Whole-cell recording of neuroblastoma x glioma cells during downregulation of a major substrate, 80K/MARCKS,of protein kinase C

Summary Differentiated neuroblastoma cells exhibit both the delayed rectifier potassium current (I _K) and the M-current (I _M). The present study was designed to determine the roles of protein kinase C (PKC) and of the calmodulin-binding protein 80K/MARCKS, a prominent substrate for PKC and possible regulator of these currents. Neuroblastoma x glioma (NG108-15) hybrid cells transfected with m1 muscarinic receptors were grown with 1% fetal bovine serum (FBS) without the prostaglandin E₁ (PGE₁) and isobutylmethylxanthine (IBMX) usually added in preparation for electrophysiological studies. Under these conditions, the usual pleomorphism was largely abolished, leaving two populations of small cells with stellate and spherically symmetrical geometries. Whole-cell patch clamping indicated that the two cell types had identical electrophysiological properties, displaying: I _k, a small current through a T-like Ca²⁺ channel, and no M-current.Stimulation with carbachol shifted the distribution of cells to a more stellate morphology within 24 hr and later (after 48 hr) reduced the PKC substrate 80K/MARCKS by 22±7%. In contrast to the stimulation of I _k observed with cardiac cells, PKC activation produced only a small inhibition of I _k, which was independent of carbachol pretreatment. Thus, PKC and 80K/MARCKS can be dissociated from the regulation of I _k in neuroblastoma cells.Supported in part by research grants from the National Institutes of Health (DK-40145 and EY-08343) and from the U.K. Medical Research Council.We thank Dr. Peter J. Parker for his generous gift of PKC, and Yvonne Vallis for her skillful assistance with the cultures and harvesting of the NG108-15 transfected cells.     

Auto and transactivation of FGF expression: Potential mechanism for regulation of myogenic differentiation

Summary Fibroblast growth factors (FGFs) are potent inhibitors of myogenic differentiation. The recent observation that the endogenous expression of acidic and basic FGF by myogenic cells decreases coordinately with differentiation suggests a regulatory role for these growth factors in myogenesis. Inasmuch as other proteins known to influence myogenesis (e.g., MyoD1 and myogenin) activate their own expression as well as the expression of other members of their family, we hypothesized that the FGFs might be capable of similar autoregulation. We examined the effect of exogenously supplied FGF on the abundance of the mRNAs encoding acidic and basic FGF in Sol 8 myoblasts, and demonstrate that either acidic or basic FGF stimulate, through paracrine mechanisms, the accumulation of the mRNAs encoding both of these FGFs. Thus FGFs can auto- and transregulate their own expression in a manner analogous to that observed for the myogenic determination proteins. In addition, similar to that previously observed for MyoD1, both acidic and basic FGF suppress myogenin expression in myoblasts. These results suggest two mechanisms whereby endogenously produced FGFs participate in the maintenance of the undifferentiated state of myogenic cells. These data provide support for paracrine, and suggest potential autocrine, roles for FGFs in the regulation of myogenic differentiation.     

Sultans of Spin: Syrian Sacred Music on the World Stage

This article examines how the performance of a variety of Islamic music in transnational cultural circuits helps to promote the idea of a style of sacred music within the category of world music. Taking as an example the performance of the mawlawiyya, or "Whirling Dervish," music and dance by a Syrian–based ensemble, I show how the idea of an authentic local Syrian sacred music tradition requires its performance globally. I use the concept of the "world stage" to examine how musical performance practices that are represented as authentic local traditions obtain both their authenticity and their local specificity through their staging in global contexts. I further explore how such musical styles as sacred and Sufi emerge as naturalized categories in world music discourse, and how processes of differentiation and commodification reconfigure both the "local" and "global." [Keywords: world music, globalization, style, Syria, Islam]     

Inhibition of Salmonella typhimurium by the products of tartrate metabolism by a Veillonella species

The inhibition of the growth of Salmonella typhimurium by a Veillonella species grown on media supplemented with tartrate was examined. Growth of Salmonella typhimurium was not inhibited by the concentrations of products metabolized by Veillonella cultures on media supplemented with 0 or 50 mmol 1^-1 of tartrate, but was inhibited on media supplemented with 100 or 150 mmol 1^-1 of tartrate. Inhibition of Salm. typhimurium was correlated with the increased production of acetate and propionate from tartrate by the Veillonella species.     

Overexpression of MerT,the mercuric ion transport protein of transposon Tn501, and genetic selection of mercury hypersensitivity mutations

The small (116 amino acids) inner membrane protein MerT encoded by the transposon Tn501 has been overexpressed under the control of the bacteriophage T7 expression system. Random mutants of MerT were made and screened for loss of mercuric ion hypersensitivity. Several mutantmerT genes were selected and sequenced: Cys24Arg and Cys25Tyr mutations abolish mercury resistance, as do charge-substitution mutations in the first predicted transmembrane helix (Glyl4Arg, Glyl5Arg, Gly27Arg, Ala18Asp), and the termination mutations Trp66Ter and Cys82Ter.     

Inhibition by light of growth and Golgi-localized glucan synthetase in the maize mesocotyl

When dark-grown maize (Zea mays L.) seedlings were exposed to red light (R), Golgi-localized glucan synthetase activity in the mesocotyl began to decrease within 1 h, and fell by approx. 70% in 12 h. The response required at least 10^-2 mol m^-2 R and saturated at 100 mol m^-2. Far-red light (FR) alone inhibited glucan synthetase, and FR reversed the inhibition by R back to the level caused by FR alone. Density gradient fractionation indicated that of the major membrane markers only the Golgi-localized glucan-synthetase activity was affected by R. Golgi-localized latent inosine-diphosphatase activity was unaffected. The kinetics of the response, the photon fluence dependence, and the reversibility by FR all correlated with the inhibition by light of elongation of the mesocotyl, indicating that light inhibits growth and glucan synthetase activity by a similar mechanism.Abbreviations FR far-red light - GS glucan synthetase - IAA indole-3-acetic acid - R red light     

Use of in situ hybridization to investigate the regulation of hippocampal corticosteroid receptors by monoamines.

The hippocampus receives major noradrenergic and serotoninergic (5-HT) innervations which interact with corticosteroid-sensitive cells. However, the subregional localization of these actions and the corticosteroid receptor types involved have not been defined and current ligand binding techniques for estimating corticosteroid receptors are hampered by several methodological limitations. We have developed in situ hybridization histochemical techniques to allow specific and sensitive estimation of glucocorticoid (GR) and mineralocorticoid receptor (MR) mRNA expression in rat hippocampus. Investigation of the effects of 5,7-dihydroxytryptamine lesions of 5-HT neurons showed significantly reduced GR and MR mRNA expression in some hippocampal subregions. Both abnormal 5-HT neurotransmission and excessive corticosteroid secretion are associated with major affective disorders, particularly depression. The crucial interaction between these two systems may occur, at least in part, at the level of regulation of hippocampal corticosteroid receptor expression.