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Biomedical subjects

C S Cooper

Publications and source records attributed to C S Cooper.

At least 109 records · Page 6Linked to original sources
PubMed1990

Chemical induction of thymomas in AKR mice: interaction of chemical carcinogens and endogenous murine leukemia viruses. Comparison of N-methyl-N-nitrosourea and methyl methanesulphonate.

The time course of development of thymic lymphoma, which occurs spontaneously in mice of the AKR strain, is accelerated by the methylating agents N-methyl-N-nitrosourea (MNU) and methyl methanesulphonate (MMS). Since MNU is a potent mutagen inducing G----A transition mutations and MMS a relatively weak mutagen, it was of interest to examine the genetic alterations associated with each class of the chemically induced tumors and to compare these alterations with those found in the spontaneous tumors. The same spectrum of genetic alterations was found for MMS-induced and spontaneous thymomas. Both showed rearrangements of c-myc and Pim-1 genes that appeared to result from integration of recombinant mink cytopathic focus-forming (MCF) proviruses but failed to reveal evidence for activation of ras oncogenes, either by DNA transfection experiments or by hybridization of DNA to specific oligonucleotide probes. Some alteration in c-myc and Pim-1 genes were also found in MNU-induced tumors, but, mainly, these involved integration of ecotropic-like rather than recombinant MCF viruses. Furthermore, MNU-induced tumors frequently (in 24% of thymomas) contained G----A transition mutations, activating the Ki-ras oncogene at codon 12 position 2. Another feature that distinguishes the MNU-induced tumors from those occurring in untreated and MMS-treated mice was the consistently high level of c-myc mRNA that occurred in the absence of c-myc gene rearrangement. Taken together, the data indicate that the mechanisms of development of tumors following treatment with MNU and MMS are distinct, and that the effect of MMS is probably to speed up the process of viral leukemogenesis.

Animals↗
PubMed1990

The synthesis and antibacterial activities of quinolones containing five- and six-membered heterocyclic substituents at the 7-position.

A series of 6-fluoro-7-substituted-1-ethyl-1,4-dihydro-4-oxoquinoline-3-carboxylic acids were prepared. The substituents at the 7-position included five- and six-membered heterocyclic rings such as oxazoline and oxazine as well as five-membered heteroaromatic rings such as oxazoles and imidazoles. The structure--activity relationships (SAR) of these compounds indicated that oxazole substituents containing a 2-methyl group had the greatest in vitro potency. The compounds showed greater in vitro antibacterial activity against Gram-positive organisms than against Gram-negative organisms.

4-Quinolones↗
PubMed1990

The effect of social support on adolescent mothers' styles of parent-child interaction as measured on three separate occasions.

The purpose of this study was to determine the effect of social support on parent-child interaction in a group of 19 adolescent mothers. The subjects participated in a 20-week model demonstration program in which they worked in a preschool classroom with skilled caregivers who modeled facilitative styles of interacting with young children. Each subject was videotaped while interacting with a 1- to 2-year-old child upon entering the program, midway through the program, and at the end. Results showed that girls who were 16 years or older significantly increased their frequency of using responsive, engaging, and elaborative styles of behavior. Those under age 16 did not show significant changes in these three behaviors. Overall, subjects significantly increased the duration of time they spent observing the child's play behavior.

Adolescent↗
PubMed1989

Detection of point mutations in N-ras and K-ras genes of human embryonal rhabdomyosarcomas using oligonucleotide probes and the polymerase chain reaction.

Previous studies have demonstrated that genes of the ras family (H, K, and N) can be activated by point mutations at codons 12, 13, and 61. In the present study we have used oligonucleotide probes corresponding to these regions to assess the role of ras gene mutations in the genesis of human rhabdomyosarcoma. To increase the sensitivity of this method the appropriate regions of the three ras genes were first amplified using the polymerase chain reaction. The results show that 35% (5/14) embryonal rhabdomyosarcomas investigated contain mutations in the N-ras or K-ras genes. Thus ras gene mutation is implicated in the development of mesenchymal and embryonal tumors in addition to its previously documented role in epithelial and hematological neoplasia.

Adolescent↗
PubMed1989

Cytogenetic abnormalities in human ependymomas.

The karyotypes of 4 human ependymomas have been determined. In one ependymoma, translocations involving chromosomes 9, 17 and 22 were observed together with the loss of the normal chromosome 17. A second ependymoma had many chromosomal alterations that included a translocation between chromosomes 1 and 2 and re-arrangements involving chromosome 17. No major consistent alterations were detected in the remaining 2 cases. Our karyotypes do not resemble the few previously published karyotypes of ependymomas, but had features, such as the alterations involving chromosome 17, that were similar to those of other brain tumours in children.

Brain Neoplasms↗
PubMed1989

Tyrosine kinase receptor indistinguishable from the c-met protein.

Growth factor receptors with protein tyrosine kinase activity are central to the control of proliferation of both normal and malignant cells. Using anti-phosphotyrosine antibodies, we have previously identified a transmembrane glycoprotein with abnormally high protein tyrosine kinase activity in a human gastric tumour cell line (GTL-16). Electrophoresis under non-reducing conditions revealed that this kinase (relative molecular mass 145,000 (145 K)) is disulphide-linked to a 50K chain in an alpha beta-complex of 190K (p190). From its novel two-chain structure, we deduced that p190 was the prototype of a new class of tyrosine kinase receptors. We now show that p190 is indistinguishable from the protein encoded by the c-met proto-oncogene and that the alpha beta-subunit structure is conserved in other human cell lines. We also show that the high level of p190 found in the GTL-16 cell line is accompanied by amplification and overexpression of c-met. This provides the first example of a functional alteration of c-met in a human tumour cell line.

Cell Line↗
PubMed1989

Mechanism of inhibition of DNA gyrase by quinolone antibacterials: a cooperative drug--DNA binding model.

We have proposed a cooperative quinolone-DNA binding model for the inhibition of DNA gyrase. The essential feature of the model is that bound gyrase induces a specific quinolone binding site in the relaxed DNA substrate in the presence of ATP. The binding affinity and specificity are derived from two unique and equally important functional features: the specific conformation of the proposed single-stranded DNA pocket induced by the enzyme and the unique self-association phenomenon (from which the cooperativity is derived) of the drug molecules to fit the binding pocket with a high degree of flexibility. Supporting evidence for and implications of this model are provided.

Anti-Bacterial Agents↗
PubMed1989

Molecular cloning and localization to chromosome 6 of mouse INT1L1 gene.

The human INT1L1 gene, which exhibits homology to the protooncogene INT1 is very closely linked to the MET gene and cystic fibrosis locus on human chromosome 7. In the present study we have isolated overlapping genomic clones that correspond to the mouse homolog of the INT1L1 gene and have used the cloned DNA as probes to examine the distribution of the mouse INT1L1 gene within a series of 35 mouse-hamster somatic cell hybrids. These analyses have localized the INT1L1 gene to mouse chromosome 6. In addition, we demonstrate that the mouse INT1L1 and MET genes are coamplified in lines of spontaneously transformed mouse NIH3T3 cells, indicating that these genes may remain closely linked within the mouse genome.

Amino Acid Sequence↗
PubMed1989

Characterization of the human cell line TE671.

The cell line TE671 has been widely used as a model of human medulloblastoma. In the present study we have demonstrated that transfection of DNA from this cell line into NIH 3T3 cells reveals the presence of an activated N-ras gene. Using oligonucleotide probes we have shown that the N-ras gene is activated by a point mutation at the third base of codon 61 resulting in the substitution of histidine for glutamine in the p21 ras gene product. We noted that this relatively uncommon activating mutation is also present in the human rhabdomyosarcoma cell line RD. Based on this finding and on the observation that several of the phenotypic characteristics of TE671, such as the presence of muscle-type nicotinic acetylcholine receptors and the intermediate filament protein desmin, are suggestive of myoid origin we investigated the possible identity of these two cell lines. Cytogenetic analysis revealed the presence of marker chromosomes common to both TE671 and RD. DNA fingerprinting using both locus specific and multilocus core probes showed indistinguishable band patterns in the two cell lines. Taken together our data show that TE671 and RD are derivatives of the same cell line and we conclude that the properties of the TE671 line should be ascribed to rhabdomyosarcoma rather than medulloblastoma cells.

Animals↗
PubMed1989

Biosynthesis of the protein encoded by the c-met proto-oncogene.

The proto-oncogene c-met encodes a transmembrane protein with structural features of a growth factor receptor. We have previously shown that the c-met protein (c-Met) is a heterodimer of two disulphide linked chains of 50 kd (alpha) and 145 kd (beta). In this work we have studied the biosynthesis of the c-met product in a gastric carcinoma cell line (GTL-16) where the c-met gene is amplified and overexpressed. Following metabolic labelling of the cells in the presence of tunicamycin, anti-met antibodies immunoprecipitate a protein of 150 kd. In pulse-chase experiments carried out in the absence of tunicamycin, a 170 kd product appears first. Within the next few minutes, this precursor modifies its SDS migration, probably as a consequence of modification(s) of its intra-chain disulphide bonds. After 45 min of chase, this single polypeptide precursor is cleaved to form a 50 kd alpha subunit and a 145 kd beta subunit that are joined by disulphide bonds in an alpha beta complex with an apparent molecular weight of 190 kd. The presence of N-linked oligosaccharides in both the precursor and the mature protein was shown by enzymatic de-glycosylation of the immunoprecipitated proteins. The half-life of the mature protein was calculated to be approximately 5h. The c-met protein has similar structure and biosynthesis in other human cell lines.

Cell Line↗
PubMed1989

Characterization of the translocation between chromosomes X and 18 in human synovial sarcomas.

Recent studies have identified a specific chromosomal translocation, t(X;18)(p11.2;q11.2), in a high proportion of human synovial sarcomas. As a first step towards characterizing the X;18 translocation we have established a synovial sarcoma cell line. Fusion of this cell line to mouse RAG cells gave rise to somatic cell hybrids that contain the derivative (X) marker chromosome in the absence of other genetic material from chromosomes 18 and X. Southern analysis of DNA from these somatic cell hybrids demonstrated that the human X chromosome markers DXS94, DXS14, DXZ1 and DXS62 were retained. In contrast DXS7, GAPDP1, ARAF1, DXS146 were not consistently present in the hybrids indicating that these markers were on the region of the X chromosome replaced by part of the long arm of chromosome 18 during the generation of the X;18 translocation. The predicted position of the translocation relative to X chromosome markers is DXS7-DXS146-X; 18-DXS14-DXZ1-DXS94.

Chromosome Banding↗
PubMed1988

Activated Ki-ras genes in bladder epithelial cell lines transformed by treatment of primary mouse bladder explant cultures with 7,12-dimethylbenz[a]anthracene.

DNA from five lines of transformed bladder epithelial cells derived from cultures of primary cells that had been treated with 7,12-dimethylbenz[a]anthracene (DMBA) can transform NIH 3T3 mouse fibroblasts in DNA transfection experiments. Southern analysis of DNA from NIH 3T3 primary and secondary transformants established that four of the DMBA-transformed cell lines contained activated cellular Ki-ras, while the remaining cell line contained a transforming gene that is unrelated to Ki-ras, N-ras, and Ha-ras. The point mutations responsible for Ki-ras activation were detected using oligonucleotide probes following selective amplification of Ki-ras specific sequences using the polymerase chain reaction. The results showed that activation of Ki-ras invariably involved a GC----AT transition mutation of the first position of codon 12. Surprisingly, a Ki-ras gene that was activated by a GC----AT transition mutation at the same position was also detected in a single transformed bladder urothelial cell line derived from control cultures of mouse bladder cells. Together, our results indicate that Ki-ras activation in the DMBA-transformed bladder cell lines may not be a direct consequence of interaction of activated DMBA metabolites with the Ki-ras gene.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1988

Structure of the met protein and variation of met protein kinase activity among human tumour cell lines.

An in vitro autophosphorylation assay has been used to demonstrate that there is considerable variation in met associated protein kinase among human tumour cell lines. Of particular note was the very high level of autophosphorylation of the 140 kD met protein (p140met) in experiments with A431 human cervical carcinoma cells. In contrast in experiments with Daoy human medulloblastoma cells we failed to detect phosphorylation of p140met; instead a high level of phosphorylation of a 132 kD protein was observed. To help understand the basis for the variation in kinase activity and to learn more about the structure of the mature met protein we have analysed p140met in SDS-polyacrylamide gels under non-reducing conditions. Under these conditions the met protein had an apparent molecular weight of 165,000 indicating that the mature met protein may exist as an alpha beta complex in which p140met (designated the beta subunit) is joined by disulphide bonds to a smaller, 25 kD, alpha-chain. We have identified a potential proteolytic cleavage site with the sequence Lys-Arg-Lys-Lys-Arg-Ser at amino acids 303-308 in the human met protein that may account for cleavage of the met protein into alpha and beta subunits.

Amino Acid Sequence↗
PubMed1988

Morphological transformation of immortalized hamster dermal fibroblasts following treatment with simple alkylating carcinogens.

We have examined the mechanism of transformation of a line of immortalized hamster dermal fibroblasts (4DH2 cells) following treatment with the simple alkylating agents, N-methyl-N-nitrosourea (MNU), N-ethyl-N-nitrosourea (ENU) and dimethyl sulphate (DMS). Treatment of 4DH2 cells with the potent point mutagens MNU and ENU gave rise to a spectrum of foci of different sizes, including progressively growing large foci and compact small foci. In contrast, treatment with the weak point mutagen DMS produced mostly large foci. The ability of cell lines derived from morphologically transformed foci to grow in soft agar in general reflects their original size. Thus most cell lines derived from large foci grew in soft agar while most lines derived from small foci did not. Transfection of cellular DNAs into the parent 4DH2 cell line and into NIH3T3 mouse fibroblasts has revealed the presence of dominantly acting transforming genes in the chemically transformed cell lines. Thus DNA from five of six cell lines derived by culturing large foci and from one of three cell lines derived by culturing small foci induced efficient morphological transformation of the recipient cells. Southern analyses of DNA from primary and secondary transfectants showed that several of the transforming genes transferred in these experiments were not closely related to H-ras, K-ras or N-ras.

Alkylating Agents↗
PubMed1988

Activating mutations in human c-Ha-ras-1 gene induced by reactive derivatives of safrole and the glutamic pyrolysis product, Glu-P-3.

Foci of transformed NIH3T3 cells were observed after transfection of plasmids containing the c-Ha-ras-1 protooncogene modified in vitro either with the 3-N,N-acetoxyacetyl derivative (N-AcO-AGlu-P-3) of the mutagenic L-glutamic acid pyrolysis product 3-amino-4,6-dimethyldipyrido-[1,2-a:3',2'-d]imidazole (Glu-P-3) or with 1'-acetoxysafrole (AcO-S), a reactive derivative of the carcinogen safrole. DNA isolated from these foci were used in a second round of transfection, and the DNA obtained from the secondary transformants was analysed to determine the nature of mutations responsible for activating the protooncogene. The polymerase chain reaction method was used to amplify sequences of the gene likely to contain activating mutations, and these regions were then subjected to selective hybridization with specific oligonucleotides to locate and identify the point mutations. Five out of six transformants induced by N-AcO-AGlu-P-3 contained mutations at codon 61. Three of the codon 61 mutations were at the first base and the other two were at the third base, all were GC----TA transversions. Two AcO-S-induced transformants contained a GC----TA transversion, in one case at the first base of codon 61, in the other at the first base of codon 12. Another AcO-S-induced transformant, and the sixth transformant induced by N-AcO-AGlu-P-3 were apparently not mutated in codon 12, 61 or 117. Both N-AcO-AGlu-P-3 and AcO-S react predominantly with guanine residues in DNA, and all the mutations identified here were at GC base pairs.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Characterization of the mouse met proto-oncogene.

The DNA sequence of cDNA clones prepared from transcripts of the mouse met proto-oncogene reveals that the mouse met gene encodes a 1380 amino acid protein with the characteristics of a growth factor receptor. This protein can be divided into several putative domains, including an intracellular protein tyrosine kinase domain, a transmembrane domain and a 929 amino acid extracellular domain, possessing a potential proteolytic cleavage site with the sequence Lys-Arg-Arg-Lys-Arg-Ser. To gain additional insights into the function of the met protein we have examined the level of met transcripts in tissues of the late-gestation mouse conceptus. Transcription of met was observed in most of the tissues analysed, but the highest levels of met mRNA were detected in the yolk sac, amnion and kidney; no transcripts were detectable in the calvaria. Chromosomal localization using a series of mouse-hamster hybrid cell lines has demonstrated that met is located on mouse chromosome 6.

Amino Acid Sequence↗