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Biomedical subjects

M Dean

Publications and source records attributed to M Dean.

At least 379 records · Page 21Linked to original sources
PubMed1986

Induction of c-fos and c-myc mRNA by epidermal growth factor or calcium ionophore is cAMP dependent.

Phorbol esters activate protein kinase C and induce expression of the c-fos and c-myc protooncogenes in density-arrested BALB/c 3T3 (A31) cells; in contrast, epidermal growth factor (EGF) does not activate protein kinase C and is a poor inducer of c-fos and c-myc in these confluent cells. We show that, when A31 cells were subconfluent and made quiescent by serum deprivation, the phorbol ester phorbol 12-myristate 13-acetate induced c-fos and c-myc mRNA poorly, whereas EGF was a better inducer. Another platelet-derived growth factor-inducible gene, JE, did not show this differential regulation by phorbol 12-myristate 13-acetate and EGF. The ability of EGF to induce protooncogene mRNA was associated with elevated levels of intracellular cAMP. First, serum-deprived cells maintained cAMP at about 2-fold higher level than density-arrested cells. Second, induction was greatly enhanced by cholera toxin and 3-isobutyl-1-methylxanthine, which increased intracellular cAMP 3- to 10-fold. The calcium ionophore A23187 mimicked EGF in that it elevated c-fos and c-myc mRNA when administered with cholera toxin and isobutylmethylxanthine. Neither cholera toxin and isobutyl-methylxanthine nor A23187 appreciably induced these mRNAs when used alone. Our results suggest that c-fos and c-myc expression can be regulated by an EGF-directed pathway that utilizes calcium and cAMP as cooperating cytoplasmic messengers.

1-Methyl-3-isobutylxanthine↗
PubMed1986

Transplantation of fetal fibroblasts and correction of enzymatic deficiencies in patients with Hunter's or Hurler's disorders.

An attempt was made at correcting the specific lysosomal enzyme deficiencies in 7 children with Hunter's or Hurler's diseases by transplantation of fetal fibroblasts. In spite of pretreating the young patients with stored blood, following a procedure employed successfully to avoid rejection of kidneys from incompatible donors, the use of serum-free media for culturing the cells before being harvested and incubation of the cells with chorionic gonadotrophin, the transplantation of fetal fibroblasts was not associated with biochemical or clinical changes. None of the seven patients showed immune reactions against the transplanted cells, HLA antigens, or the missing enzymes.

Animals↗
PubMed1986

c-myc regulation during retinoic acid-induced differentiation of F9 cells is posttranscriptional and associated with growth arrest.

We have shown that c-myc mRNA levels decrease more than 20-fold when F9 teratocarcinoma stem cells are induced to arrest growth and terminally differentiate to parietal endoderm after exposure to retinoic acid and cyclic AMP (Campisi et al., Cell 36:241-247, 1984). Here, we demonstrate that although growth arrest and full expression of the differentiated phenotype required about 3 days, c-myc mRNA declined abruptly between 8 and 16 h after the addition of retinoic acid and cyclic AMP. The decline was independent of cyclic AMP. We found little or no change in the level of c-myc transcription during differentiation, although two other genes showed marked transcriptional regulation. Thus, decreased c-myc mRNA is a consequence of very early posttranscriptional regulation directed by retinoic acid. Differentiation was not fundamental to this regulation. We have shown that sodium butyrate blocks expression of the differentiated phenotype if added within 8 h of retinoic acid and cyclic AMP (Levine et al., Dev. Biol. 105:443-450, 1984). However, butyrate did not inhibit the decrease in c-myc mRNA. Furthermore, F9 cells partially arrested growth without differentiating when grown in isoleucine-deficient medium. Under these conditions, c-myc mRNA levels also declined. Our results suggest that induction of differentiation-specific genes may be under retinoic acid-mediated control dissimilar from that responsible for the decay of c-myc mRNA. In addition, they raise the possibility that growth arrest may be initiated by reduced c-myc expression.

Animals↗
PubMed1986

Further linkage data on cystic fibrosis: the Utah Study.

We reported earlier complete linkage between cystic fibrosis and an RFLP of the met proto-oncogene revealed by the probe pmetH. Another clone, pmetD, detects another polymorphism with the TaqI restriction enzyme. Further linkage studies, now involving 22 families, have confirmed the tight linkage of cystic fibrosis to the MET and D7S8 loci. Significant allelic association was found between CF and allelic series defined by the pmetH probe.

Alleles↗
PubMed1986

The human met oncogene is a member of the tyrosine kinase family.

Prolonged exposure of a nontumorigenic human osteogenic sarcoma cell line (HOS) with the direct acting carcinogen N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) gave rise to morphologically transformed cells which were tumorigenic in nude mice and termed MNNG-HOS. We have shown that DNA from MNNG-HOS cells will transform NIH/3T3 cells and have isolated greater than 35 kb of human DNA containing an oncogene, termed met. The activated met oncogene expresses a novel 5.0 kb RNA transcript which is a hybrid RNA derived from a DNA rearrangement involving two distinct genetic loci termed met and tpr (translocated promoter region). The met proto-oncogene has been localized to 7q21-q31 by in situ hybridization. This locus expresses a 9.0 kb RNA in fibroblast and epithelial cell lines, but is not commonly expressed in cell lines derived from the hematopoietic cell lineage. In contrast, the tpr locus is on chromosome 1, and expresses a 10.0 kb RNA in all human cell lines tested. The novel 5.0 kb met oncogene RNA is 3' co-terminal with the 9.0 kb met proto-oncogene RNA, while the 5' portion of this RNA uses at least two exons derived from the 10.0 kb tpr RNA. These exons are small and are presumably in the promoter region of both tpr and tpr-met transcripts. Nucleotide sequence analysis of the 3' end of met shows that it is a member of the tyrosine kinase family of genes. Peptide antibody to the C-terminal coding region of met immunoprecipitates a 65 kilodalton (kd) polypeptide (p65) in both MNNG-HOS cells and met transformed NIH/3T3 cells. This product also has tyrosine kinase activity in vitro and is presumed to correspond to the tpr-met product. The same antibody detects three larger met-related polypeptides of 160, 140, and 110 kd in human fibroblasts and epithelial cells by in vivo labeling with [35S]methionine. However, only one of the three met proto-oncogene polypeptides, p140, appears to be phosphorylated in the in vitro kinase assay. High levels of in vitro 32P incorporation into p140 met are observed in 4 out of 30 human epithelial cancer cell lines tested. Activation of the met oncogene in MNNG-HOS cells results from a DNA rearrangement possibly mediated in vitro by MNNG. The mode of activation of met may therefore be similar to the epidermal growth factor (EGF)R/v-erbB oncogene; or the bcr/c-abl rearrangement present in the Philadelphia chromosome translocation which is found in chronic myelogenous leukemias.

Base Sequence↗
PubMed1985

Transplantation of amniotic epithelial membranes in patients with mucopolysaccharidoses.

This paper reports the biochemical results of transplanting human amniotic epithelial cells in 3 children with Hunter's and 2 with Hurler's disease. A transient and modest increase of alpha-L-idurono-2-sulphate sulphatase or alpha-iduronidase was observed in the white cells collected from 1 patient with Hunter's and 1 with Hurler's disease. No variation in the excretion of glycosaminoglycans or oligosaccharides was detected in all 5 patients. There was no evidence of immune response towards the transplanted cells or the specifically deficient enzyme. Thus, in spite of the absence of the major histocompatibility antigens, HLA A, B, C and DR, on the surface of the amniotic epithelial cells, no long-term correction of lysosomal enzyme deficiencies was achieved by transplanting amniotic epithelial membranes collected at the end of the gestational period.

Amnion↗
PubMed1984

Carotid surgery without angiography.

We propose that circumstances exist in which angiography is not necessary or is unwarranted for the diagnosis and treatment of carotid arterial disease. High quality real-time B-mode ultrasonographic imaging, combined with both pulsed gated, and continuous wave Doppler analysis, shows a remarkably close correlation with the pathologic abnormality identified at operation. Scanning in the vascular laboratory not only provides quick, noninvasive, accurate assessment of the atherosclerotic disease, it can also provide plaque and blood flow detail not previously attainable. Carotid surgery can be effectively and safely performed in selected patients with the aid of ultrasonography and Doppler analysis without the need for invasive angiographic imaging.

Aged↗
PubMed1984

Cell-cycle control of c-myc but not c-ras expression is lost following chemical transformation.

Cellular oncogenes are DNA sequences implicated in the genesis of cancer, but their functions in the transformation process are not understood. Our experiments provide data linking expression of two well-studied proto-oncogenes, c-myc and c-rasKi, to current knowledge of proliferation control and its perturbation by differentiation and chemical transformation. Growth stimulation of quiescent cells by serum elevates expression of the myc proto-oncogene in Balb/c 3T3 (A31) cells. In two chemically transformed A31 derivatives (BPA31 and DA31), c-myc expression is constitutive. The levels of c-myc mRNA in quiescent and growing transformed cells are nearly the same, and are only slightly elevated compared to the level found in growing A31 cells. By contrast, c-rasKi expression is cell-cycle-dependent in BPA31 cells. The relative abundance of c-rasKi mRNA begins to increase in mid- to late G0/G1. During terminal differentiation of teratocarcinoma stem cells (F9) into nonproliferating endoderm, relative mRNA abundance is diminished more markedly for c-myc than for c-rasKi. These results demonstrate that expression of the myc and rasKi proto-oncogenes is dependent upon the cellular growth state, and that growth control exhibits growth-factor-dependent, cell-cycle-timed oncogene expression. In the case of the BPA31 cells, c-myc is not rearranged, amplified, or overexpressed. However, the oncogene has lost its cycle-dependent regulation in the chemically transformed cells.

Actins↗
PubMed1984

Specific regulation of c-myc oncogene expression in a murine B-cell lymphoma.

The c-myc oncogene has been implicated in a wide spectrum of B-cell neoplasias. In normal cells, the level of expression of the c-myc gene correlates with growth status. In the present study, we examined the effect of receptor-mediated inhibition of growth on c-myc expression in a B-cell lymphoma. The murine lymphoma line WEHI 231 has been characterized as an early B cell; it bears surface-bound IgM and has unrearranged c-myc genes. Following treatment of a WEHI 231 culture with anti-mouse Ig antiserum, the cells undergo one round of division and further proliferation is inhibited. We observed that this treatment specifically affected cytoplasmic levels of c-myc mRNA. An initial early increase is followed by a precipitous drop such that by 4 hr (after exposure) the amount of c-myc mRNA is below control values by a factor of approximately equal to 10. The drop in c-myc precedes cessation of DNA synthesis. During the 2- to 4-hr period, c-myc mRNA had a maximal half-life of between 20 and 30 min. In contrast, even 24 hr after anti-Ig exposure, the amounts of most major mRNAs, including mu heavy chain and actin, were not significantly altered. These results indicate that expression of an unrearranged c-myc gene can be selectively responsive to receptor-mediated regulatory events.

Animals↗
PubMed1984

Overproduction of immunoglobulin mRNA by a murine myeloma MOPC 315 variant cell line.

The mouse myeloma MOPC 315 cell line synthesizes and secretes IgA (lambda 2) immunoglobulin. A spontaneously arising variant of the MOPC 315 line, which had been isolated as apparently oversecreting IgA protein, has been characterized. The variant line has been shown to synthesize and secrete increased levels of heavy chain, light chain, and J chain polypeptide compared to the parental wild-type cells from which it was isolated. The steady-state levels of cytoplasmic mRNA for these polypeptides are increased commensurately in the over-producing line. For the heavy chain, enhanced transcription, and possibly increased gene dosage, appear to be involved. The increased levels of the three individual immunoglobulin polypeptide chains suggest that the variant line displays a coordinate regulation of expression of immunoglobulin genes.

Animals↗
PubMed1984

Cellular oncogenes, growth factors, and cellular growth control.

In this article we relate the functioning of oncogenes, particularly myc and ras, to current ideas regarding regulation of mammalian cell growth by growth factors. Assuming the genetic basis of transformation to be alterations of several proto-oncogenes, the mechanisms by which transformation could diminish growth control are numerous. The oncogene could interact with a growth factor in several ways. Mutations could alter the quantity of an oncogene's product or its quality through primary structure or covalent modifications such as phosphorylations. Oncogenes could code for a receptor for a growth factor. Various alterations parallel to the above set could then affect growth factor function via receptor changes (including abolished requirement for the factor). Some oncogenes might operate during the chain of intracellular events that must follow growth stimulation. Introduction of such an oncogene (e.g., the coding region for a DNA virus T antigen) would bypass requirements for both growth factors and receptors. Various observations regarding the oncogenes, cell cycle-timed events, and growth factors have been presented in a way we hope will suggest experiments designed to provide a basis for understanding growth regulation at the genetic, biochemical, and cellular levels in normal cells and tumorigenic cells, which have deranged growth regulation.

Cell Cycle↗