Effects of inorganic iodide, epidermal growth factor and phorbol ester on hormone synthesis by porcine thyroid follicles cultured in suspension.

Porcine thyroid follicles cultured in suspension for 96 h synthesized and secreted thyroid hormones in the presence of thyrotropin (TSH). The secretion of newly synthesized hormones was assessed by determining the contents of thyroxine (T4) and triiodothyronine (T3) in the media and by paperchromatographic analysis of 125I-labelled hormones in the media where the follicles were cultured in the presence and absence of inhibitors of hormone synthesis. The hormone synthesis and secretion was modified by exogenously added NaI (0.1-100 microM). The maximal response was obtained at 1 microM. Thyroid peroxidase (TPO) activity in the cultured follicles with TSH for 96 h was dose-dependently inhibited by NaI. One hundred microM of NaI completely inhibited TSH-induced TPO activity. Moreover, both epidermal growth factor (EGF: 10(-9) and 10(-8) M) and phorbol 12-myristate 13-acetate (PMA: 10(-8) and 10(-7) M) inhibited de novo hormone synthesis. An induction of TPO activity by TSH was also inhibited by either agent. These data provide direct evidences that thyroid hormone synthesis is regulated by NaI as well as TSH at least in part via regulation of TPO activity and also that both EGF and PMA are inhibitory on thyroid hormone formation.     

Identification of a novel amino acid, o-bromo-L-phenylalanine, in egg-associated peptides that activate spermatozoa

Eight sperm-activating peptides containing a novel amino acid were isolated from the egg jelly of the sea urchin Tripneustes gratilla. Accurate mass measurement of the peptide in FAB mass spectrometry showed that the mass of the novel amino acid residue was 224.978. On the basis of the isotopic ion distribution and the degree of unsaturation, the mass value indicated that the elemental composition of the amino acid residue was C9H8O1N1Br1, suggesting that the novel amino acid was bromophenylalanine. Proton NMR spectroscopy, amino acid analysis, and RP-HPLC with three synthetic isomers of bromophenylalanine demonstrated that o-bromophenylalanine was the novel amino acid. Derivatization of the amino acid with Marfey's reagent, (1-fluoro-2,4-dinitrophen-5-yl)-L-alanine amide (FDAA), further indicated that the amino acid was the L-isomer. In other sperm-activating peptides isolated from the egg jelly of the sea urchin, both m- and p-bromophenylalanines were discovered. The presence of m-bromophenylalanine has not been previously reported in natural products, while p-bromophenylalanine is found in theonellamide F, an antifungal bicyclic peptide from a marine sponge.     

Preparation of a fluorescent derivative of benzoylecgonine, and preliminary studies of its application to the analysis of urine

A sensitive high-performance liquid chromatographic method using 3-bromomethyl-6,7-dimethoxy-1-methyl-2(1H)-quinoxalinone (Br-DMEQ) as a fluorescent labeling reagent is described for the determination of benzoylecgonine (BE) and ecgonine (EC). The Br-DMEQ derivatives of BE and EC were separated on a C₁₈ column and detected at 455 nm with excitation at 370 nm. The detection limits of the proposed method were 18.7 fmol for BE and 12.5 pmol for EC at a signal-to-noise ratio of 3. Relative standard deviations of five replicate measurements were 1.94% (10 pmol) and 2.98% (50 pmol) for BE and 6.3% (250 pmol) and 5.62% (1.25 pmol) for EC. This method was applied to the determination of BE in human urine. BE was extracted from urine by solvent extraction with chloroform—isopropyl alcohol (9:1, v/v) solution. Levels of 2.5 · 10⁻⁸ M BE in urine (25 pmol/ml) could be determined.     

Genetic and behavioral analysis of flagellar switch mutants of Salmonella typhimurium.

At the interface between the sensory transduction system and the flagellar motor system of Salmonella typhimurium, the switch complex plays an important role in both sensory transduction and energy transduction. To examine the function of the switch complex, we isolated from 10 cheY mutants 500 pseudorevertants with a suppressor mutation in one of the three genes (fliG, fliM, and fliN) encoding the switch complex. Detailed mapping revealed that these suppressor mutations were localized to several segments of each switch gene, suggesting localization of functional sites on the switch complex. These switch mutations were introduced into the wild-type background and into a chemotaxis deletion background. Behavior of the pseudorevertants and their derivatives (1,500 strains in all) was observed by light microscopy. In the chemotaxis deletion background, about 70% of the switch mutants showed smooth swimming and the rest showed more or less tumbly swimming. There was some correlation between the mutational sites and the swimming patterns in the chemotaxis deletion background, suggesting that there is segregation of functional sites on the switch complex. The interaction of the switch complex with the chemotaxis protein, CheY, and the stochastic nature of switching in the absence of CheY are discussed.     

The blasticidin S resistance gene (bsr) selectable in a single copy state in the Bacillus subtilis chromosome

The blasticidin S resistance gene (bsr), originally isolated from Bacillus cereus, was studied in Bacillus subtilis. It was found that a 617 bp fragment including the intact bsr gene and its 5' flanking region could confer BS resistance on B. subtilis when integrated in its chromosome, even in a single copy state. The construction of a bsr gene cassette and its practical application as a novel selection marker for B. subtilis are reported.     

Hemolysis of human erythrocytes under hydrostatic pressure is suppressed by cross-linking of membrane proteins

The effects of cross-linking of membrane proteins on hemolysis of human erythrocytes under high pressure (2.0 kbar) were examined. The membrane proteins were cross-linked by oxidation of their SH-groups with diamide (0.05-0.5 mM) under different pressures (1-1,000 bar) at which no hemolysis occurs. As the pressure during diamide treatment was raised, the degree of hemolysis under 2.0 kbar and the quantity of cytoskeletal proteins extracted in a low ionic strength medium were gradually decreased. However, both values were increased by reduction with dithiothreitol. From the determination of membrane SH-groups, it was found that cross-linking of membrane proteins by diamide was accelerated under pressure. Only in erythrocytes treated with diamide under pressure were parts of spectrin and ankyrin, in addition to band 3 and band 4.2 proteins, extracted by using Triton X-100. One- and two-dimensional SDS-PAGE of membrane proteins showed that cross-linking of the membrane with cytoskeletal meshwork through linking proteins, in addition to that of membrane proteins themselves, was formed only in the diamide treatment under pressure. These results indicate that pressure-induced hemolysis is greatly suppressed by the supramolecular-weight polymers formed among membrane proteins, and that the high pressure technique is useful for cross-linking membrane proteins with diamide.     

Parathyroid hormone-related protein is a possible autocrine growth inhibitor for lymphocytes

Adult T-cell leukemia (ATL)-related cells have the ability to produce a newly-isolated calcium-regulating protein, parathyroid hormone-related protein (PTHrP). The present study revealed that lectin-stimulated normal lymphocytes produce immunoreactive (IR)-PTHrP. When the T-cell-enriched fraction was purified from normal lymphocytes and then treated with lectin, a similar amount of IR-PTHrP was detected, suggesting that IR-PTHrP is an actual product of T-lymphocytes. A biologically active fragment of PTHrP, PTHrP(1-34), suppressed DNA synthesis in lectin-stimulated lymphocytes at concentrations greater than 50 pg/mL; the same concentration range of IR-PTHrP detected in the cultured media of lectin-stimulated lymphocytes. Therefore, it is reasonable to postulate that PTHrP is a cytokine inhibiting the cellular growth of normal lymphocytes.     

Ca2(+)-independent secretory mechanism of thyrotropin-releasing hormone (TRH) involves protein kinase C in rat pituitary cells

Thyrotropin-releasing hormone (TRH) stimulates biphasic prolactin (PRL) secretion from rat pituitary GH3 cells. The pretreatment of cells with EGTA (100 microM) plus arachidonic acid (15 microM), a condition which decreased TRH-responsive intracellular Ca2+ pools, eliminated the activity of TRH on burst PRL secretion (2 min) but did not alter that on sustained PRL secretion (30 min). However, the treatment of cells with EGTA, arachidonic acid and H-7 (300 microM), a potent inhibitor of protein kinase C (PKC), almost completely suppressed the activity of TRH for sustained PRL secretion. In cells down-modulated for PKC, TRH abolished this Ca2(+)-independent sustained PRL secretion. These results suggest that TRH acts through a separate, Ca2(+)-independent secretory mechanism, besides by modulating the Ca2(+)-dependent mechanism and that PKC is involved in this Ca2(+)-independent secretory pathway.