkyltransferase when compared to levels in other parts of the world.The approaches described appear promising for assessing the role of AFB1 in the etiology of human liver cancer and of nitrosamines as possible causative agents in oesophageal or stomach cancer.
A set of stage‐dependent embryonic antigens expressed in cell cultures of BALB/c mouse embryos and in transformed cell lines
Authors: Gerhards Roswitha E. , Mehnert Franz E. 
Published: December 2004

AbstractA rabbit antiserum (A2) directed against the detergent‐solubilized fraction of the simian virus 40‐transformed mouse embryo fibroblast cell line VLM detects common antigens in primary cell cultures from BALB/c mouse embryos and in transformed cell lines from various species. Positively reacting cell cultures show a set of polypeptides with molecular weight species p86, p74, p68, p46, p42, p40, and p35. As tested by Western blotting procedures, all immunoprecipitated proteins carry immunologically reactive determinants. By analysis with two‐dimensional gel electrophoresis, all precipitated polypeptides show charge heterogeneities. Concerning the two major members of the protein set, p40 consists of at least four subspecies with isoelectric points in the range of pH 6.2–6.8, whereas p35 is composed of two subspecies focusing between pH 6.4 and pH 7.2. By comparison of the two‐dimensional patterns of p35 of various transformed cell lines, a basic (pH 6.6–7.2) and an acidic (6.4–6.6) charge type of p35 could be observed. Comparative analyses of primary cell cultures from 12–16‐day mouse embryos show the immunoprecipitated set of polypeptides only in the 16‐day embryo cell cultures. After six further propagations, these cells express the immunoreactive proteins as strongly as the primary cell cultures. In embryonic, cell cultures of day 14 of gestation the expression of this set of antigens is induced only when cells are propagated at least six times. Under identical conditions these proteins could not be induced in cell cultures of 18‐day‐old mouse embryos. None of the polypeptides could be immunoprecipitated from primary mouse kidney cell cultures of 12‐day‐old mice even when the cultures were propagated at least‐15 times. This set of polypeptides is also present in simian virus 40‐transformed cells of hamster, rat, monkey, and human origin. These findings suggest that in simian virus 40‐transformed mouse cells, in addition to p53, the synthesis of other embryonic antigens is reactivated. The presence of the described set of polypeptides in polyoma virus‐transformed cells of rat and mouse origin and in cell lines derived from malignant human tumors might indicate common functions in metabolic patterns of transformed cells.
Assembly and dynamics of the actin filament system in nonmuscle cells
Authors: Pollard Thomas D. 
Published: December 2004

AbstractKinetic analysis has provided a detailed quantitative description of the mechanism of actin polymerization as well as the methods to analyze the mechanisms of action of actin‐binding proteins. In Acanthamoeba, five different proteins regulate the pool of monomers available for polymerization, cap the end of filaments, sever filaments, and cross‐link filaments. Remarkably, many of these interactions involve very‐low‐affinity bonds between the protein molecules.
In vivo biosynthesis of clathrin and other coated vesicle proteins from rat liver
Authors: Pierce L. Ross , Zurzolo Chiara , Edelhoch Harold 
Published: December 2004

AbstractA biosynthetic study of rat liver coated vesicle (CV) proteins was undertaken by using in vivo labeling with L‐[35S]methionine. CVs were isolated and purified by using standard procedures and characterized by electron microscopy, sedimentation, and sodium dodecyl sulfate polyacrylamide gel electrophoresis followed by fluorography, or by gel slicing and liquid scintillation counting. After 51/2 min of labeling (the earliest time examined), incorporation of radioactive clathrin heavy‐chain (180‐kD (kilodalton)) subunits as well as a 90‐kD CV‐associated protein into purified CVs was demonstrated. The level of labeled 180‐kD clathrin in coated vesicles increased rapidly during the First 2 hr of labeling and then continued to rise at a slower rate between 4 and 16 hr. This slow accumulation of labeled clathrin heavy chains in the CV pool may reflect early compartmental sequestration of a fraction of newly synthesized clathrin with delayed assembly into free CVs. By 16 hr of labeling, clathrin 180‐kD chains and the 90‐kD CV‐associated protein accounted for approximately 48 and 26%, respectively, of the radioactivity in all CV proteins. Two proteins of MWa 68 kD and 53 kD showed marked declines in cpm/unit protein between 30 min and 4 hr, raising the possibility that these species may, be transferred out of CVs during or after transport without loss of the other CV proteins. The possibility is also raised that clathrin heavy chains may be recycled during CV formation. Possible heterogeneity within individual CV preparations with respect to protein composition and derivation from both plasma membrane and Golgi regions are proposed.