Search PubMed⌕ Search

Biomedical subjects

W M Mitchell

Publications and source records attributed to W M Mitchell.

At least 109 records · Page 6Linked to original sources
PubMed1973

Synthesis of (3H)DNA complementary to ovalbumin messenger RNA: evidence for limited copies of the ovalbumin gene in chick oviduct.

Accumulation of ovalbumin messenger RNA in chick oviduct is absolutely dependent upon estrogen. After estrogen treatment, ovalbumin comprises 60-65% of the total oviduct protein. We used maximally stimulated animals to extract and partially purify the ovalbumin messenger RNA. The final product was enriched about 100-fold in activity with respect to this specific messenger RNA. This ovalbumin messenger RNA fraction was used to direct the synthesis of a complementary [(3)H]DNA in the presence of RNA-dependent DNA polymerase isolated from avian myeloblastosis virus. The complementary [(3)H]DNA (specific radioactivity, 8 x 10(7) cpm/mug) was a faithful transcript since about 90% would hybridize back to the original messenger RNA template. Ovalbumin complementary [(3)H]DNA was reannealed with an excess of chick-oviduct total DNA. The kinetics of this reaction indicate that only one copy of the ovalbumin gene exists in each haploid genome. These data suggest that estrogen may affect the oviduct genome to stimulate production of large numbers of ovalbumin messenger RNA molecules from a single copy of the ovalbumin gene.

Animals↗
PubMed1973

Biologic and immunologic characterization and physical separation of ACTH and ACTH fragments in the ectopic ACTH syndrome.

Extracts of tumors from 32 patients with the ectopic ACTH syndrome were subjected to simultaneous bioassay and radioimmunoassays for ACTH. Radioimmunoassays were performed using three antisera, one of which reacts with the extreme N-terminal 1-13 amino acid sequence of ACTH, the second with the N-terminal 1-23 sequence of the ACTH molecule, and the third with the C-terminal 25-39 amino acid sequence of ACTH. There was, in general, good correlation between bioactivity and N-terminal ACTH immunoreactivity. However, there were large excesses of both extreme N-terminal and C-terminal immunoreactive materials in most tumor extracts, which were not found in extracts of three human pituitaries. Three tumor extracts were subjected to molecular sieve chromatography on Sephadex G-50 fine resin. The bioactive ACTH eluted in the same fractions as pituitary ACTH (mol wt approximately 4,500 daltons) and reacted equally in all three ACTH radioimmunoassay systems. The bioactive tumor ACTH was neutralized by incubation with the C-terminal antiserum, indicating it has an intact C-terminal sequence of amino acids. The next several fractions from the Sephadex column contained a material, mol wt approximately 3,100, which was biologically inactive and had C-terminal immunoreactivity but no N-terminal or extreme N-terminal immunoreactivity. Incubation with the N-terminal 1-23 ACTH antiserum did not adsorb these C-terminal fragments, indicating they lacked an intact sequence of amino acids in this region. A smaller ACTH fragment (mol wt approximately 1,800 daltons) eluted in still later fractions and reacted with the extreme N-terminal antiserum but not with the N-terminal or C-terminal antisera. It had no steroidogenic activity, but appeared to have significant melanocyte-stimulating activity. It is concluded that, in addition to an ACTH similar, if not identical, to pituitary ACTH, tumors of patients with the ectopic ACTH syndrome contain both N-terminal and C-terminal ACTH fragments.

Adrenocorticotropic Hormone↗
PubMed1970

Epidermal growth factor: high and low molecular weight forms.

In crude homogenates of the submaxillary gland of the male mouse, epidermal growth factor (EGF) activity was found almost entirely in a high molecular weight complex (about 74,000 daltons). This high molecular weight form may be reversibly dissociated into EGF and an EGF-binding protein. EGF was found to have a molecular weight of approximately 6400. The EGF-binding protein has a molecular weight of 29,000, and shows arginyl-esterase activity.

Amino Acids↗