Sulfonylurea binding to a low-affinity site inhibits the Na/K-ATPase and the KATP channel in insulin-secreting cells.

We have used hamster insulinoma tumor (HIT) cells, an insulin-secreting tumor cell line, to investigate modulation of the Na/K-ATPase and of the ATP-sensitive K channel (K(ATP)) by the sulfonylurea glyburide. Membrane proteins from cells cultured in RPMI with 11 mM glucose have at least two glyburide receptor populations, as evidenced by high and low binding affinity constants, (K(d) = 0.96 and 91 nM, respectively).

A novel strategy for the investigation of clonality in precancerous disease states and early stages of tumor progression.

A novel strategy for clonality determination from only 100 cells using the polymerase chain reaction in amplifying a 511 bp region located within the first intron of the human hypoxanthine phosphoribosyl transferase (HPRT) gene has been devised. The strategy rests on several observations: that this region in females contains two HpaII/MspI sites whose methylation remains both obligate with X chromosome inactivation and independent of tumor progression; and that this region contains single base allelic polymorphisms in 5-10% of females which can be detected by denaturing gradient gel electrophoresis (DGGE) on the PCR product. In polymorphic individuals, multiple bands (homo- and heteroduplexes) indicate multiclonality, single bands indicate monoclonality, and their comparative migrations indicate clonal identity/non-identity.

Impairment of hypothalamic-pituitary-thyroid function in rats treated with human recombinant tumor necrosis factor-alpha (cachectin).

Tumor necrosis factor-alpha (TNF; cachectin), a peptide secreted from stimulated macrophages, mediates some of the metabolic derangements in inflammatory and neoplastic disorders. To determine whether TNF is responsible for the changes in hypothalamic-pituitary-thyroid (HPT) function in nonthyroid illnesses, we administered synthetic human TNF to male Sprague-Dawley rats. The rats were given TNF or saline (control; both pair fed and nonpair fed) iv (six to eight per group).

Thyroid hormone 5'-deiodinase activity, nuclear binding, and effects on mitogenesis in UMR-106 osteoblastic osteosarcoma cells.

The hyperthyroid state in vivo is associated with an increase in osteoblast number and activity, suggesting that thyroid hormone may stimulate osteoblast replication and function. We therefore examined the effects of T3 (16-1170 pM) on replication rate as assessed by cell counts in UMR-106 osteoblastic osteosarcoma cells cultured for 5-10 days in medium supplemented with 10% hormone-stripped fetal calf serum (FCS). Despite the virtual absence of thyroid hormone in the control medium (total T3 concentration, 0.

Triac reduces serum TSH without decreasing alpha and beta TSH messenger RNAs.

Triac, 3,5,3'-triiodothyroacetic acid, was administered at doses of 1, 3, 9 or 30 micrograms/100 g body weight to hypothyroid rats to determine its effects on TSH secretion and pituitary mRNA content. Triac caused a dose-dependent decrease in serum TSH 6 h after injection. Pituitary content of mRNA subunits either remained at hypothyroid levels or increased at 6 h.

Hormonal control of thyrotropin and growth hormone secretion in a human thyrotrope pituitary adenoma studied in vitro.

Pituitary thyrotrope tumours are a rare cause of hyperthyroidism. Prior in vitro studies of these tumours have revealed various patterns of differentiation and secretory activity. We have characterized the histological, biochemical, molecular and physiological features of a thyrotrope adenoma in order to define its origin and autonomy.

Human chorionic gonadotropin stimulates iodide uptake, adenylate cyclase, and deoxyribonucleic acid synthesis in cultured rat thyroid cells.

hCG stimulates thyroid function, but it has been suggested that it is impurities in commercial hCG preparations or a variant of hCG that are responsible for the thyrotropic activity. In this study, we tested the thyrotropic activity of purified and commercial hCG and compared its action with that of bovine TSH (bTSH) in cultured rat FRTL-5 cells in regard to stimulation of iodide uptake, activation of adenylate cyclase, and synthesis of DNA. Iodide uptake was measured after incubation of the cells for 48-72 h with the test hormones, followed by a 40-min incubation with 0.

Triiodothyronine inhibits phorbol ester-induced thyrotropin release from elutriated bovine thyrotrophs.

The inhibitory effect of T3 on TSH release was studied on a population of thyrotroph-enriched cells prepared from bovine pituitary glands by centrifugal elutriation. The cells (2.0 X 10(5)/ml) were cultured for 2 days and then exposed to TRH, phorbol-12 myristate-13 acetate (PMA), or calcium ionophore (A23187) with or without 100 nM T3 for two different preincubation periods, 3 h and 24 h.

Hypothalamic secretion of thyrotropin releasing hormone declines in aging rats.

Young and aged male rats were used in experiments to investigate a possible decline in hypothalamic secretion of thyrotropin releasing hormone (TRH) to the anterior pituitary of aging mammals. We observed a 66% decrease in basal TRH release by incubated rat hypothalami with aging. Thyroid hormone-responsive hepatic alpha-glycerophosphate dehydrogenase (GPD) and malic enzyme (ME) levels in aged rats did not differ from 5-month-old controls in spite of a significant fall in serum thyroxine (T4) levels with aging.

Influence of thyroidal status on pituitary content of thyrotropin beta- and alpha-subunit, growth hormone, and prolactin messenger ribonucleic acids.

Thyroidectomized rats were used to study the effects of a single injection of T3 on pituitary mRNA synthesis and hormone secretion. T3 was injected ip at doses of 0, 0.2, 1, or 5 micrograms/100 g body weight, and and animals were killed 24 h later.

Differential expression of thyrotropin hormone genes by GH3 cells and the normal rat pituitary.

RNAs from GH3 cells, a rat clonal cell line, and anterior pituitaries of normal rats have been isolated and assayed for the presence of transcripts coding for the alpha- and beta-subunits of thyrotropin hormone (TSH) by hybridization to their respective cDNAs. Northern analysis indicated that GH3 cells lack both TSH transcripts, and that normal anterior pituitary cells contain mRNA for both the alpha- and beta-subunits approximating 800 and 700 nucleotides, respectively. An examination of the DNAs from GH3 cells and normal anterior pituitary tissue revealed no organizational difference when the restriction digests were subjected to Southern analysis.

Immunoglobulin heavy-chain enhancer requires one or more tissue-specific factors.

Enhancer sequences are regulatory regions that greatly increase transcription of certain eukaryotic genes. An immunoglobulin heavy-chain variable gene segment is moved from a region lacking enhancer activity to a position adjacent to the known heavy-chain enhancer early in B-cell maturation. In lymphoid cells, the heavy-chain and SV40 enhancers bind a common factor essential for enhancer function.

The effect of estrogen on the concentration of ovalbumin gene sequence in the 2 M NaCl residual fraction of oviduct chromatin.

Oviduct chromatin was isolated from both estrogenized and non-estrogenized hens. Extraction of the chromatin with 2 M NaCl removed a majority of the proteins, and the resulting DNA was then separated into two components: (1) a major fraction which was virtually protein-free; and (2) a minor fraction which was complexed with proteins. It was found that the DNA fraction that is complexed with proteins contained ovalbumin gene sequences and that the concentration of these sequences could be boosted by estrogen-treatment.

Simple isolation of DNA hydrophobically complexed with presumed gene regulatory proteins (M3).

Chromatin from chicken reticulocytes and mouse Ehrlich ascites tumor cells has been extracted with 2 M NaCl, leaving a portion of the DNA still complexed with a fraction of nonhistones (designated M3, since it can be dissociated from DNA in solutions of 3 M NaCl containing 5 M urea). The DNA complexed with M3, separated from the bulk DNA by centrifugation, was found to contain sequences poorly represented in bulk DNA. Specifically we found that DNA--M3 complexes isolated from chicken reticulocyte chromatin were enriched in globin gene sequences by 20-fold relative to unfractionated DNA and by over 1000-fold relative to DNA rendered free of protein following the extraction of chromatin with 2 M NaCl.

Induction of cleft palates by triamcinolone acetonide: re-examination of the problem.

We have examined the uptake of 3H-triamcinolone acetonide (3H-TAC) into various maternal and embryonic tissues of A/J mice. We report that the fetal tissues were able to retain TAC for long periods, although the concentrations of TAC in the maternal tissues were significantly lower. We have also examined the binding of 3H-TAC both to nuclei and cytosols from maxillary processes.