PubMed Health⌕ Search

Biomedical subjects

J E Rall

Publications and source records attributed to J E Rall.

At least 19 recordsLinked to original sources
PubMed1989

Thyroid hormone-mediated transcriptional activation of the rat liver malic enzyme gene by dehydroepiandrosterone.

Dehydroepiandrosterone (DHEA), a naturally occurring steroid secreted from the adrenal, has been reported to decrease the body weight gain in rodents without suppressing food intake and to stimulate malic enzyme activity in liver (Tepperman, H. M., de la Garza, S. A., and Tepperman, J. (1968) Am. J. Physiol. 214, 1126-1132). Herrin, we demonstrate that DHEA induces hepatic malic enzyme activity by increasing the rate of transcription of the malic enzyme gene. This transcriptional activation of the malic enzyme gene is dose dependent, i.e. the treatment of euthyroid male rats with daily doses of 17.5 and 35 mg of DHEA/100 g of body weight for 7 days elevated the rate of malic enzyme gene transcription in liver above the basal levels 4-5- and 8-9-fold, respectively. The levels of nuclear malic enzyme RNA, cytoplasmic malic enzyme mRNA, and enzyme activity were increased correspondingly. Malic enzyme stimulation by DHEA was liver specific, i.e. malic enzyme activity in brain, heart, kidney, and testis was unchanged. Thyroid hormone is required for the induction of hepatic malic enzyme activity by DHEA since in hypothyroid animals, DHEA was without effect. However, stimulatory effects of thyroid hormone and DHEA on malic enzyme expression are additive in euthyroid rat livers at both levels of gene transcription and enzyme activity.

Animals↗
PubMed1989

Structural characterization of the rat malic enzyme gene.

We have identified and characterized lambda bacteriophage clones containing genomic DNA encoding rat malic enzyme [(S)-malate:NADP+ oxidoreductase (oxaloacetate-decarboxylating); EC 1.1.1.40]. The malic enzyme gene is unexpectedly large, spanning at least 95 kilobases. It is divided into 14 exons that range in size from 76 to 1513 base pairs. The sizes and boundaries of the exons were determined by Southern blotting and DNA sequencing. The sequences at the 5' and 3' ends of each intron conformed to the consensus sequence for mammalian introns. S1 nuclease and primer-extension assays showed that transcription of the malic enzyme gene initiates at multiple sites, the strongest one at position -31 relative to the ATG. "TATA and CCAAT box" homologies are not present in the proximal promoter region. Analysis of the 3' end of the gene showed that the utilization of alternate polyadenylylation signals in exon 14 results in two mRNAs with 3' untranslated regions of 345 and 1345 nucleotides, respectively.

Amino Acid Sequence↗
PubMed1988

Transcriptional activation and stabilization of malic enzyme mRNA precursor by thyroid hormone.

One of the responses to the administration of thyroid hormone is an increase in malic enzyme (EC 1.1.1.40) mRNA in rat liver. We have previously shown that 3,5,3'-triiodo-L-thyronine (T3) causes a 3-4-fold increase in the rate of transcription of the malic enzyme gene as determined by in vitro run-off assays with the cDNA probe following T3 treatment for 10 days (Dozin, B., Magnuson, M.A., and Nikodem, V. M. (1986) J. Biol. Chem. 261, 10290-10292). Since the level of cytoplasmic mRNA increases 10-15-fold, one or more additional mechanisms must be operative to produce the full effect. We have now analyzed the time course of the effect of T3 on the rate of transcription and the accumulation of malic enzyme RNA in the nucleus using malic enzyme cDNAs and intronic probes. There is an approximately 10-12-fold increase in the level of nuclear RNA accompanied by the same increase in cytoplasmic mRNA, showing a half-rise time of about 60 h. The 3-4-fold increase in the transcription rate occurred with a half-time of about 18 h. The relative values for either the increase in transcriptional activity or the increase in the level of malic enzyme RNA in the nucleus were identical irrespective of the probes used. As a control, we examined the effect of a high carbohydrate diet which is known to increase malic enzyme mRNA without affecting either transcriptional rate or nuclear RNA (Dozin, B., Rall, J. E., and Nikodem, V. M. (1986) Proc. Natl. Acad. Sci. U.S.A. 83, 4705-4709). As expected, no change in the level of malic enzyme RNA in the nucleus was found with the intronic probes. We conclude that T3 both activates transcription of the malic enzyme gene in rat liver and decreases the rate of degradation of pre-mRNA coding for malic enzyme.

Animals↗
PubMed1986

Tissue-specific control of rat malic enzyme activity and messenger RNA levels by a high carbohydrate diet.

In euthyroid rats fed a high carbohydrate fat-free diet for 10 days, the mass of cellular malic enzyme mRNA in liver is increased 7- to 8-fold above the basal level. Malic enzyme activity is stimulated to the same extent. This effect does not result from an increase either in the transcriptional activity of the malic enzyme gene, as determined by nuclear run-off transcription assay, or in the content of intranuclear malic enzyme RNA sequences. Mathematical modeling shows that this increase in cytoplasmic mRNA is compatible with retarded degradation of cytoplasmic mRNA. Regulation of malic enzyme by carbohydrates is liver-specific, since no response is observed in the following nonhepatic tissues: brain, heart, spleen, kidney, testis, and lung. Furthermore, the amplitude of the response in liver depends on the thyroid state of the animals, being lower (by a factor of approximately 4) in hypothyroidism and higher (12- to 15-fold) when normal animals are injected simultaneously with a daily dose of 15 micrograms of triiodothyronine per 100 g of body weight for 10 days. Since thyroid hormones regulate liver malic enzyme synthesis predominantly at the nuclear level and carbohydrates at the cytoplasmic level, the additive effect of triiodothyronine and a high carbohydrate diet on the activity of malic enzyme is readily explicable.

Animals↗
PubMed1983

The effects of thyroid hormone on in vitro phosphorylation, acetylation, and ADP ribosylation of rat liver nuclear proteins.

The effect of thyroid hormone on acetylation, phosphorylation and ADP ribosylation of rat liver nucleoproteins was studied by incubating intact nuclei with labeled precursors. Acetylation, which occurred in histones and low molecular weight proteins (less than 30,000), was depressed in nuclei from thyroidectomized animals. The administration of L-3,5,3'-triiodothyronine (T3) increased acetate incorporation to 50% over control levels. Incorporation of labeled phosphate from ATP into most proteins was decreased in nuclei from thyroidectomized animals and increased by the administration of T3. The greatest increase produced by T3 (to 140% of control values) was seen in proteins of molecular weight greater than 68,000. Nuclei from thyroidectomized animals incorporated less ADP ribose in most proteins. Both high molecular weight proteins (greater than 68,000) and low molecular weight proteins (less than 30,000) showed a further decrease in ADP ribose incorporation in nuclei from thyroidectomized rats given T3. However, a few proteins of the middle molecular weight class showed increased ADP ribose incorporation subsequent to the injection of T3. It is suggested that a generalized increase in protein synthetic rates previously noted to be caused by T3 is accompanied by increased acetylation and phosphorylation of histones and other proteins. These changes could accelerate transcription of already active genes.

Acetylation↗
PubMed1981

Thyroglobulin interactions with thyroid membranes. Relationship between receptor recognition of N-acetylglucosamine residues and the iodine content of thyroglobulin preparations.

Bovine thyroglobulin has been subjected to sequential glycohydrolase treatment in order to define further the components of the carbohydrate chain which are important in binding of the glycoprotein to bovine thyroid membranes. Preparations of asialoagalactothyroglobulin exhibit the best binding, suggesting that exposed N-acetylglucosamine residues on the B carbohydrate chain of thyroglobulin play an important role in the interaction of thyroglobulin with the thyroid membranes. Enhanced binding of asialoagalactothyroglobulin to microsomal, lysosomal, and Golgi membranes, as well as to thyroid cells in culture, was also observed. Isopycnic rubidium chloride gradient centrifugation, a procedure used in the isolation of thyroglobulin molecules with a low iodine content, also isolates thyroglobulin molecules with a low sialic acid content and with an increased ability to interact with wheat germ agglutinin, a lectin which recognizes exposed N-acetylglucosamine residues. The studies further indicate that there is a correlation between iodine content, exposed N-acetylglucosamine residues, and the binding of thyroglobulin to thyroid membranes.

Acetylglucosamine↗
PubMed1980

Affinity labeling of rat liver thyroid hormone nuclear receptor.

The thyroid hormone receptor from rat liver nuclei has been covalently labeled with the N-bromoacetyl derivatives of L-thyroxine (T4) and 3,3',5-triiodo-L-thyronine (T3). Displacement binding studies showed that, in the presence of 100-fold molar excess of unlabeled N-bromoacetyl-T3 or T4, binding of [125I]T3 or [125I]T4 was nearly totally inhibited. Heat inactivation of the receptor (55 degrees C for 15 min) resulted in parallel losses in the binding of T3 (95%) and N-bromoacetyl-T3 (93%). These results indicated that T3 and T4 and their bromoacetyl derivatives compete for the same binding site. The nuclear receptor showed identical behavior in high-pressure liquid chromatography (HPLC) whether bound to T3 or T4 or covalently labeled with their bromoacetyl derivatives. HPLC provided a single-step 100-fold purification of the nuclear receptor. Na-DodSO4 gel electrophoresis of the nuclear receptor labeled with N-bromoacetyl derivatives of [125I]T3 or [125I]T4 showed one major radioactive component with a molecular weight of 56,000. Furthermore, in the absence of denaturant, the nuclear receptor either bound to [125I]T3 or covalently labeled with N-bromoacetyl-[125I]T3 showed identical mobility. These results suggested that the nuclear receptor is a single polypeptide chain and binds either T3 or T4. Nuclear receptors covalently linked with N-bromoacetyl derivatives of [125I]T3 or [125I]T4 may be useful as a marker for the preparative purification of receptor.

Affinity Labels↗
PubMed1979

Thyroglobulin interactions with thyroid plasma membranes. The existence of specific receptors and their potential role.

Thyroglobulin binds to isolated thyroid plasma membrane preparations. Binding is pH- and temperature-dependent with 10-fold better binding at pH 5.0 and 37 degrees C than at 0 degrees C and pH 6.0 through pH 7.5. Binding is, however, maximal in 90 min at all pH values and temperatures examined. Although salts can inhibit or enhance thyroglobulin binding depending on the temperature or pH, conditions approaching those of the physiological state are not inhibitory; physiological conditions do inhibit thyrotropin binding to the same membrane preparations. 125I-Labeled thyroglobulin binding is poorly reversed by unlabeled thyroglobulin at all pH values and temperatures studied; excess unlabeled thyroglobulin can, however, readily prevent binding. At pH values greater than 6.0 and at 0 degrees C, the iodine content of thyroglobulin can affect binding, and the 27 S thyroid iodoprotein is relatively ineffective in preventing the binding of the 19 S species. At pH 5.0 and 37 degrees C, there is no difference in binding of highly and less iodinated thyroglobulin, and the 27 S thyroglobulin iodoprotein is effective in preventing 19 S thyroglobulin binding. The complex nature of these results is interpreted in the light of additional data which show (i) that the thyroid membrane recognizes asialothyroglobulin and (ii) that at pH 5.0 and 37 degrees C a membrane-associated neuraminidase is activated which removes sialic acid from thyroglobulin. Vibrio cholerae neuraminidase can substitute for the endogenous neuraminidase. The receptor on thyroid membranes for asialothyroglobulin is similar to the asialoglycoprotein receptor on liver membranes (Morell, A.G., Gregoriadis, G., Scheinberg, I.H., Hickman, J., and Ashwell, G. (1971) J. Biol. Chem. 246, 1461-1467) in that sialic acid on the receptor is critical for receptor expression. It is distinct from the liver asialoglycoprotein receptor in its binding specificity and in its sensitivity to different bacterial and mammalian neuraminidase preparations. Relationships between thyroglobulin and thyrotropin receptors on thyroid membranes are explored, and the functional role of the thyroglobulin receptor is discussed.

Animals↗
PubMed1978

Analysis of hog thyroglobulin. Identification of galactosamine and absence of lysinoalanine, a potential product of tyrosine coupling.

A small peak in the amino acid analysis of hog thyroglobulin was observed in the region reported for lysinoalanine and galactosamine. Since galactosamine had been previously reported absent in hog thyroglobulin, the possibility that this peak was lysinoalanine, a potential product of the coupling of two iodotyrosines, was investigated. Tests, however, showed that the material was galactosamine and that hog thyroglobulin contains no significant amount of lysinoalanine. Approximately 5 moles of galactosamine were found per mole of thyroglobulin.

Animals↗
PubMed1975

Relationship between iodination and the polypeptide chain composition of thyroglobulin.

Thyroglobulin was isolated from thyroid glands of normal guinea pigs and from animals treated with thiouracil. These preparations were fractionated by isopyknic centrifugation in RbCl into proteins of varying iodine content. When the disulfide bonds of these protein fractions were reduced and analyzed by polyacrylamide gel electrophoresis in Na dodecyl-SO4, t hree species were observed with molecular weights of 295,000 (A), 210,000 (B), and 110,000 (C). Species A comprised 80% of the protein in thyroglobulin of 0.04% iodine and 13% in thyroglobulin of 0.68% iodine content. Species C showed the opposite relationship, comprising 10% of the low and 70% of the high iodine thyroglobulin. Species B was relatively independent of the iodine content and represented approximately 20% of the protein. Iodine analysis of these proteins showed species A to be lowest and species C highest. It appears that the subunit composition of thyroglobulin depends on the degree of iodination and that species A should be the only one present in the absence of iodination.

Animals↗
PubMed1975

Elementary chain composition of guinea pig thyroglobulin.

Thyroglobulin obtained from guinea pigs was examined by Na dodecyl-SO4-polyacrylamide gel electrophoresis after reduction and alkylation. In contrast to thyroglobulin from other mammalian sources, only three groups of polypeptide chains accounted for 95% or more of the protein. Determinations of the molecular weights of these purified proteins by equilibrium centrifugation in 6 M guanidine HCl gave values of 295,000 (species A), 210,000 (species B), and 110,000 (species C). Molecular weights determined by gel filtration in 6 M guanidine HCl gave similar results. Due to the large size of the polypeptides, satisfactory molecular weights could not be obtained from Na dodecyl-SO4-polyacrylamide gel electrophoresis. Amino acid analysis of the three species was similar to that of whole thyroglobulin. Only slightly higher level of lysine and histidine and a lower level of glutamic acid were seen in species C. The iodine contents were found to range from 0.07 to 0.12 to 0.20% for species A, B, and C, respectively.

Amino Acids↗
PubMed1975

Thyroid nodularity in children.

Of 5,179 school children surveyed in Utah, Nevada, and Arizona for thyroid abnormalities because of possible exposure to radiation from fallout, nodularity of the thyroid was found in 98 (1.8%). In 34, the nodularity represented lobulation associated with adolescent goiter, and in 31, thyroiditis. Two malignant neoplasms were found. In a normal childhood population in which nodularity is incidentally discovered on physical examination, the risk of nodularity being malignant is approximately 2%. Factors that favor exploration of thyroid nodules in children are discreteness, growth of the mass, singleness, and absence of other thyroid disease.

Adenoma↗
PubMed1975

Occurrence and natural history of chronic lymphocytic thyroiditis in childhood.

In a six-year survey of 5,179 school children in Arizona, Utah, and Nevada 62 cases of chronic lymphocytic thyroiditis were identified giving a prevalence of 1.2%. Thyroids were enlarged in 85%, firm in 60%, and had an irregular or lobulated surface in 75%. Antibodies to thyroglobulin were demonstrable in the serum at some time during the course of the disease in 76% by the tanned red blood cell technique and in 93% by radioimmunoassay. Serum TSH concentrations were elevated in seven of 15 subjects. Many of the cases were early or mild thyroiditis and, in most instances, subjects were asymptomatic and considered clinically euthyroid. Two subjects were hypothyroid, and two appeared clinically hyperthyroid. Spontaneous resolution of thyroiditis occurred in 15 of 32 individuals who received no treatment. Resolution occurred in 14 of 30 children treated with thyroid hormone supplement. The results suggest that lymphocytic thyroiditis in children may be present without symptoms and in many is a self-limiting disorder from which complete recovery occurs spontaneously.

Adolescent↗