Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.27.4 (ribonuclease)
 6,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mpl ligand (thrombopoietin [TPO]) is the physiological regulator of platelet production. In mice, mRNA encoding the Mpl ligand (Mpl-L) is predominantly found by Northern blot analysis in the liver and kidney. To investigate the mode of regulation of the Mpl-L gene, we have developed several experimental models of severe thrombocytopenia differing in their kinetics and an opposite model of chronic thrombocytosis. Northern analysis performed at various times after induction of a thrombocytopenic state demonstrates that, whatever the number of circulating platelets, no change in Mpl-L mRNA level occurs in liver and kidney. By ribonuclease protection assays, we analyzed the ratios between mRNAs coding for the wild-type Mpl-L form and various splice variants encoding inactive or nonsecreted Mpl-L proteins. No modification in levels of these various isoforms was detected confirming the data of a previous report. Because the highest level of Mpl-L bioactivity in sera was observed only in mice with drastically reduced numbers of both platelets and megakaryocytes, these results further suggest that not only platelets, but also megakaryocytes, must be involved in the regulation of the level of circulating Mpl-L. In addition, we show that no downregulation of wild-type Mpl-L mRNA and no change in the ratio of Mpl-L mRNA isoforms were detected in mice in which a chronic thrombocytosis was induced. Together, these different models extend and further confirm that the regulation of Mpl-L does not occur at a transcriptional level or by a modulation in the ratios of Mpl-L mRNA isoforms.
 ...
PMID:Constitutive expression of Mpl ligand transcripts during thrombocytopenia or thrombocytosis. 883 50

A system for quantitative determinations of human thyroid peroxidase (TPO) in biological fluids has been obtained, based on the use of enzyme-linked immunosorbent assay. Immunochemical properties of TPO were studied under variable conditions, and a new method for isolating the protein from microsomes, mitochondria, and cytosol of thyroid glands of patients with diverse thyroid diseases was developed. The procedure involves solubilization of subcellular fractions with detergents, their sonication, two sequential runs of chromatography (on sorbents with immolbilized monoclonal antibodies against TPO and goat anti-human immunoglobulin antibodies), treatment with ribonuclease, and dialysis. Highly purified preparations of intact TPO and a product of its limited trypsinolysis are expected to be used as research tools and components of high-sensitivity immunoassays.
 ...
PMID:[Characteristics of immunoaffinity chromatography and a new method for isolation of human thyroid peroxidase from subcellular fractions of thyroid gland]. 1676 81