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Biomedical subjects

E D Adamson

Publications and source records attributed to E D Adamson.

103 records · Page 6Linked to original sources
PubMed1977

Biochemical markers of the progress of differentiation in cloned teratocarcinoma cell lines.

The progeny of single teratocarcinoma cells will give rise to several different cell types in vitro, and the latter were shown to be functionally differentiated by biochemical criteria. In all these studies, cloned lines of mouse teratocarcinoma cells were assayed during the course of differentiation for some biochemical products characteristic of the tissues formed. The carcinoembryonic protein, alpha-foetoprotein, was not synthesized by undifferentiated embryonal carcinoma (EC) cells, but was synthesized in increasing amounts during their differentiation to endoderm-type cells in suspension culture. alpha-Foetoprotein was shown to be a product of endoderm cells, but not all endoderm cells synthesized this protein. During the course of further differentiation when EC cells or aggregates were grown in tissue-culture dishes, other biochemical products appeared. In cultures containing predominantly nerve-type cells, there was a 30-fold increase in the specific activity of acetylcholinesterase, with concomitant appearance of the aldolase isoenzyme characteristic of mouse brain. In some cultures, a small amount of muscle-type cell formation was marked by the appearance of the MB isoenzyme of creatine phosphokinase. Generally, biochemical differentiation was immature.

Acetylcholinesterase↗
PubMed1976

Studies on the activity of the X chromosomes in female teratocarcinoma cells in culture.

Embryonal carcinoma cells derived from murine teratocarcinomas are able to differentiate into the same variety of tissue types as early embryonic cells. Because embryonal carcinoma cells resemble those of the embryo at a stage before X chromosome inactivation has occurred in females embryonal carcinoma cells containing two X chromosomes were examined to determine whether both are genetically active. The specific activities of X-linked enzymes were measured in embryonal carcinoma cells containing either one or two X chromosomes. The activities in both cell types were similar, suggesting that only one X chromosome was active in the female cells. Further support for this conclusion came from experiments in which azaguanine-resistant mutants were recovered with similar frequencies from embryonal carcinoma cell lines containing one and two X chromosomes. Late replication of an X chromosome DNA was detected in one embryonal carcinoma cell line with two X chromosomes but not in another. This suggests that cells of these two lines were arrested at different developmental stages, and that late DNA replication may not be a necessary adjunct of X inactivation. Evidence is presented which suggests that X chromosome reactivation does not occur during differentiation of the cells in vitro.

Adenine Phosphoribosyltransferase↗
PubMed1976

Isoenzyme transitions of creatine phosphokinase, aldolase and phosphoglycerate mutase in differentiating mouse cells.

Extracts of embryonic mouse tissues (skeletal, cardiac and smooth muscle, and brain) were analysed by Cellogel electrophoresis for their isoenzymic distributions of three enzymes, creatine phosphokinase, aldolase and phosphoglycerate mutase. Embryonic tissues from the 12th day to the end of gestation were examined for isoenzyme transitions, and it was found that the adult forms of these enzymes appeared during gestation. Extracts from cloned teratocarcinoma cells were similarly examined in order to determine their degree of bio-chemical differentiation. Undifferentiated embryonal carcinoma cells contained only the early embryonic forms of all three enzymes, while differentiated cells formed in vivo, and in some cases in vitro, started to express the adult types of creatine phosphokinase and aldolase. Thus, biochemical parallels have been demonstrated between developing embryonic tissues and teratocarcinoma cells differentiating in vitro.

Animals↗
PubMed1975

Analysis of the forms of acetylcholinesterase from adult mouse brain.

The solubilization of 80% of the acetylcholinesterase activity of mouse brain was performed by repeated 2h incubations of homogenates at 37 degrees C in an aqueous medium. Analysis of the soluble extract by gel filtration on Sephadex G-200 showed that up to 80% of the enzyme activity was eluted in a peak which was estimated to consist of molecules of about 74000mol.wt. This peak was called the monomer form of the enzyme. After 3 days at 4 degrees C, the soluble extract was re-analysed and was eluted from the column in four peaks of about 74000, 155000, 360000 and 720000 mol.wt. Since the total activity of the enzyme in these peaks was the same as that in the predominantly monomer elution profile of fresh enzyme, we concluded that the monomer had aggregated, possibly into dimers, tetramers and octomers. Extracts of the enzyme were analysed by polyacrylamide-gel electrophoresis and the resulting multiple bands of enzyme activity on gels were shown to separate according to their molecular sizes, that is by molecular sieving. All these forms had similar susceptibilities to the inhibitors eserine, tetra-isopropyl pyrophosphoramide and compound BW 284c51 [1,5-bis-(4-allyldimethylammoniumphenyl)pentan-3-one dibromide]. Thus the forms of the enzyme in mouse brain which can be detected by gel filtration and polyacrylamide-gel electrophoresis may all be related to a single low-molecular-weight form which aggregates during storage. This supports similar suggestions made for the enzyme in other locations.

Acetylcholinesterase↗
PubMedDate not supplied

Tissue and cell type-specific expression of two human c-onc genes.

Cellular genes containing nucleotide sequences homologous to retroviral oncogenes (v-onc) have been identified in the genomes of a variety of species of both the vertebrate and invertebrate phyla. Expression of such genes, termed c-onc genes, has been shown to be tissue-specific in chickens and mice and to be modulated during murine development and differentiation of human haematopoietic cells. We report here that the level of the c-fos gene transcripts is 100-fold greater in human term fetal membranes than in other normal human tissues and cells. These levels of c-fos expression in human amniotic and chorionic cells are close to the level of v-fos expression that results in the induction of osteosarcomas in mice and transformation of fibroblasts in vitro. This observation suggests that the induction of neoplastic transformation by the FBJ murine osteosarcoma virus may require the expression of the fos gene product at high levels in an inappropriate cell type. In contrast, the human c-fms gene is expressed at high levels specifically in term placenta and trophoblastic cells. The tissue and cell type-specific patterns of c-fos and c-fms expression suggest that the physiological function of the c-fos and c-fms encoded proteins may be associated with those embryo-derived cells whose primary functions are protection and nourishment of the human fetus.

Adult↗
PubMedDate not supplied

The transcriptional factor Egr-1 is synthesized by baculovirus-infected insect cells in an active, DNA-binding form.

The Egr-1 (zfp-6) gene encodes a zinc-finger-containing nuclear protein that is rapidly and transiently induced in quiescent cells treated with mitogens. We have constructed baculovirus vectors that synthesize mouse Egr-1 protein initiating at two putative ATG start sites. The ATG site producing the larger protein (Mr, 80,000) is similar, if not identical, to Egr-1 synthesized by serum-stimulated quiescent mouse fibroblasts, thus identifying the likely site for translation. The protein synthesized by the insect cells is active as assayed by its ability to bind to a specific DNA sequence that has been identified as an Egr-1 binding site. The insect cell system will allow further studies of the structure and function of the Egr-1 product, a protein that appears to be an important "master switch" for other genes.

Animals↗