Glycosphingolipids in cultured lens epithelial cells from dog and rhesus monkey

Vertebrate lens tissues contain several species of acidic andneutral glycosphingolipids in relatively high amounts. However,the epithelia with capsule from dog and rhesus monkey lenseshad a simpler composition and lower content of glycosphingolipidsthan whole lenses. Gangliosides and neutral glycosphingolipidsin monolayer cultures of lens epithelial cells were also differentfrom those in whole lenses. Although -galactosyl (Gal1-3Ga1-R)or Lewis^x (Galß1-4[Fuc1-3]GlcNAc-R) epitopes werefound in glycosphingolipids from whole lenses, they were notdetected in those from monolayer cultures of dog and rhesusmonkey lens cells. In addition, significant changes in ganglio-seriesgangliosides were induced in monolayer cultures of both cells,where GM3 and GD3 were predominant. Immunofluorescence studyrevealed a characteristic distribution of cell surface gangliosidesin confluent monolayers. These findings suggest that glycosphingolipidsynthesis in lens epithelia is intrinsically different fromthat in cortical and nuclear fibres, and that the expressionof Lewis^x and -galactosyl epitopes in glycosphingolipids appearsto be associated with the differentiation of epithelial cellsto fibres. gangliosides glycosphingolipids lens epithelial cells Lewis^x rhesus monkey.     

Global bifurcation structure of a Bonhoeffer-van der Pol oscillator driven by periodic pulse trains

The Bonhoeffer-van der Pol (BVP) oscillator is a valuable dynamical system model of pacemaker neurons. Isochrons, phase transition curves (PTC), and two dimensional bifurcation diagrams served to analyze the neuron's response to periodic pulse stimuli. Responses are described and explained in terms of the nonlinear dynamical system theory. An important issue in the generation of spikes by pacemaker neurons is the existence of both slow and fast dynamics in the state point's trajectory in the phase plane. It is this feature in particular that makes the BVP oscillator a faithful model of living pacemaker neurons. Comparison of the model's responses with those of a living pacemaker was based also on return maps of interspike intervals. Analyzed in detail were the complex discharges called stammering which involve interspike intervals that arise unpredictably and exhibit histograms with several modes separated by the equal intervals.Supported by Trent H. Wells Jr. Inc.     

High pressure conditions stimulate expression of chloramphenicol acetyltransferase regulated by the lac promoter in Escherichia coli

Abstract Recombinant plasmids with the chloramphenicol acetyltransferase (CAT) structural gene behind several kinds of promoters were tested for expression in Escherichia coli during growth at atmospheric pressure (0.1 MPa) and at high pressure (30 MPa). Expression of the CAT gene from the lac promoter was remarkably activated (approx. 78-fold) by high pressure in the absence of the inducer isopropyl-β-d-thiogalactopyranoside (IPTG). The stimulation of the CAT activity by the lac promoter at high pressure did not simply result from an increased plasmid copy number, because the CAT activities from the other promoters and β-lactamase activities were unaffected at high pressure.     

Extra-weak chemiluminescence of drugs XV. Method for determining stability of Toki-shakuyaku-san extract granules

The purpose of the study was to evaluate the quality of Toki-shakuyaku-san extract granules (TJ-23) using chemiluminescence (CL). A linear relationship was obtained between the log value of the CL of TJ-23 and the reaction temperature. An excellent correlation (r= 0.999) was found between the slope of this curve (ΔA) and the colour intensity due to the browning reaction occurring at the early stage of the Maillard reaction.     

Suramin interrupts androgen-inducible autocrine loop involving heparin binding growth factor in mouse mammary cancer (Shionogi carcinoma 115) cells

The androgen-dependent clonal cell line SC-3, derived from Shionogi carcinoma 115, secretes a fibroblast growth factor (FGF)-autocrine growth factor in response to androgen, which is able to bind to FGF receptors. In SC-3 cells, FGF receptor expression is upregulated by the SC-3-derived growth factor, providing a means of amplifying an autocrine loop of cell growth. In the present investigations, the effect of the polysulfonated naphthylurea suramin on this autocrine loop and its amplification in SC-3 cells were studied. Suramin inhibited androgen-dependent growth of SC-3 cells in a concentration-dependent fashion: ～50% inhibition was observed at 25 μM. [³H]Thymidine incorporation into the cells stimulated with partially purified SC-3-derived growth factor was inhibited by suramin in a similar way. Additionally, suramin inhibited acidic (a) or basic (b) FGF-induced cell proliferation, though relatively high concentrations were necessary to achieve the maximal inhibition. Pretreatment of SC-3 cells with suramin decreased cell surface ¹²⁵I-bFGF binding without altering dissociation constant (Kd) of the binding sites. When the cells were incubated with 250 μM suramin for 24 h, the maximum binding (Bmax) decreased to almost 50% of the control. Treatment with suramin also decreased the levels of FGF receptor-1 mRNA to a similar extent, whereas it appeared not to affect the levels of β-actin mRNA. Moreover, suramin completely blocked androgen- or bFGF-induced accumulation of FGF receptor-1 mRNA. The inhibitory effects of suramin on FGF receptor expression were reversed by simultaneous addition of high concentrations of bFGF. These results indicate that suramin exerts its potent antiproliferative action on SC-3 cells through inhibition of an androgen-inducible autocrine loop involving SC-3-derived growth factor and FGF receptor. © 1993 Wiley-Liss, Inc.