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Biomedical subjects

G N Burrow

Publications and source records attributed to G N Burrow.

At least 91 records · Page 5Linked to original sources
PubMed1981

Simultaneous thyrotropin stimulation of thyroid protein synthesis and degradation determined by leucine pool sampling in nascent peptides.

TSH stimulated protein synthesis in calf thyroid slices, but this effect was masked by the simultaneous stimulation of thyroglobulin hydrolysis. These simultaneous effects on both synthesis and degradation were separated by determining the specific activity of amino acids serving as precursors for protein synthesis. Precursor pool specific activity was determined in thyroid nascent peptides which had been purified by epichlorohydrin triethanolamine cellulose chromatography from thyroid polysomes. TSH had no effect on the crude incorporation of [3H]leucine into thyroid protein, even though specific activity of the precursor pool [3H]leucine was diluted. As a consequence, TSH actually stimulated thyroid protein synthesis 2.6-fold. The proportion of nascent peptides immunoprecipitable by antithyroglobulin serum was unchanged by TSH, indicating a general stimulation of protein synthesis.

Animals↗
PubMed1981

DDAVP treatment of diabetes insipidus during pregnancy and the post-partum period.

A 23 year old woman with diabetes insipidus who had previously been treated with pitressin, pituitary snuff and chlorpropamide, was treated with DDAVP during pregnancy. DDAVP concentrations immunoassayed as vasopressin were determined in maternal serum and breast milk. Oxytocin antibodies were also determined in maternal serum.

Adult↗
PubMed1980

Regulation of ornithine decarboxylase activity by corticotropin in adrenocortical tumor cell clones: roles of cyclic AMP and cyclic AMP-dependent protein kinase.

In Y1 adrenocortical tumor cells, corticotropin (ACTH), cyclic AMP, and 8-bromoadenosine 3',5'-monophosphate (8BrcAMP) stimulated ornithine decarboxylase activity (L-ornithine carboxy-lyase, EC 4.1.1.17) and steroidogenesis. The concentrations required for half-maximal activation of ornithine decarboxylase were 60 pM for ACTH and 1 mM for 8BrcAMP; the concentrations required for half-maximal activation of steroidogenesis were 50 pM for ACTH and 0.2 mM for 8BrcAMP. Ornithine decarboxylase activity increased 1.5 hr after the addition of these agents, reached a maximum between 4 and 6 hr, and then declined. Mutant clones with impaired ACTH-responsive adenylate cyclase systems [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1]did not respond to ACTH with increased ornithine decarboxylase activity, but they responded normally to added cyclic AMP. These results indicate that adenylate cyclase and cyclic AMP are necessary for the stimulation of ornithine decarboxylase activity by ACTH. In a series of Y1(Kin) mutants with altered cyclic AMP-dependent protein kinase activities (ATP:protein phosphotransferase, EC 2.7.1.37), the effects of ACTH on ornithine decarboxylase also were attenuated. These findings suggest that cyclic AMP-dependent protein kinase also plays a necessary role in the stimulation of ornithine decarboxylase activity by ACTH. The effects of ACTH on ornithine decarboxylase in the Kin mutants, however, were quantitatively different from the effects on steroidogenesis and did not closely reflect the degree of defect in cyclic AMP-dependent protein kinase activity. These differences suggest that the pathways of ACTH action leading to stimulation of steroidogenesis and ornithine decarboxylase activity diverge subsequent to activation of the protein kinase.

Adenylyl Cyclases↗
PubMed1980

Synthesis of very high molecular weight thyroglobulin in three heterologous systems.

Calf thyroid RNA has been translated in the wheat germ and messenger-dependent reticulocyte lysate cell free systems and in Xenopus laevis oocytes. Peptides immunologically related to and comigrating with 330 000 molecular weight thyroglobulin as well as both larger and smaller immunopeptides have been synthesized. The smaller molecular weight peptides were due at least in part to degradation during incubation despite the presence of protease inhibitors. The larger molecular weight peptides could represent degradation products of a single polypeptide chain with a molecular weight of 660 000. The 330 000 molecular weight peptides would then represent cleavage of the protomer into two subunits. To support this possibility, thyroid polysomal RNA large enough to code for a peptide with a molecular weight of 660 000 has been shown to be active in thyroglobulin synthesis and to maintain its integrity under denaturing conditions.

Animals↗
PubMed1980

Iodination and the structure of human thyroglobulin.

We have studied human thyroglobulin of extremely low iodine content obtained from a goitrous cretin who had no measurable peroxidase activity in his thyroid gland. Thyroglobulin from these patients is of interest because of the possibility that poorly iodinated thyroglobulin is particularly susceptible to dissociation and proteolysis. In the present study our data indicated that poorly iodinated thyroglobin isolated under conditions inhibiting proteolysis possessed properties similar to normal human thyroglobulin in its secondary, tertiary, and quaternary structures.

Adult↗
PubMed1979

Synthesis of high molecular weight thyroglobulin peptides by thyroid polysome in vitro.

Bovine thyroid polysomes were isolated under conditions which had yielded large polysomes in other systems. Between 25 and 40% of the protein synthesized by these polysomes could be precipitated by thyroglobulin antibody. When these immunoprecipitates were separated by dodecyl sulfate-polyacrylamide gel electrophoresis (4% running gel), over 50% of the radioactivity was located in the regions of polypeptides greater than 100,000 daltons. Between 11 and 13% of the total radioactivity was found as a single peak co-migrating with the main band of bovine thyroglobulin (Mr = 330,000). Peaks of radioactivity were also found in regions of molecular weights between 130,000 and 200,000. When the immunoprecipitates were separated in a 10% running gel, about 50% of the radioactivity was located in the top 8 mm of the gel. Most of the remaining radioactivity was distributed in regions corresponding to molecular weights greater than 68,000. No peak of radioactivity was seen corresponding to peptides of 15,000 daltons.

Animals↗
PubMed1979

Regression of pituitary tumors, a possible effect of bromergocryptine.

With the advent of the prolactin radioimmunoassay and more sensitive methods of roentgenologic examination, prolactin-secreting pituitary tumors are now being diagnosed with much greater frequency. Definitive treatment has been considered to involve transphenoidal hypophysectomy. The symptoms of hyperprolactinemia including amenorrhea, galactorrhea and infertility can usually be controlled without difficulty by bromergocryptine therapy, but little is known regarding continued tumor growth. Bromergocryptine and other ergot alkaloids have been shown to decrease the production of prolactin and to inhibit the rate of pituitary tumor growth in animal studies. In man, evidence for a similar effect is not as clear. The present study demonstrates tumor regression associated with bromergocryptine therapy in two patients.

Adult↗
PubMed1979

Effect of thyrotropin on the phosphorylation of thyroid chromosomal proteins.

Thyrotropin (TSH) stimulated the phosphorylation of histone H1 in calf thyroid slices but had no effect on other classes of histones. Phosphorylation of total phenol-soluble nonhistone chromosomal proteins was not affected by incubation with TSH. However, when these phenol-soluble nonhistone chromosomal proteins were analysed by two-dimensional gels involving isoelectrofocusing and dodecyl sulfate-polyacrylamide gel electrophoresis, TSH was shown to stimulate the phosphorylation of two specific groups of phosphoproteins with molecular weights between 35,000 and 45,000 and isoelectric points at pH values of 5.4-6.0. This increase in phosphorylation with TSH stimulation was confirmed by quantitative analysis of one-dimensional isoelectrofocusing gels.

Animals↗
PubMed1979

Stimulation of thyroglobulin synthesis in thyroid polysomes by soluble factors from reticulocyte lysate.

The addition of rabbit reticulocyte lysate supernate to membrane-bound calf thyroid polysomes resulted in stimulation of [3H]leucine incorporation into acid-precipitable material; 91% of these total radioactive peptides was precipitated by thyroglobulin antibodies. The ability of reticulocyte lysate supernate to stimulate thyroglobulin syntheis was pH and temperature sensitive. The addition of 25 microM aurintricarboxylic acid resulted in an 85% inhibition of [3H]leucine incorporation.

Animals↗
PubMed1978

Thyroid hormone analogs and fetal goiter.

Transfer of iodothyronine across the placenta in most species occurs only with difficulty. Recently, biologically active, nonhalogenated thyroid hormone analogs have been synthesized with properties which might favor placental transfer. To test this possibility, we compared the doses of T4, T3, and thyroid hormone analogs necessary to prevent propylthiouracil-induced goiter formation in rat fetuses. T4 and T3 prevented fetal goiter, but in doses that caused maternal hyperthyroidism; in contrast, the thyroid hormone analogs prevented fetal goiter in doses that were not thyrotoxic to the mother.

Animals↗
PubMed1978

Hypoglycemia-induced prolactin release.

Recent advances in neurosurgical techniques have made it possible to remove pituitary adenomata with minimal morbidity and mortality. These developments have focused attention on early recognition of pituitary tumors, before the onset of visual disturbances or endocrine dysfunction. We have studied the prolactin response to insulin-induced hypoglycemia as an aid in the evaluation of patients with hypothalamic and pituitary disease. Regular insulin 0.1 units/kg was administered intravenously to normal subjects, to patients with pituitary tumors, and to patients with idiopathic galactorrhea. While the normal subjects regularly showed a prolactin response to hypoglycemia, this was observed infrequently in the other groups. It is possible that prolactin nonresponsiveness to insulin hypoglycemia may reflect nonspecific pituitary damage or may represent an abnormality specific to patients with galactorrhea. Our data suggest that the prolactin response to insulin hypoglycemia is a sensitive index of hypothalamic-pituitary dysfunction.

Adult↗