Biomedical subjects

C B Lazier

Publications and source records attributed to C B Lazier.

41 records · Page 3Linked to original sources

PubMed1979

A high-affinity oestrogen-binding protein in cockerel liver cytosol.

In contrast with several earlier reports, cytosol from cockerel liver contains a significant concentration of a protein that binds oestradiol with high affinity. To demonstrate the activity, certain alterations in the conventional method of preparation of cytosol must be made. Homogenization in sucrose-containing buffer at pH 8.4 in the presence of proteinase inhibitors and rapid fractionation of the cytosol with (NH4)2SO4 enables demonstration of a single class of oestradiol-binding sites with a Kd of about 1 nM and specificity only for oestrogens. The concentration is about 300 sites per cell in liver from 2-week-old cockerels. Oestradiol treatment in vivo decreases the number of exchangeable cytosol oestradiol-binding sites by about 80% for 1--4h, after which time it is gradually restored. Gel filtration of the cytosol preparation in the presence of high salt concentrations reveals that most of the oestradiol-binding activity is in high-molecular-weight aggregates, but a mild trypsin treatment generates a specific binding protein with an approximate mol.wt. of 40 000. This protein may be an oestrogen receptor.

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PubMed1978

Ontogeny of the vitellogenic response to oestradiol and of the soluble nuclear oestrogen receptor in embryonic-chick liver.

A specific high-affinity oestradiol-binding protein was characterized in salt extracts of liver nuclei of the developing chick embryo. It is present in very small amounts at day 10 of development and is marginally stimulated by oestradiol injection into the yolk sac on day 8. Injection of oestradiol on day 10 evokes a substantial increase in the nuclear oestradiol-binding activity measured on day 12 of development. This oestradiol-binding protein has properties of sedimentation, hormone specificity and high-affinity binding very similar to those of the soluble nuclear receptor in hatched chicks. Livers from the 12-day embryos injected 48 h earlier with oestradiol do not synthesize vitellogenin, as judged by a specific immunochemical and electrophoretic assay for this oestrogen-induced protein. Traces of vitellogenin synthesis can be induced in 13-day-embryo liver, and a substantial response, equivalent to that in hatched chicks, is seen in liver from 15-day embryos injected on day 13. The development of the ability of oestradiol to increase the concentration of the soluble nuclear receptor appears to be one, but not the only, critical factor involved in the development of the ability of chick liver to synthesize vitellogenin.

Animals↗

PubMed1977

Interaction of the anti-oestrogen, nafoxidine hydrochloride, with the soluble nuclear oestradiol-binding protein in chick liver.

Nafoxidine hydrochloride (Upjohn, 11100A)injected with oestradiol into immature chicks inhibits the hormone-induced increase in [3H]oestradiol-binding activity in salt extracts of liver nuclei as well as the subsequent production by liver of egg-yolk phosphoprotein. Substantial inhibition of both oestradiol-induced responses is seen when nafoxidine is given in a dose approximately equimolar with that of oestradiol. In vitro nafoxidine competitively inhibits binding of [3H]oestradiol in nuclear extracts. The Ki for the inhibition is 43 nM, which indicates an affinity of nafoxidine for the binding protein about 4% of that of oestradiol. The inhibitory action of nafoxidine in vivo thus is more potent than the relative binding affinity determined in vitro might indicate. One possible explanation is that the primary site of nafoxidine action is at a point proximal to nuclear receptor interaction. Nafoxidine injected alone into the chick does not induce phosphoprotein synthesis, but it does increase [3H]oestradiol-binding activity in extracts of liver nuclei to a limited extent. No differences in the properties of the oestradiol-binding activity in extracts from nafoxidine-treated chicks or from oestradiol-treated chicks were detected. Chick liver cytosol does not contain detectable high-affinity oestradiol-binding activity. A low-affinity oestradiol-binding component with a sedimentation coefficient of 3.5S was found, but it was unaffected by treatment of chicks with earlier nafoxidine or oestradiol. The results suggest a difference in the mechanism of oestradiol action in the chick liver and in the widely studied rat uterus, on which the usual model for oestradiol action is largely based.

Animals↗

PubMed1971

Chemical composition of an oestrogen-induced calcium-binding glycolipophosphoprotein in Xenopus laevis.

1. Oestrogen treatment has previously been shown to induce the formation of large amounts of a serum protein, vitellogenin (xenoprotein), in Xenopus laevis. Vitellogenin was purified from serum by dimethylformamide precipitation and was shown to be homogeneous by a variety of electrophoretic techniques. 2. The molecular weight of vitellogenin was estimated by gel filtration to be about 6x10(5). The chemical constituents of vitellogenin were determined and lead to the characterization of this protein as a serum calcium-binding glycolipophosphoprotein. 3. The extractable lipid accounted for 12% of vitellogenin. Gas-liquid-chromatographic analysis of the saponified lipid moiety showed the presence of palmitic acid, palmitoleic acid, stearic acid, oleic acid and linoleic acid in the molecular proportions 6.8: 1.5: 1.0: 3.6: 1.4. 4. The carbohydrate moiety consisted of 0.4g of hexose, 0.77g of hexosamine and 0.18g of sialic acid/100g of vitellogenin. 5. The calcium and phosphorus contents were 0.85 and 1.65g/100g of vitellogenin respectively. 6. Serum from oestrogen-treated animals injected with (45)CaCl(2) contained 9.7 times the radioactivity present in serum from untreated (45)CaCl(2)-injected animals. Of the radioactivity due to (45)CaCl(2) in the serum of oestrogen-treated animals 72% was non-diffusible on dialysis. Of this activity 65.4% was associated with the vitellogenin band on cellulose acetate electrophoresis.

Animals↗

PubMed1971

Studies on the induction and biosynthesis of vitellogenin, an oestrogen-induced glycolipophosphoprotein.

1. Oestrogen treatment induces the formation of a Ca(2+)-binding glycolipophosphoprotein, vitellogenin, in Xenopus laevis. 2. The incorporation of l-[4,5-(3)H]-leucine into vitellogenin in vivo and in vitro was observed 12-24h after hormone treatment and increased progressively up to 21 days after treatment. 3. Vitellogenin is shown to be the major protein component biosynthesized and released into the incubation medium in vitro by livers from oestrogen-treated animals. 4. The biosynthesis in vitro of vitellogenin was inhibited by cycloheximide and carbonyl cyanide m-chlorophenylhydrazone, stimulated by increased Ca(2+) concentrations and decreased by raising the incubation temperature from 22 to 37 degrees C. 5. Incorporation of labelled amino acids into vitellogenin began after approx. 2h. No lag phase was noted for the incorporation of labelled amino acids into total tissue proteins. 6. The incorporation of label from [(32)P]phosphate and [2-(14)C]acetate into the protein as well as into the lipid moiety of vitellogenin showed a lag phase similar to that noted for the incorporation of amino acids. 7. These results suggest that the release of vitellogenin into the incubation medium occurs about 2h after the initiation of its biosynthesis.

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