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Biomedical subjects

B D Weintraub

Publications and source records attributed to B D Weintraub.

At least 19 recordsLinked to original sources
PubMed1979

mRNA-directed biosynthesis of alpha subunit of thyrotropin: translation in cell-free and whole-cell systems.

mRNA from mouse thyrotropic pituitary tumors was translated in frog oocytes (a whole-cell system) and in wheat germ extract and reticulocyte lysate (cell-free systems) in the presence of [(35)S]methionine. Synthesized peptides related to thyrotropin were identified in the three systems by immunoprecipitation with subunit-specific antisera developed against the alpha subunit of ovine lutropin (luteinizing hormone) and the beta subunit of bovine thyrotropin. In wheat germ extract and reticulocyte lysate, a single immunoprecipitable form of the alpha subunit of thyrotropin was synthesized with an apparent molecular weight of 14,000 by sodium dodecyl sulfate/polyacrylamide gel electrophoresis. In the frog oocyte, three forms of immunoprecipitable alpha subunit of thyrotropin were synthesized with apparent molecular weights of 20,000, 14,000, and 10,000. The 20,000 form is similar to unlabeled rat pituitary standard alpha subunit and (35)S-labeled mouse tumor alpha subunit in cell cultures (20,000-21,000); thus, it may represent a precursor-cleaved and glycosylated form. The 14,000 form synthesized in all three systems probably represents the pre-alpha subunit of thyrotropin; the 10,000 form, synthesized only in the frog oocyte, could be a proteolytically cleaved but unglycosylated form. Because only the alpha subunit of thyrotropin was identified and no larger molecular weight immunoprecipitable form of either subunit was detected in any of the translation systems, alpha and beta subunits of thyrotropin appear to be translated from separate mRNAs.

Animals↗
PubMed1979

Comparison of bovine and mouse pituitary glycoprotein hormone pre-alpha subunits synthesized in vitro.

Poly(A)-containing RNA isolated from bovine and mouse pituitaries and a mouse pituitary thyrotropic tumor was translated in a wheat germ cell-free biosynthetic system. A precursor of the glycoprotein hormone alpha subunit, "pre-alpha," was immunoprecipitated from the translation mixtures with antiserum against bovine luteinizing hormone (LH; lutropin) alpha. The specificity of the immunoprecipitation was shown by competition with authentic bovine LHalpha and lack of competition with bovine thyroid-stimulating hormone (TSH; thyrotropin) beta. Bovine and mouse pre-alpha subunits migrated identically in sodium dodecyl sulfate gradient polyacrylamide slab gels with an apparent molecular weight of about 17,000. Pre-alpha comprised 2-3% and 20-30% of the total proteins translated with pituitary and pituitary tumor mRNA, respectively. Microanalysis of amino acid sequence of the pre-alpha subunits containing various radiolabeled amino acids gave the following partial sequence for mouse tumor pre-alpha: [Formula: see text] Met was also found in positions 1, 14, and 17 in mouse pituitary pre-alpha but only in residue 1 of the bovine pituitary pre-alpha subunit. Leu was found in identical positions in bovine pituitary pre-alpha, with an additional Leu in position 17. Leu in the common positions (12, 15, 19, and 22) has also been found in human choriogonadotropin pre-alpha subunit [Birken, S., Fetherston, J., Desmond, J., Canfield, R. & Boime, I. (1978) Biochem. Biophys. Res. Commun. 85, 1247-1253]. The data demonstrate that pituitary as well as placental glycoprotein hormone alpha subunits are synthesized with an amino-terminal hydrophobic extension, in accord with the "signal hypothesis" for secreted proteins. Furthermore, the positions of the hydrophobic amino acid Leu have been strictly conserved in pre-alpha subunits from various species and in two different tissues, the pituitary and placenta.

Amino Acid Sequence↗
PubMed1979

Ultrastructural concomitants of sodium butyrate-enhanced ectopic production of chorionic gonadotropin and its alpha subunit human bronchogenic carcinoma (ChaGo) cells.

Sodium butyrate treatment of cultures of ChaGo (human lung cancer) cells resulted in increased production of human chorionic gonadotropin (hCG) and its alpha subunit (hCG-alpha) and induced a variety of morphologic changes. Elongation and flattening of cells were seen by light microscopy. Immunocytochemistry with antisera against hCG and against hCG-alpha showed an increase in cells containing stainable hCG-alpha. Scanning electron microscopy demonstrated enhanced adhesion of cells to glass cover slips, with elongation, flattening, and decreased cytoplasmic blebs. Ultrastructural changes were examined by transmission electron microscopy and evaluated quantitatively by an unbiased observer. Significant findings included increases in perinuclear tonofilaments, smooth endoplasmic reticulum vesicles, dense mitochondrial inclusions, and lipid granules, as well as decreases in intercellular desmosomes, free polyribosomes, mitochondrial dense granules, and Golgi complexes. The most notable change, a marked decrease in condensed chromatin clumps, may have reflected a butyrate-induced biochemical modification of chromatin leading to enhanced accessibility of certain genes for transcription.

Butyrates↗
PubMed1978

Sexual precocity in a male due to thoracic polyembryoma.

A 7-year-old boy with sexual precocity of recent onset was found to have elevated levels of chorionic gonadotropin, alpha fetoprotein, and testosterone. Removal of a retropleural, posterior mediastinal mass with an intraspinous epidural extension was followed by prompt declines in the plasma concentrations of the tumor markers and cessation of adolescent development. The neoplasm proved to be a polyembryoma, unusual in the multiplicity of its embryoid bodies and extra gonadal location. Following local irradiation and two years of systemic chemotherapy, the patient, now 13 years of age, has done well except for evidence of testicular tubular insufficiency.

Child↗
PubMed1978

Excess production of free alpha subunits by mouse pituitary thyrotropic tumor cells in vitro.

Primary cultures from three serially transplanted mouse pituitary thyrotropic tumors, Furth 97A, 97B, and 97C, and one newly generated tumor, NIH 101A, were shown to secrete free alpha subunits and a beta subunit (TSH-beta) in addition to intact TSH. The three glycopeptides were measured in specific, heterologous radioimmunoassays. Basal secretion of alpha subunit was found to be in excess in all four thyrotropic tumor cultures, ranging from 5.7- to 8.9-fold higher than that of intact TSH and 30- to 35-fold higher than that of free TSH-beta. In cultures from 97A, TRH (10(-7) M) stimulated the secretion of TSH, alpha subunit, and TSH-beta by 175-185% and (T4, 10(-5) M) inhibited TSH to 19%, alpha subunit to 68%, and TSH-beta to 58% of control. Secretion of TSH and its subunits in cultures from 97B was not consistently affected by TRH or T4. In cultures from 97C, TSH and alpha secretion was inhibited in a dose-dependent fashion by T3 from 2.5 x10(-9) to 1.6x10(-7) M. Gel chromatography of incubation media from tumor 97A revealed elution volumes of TSH and alpha similar to those of purified rat glycopeptides and confirmed the excess secretion of free alpha subunit. In contrast, the alpha to TSH ratios in media from cultures of pituitary cells from normal and thyroidectomized rats were 1.6 and 0.8, respectively. The total production of TSH and its subunits was measured in cultures from tumor 97A and confirmed that alpha subunit was synthesized excessively. The ratio of the plasma concentrations of alpha to TSH in tumor-bearing mice was 1.6 compared to 1.3 in thyroidectomized mice, and 0.36 in thyroidectomized rats. The alpha to TSH ratios in extracts of the corresponding thyrotropic tissues (tumor or pituitary) were 2.7, 1.7, and 0.40, respectively. These data are analogous to those reported in humans with thyrotropic and certain other pituitary tumors, and support hypothesis that the subunits of glycoprotein hormones are independently synthesized.

Animals↗
PubMed1978

Thyrotropin binding to cultured lymphocytes and thyroid cells.

The TSH-binding properties of human lymphocytes in continuous culture were studied and compared to those of bovine and human thyroid cells in primary culture. Both lymphocytes and thyroid cells had maximal TSH-binding capacity at pH 5.2. At pH 7.4, thyroid cells bound 15% but lymphocytes bound only 3% of the amount bound at pH 5.2. At 37 C, maximal binding of [125I]iodo-TSH to lymphocytes was reached within 60--90 min and maximal binding to thyroid cells was reached within 15--20 min. TSH binding to lymphocytes was salt sensitive, being inhibited to 50% by 0.2 mM MgCl and 0.4 mM CaCl2 and by 20 mM Kl, KCl, and NaCl. The saturable binding of bovine TSH (bTSH) to thyroid cells at pHs 5.2 and 7.4 was above 90% of the total binding. Saturable binding of bovine TSH (bTSH) to thyroid cells at pHs 5.2 and 7.4 was above 90% of the total binding. Saturable binding to lymphocytes at pH 5.2 was also above 90%, but at pH 7.4 was 75% of total. At pH 5.2, both cell types displayed identical displacement curves of [125I]iodo-bTSH by unlabeled bTSH. Pure hCG, human placental lactogen, human GH, and insulin cross-reacted to less than 1% with [125I]iodo-bTSH binding to lymphocytes at pH 5.2, whereas a crude preparation of hCG and human FSH plus human LH showed a strong cross-reaction. Nonhormone glycoproteins, including mucin, normal human gamma-globulin, and bovine thyroglobulin showed intermediate cross-reactivity. At pH 7.4, the cross-reactivity of normal human gamma-globulin, bovine thyroglobulin, and pure hCG with bTSH binding to both lymphocytes and thyroid cells was below 1%. The TSH-binding properties of lymphocytes and thyroid cells show many similarities but differ in kinetics and the relative binding capacity at neutral pH. Although the physiological significance of these differences is not yet clear, cultured cells provide a convenient system for studies of TSH-receptor interaction.

Animals↗
PubMed1978

Effect of intravenous pyridoxine on plasma prolactin in hyperprolactinemic subjects.

Intravenous pyridoxine has been reported to lower plasma PRL in normal subjects and in patients with the amenorrhea-galactorrhea syndrome. We tested the effect of pyridoxine (300-mg iv bolus) on plasma PRL in nine patients with hyperprolactinemia due to a variety of causes. There was no effect of pyridoxine on elevated plasma PRL in any of the nine hyperprolactinemic subjects. The potential utility of pyridoxine in the long term treatment of the galactorhea-amenorrhea syndrome will require further study.

Female↗
PubMed1978

Large molecular weight TSH-beta: the sole immunoactive form of TSH-beta in certain human sera.

The beta subunit of TSH (TSH-beta) usually cannot be detected (less than 0.2 ng/ml) in the serum of normal individuals, whereas patients with primary hypothyroidism exhibit elevated TSH-beta levels (0.2-9.3 ng/ml), which increase further after the administration of TRH. Two patients were found to have large TSH-beta as the only form of serum TSH-beta immunoactivity. Patient A was a euthyroid woman with a goiter; TSH and alpha subunit levels were normal (1 microU/ml and 0.6 ng/ml, respectively); TSH-beta was elevated (8-24 ng/ml). Patient B was a woman with borderline hypothyroidism, an elevated serum TSH level (19 microunits/ml), a normal serum alpha level (2.4 ng/ml), and an elevated serum TSH-beta level (1.8-3.6 ng/ml). Dilutions of both patients' sera demonstrated nonparallelism of their serum TSH-beta to standard TSH-beta. The elevated serum TSH-beta levels did not increase after TRH, although TSH and alpha subunit increased appropriately. After the administration of dexamethasone or T4 to patient B, serum TSH-beta did not decrease, although TSH and alpha decreased. Gel chromatography and rechromatography of the patients' sera on a Sephadex G-100 column showed elution of all TSH-beta immunoactivity in or near the void volume (Vo; greater than 150,000 mol wt), whereas sera of hypothyroid patients demonstrated less than 7% of TSH-beta immunoactivity in the Vo. By chromatography on a Sephadex G-200 column, the TSH-beta immunoactivity had a 160,000 mol wt in patient A and 200,000 mol wt in patient B. Incubation of labeled or unlabeled TSH-beta with serum or gamma-globulin fractions from both patients resulted in no significant increase in the binding of TSH-beta to serum components, as determined by both gel chromatography and precipitation with antihuman gamma-globulin. Large TSH-beta was stable after incubation with 6 M guanidine. Ribonuclease failed to affect the large TSH-beta. Inter-chain disulfide bonding was not demonstrated in large TSH-beta after treatment with three different reducing agents (mercaptoethanol, sodium sulfite, and dithioerythritol). Treatment with trypsin did not convert the large TSH-beta immunoactivity to standard TSH-beta. These experiments demonstrated that the large TSH-beta immunoactivity was not caused by binding of TSH-beta to an immunoglobulin or other serum protein or by aggregation of TSH-beta molecules. The significance of these apparently covalently bonded large forms of TSH-beta immunoactivity is not yet known; the presence of small amounts of a large molecular weight form in the serum of hypothyroid patients and normal pituitary extracts raises the possibility that they may be components of normal TSH biosynthesis or represent posttranslational modifications.

Adult↗
PubMed1978

Ectopic hormones.

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Adrenocorticotropic Hormone↗
PubMed1978

Influence of chemotherapeutic agents on chorionic gonadotropin-alpha subunit secretion in a human lung cancer cell line (ChaGo): discordance of cytotoxic and secretory effects.

Cells from cultures of ChaGo, a cell line of a human lung cancer that ectopically produces chorionic gonadotropin (hCG) and its alpha subunit (hCG-alpha) were exposed to five different cancer chemotherapeutic agents in vitro in separate experiments (one drug/expt). The control doubling time averaged 4 days, with molar biphasic secretory rates of hCG-alpha ranging from a high of 58.1 to a low of 10.5 pmoles/10(6) cells/24 hours. Drug concentrations were chosen to induce a 30-60% inhibition of cell replication over a period of 8-10 days. Neither methotrexate nor vincristine demonstrated major effects on extracellular hCG-alpha production, but each agent moderately depressed cell number and each produced major inhibition of intracellular protein synthesis. Procarbazine inhibited marker production only in slight excess of inhibition of cell growth and cell protein. Actinomycin D and mechlorethamine, however, had profound effects on inhibition of hCG-alpha production in excess of cell growth. Our results indicated that cancer chemotherapeutic agents have specific and differing effects on cell growth and cell protein on the one hand and marker production on the other. These data suggested a mechanism for certain cases of discordance between hormone production and clinical status.

Antineoplastic Agents↗
PubMed1977

Ectopic production of chorionic gonadotropin and its subunits by islet-cell tumors. A specific marker for malignancy.

We measured human chorionic gonadotropin (hCG) and its subunits in 76 patients with islet-cell tumors. Seventeen of 27 patients with functioning islet-cell carcinomas had elevated plasma levels of hCG or one of its subunits (hCG-alpha and hCG-beta). Secretion was often discordant; the most frequent finding was an elevated level of hCG-alpha alone. In one patient responding to streptozocin, changes in hCG-alpha correlated with the clinical course. Studies of tumor extracts suggested that the markers observed in the circulation were being produced in the tumor itself. In contrast, none of the 43 patients with benign disease or the six patients with nonfunctioning malignant tumors had elevated levels of hCG, hCG-alpha or hCG-beta. These data show that hCG and its subunits are prevalent and specific markers for islet-cell carcinoma, and suggest that ectopic secretion results from malignant derepression of the genome rather than overproduction by an aberrant "cell rest."

Adenoma, Islet Cell↗