PubMed Health⌕ Search

Biomedical subjects

R W Wiseman

Publications and source records attributed to R W Wiseman.

At least 73 records · Page 4Linked to original sources
PubMed1992

Clonal origin of epithelial ovarian carcinoma: analysis by loss of heterozygosity, p53 mutation, and X-chromosome inactivation.

BACKGROUND: It has been suggested that multiple sites of epithelial ovarian carcinoma on the peritoneal surface reflect polyclonal disease arising from multiple primary tumors in the peritoneal mesothelium, rather than monoclonal disease spread by metastases from one primary ovarian cancer. PURPOSE: The purpose of this study was to investigate whether ovarian cancer has a monoclonal or polyclonal origin. METHODS: DNA specimens were obtained from peripheral blood lymphocytes (normal DNA) and from multiple tumor deposits of 17 women with epithelial ovarian carcinoma: primary tumors, metastatic deposits, and ascites. The clonal origin of each tumor was determined by performing (a) analysis to detect loss of heterozygosity at five loci on chromosomes 5, 11, 13, and 17; (b) sequencing of exons 5-8 of the p53 gene; and (c) X-chromosome inactivation analysis of the phosphoglycerate kinase (PGK) gene. RESULTS: In 15 of the 17 cases analyzed, there was clear evidence of monoclonal origin. The probability that the genetic events documented in these 15 cases occurred as independent events in each tumor deposit ranged from 2.5 x 10(-1) to 3.7 x 10(-16). In two cases, the pattern of allelic deletion and p53 gene mutation was compatible with either a monoclonal origin or origin from two primary ovarian tumors. CONCLUSIONS: The results did not support the hypothesis that ovarian cancer is a multifocal, polyclonal disease. Instead, the data suggest that sporadic epithelial ovarian carcinoma has either a monoclonal or a dual primary origin. IMPLICATIONS: These findings have important implications for understanding of the natural history of ovarian cancer and for clinical strategies aimed at prevention and early detection. Further studies will be required to determine the clonal origin of familial hereditary ovarian cancer.

Alleles↗
PubMed1992

Assignment of a locus for familial melanoma, MLM, to chromosome 9p13-p22.

Linkage analysis of ten Utah kindreds and one Texas kindred with multiple cases of cutaneous malignant melanoma (CMM) provided evidence that a locus for familial melanoma susceptibility is in the chromosomal region 9p13-p22. The genetic markers analyzed reside in a candidate region on chromosome 9p21, previously implicated by the presence of homozygous deletions in melanoma tumors and by the presence of a germline deletion in an individual with eight independent melanomas. Multipoint linkage analysis was performed between the familial melanoma susceptibility locus (MLM) and two short tandem repeat markers, D9S126 and the interferon-alpha (IFNA) gene, which reside in the region of somatic loss in melanoma tumors. An analysis incorporating a partially penetrant dominant melanoma susceptibility locus places MLM near IFNA and D9S126 with a maximum location score of 12.71. Therefore, the region frequently deleted in melanoma tumors on 9p21 presumably contains a locus that plays a critical role in predisposition to familial melanoma.

Adolescent↗
PubMed1992

Mammalian skeletal muscle fibers distinguished by contents of phosphocreatine, ATP, and Pi.

We tested the proposition that muscle cell types have different contents of phosphocreatine (PCr), ATP, and Pi by 31P NMR spectroscopy and HPLC analyses of adult rat and mouse muscles containing various volume fractions of different fiber types. There was a 2-fold difference in the PCr content between muscles with a high volume fraction of fiber types 1 and 2x versus those with fast-twitch (types 2a and 2b) fiber types. Pi content was low, and PCr and ATP contents were high in muscles with large contents of type 2b and 2a fibers; the reverse was true in muscles with a large volume fraction of type 1 and 2x fibers. There is a large range in the Pi/PCr ratios in normal resting muscles, from less than 0.05 in type 2 to 0.51 in type 1 fibers, depending upon the distribution of their component fiber types. In all muscles, the peak area resulting from the beta phosphate of ATP constituted approximately 13% of the sum of all peak areas observable in the 31P spectrum. Fiber types 2a and 2b were not distinguishable, and the content of type 2x fibers was similar to type 1 fibers. From the profile of these metabolites, we could distinguish only two classes of fibers. For type 2a and 2b fibers, the intracellular concentrations were 8 mM ATP, 39 mM total creatine, 32 mM PCr, 0.8 mM Pi, and 8 microM ADP. For type 1 and 2x fibers, these quantities were 5 mM ATP, 23 mM total creatine, 16 mM PCr, 6 mM Pi, and 11 microM ADP. Thus our results establish an additional criterion upon which to distinguish skeletal muscle cells, one based on the resting content of bioenergetically important metabolites. These results also provide the basis for estimating skeletal muscle fiber-type composition from noninvasive NMR spectroscopic data.

Adenosine Triphosphate↗
PubMed1992

High-performance liquid chromatographic assays for free and phosphorylated derivatives of the creatine analogues beta-guanidopropionic acid and 1-carboxy-methyl-2-iminoimidazolidine (cyclocreatine).

Creatine and phosphocreatine are substrates for creatine kinase which is a key enzyme involved in energy transfer within the cell. Analogues of creatine have been fed to animals to determine the role this enzyme plays in energy metabolism, but progress in interpretation has been hampered by the lack of quantitative techniques to determine tissue content of these compounds. We describe the separation and quantitation of substituted guanidino compounds and their phosphorylated forms by high-performance liquid chromatography. First, a cation-exchange column is used to assay free creatine and its unphosphorylated analogues, and then phosphocreatine and its phosphorylated analogues as well as adenylate content (AMP, ADP, ATP) are assayed on an anion-exchange column. These methods have proven successful in measuring the chemical contents of these compounds in neutralized perchloric acid extracts of mammalian skeletal muscles. The sensitivity of this method ranges from 50 to 200 pmol, which is adequate to provide information from tissue extracts of 5- to 10-mg samples.

Animals↗
PubMed1992

Detection of frequent allelic loss on proximal chromosome 17q in sporadic breast carcinoma using microsatellite length polymorphisms.

Analyses of losses of heterozygosity and linkage studies have implicated a gene(s) on chromosome 17q in the genesis of sporadic and early-onset familial breast carcinomas, respectively. To define the critical region of 17q, we examined DNAs from a series of 20 sporadic breast carcinomas and corresponding blood samples for allelic losses of chromosome 17q using microsatellite length polymorphisms. With these highly informative markers (average heterozygosity, 0.73), we observed frequent deletions of 17q at several loci. We found that D17S250 was deleted in 50% (7 of 14), THRA1 in 79% (11 of 14), D17S579 in 59% (11 of 19), NME1 in 29% (5 of 17), MPO in 36% (4 of 11), and GH in 25% (4 of 16) in the tumor set examined. A common region of deletion was found that was flanked by D17S250 to D15S579. These markers have recently been localized to a 6-cM interval of proximal chromosome 17q in bands 17q11.2-q21 and map within the region of the early-onset familial breast cancer locus, implying that the same gene or genes may be involved in both sporadic and familial breast tumors. Thyroid hormone receptor alpha and retinoic acid receptor alpha are two potential candidate genes in this region.

Base Sequence↗
PubMed1992

Vascular oxidative metabolism under different metabolic conditions.

Control of respiration in vascular smooth muscle was examined while the metabolic state of the tissue was manipulated. During KCl-induced contractures in the presence of 5 mM glucose, oxygen consumption increased by 10 nmol/per min g without any decrease in phosphocreatine (PCr) or ATP as determined by 31P-NMR indicating a control of respiration which does not involve changes in high-energy phosphates (e.g., ADP, phosphorylation potential). However, when aortae with resting tone in the absence of substrate were then provided with 5 mM 2-deoxyglucose as the sole substrate, oxygen consumption increased 7.4 nmol/min per g while PCr decreased by more than 50% (resulting in a 2-fold increase in the calculated free ADP) with no change in tension from resting tone. During a subsequent KCl induced contracture in the presence of 2-deoxyglucose, oxygen consumption increased an additional 7.2 nmol/min per g while PCr continued to decline. Therefore, at least two mechanisms of respiratory control may exist in sheep aorta, one dependent and the other independent of changes in high-energy phosphates.

Adenosine Diphosphate↗
PubMed1992

Characterization of the Syrian hamster c-Ha-ras gene and intron-D-exon transcript.

The coding sequences as well as 5'- and 3'-flanking sequences of the Syrian hamster c-Ha-ras gene were deduced from cDNA clones derived from embryo fibroblast cell lines. Sequences of introns B, C, and D were obtained from genomic DNA after amplification by the polymerase chain reaction. Sequence comparisons with rat, mouse, and human c-Ha-ras genes revealed a high degree of homology. One of 12 cDNA clones contained intron-D-exon (IDX) sequences due to alternative splicing that would encode a p19 Ha-ras gene product. Conservation between species suggests a functional role for the IDX, possibly as a negative control of p21 Ha-ras expression.

Amino Acid Sequence↗
PubMed1992

Tension responses of sheep aorta to simultaneous decreases in phosphocreatine, inorganic phosphate and ATP.

1. Tension responses of sheep aortae were investigated when different substrates were included in the superfusing medium. The magnitude of tension development was similar whether or not 5 mM glucose was present in the medium. However, the rate of tension development was greater in the absence of glucose. 2. When 5 mM 2-deoxyglucose (2DG) was present in the medium, the magnitude of tension generation was 1.6 times that in the absence of exogenous substrate. A second sequential contraction with 2DG generated tension 1.25 times that in the absence of exogenous substrate. The rate of tension development during the first contraction in the presence of 2DG was similar to that in the absence of substrate. However, the second contraction in the presence of 2DG had a substantially increased rate of tension development. 3. 31P nuclear magnetic resonance (NMR) spectroscopy revealed that, at resting tone, in the presence of 2DG, inorganic phosphate (P(i)) and phosphocreatine (PCr) simultaneously decrease while 2-deoxyglucose-6-phosphate accumulates. During contraction-relaxation cycles, in the presence of 2DG, P(i) and PCr become undetectable while ATP declines to approximately 50% of control values as determined by NMR. During the second contraction in the presence of 2DG, the area of the ADP resonance was similar to that of the alpha-ATP resonance. 4. The increase in the magnitude of tension generation, during 2DG administration, correlated with a decrease in P(i) levels. The rate of relaxation from a contraction, in the presence of 2DG, was slower than in the presence of glucose or in the absence of exogenous substrate. These results are consistent with the role of P(i) in the release of the proposed 'latch-bridge' state of maintained contraction at low energy demand. 5. The increase in isometric tension generation during contraction in the presence of 2DG appears to be related to the decreased levels of P(i). In the presence of 2DG, the reduction of PCr and of ATP occur to a similar extent to that during hypoxia, yet no inhibition of force takes place. The low levels of ATP and PCr reported with 2DG administration in these studies do not energetically limit the contractile apparatus.

Adenosine Triphosphate↗
PubMed1991

Loss of a tumor suppressor gene function is correlated with downregulation of chondrocyte-specific collagen expression in Syrian hamster embryo cells.

We previously described the isolation of closely related, preneoplastic Syrian hamster cell lines that have retained (supB+) or lost (supB-) the ability to suppress the anchorage-independent growth and tumorigenicity of a sarcoma cell line (BP6T) in cell hybrids. In this report, we have used differential cDNA screening to clone several genes that are expressed in supB+ cells and downregulated in supB- cells. The nontumorigenic supB+ and supB- variants are advantageous for differential cDNA cloning because multiple independent cell lines differing in their tumor suppressor activity have been isolated. Differentially expressed cDNAs were isolated and placed into one of four groups based on DNA cross-hybridization. Representative cDNAs from Groups I and II, which were expressed at relatively high levels in two independently derived supB+ cell lines (DES4 and 10W) and downregulated in the supB- and tumor cell lines, were sequenced. The DNA and predicted amino acid sequences of these genes were found to be highly homologous to the chondrocyte-specific collagens type II and type IX. In contrast to the chondrocyte-specific collagens, another collagen isoform, collagen type I, was expressed at similar levels in both supB+ and supB- cells. These results suggest that carcinogen-induced immortalization selected for chondrocyte-like cell lines from the mixed embryo cell population. As these cells progressed toward tumorigenicity, the ability to express the chondrocyte differentiation markers was lost concomitantly with the ability to suppress the tumorigenicity of the BP6T sarcoma cell line. These results are consistent with the hypothesis that the supB+ tumor suppressor gene is involved in the regulation of differentiation. The identification of genes regulated by this suppressor gene may aid in its isolation.

Animals↗
PubMed1991

Identification of genes associated with tumor suppression in Syrian hamster embryo cells.

Loss of a tumor-suppressor gene function appears to play a critical role in the multistep process of neoplastic transformation of Syrian hamster embryo (SHE) cells in vitro. Clonal variants of two independent, preneoplastic cell lines have been isolated that have either retained (termed supB+) or lost (termed supB-) the ability to suppress the tumorigenicity of a highly malignant benzo[alpha]pyrene-transformed SHE cell line (BP6T) in cell hybrids. We have pursued several approaches in an attempt to identify genes that are responsible for tumor suppression in these cells. The only consistent differences detected in two-dimensional gel analyses of supB+ and supB- cellular proteins were decreases in the levels of two high molecular weight isoforms of tropomyosin in supB- cells. Differential screening of a supB+ cDNA library for genes that are preferentially expressed in supB+ cells yielded cDNA clones for four genes, i.e., collagen type II, collagen type IX, H19, and a previously unidentified gene (clone 5). Nuclear run-on assays suggested that higher transcription rates were responsible for the increased steady-state levels of some of these transcripts in supB+ cells. DNA sequence comparisons showed that two copies of a 9 bp element, previously identified in each of the mouse H19 enhancers, were also present in the 5' flanking region of the rat type II collagen gene. A transcription factor that controls expression of the collagen and H19 genes through binding to this conserved motif would be an attractive candidate for the supB+ gene or at least a mediator of the supB+ phenotype.

Animals↗
PubMed1990

Activation of cellular oncogenes by chemical carcinogens in Syrian hamster embryo fibroblasts.

Carcinogen-induced point mutations resulting in activation of ras oncogenes have been demonstrated in various experimental systems such as skin carcinogenesis, mammary, and liver carcinogenesis. In many cases, the data support the conclusion that these point mutations are critical changes in the initiation of these tumors. The Syrian hamster embryo (SHE) cell transformation model system has been widely used to study the multistep process of chemically induced neoplastic transformation. Recent data suggest that activation of the Ha-ras gene via point mutation is one of the crucial events in the transformation of these cells. We have now cloned the c-Ha-ras proto-oncogene from SHE cDNA-libraries, and we have performed polymerase chain reaction and direct sequencing to analyze tumor cell lines induced by different chemical carcinogens for the presence of point mutations. No changes were detectable at codons 12, 13, 59, 61, and 117 or adjacent regions in tumor cell lines induced by diethylstilbestrol, asbestos, benzo(a)pyrene, trenbolone, or aflatoxin B1. Thus, it is not known whether point mutations in the Ha-ras proto-oncogene are essential for the acquisition of the neoplastic phenotype of SHE cells. Activation of other oncogenes or inactivation of tumor suppressor genes may be responsible for the neoplastic progression of these cells. However, in SHE cells neoplastically transformed by diethylstilbestrol or trenbolone, a significant elevation of the c-Ha-ras expression was observed. Enhanced expression of c-myc was detected in SHE cells transformed by benzo(a)pyrene or trenbolone.

Animals↗
PubMed1989

Multiple mechanisms for the carcinogenic effects of asbestos and other mineral fibers.

Asbestos and other mineral fibers are carcinogenic to humans and animals but differ from many carcinogens in that they do not induce gene mutations. An understanding of these interesting human carcinogens, therefore, is an important problem in cancer research. Asbestos and other fibers induce predominantly two types of cancers: mesotheliomas and bronchogenic carcinomas. Fiber size is an important factor in the carcinogenic activity of these substances as has been shown for mesothelioma induction. For bronchogenic carcinomas, but not for mesotheliomas, a synergistic effect of asbestos exposure and cigarette smoke has been observed in humans. The mechanisms by which fibers alone versus fibers in concert with other carcinogens induce cancers are probably distinct. In addition to fiber dimensions, fiber durability and surface properties of fibers are important properties affecting carcinogenicity. Evidence exists that asbestos is a complete carcinogen, an initiator and a promoter. Multiple mechanisms must be operative to explain the diverse effects of mineral fibers. Although asbestos is inactive as a gene mutagen, there is now clear evidence that it induces chromosomal mutations (aneuploidy and aberrations) in a wide variety of mammalian cells including mesothelial cells. Asbestos also induces transformation of cells in culture including mesothelial cells and fibroblasts. A mechanism for cell transformation, which is dependent on fiber dimension, has been proposed. The fibers are phagocytized by the cells and accumulate in the perinuclear region of the cells. When the cell undergoes mitosis, the physical presence of the fibers interferes with chromosome segregation and results in anaphase abnormalities. The transformed cells show aneuploidy and other chromosome abnormalities.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Detection of activated proto-oncogenes in N-nitrosodiethylamine-induced liver tumors: a comparison between B6C3F1 mice and Fischer 344 rats.

DNA from B6C3F1 mouse and Fischer 344 rat liver tumors induced by N-nitrosodiethylamine (DEN) were examined for the ability to induce morphological transformation of NIH3T3 cells. DNAs from 14 of 33 of the mouse liver tumors induced by a single injection of DEN at 12 or 15 days of age were positive in this assay while DNA from only one of 28 DEN-induced rat liver tumors was active. Southern blot analysis of the NIH3T3 transformants derived from the mouse liver tumors revealed amplified and/or rearranged restriction fragments homologous to the H-ras proto-oncogene. DNA from two independent foci induced by the rat tumor DNA did not hybridize to probes for members of the ras gene family or c-raf. Activating mutations in the H-ras genes from the DEN-induced mouse liver tumors were characterized by selective oligonucleotide hybridization and the detection of a new XbaI restriction site by Southern blot analysis. In activated H-ras genes from the DEN-induced mouse liver tumor DNA, seven of 14 had a CG----AT transversion at the first base of the 61st codon, three of 14 had an AT----GC transition and four of 14 had the AT----TA transversion at the second base of codon 61. This spectrum of mutations is very similar to that recently observed in activated H-ras genes found in spontaneously occurring B6C3F1 mouse liver tumors. Taken together, the data suggest that the DEN-induced rat and mouse liver carcinogenesis may involve genetic targets other than or in addition to the H-ras gene.

Animals↗
PubMed1987

Structure-activity studies of the hepatocarcinogenicities of alkenylbenzene derivatives related to estragole and safrole on administration to preweanling male C57BL/6J x C3H/HeJ F1 mice.

Further information on the structure-activity relationships among the synthetic and naturally occurring alkenylbenzene derivatives was obtained by examining their hepatocarcinogenicities for mice following administration of one or a few doses prior to weaning. Under these conditions preweanling male C3H/HeJ mice were more susceptible than male C57BL/6J mice or females of either strain to liver tumor induction by 1'-hydroxyestragole (1'-hydroxy-1-allyl-4-methoxybenzene) and 1'-hydroxysafrole (1'-hydroxy-1-allyl-3,4-methylenedioxybenzene). Male C57BL/6J X C3H/HeJ F1 mice given a single dose of 1'-hydroxyestragole at 12 days of age developed approximately twice as many hepatomas per liver as did those given the same dose per g of body weight at 1 day of age. The acetylenic compounds 1'-hydroxy-2',3'-dehydroestragole and 1'-hydroxy-2',3'-dehydrosafrole were the most potent derivatives studied; they were 5- and 10-fold more potent (based on the average numbers of hepatomas per liver) than the corresponding allylic benzene derivatives. 1'-Acetoxyestragole and 1'-acetoxysafrole had activities similar to those of their respective 1'-hydroxy derivatives; estragole derivatives were consistently 2- to 3-fold more potent than the related safrole derivatives. 1'-Hydroxyelemicin (1'-hydroxy-1-allyl-3,4,5-trimethoxybenzene), its acetic acid ester 1'-oxoestragole, and 3'-bromo-trans-anethole (3'-bromo-1-trans-propenyl-4-methoxybenzene) each had very weak, but statistically significant, hepatocarcinogenic activity. The propenylic derivatives cis-anethole, trans-isosafrole, 1:1 cis,trans-isosafrole, 3'-hydroxy-trans-anethole, piperine, and trans-cinnamaldehyde showed no hepatocarcinogenic activity at the levels examined. In contrast, the propenylic derivatives cis- and trans-asarone (1-propenyl-2,4,5-trimethoxybenzene) were each active; the hepatocarcinogenicities of the asarones were not inhibited by prior administration of pentachlorophenol, a sulfotransferase inhibitor that abolished the hepatocarcinogenicity of estragole under the same conditions. Furthermore, precocene II (6,7-dimethoxy-2,2-dimethyl-2H-1-benzopyran), a cyclic propenylic plant metabolite and asarone analogue, showed strong hepatocarcinogenic activity similar to that of 1'-hydroxy-2',3'-dehydroestragole and 1'-hydroxy-2',3'-dehydrosafrole; precocene I (the 7-methoxy analogue of precocene II) was less active than precocene II but more active than cis-asarone.

Age Factors↗
PubMed1987

Cellular and molecular mechanisms of multistep carcinogenesis: relevance to carcinogen risk assessment.

Carcinogenesis is a multistep process involving alterations in at least two distinct classes of genes. Protooncogenes are activated qualitatively or quantitatively in certain tumors, and they appear to act as positive proliferative signals for neoplastic growth. In contrast, tumor suppressor genes are normal genes that must be inactivated or lost for tumor development. When active, tumor suppressor genes control neoplastic growth in a negative manner. Chemicals may influence the carcinogenic process by mutational activation of protooncogenes and/or inactivation of tumor suppressor genes. The types of genetic alterations involved in these mutational events are diverse, and their dose-response curves may be varied. In addition, chemical carcinogens may act on nonmutational processes such as the clonal expansion of premalignant cells. The carcinogenic risk of a specific chemical is a composite of its effects on multiple genetic and epigenetic processes.

Animals↗