bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of env gene recombination in X‐ray‐induced thymomas of C57BL76 mice
Authors: Nairn Rodney S. , McLntyre Bradley W. , Richie Ellen R. , Allison James P. 
Published: February 2007

AbstractA role for specific recombination events at the env region of endogenous murine leukemia virus (MuLV) sequences in radiation carcinogenesis in C57BL mice has been suggested by a number of studies. We characterized env‐related cell surface antigens from a primary, x‐ray‐induced, and several transplanted C57BL/6 thymomas of viral and radiation etiologies by immunoprecipitation and two‐dimensional peptide mapping. DNA from lymphoma cells was also analyzed by Southern blotting for evidence of mink cell focus‐forming (MCF) type env recombination events. Although gp70 molecules with novel structural determinants were found on all transplanted lymphomas examined, expression of novel env antigens was variable among these lymphomas, and there was a lack of correlation of characteristic MCF‐type env recombination events in endogenous retrovirus DNA sequences with novel env antigens on lymphoma cell surfaces. Neither novel gp70 antigens nor MCF‐type env provirus recombinant structures were consistent features of the C57BL/6 thymomas of radiation etiology examined in this study, even though MCF‐type env recombination events have been suggested as etiologically significant in MuLV‐mediated lymphomagenesis in both RadLV and x‐ray‐induced tumors in C57BL/6 mice.
Constitutive and phorbol‐myristate‐acetate regulated antioxidant defense of mouse epidermal JB6 cells
Authors: Crawford Dana R. , Amstad Paul A. , Foo Debra D. Yin , Cerutti Peter A. 
Published: February 2007

AbstractBecause oxidative processes can participate in tumor promotion, it is likely that the cellular antioxidant defense also plays a role. We have compared the levels of the three major antioxidant enzymes, Cu, Zn‐superoxide dismutase (SOD), catalase and glutathione peroxidase (GPx), in promotable mouse epidermal JB6 cells clone 41 and nonpromotable cells, clone 30. We found that the constitutive activities of SOD and catalase were approximately twice as high in clone 41 as in clone 30 while the GPx activities were comparable. Correspondingly, catalase protein concentrations were higher in clone 41, according to immunoblots. Northern blot analysis indicated that the steady‐state mRNA concentrations for SOD and catalase, but not for GPx, were considerably higher in clone 41 than in clone 30. Southern blot analysis showed no difference between the two clones in their complements of the SOD and catalase genes. Clone 41 also contained slightly higher constitutive levels of glutathione. The higher antioxidant capacity of promotable clone 41 may protect it from excessive toxicity of oxidant promoters and allow growth stimulation.Certain tumor promoters that lack oxidizing properties may generate a cellular prooxidant state by a variety of mechanisms (e.g., it had been reported that the phorbol ester PMA decreases the activities of catalase and SOD in mouse skin). We found for JB6 cells that this loss of enzyme activity was due to a decrease in the steady‐state concentrations of catalase and SOD mRNA. No significant changes in the rates of transcription were detected in nuclear run‐off experiments. The observed decreases in catalase and SOD can be considered as part of the complex reprogramming of gene expression that is set in motion by phorbol‐12‐myristate‐13‐acetate.
Prevalence of nucleoside diphosphate kinase autophosphorylation in human colon carcinoma versus normal colon homogenates
Authors: Francis Brian , Overmeyer Jean , John William , Marshall Ernest , Haley Boyd 
Published: February 2007

AbstractThe G‐regulatory proteins of adenylate cyclase, tubulin, and the ras oncogene protein product require the production of GTP from ATP in order to exert their effects within the cell. This implies that the activity of nucleoside diphosphate kinase (NDPK) plays a major role in the regulation of cellular events requiring GTP and that the level of activity of this enzyme is critical. This report presents a simple method for trapping a specific isozyme of NDPK in its high‐energy phosphorylated form (NDPK∼P) using EDTA and demonstrates that this NDPK∼P is tenfold higher in malignant colon tumor tissue than in normal colon tissue. This autophosphorylation of the 21,000 and 24,000 Mr subunits of NDPK occurs rapidly at Oß, will use either [γ32P]ATP, [γ32P]GTP, or the corresponding 8‐azidopurine photoprobes, is intramolecular, displays saturation effects, and is prevented from forming if GTPγS is added. Dephosphorylation in the homogenate occurs rapidly upon addition of Mg2+ or any nucleoside‐5′‐diphosphate. The subunits autophosphorylated in the homogenates are mostly in the soluble phase, and they comigrate with the subunits of pure NDPK from human erythrocytes. Cross‐addition of normal and malignant homogenates does not decrease the level of autophosphorylation of NDPK, which indicates that the level of NDPK∼P may be a quantitative measure of the level of this specific NDPK isozyme form. Assays for NDPK activity show correspondingly elevated levels in the malignant homogenates. Using western blot and photoaffinity labeling techniques, we distinguished the NDPK∼P subunits from two closely migrating GTP‐binding proteins. These were identified as the ras gene protein product and a 20,000 Mr protein, which comigrates identically with ADP‐ribosylating factor (ARF). The ARF also comigrates in a tight band that is phosphorylated by [γ32P]ATP or [γ32P]GTP when Mg2+ is present.
Enhanced Deoxyribonuclease Activity in Human Transformed Cells and in Bloom's Syndrome Cells
Authors: Mezzina Mauro , Nocentini Silvano , Nardelli Jeannette , Renault Georges , Moustacchi Ethel , Sarasin Alain 
Published: February 2007

AbstractHuman hereditary diseases such as xeroderma pigmentosum, Fanconi's anemia, ataxia telangiectasia, and Bloom's syndrome are characterized by a proneness for developing cancer associated with abnormalities in the processing of DNA damage. The molecular defects responsible for predisposing human tissues to cancer are still not well understood, despite the fact that a considerable amount of work has already been done on this problem. In this paper, we show that in human tumor cell lines, in cells transformed by DNA tumor viruses, and in cells derived from certain cancer‐prone disorders, the level of activity of a 42‐kDa deoxyribonuclease is many times higher than in diploid untransformed control cells. This suggests that this activity is linked to, or may play a role in, malignant transformation.
Denaturing Gradient Gel Analysis of Single‐Base Substitutions at a Mouse Adenine Phosphoribosyltransferase Splice Acceptor Site
Authors: Dlouhy Stephen R. , Schaff Dennis A. , Trofatter James A. , Liu Hsiao‐Sheng , Stambrook Peter J. , Tischfield Jay A. 
Published: February 2007

AbstractDenaturing gradient gel electrophoresis (DGGE) can detect single‐base changes in DNA. We used site‐directed mutagenesis to produce all six possible single‐base substitutions at a splice acceptor consensus AG dinucleotide within the mouse adenine phosphoribosyltransferase (aprt) gene. Studies of mouse and Chinese hamster cell aprt indicate a high level of both spontaneous and induced mutations in this region. We systematically evaluated each of the six mutations by DGGE. Five of the six mutant sequences could be distinguished from wild‐type by DGGE analysis of a 560‐bp fragment containing the mutation. However, one mutant could not be distinguished from wild‐type, and some of the mutant constructs could not be distinguished from each other. Analysis of DNA heteroduplexes consisting of wild‐type and mutant strands or two different mutant strands enabled all mutant constructs to be distinguished from wild‐type and from each other. The pairwise mixtures resulted in 24 different heteroduplexes, all of which were less stable than the parental homoduplexes. End labeling of DNA prior to heteroduplex formation and subsequent DGGE analysis enabled us to determine the relative destabilization caused by different types of single‐base mismatches.
Interleukin‐1 Beta Gene Deregulation Associated With Chromosomal Rearrangement: A Candidate Initiating Event for Murine Radiation‐Myeloid Leukemogenesis?
Authors: Silver Andrew , Boultwood Jacqueline , Breckon George , Masson Walter , Adam Julie , Shaw Alan R. , Cox Roger 
Published: February 2007

AbstractThe incidence of acute myeloid leukemia (AML) in CBA/H mice following exposure to single acute doses of ionizing radiation has previously been determined. A high proportion of these AMLs are characterized by rearrangement of murine chromosome 2 in the C2 and/or E5‐F regions, and there is evidence that these events are a direct consequence of radiation damage to multipotential hemopoietic cells. Using a combination of in situ chromosome hybridization and mRNA analyses, we show that the cytokine gene interleukin‐1β (IL‐1β) is encoded in the chromosome 2 F region and is translocated in a chromosome 2 ‐> 2 rearrangement in an x‐ray‐induced AML (N36). Also, IL‐1β is specifically deregulated in N36and in two other chromosome 2‐rearranged AMLs but not in a fourth, which has two cytogenetically normal chromosome 2 copies. We suggest that radiation‐induced specific chromosome 2 rearrangement associated with IL‐1β deregulation may initiate murine leukemogenesis through the uncoupling of normal proliferative control mechanisms in multipotential hemopoietic cells.
The Role of Methylation in Regulating the Expression of the Alpha‐Fetoprotein Gene in Developing Rat Liver and Hepatoma Cell Lines
Authors: Smith Catharine L. , Nordloh Peter W. , Chiu Jen‐Fu 
Published: February 2007

AbstractWe have examined four possible sites of methylation in the 5′ flanking region of the alpha‐fetoprotein (AFP) gene during liver development in the rat, paying particular attention to the neonatal period, in which AFP gene transcription changes rapidly. These sites are found in Mspl/Hpall sites located at ‐ 4197, ‐ 3038, ‐ 2431, and + 3 bp relative to the transcription start site. Three of these sites are associated with sequence regions important for the regulation of AFP gene transcription. We found that, in general, the 5′ flanking region of the gene was methylated more in the adult liver than in the livers of fetal and neonatal rats. In addition, the degree of methylation of all four sites examined was increased in the adult liver. One of these sites showed increased methylation as AFP gene activity decreased, whereas the others became more methylated only after transcriptional activity of the gene had ceased. In particular, the site ( + 3 bp) just adjacent to the transcriptional initiation site of the gene was fully methylated in the adult liver In various rat hepatoma and liver cell lines methylation of this same site showed a particularly close correlation with the amount of transcriptional activity of the AFP promoter in these cell lines. Treatment of the hepatoma and liver cell lines with dexamethasone, which influences AFP gene expression, did not result in any changes in methylation of these sites in the 5′ flanking region.
Efficient Immortalization by SV40 T DNA of Skin Fibroblasts From Patients With Wilms' Tumor Associated With Chromosome 11p Deletion
Authors: Kano Yoshio , Little John B. 
Published: February 2007

AbstractWe report that transfection with a plasmid containing the SV40 early region (T) leads to a very high frequency of immortalization in two different strains of human diploid fibroblasts, each with a partial deletion of the short arm of chromosome 11. Immortalization often occurred without a recognizable “crisis” phase. Preimmortal cells showed a high frequency of spontaneous mutations and chromosomal aberrations. These results suggest that a gene involved in the control of senescence of human cells in vitro may be associated with this chromosome.
Major Urinary Protein as a Negative Tumor Marker in Mouse Hepatocarcinogenesis
Authors: Dragani Tommaso A. , Manenti Giacomo , Sacchi Marina R. M. , Colombo Bruno M. , Porta Giuseppe Della 
Published: February 2007

AbstractA cDNA clone isolated by differential screening of a mouse liver cDNA library using RNA probes from normal adult liver and from hepatocellular tumors showed, on northern blot analysis, a single transcript of 1 kb present at high levels in normal adult mouse liver but at 15‐ to 100‐fold reduced levels in spontaneous and p‐dimethylaminoazobenzene‐ or urethan‐induced liver tumors. The transcript, which was absent in two‐wk‐old mouse liver, is coded by a developmentally regulated gene. Nucleotide sequence analysis demonstrated that the isolated clone encoded a major urinary protein (MUP). Immunocytochemistry analysis, using a goat antibody to MUP on histologic liver sections containing diethylnitrosamine‐induced liver nodules, showed that the decrease in MUP levels also occurred in microscopic nodules. Therefore, MUP decrease represents an early event in the development of mouse liver tumors, and it may be used as a tumor marker in mouse hepatocarcinogenesis.
Detection of epstein‐barr viral genomes in lymph nodes of Hodgkin's disease patients
Authors: Bignon Yves‐Jean , Bernard Dominique , Curé Hervé , Fonck Yvette , Pauchard Jacques , Travade Philippe , Legros Michel , Dastugue Bernard , Plagne Robert 
Published: February 2007

AbstractPrevious studies using Southern blot analysis or in situ hybridization have shown that approximately 20% of patients with Hodgkin's disease have Epstein‐Barr virus (EBV) in involved tissues. We used the more sensitive polymerase chain reaction (PCR) technique to determine if a higher percentage of EBV could be detected. Of the 16 Hodgkin's disease patients studied, the PCR technique detected EBV in eight (50%). No prognostic significance was associated with the presence of EBV in the eight EBV‐positive patients, and the presence of EBV was not associated with B cell monoclonality.
N‐methyl‐N‐nitrosourea‐lnduced mutations in a shuttle plasmid replicated in human cells
Authors: Sikpi Matthew O. , Waters Larry C. , Kraemer Kenneth H. , Preston R. Julian , Mitra Sankar 
Published: February 2007

AbstractThe supF gene of the recombinant shuttle plasmid pZ190 (modified pZ189) was used as a target to study the nature of mutations induced by N‐methyl‐N‐nitrosourea (MNU) in human cells. Treatment of the intact plasmid with MNU followed by its replication in human lymphoblastoid cells led to extensive inactivation and no detectable mutations of the plasmid. However, exposure of the supF DNA fragment alone, followed by its ligation into the vector, caused a ten‐fold increase in mutant frequency when replicated in O6‐methylguanine‐DNA methyltransferase‐deficient cells (from 0.54 × 10−3to5.8 × 10−3) and an 80‐fold increase when replicated in cells containing normal levels of the enzyme (from 0.047 × 10−3to3.8 × 10−3). About 45% of the mutant plasmid molecules recovered from human cells contained deletions and insertions. Sixty to 70% of the mutant molecules of wild‐type size contained a single‐base substitution. Most of these changes were of the G.C ‐A.T type, consistent with the hypothesis that O6‐methylguanine is the primary mutagenic adduct induced by MNU. However, the distribution of mutation sites was highly nonrandom; more than half of all mutations were localized at the G.C position 123, and the rest were distributed in about a dozen sites. The high yield of mutations induced in the supF DNA in a host cell whose capacity for the removal of O6‐methylguanine far exceeded the amount present in the supF suggests that the repair of damages in extrachromosomal DNA may be inefficient. This is supported by the observation that the yield of mutations in supF transfected into lymphoblastoid cells devoid of repair activity for O6‐methylguanine was comparable to that observed with repair‐proficient host cells. The present data, together with results of mutations induced in pZ189 by other agents, strongly suggest that one major determinant of mutational hot spots is the structure of the target DNA itself.
Direct sequencing analysis of transmembrane region of human neu gene by polymerase chain reaction
Authors: Saya Hideyuki , Ara Seiji , Lee Polly S. Y. , Ro Jungsil , Hung Mien‐Chie 
Published: February 2007

AbstractThe neu gene in rat neuro/glioblastoma was found to be activated by a single point mutation in the DNA sequence encoding the transmembrane region of the neu‐encoded p185 protein. The human homologue of the rat neu gene, termed c‐erbB‐2 or HER‐2, can also be activated in vitro by a similar mutation in the corresponding region. Although the human neu gene was shown to be amplified/overexpressed in a large portion of human breast and ovarian cancer, no reports indicate that the human neu gene is activated by a point mutation in human tumor. To study the possible point mutation of neu gene in human tumors, we characterized the genomic structure in the transmebrane region of human neu gene, which in turn allowed us to determine DNA sequence in this region directly following DNA amplification by polymerase chain reaction. We analyzed 7 tumor cell lines (2 breast cancer, 1 neuroblastoma, 1 rhabdomyosarcoma, and 3 glioma) and 11 tumor tissue samples (8 breast and 3 ovarian cancers). No mutation was found in the transmembrane region of human neu gene. Our results suggest that unlike the rat neuro/glioblastoma, the single point mutation in the transmembrance region of the human neu gene is a rare event in human tumors. In this study, we developed a technique for direct DNA sequencing of the transmembrane region of the human neu gene. This technique makes it possible to screen a large number of tumor samples.
Deregulation in trans of c‐myc expression in immortalized human urothelial cells and in T24 bladder carcinoma cells
Authors: Stacey Simon N. , Nielsen Inger , Skouv Jan , Hansen Claus , Autrup Herman 
Published: February 2007

AbstractThe expression of a number of cellular oncogenes was investigated in human urothelial cell lines with different in vitro growth properties. Constitutively elevated levels of expression of c‐myc RNA were found in Hu609, an immortalized, nontumorigenic cell line that was derived from normal urothelium, and in the bladder carcinoma cell line T24. Potential mechanisms that might underlie deregulation of c‐myc expression in these cells were investigated. It was found that the c‐myc gene was apparently intact and not amplified in Hu609 and T24. No increased stability of c‐myc RNA was detected. A c‐myc–CAT fusion construct containing 2.5 kb of normal c‐myc5′ sequences showed levels of expression that paralleled the overexpression of the endogenous gene, indicating that the high constitutive levels of c‐myc expression were due, at least in part, to alterations in the activities of cellular trans‐acting transcriptional regulators.
Enhancement of viral and DNA mediated transformation of cloned rat embryo fibroblast cells by 3‐aminobenzamide
Authors: Su Zao‐Zhong , Zhang Peiquan , Fisher Paul B. 
Published: February 2007

AbstractWe have analyzed the effect of the poly(ADP‐ribose) synthesis inhibitor 3 aminobenzamide (3AB) on de novo and methyl methanesulfonate (MMS) and y irradiation enhancement of viral transformation of a cloned rat embryo fibroblast cell line, CREF, by a cold‐sensitive host‐range mutant of type 5 adenovirus, H5hr1. Additionally, we have evaluated the effect of 3AB on the transformation of CREF cells following transfection with a gene conferring resistance to hygromycin (hyg) or the neomycin analogue G418 (neo) in combination with a cloned type 5 adenovirus E1A transforming gene (Ad5 E1A) or the Ha‐ras (T24) oncogene. 3AB induced a dose‐and time‐dependent increase in the level of de novo MMS‐enhanced and y irradiation‐enhanced transformation of CREF cells by H5hr1, whereas it did not induce morphological transformation in uninfected control, MMS‐pretreated, or y irradiation‐pretreated CREF cells. Temporal kinetic studies indicated that 3AB was most effective in enhancing de novo and MMS‐enhanced and y irradiation‐enhanced viral transformation when applied early after viral and carcinogen plus viral infection and when present for extended time periods (4‐5 wk). 3AB also increased the frequency of resistant colonies following transfection with several cloned genes, including hyg, neo', and protein kinase C (which also contained a neor gene), and the frequency of morphological transformation of CREF cells following cotransfection with a hyg gene and an Ad5 E1A or an activated Ha‐ras (T24) gene. In contrast, 3AB exerted the opposite effect, i.e., an inhibitory effect, when applied to NIH 3T3 cells transfected with a hyg' or neo' gene, alone or in combination with a T24 gene. The ability of 3AB to enhance the frequency of transformation of CREF cells was not associated with a selective effect on the growth of H5hr1 transformed CREF cells in monolayer or agar culture. Similarly, 3AB did not after the percentage of MMS‐or y irradiated‐pretreated H5hr1‐infected cells retaining free Ad5 DNA or the random pattern or quantity of viral DNA integration in control or carcinogen‐treated H5hr1‐transformed cells. These results suggest that cellular processes regulated by the nuclear enzyme ADPRT, or additional processes modified by 3AB, may be important mediators of stable transformation induced by transfected DNA and both de novo and carcinogen‐enhanced viral transformation of specific target cells.
Detection of genomic alterations in carcinogen‐induced mouse liver tumors by DNA fingerprint analysis
Authors: Müller Oliver , Alonso Angel , Buchmann Albrecht , Bauer‐Hofmann Richard , Bock Karl‐Walter , Schwarz Michael 
Published: February 2007

AbstractDNA fingerprint analysis was used to study structural abnormalities in the genome of mouse liver tumor cells. Liver tumors were induced in three strains of mice, namely C57BL/6J, C3H/He and B6C3F1, by a single injection of 20 μg/g body wt. diethylnitrosamine on day 15 after birth. DNA from liver tumors was digested with Hinfl restriction enzyme and hybridized on Southern blots with wild‐type bacteriophage M13 DNA as probe. The resulting fingerprints of tumor DNA were compared with those of DNA from normal liver tissue. Genomic aberrations were detected in two out of 68 tumors analyzed, one stemming from a C57BL/6J and the other from a C3H/He mouse.
Retinoid‐enhanced gap junctional communication is achieved by increased levels of connexin 43 mRNA and protein
Authors: Rogers Michael , Berestecky John M. , Hossain Mohammad Z. , Guo Huiming , Kadle Ranjana , Nicholson Bruce J. , Bertram John S. 
Published: February 2007

AbstractNatural and synthetic retinoids are potent inhibitors of experimental carcinogenesis in animals and cause reversion of premalignant lesions in humans. In the model C3H 10T1/2 cell system, retinoids enhance postconfluent growth control, reversibly inhibit carcinogen‐induced transformation, and enhance gap junctional intercellular communication. These effects are highly correlated. 10T1/2 cells were found to express low levels of connexin 43, a gap junctional protein first found in the heart. After treatment of confluent 10T1/2 cells with the synthetic retinoid tetrahydrotetramethylnapthalenylpropenylbenzoic acid (TTNPB), levels of connexin 43 mRNA and protein increased within 6 h of treatment, while elevation of junctional communication was detected within 12‐18 h. The maximally effective concentration of TTNPB (10−8 M) caused an approximate 10‐fold elevation of connexin 43 gene transcripts after 72 h. Indirect immunofluorescence microscopy using a polyclonal antibody to the synthetic C‐terminal region of connexin 43 demonstrated that TTNPB induced many fluorescent plaques in regions of cell‐cell contact. These results provide a molecular basis for the retinoid‐enhanced junctional communication in 10T1/2 cells. It is proposed that one action of retinoids is to modulate the intercellular transfer of signal molecules. These could mediate many of the physiological actions of retinoids on growth control and carcinogenesis.