Biochemical and biophysical research communications
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Biochem. Biophys. Res. Commun. · Apr 1989
Translational regulation of ferritin synthesis in rat spleen: effects of iron and inflammation.
Translational control of ferritin synthesis was studied in rat spleen, and compared with that for liver, heart and brain, in response to iron and inflammation. Spleen concentrations of total RNA in the ribonucleoprotein (mRNP) fraction was comparable to that for liver, while polyribosomal RNA was less. Both fractions were ten-fold lower in heart and brain. ⋯ The findings were confirmed by hybridization studies of mRNPs and polyribosomes separated in sucrose gradients. Turpentine-induced inflammation also caused a shift in ferritin mRNA from the mRNP to the polyribosome fraction of spleen and liver, over 12 h. We conclude that as in liver, spleen ferritin synthesis is under translational control by iron, and that both tissues also respond to inflammation by shifting of ferritin mRNA to the polyribosomes.
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Biochem. Biophys. Res. Commun. · Jan 1988
Different molecular weight forms of opioid receptors revealed by polyclonal antibodies.
Polyclonal antibodies were raised against a purified opioid receptor from bovine brain (Cho, et. al., 1986), and shown to inhibit 3H-diprenorphine binding to this receptor in a dose-dependent fashion. These antibodies were then used to characterize opioid-binding material present in rat brain and in NG108-15 neuroblastoma-glioma hybrid cells. ⋯ In contrast, the polyclonal antibodies reacted with a 45,000 molecular weight species in NG108-15 neuroblastoma-glioma hybrid cells; moreover, this band was specifically reduced in NG108-15 cells in which opioid receptors had been down-regulated by incubation with D-ala2-D-leu5-enkephalin for 24 hours. Thus at least two distinct opioid receptor molecules have been identified, which have antigenic similarities.
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Biochem. Biophys. Res. Commun. · Nov 1987
Specific opioid binding sites for dermorphin in rat brain. A radioreceptor assay using the tritiated hormone as primary ligand.
Dermorphin, a heptapeptide amide isolated from amphibian skin, is the most potent of the naturally occurring opioid peptides. (3H)-dermorphin (52 Ci/mmol, 1294 GBq/mmol) was prepared by catalytic tritiation of the synthetic (2,5-iodotyrosyl 1,5)-dermorphin precursor. High affinity specific binding sites for dermorphin were labeled in rat brain membranes using tritiated dermorphin as primary ligand. The binding was saturable and time-dependent. ⋯ Dermorphin and the specific opiate antagonist naloxone inhibited specific (3H)-dermorphin binding in a concentration dependent manner. The displacement curves could be fit to a simple competitive model assuming only one population of binding sites, with IC 50 of 1.6 nM and 3.4 nM for dermorphin and naloxone, respectively. The use of tritiated dermorphin will be helpful to ascertain unequivocally the selectivity of dermorphin for the different opioid receptor subtypes in the central nervous system.
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Biochem. Biophys. Res. Commun. · Apr 1986
Sequential binding of actin monomers to plasma gelsolin and its inhibition by vitamin D-binding protein.
Functional studies that distinguish free from actin-bound gelsolin based on the ability of the former to sever actin filaments reveal that the binding of actin monomers to gelsolin is highly cooperative and can be prevented by prior incubation of actin with vitamin D-binding protein (DBP), even though the apparent affinity of gelsolin for actin is 50-fold greater than that of DBP. Measurements of actin binding by immunoprecipitation and pyrene-actin fluorescence establish that DBP-actin complexes do not bind to gelsolin and that DBP removes one of the actin monomers in a 2:1 actin-gelsolin complex. These studies may explain why DBP-actin complexes exist in blood plasma in vivo in the presence of free gelsolin and suggest that the interaction of gelsolin with actin in cells and plasma may be regulated in part by actin monomer binding proteins.
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Biochem. Biophys. Res. Commun. · Feb 1985
Uridine diphosphate reductase of Ehrlich ascites tumor is insensitive to hydroxyurea.
Uridine diphosphate (UDP) reductase was isolated in the supernatant fraction obtained after the acidification of the cytosol of Ehrlich ascites tumor cells, and was found insensitive to 10 mM hydroxyurea. However, cytidine diphosphate (CDP) reductase, being separated concurrently in the precipitate fraction, was readily inhibited. In the cytosol fraction of either Ehrlich ascites tumor, Yoshida ascites sarcoma or regenerating rat liver after partial hepatectomy, UDP reduction activity, in contrast to CDP reduction activity, is not sensitive to hydroxyurea.