Resonant transport of light from planar polymer waveguide into liquid-crystal microcavity.

We demonstrate the resonant transfer of light from a planar waveguide to a nematic liquid-crystal microdroplet immersed in water. A wide spectrum of light from a supercontinuum laser source is coupled into a high-refractive-index polymer waveguide using a prism-film coupler. The waveguide is in contact with a water dispersion of droplets from the nematic liquid-crystal 5CB. The evanescent field of the light in the waveguide is resonantly coupled to the whispering-gallery mode resonances, sustained by 5 - 20 µm-sized nematic liquid-crystal droplets, which are in close proximity to the waveguide. The resonant transfer of light is tuned by the temperature-induced shifting of the WGM resonances due to the temperature dependence of the refractive index of the nematic liquid crystal. The measurements are compared to the calculations of the coupled-mode theory.

Surfactant sensing based on whispering-gallery-mode lasing in liquid-crystal microdroplets.

Lasing of whispering-gallery modes in nematic liquid-crystal microdroplets, floating in water, is demonstrated. It is shown that millimolar concentrations of sodium dodecyl sulfate in water effect the orientation of liquid-crystal molecules in the microdroplet, which changes the lasing spectrum. The presence of targeted molecules in water can be monitored by simply measuring and recognizing the spectrum of light, lasing from a small liquid-crystal droplet in water.

Direct and inverted nematic dispersions for soft matter photonics.

General properties and recent developments in the field of nematic colloids and emulsions are discussed. The origin and nature of pair colloidal interactions in the nematic colloids are explained and an overview of the stable colloidal 2D crystalline structures and superstructures discovered so far is given. The nature and role of topological defects in the nematic colloids is discussed, with an emphasis on recently discovered entangled colloidal structures. Applications of inverted nematic emulsions and binding force mechanisms in nematic colloids for soft matter photonic devices are discussed.

3D microlasers from self-assembled cholesteric liquid-crystal microdroplets.

We demonstrate a tunable and omnidirectional microlaser in the form of a microdroplet of a dye-doped, cholesteric liquid crystal in a carrier fluid. The cholesteric forms a Bragg-onion optical microcavity and the omnidirectional 3D lasing is due to the stimulated emission of light from the dye molecules in the liquid crystal. The lasing wavelength depends solely on the natural helical period of the cholesteric and can be tuned by varying the temperature. Millions of microlasers can be formed simply by mixing a liquid crystal, a laser dye and a carrier fluid, thus providing microlasers for soft-matter photonic devices.

Electrically tunable diffraction of light from 2D nematic colloidal crystals.

We show that diffraction of visible light from 2D dipolar nematic colloidal crystals can be tuned electrically. When the external electric field of approximately 1 V/microm is applied in a direction perpendicular to the plane of the 2D colloidal crystal, the induced strain is highly anisotropic, and the inter-colloidal spacing changes by as much as 20% along one direction and approximately 2% along the perpendicular one. Although the speed of response is in the range of several seconds, this novel mechanism could provide interesting photonic applications.

Lipopeptide adjuvants: monitoring and comparison of P3CSK4- and LPS-induced gene transcription.

Bacteria-derived synthetic lipoproteins constitute potent macrophage activators in vivo and are effective stimuli, enhancing the immune response especially with respect to low or non-immunogenic compounds. N-palmitoyl-S-[2,3-bis(palmitoyloxy)-(2R,S)-propyl]-(R)-cysteinyl-seryl-(lysyl)3-lysine (P3CSK4), exhibiting one of the most effective lipopeptide derivatives, represents a highly efficient immunoadjuvant in parenteral, oral, nasal and genetic immunization either in combination with or after covalent linkage to antigen. In order to further elucidate its molecular mode of action with respect to the transcriptional level, we focused our investigations on the P3CSK4-induced modulation of gene transcription. We could show that P3CSK4 activates/represses an array of at least 140 genes partly involved in signal transduction and regulation of the immune response. P3CSK4 activates the expression of tumor suppressor protein p53 (p53), c-rel, inhibitor of nuclear factor kappa B (NFkappaB) alpha (IkappaB alpha), type 2 (inducible) nitric oxide (NO) synthase (iNOS), CD40-LR, intercellular adhesion molecule-1 (ICAM-1) and interleukin 1/6/15 (IL-1/6/15). We detected no activation of heat shock protein (HSP) 27, 60, 84 and 86, osmotic stress protein 94 (Osp 94), IL-12, extracellular signal-regulated protein kinase 1 (ERK1), p38 mitogen activated protein (MAP)-kinase (p38), c-Jun NH2-terminal kinase (JNK), signal transducer and activator of transcription 1 (STAT1), CD14 and caspase genes. Furthermore, we monitored inhibition of STAT6, Janus kinase 3 (Jak3) and cyclin D1/D3 gene transcription after stimulating bone marrow-derived macrophages (BMDM) with lipopeptide. In addition, we monitored significant differences after lipopeptide and lipopolysaccharide (LPS) stimulation of bone marrow-derived murine macrophages. Our findings are of importance for further optimizing both conventional and genetic immunization, and for the development of novel synthetic vaccines.

Effect of nitric oxide on shock-induced hepatic heme oxygenase-1 expression in the rat.

Recent evidence suggests that the hepatic expression of heme oxygenase-1 (HO-1) may preserve hepatocellular integrity after hemorrhagic shock and resuscitation (HR). Because nitric oxide (NO) has been shown to modulate HO-1 expression in cultured cells in vitro, we determined its potential role in the regulation of HO-1 expression after HR in the rat liver in vivo. HO-1 mRNA and protein were highly induced and HO enzyme activity was higher after HR when compared with time-matched sham controls. Administration of the NO donor, molsidomine (MOL) (3 mg. kg(-1)), during resuscitation attenuated the accumulation of HO-1 mRNA and protein and the rise in HO activity. In addition, MOL prevented the shock-induced increase in DNA binding activity of the transcription factor, activator protein-1 (AP-1), but did not alter the activity of nuclear factor-erythroid 2 related factor (Nrf-2), nuclear transcription factor-kappaB (NF-kappaB), and hypoxia-inducible factor-1 (HIF-1). The suppressing action of MOL was not confined to HO-1, because the hepatic expression of the 70-kd major heat shock protein (HSP) in response to HR was also diminished. Moreover, MOL prevented the HR-induced increase in the serum activity of alanine transaminase (ALT) and alpha-glutathione-S-transferase (alpha-GST) that could otherwise be observed after HR. In contrast, the NO synthase inhibitor, N(omega)-nitro-L-arginine methyl ester (L-NAME) (1 mg.kg(-1)), had either no or only minor effects on the primary experimental endpoints. These findings would be consistent with a reduction of shock-induced liver damage by exogenous NO, which in turn prevents the subsequent activation of injury-sensitive transcription factors, thus attenuating the expression of stress-inducible proteins such as HO-1.

Direction of the recognition specificity of cytotoxic T cells toward tumor cells by transduced, chimeric T-cell receptor genes.

Cellular transformation does not necessarily require the expression of proteins with neoantigenic properties, and for this reason, immunosurveillance does not register all tumor cells. They frequently express potentially immunogenic components, but are able to escape elimination by immune mechanisms. One explanation for this escape is poor antigen presentation by the tumor cells, resulting in little or no measurable antitumor immunity in immunocompetent hosts. T cells remain naive or even become anergic to the tumor cells. Reasons for the deficient antigen presentation by the tumor cells include the reduced or absent expression of major histocompatibility complex (MHC) molecules and the absence of tumor antigens in the groove of class I or class II MHC molecules as a consequence of defective protein processing. Other reasons are the absence or inadequate levels of expression of adhesion molecules, the absence or inadequate levels of costimulatory molecules or the expression of lymphocyte suppressive cytokines like transforming growth factor (TGF-ß) or interleukin 10 (IL-10) by tumor cells (1-5).

Immunostimulation by bacterial components: I. Activation Of macrophages and enhancement of genetic immunization by the lipopeptide P3CSK4.

Synthetic lipopeptides derived from the N-terminus of bacterial lipoprotein constitute potent macrophage activators and polyclonal B-lymphocyte stimulators. They are also efficient immunoadjuvants in parenteral, oral and nasal immunization either in combination with or after covalent linkage to an antigen. Here we show how alterations in the molecular structure influence their biological properties indicating P3CSK4 as one of the most active members of a lipopentapeptide fatty acid library. This compound resulted in a most pronounced macrophage stimulation as indicated by NO release, activation of NFkappaB translocation, and enhancement of tyrosine protein phosphorylation. Furthermore, P3CSK4 activates/represses an array of at least 140 genes partly involved in signal transduction and regulation of the immune response. Finally we have evidence that P3CSK4 constitutes an effective adjuvant for DNA immunizations, especially increasing weak humoral immune responses. Our findings are of importance for further optimizing both conventional and genetic immunization, and for the development of novel synthetic vaccines.

Prolactin and interleukin-2 receptors in T lymphocytes signal through a MGF-STAT5-like transcription factor.

The cell surface receptors for PRL and interleukin-2 (IL-2) are structurally distinct, but share regulatory tasks in T lymphocytes. They can stimulate proliferation and activate transcription of over-lapping sets of genes of T cells. PRL and IL-2 receptor activation are both linked to the Jak/Stat (signal transducer and activator of transcription) pathway. We investigated the ability of PRL and IL-2 to activate Stat proteins in different T cell lines. The DNA binding specificities, the reactivities toward Stat-specific antisera, and the mol wt of IL-2- and PRL-induced DNA-binding proteins in Nb2 and C196 T cell lines were investigated. A comparison with the Stat proteins induced by interferon-gamma, PRL, and IL-6 in T47D mammary tumor cells was made. We found that these parameters were indistinguishable for one of the PRL- and IL-2-induced factors. A transcription factor closely related to mammary gland factor-Stat5 is rapidly activated upon interaction of IL-2 and PRL with their respective receptors. Activation of a second protein related to Stat1 was also observed. Our results emphasize the role of PRL as a regulator of the immune response and indicate that the Stat factors mammary gland factor-Stat5 and Stat1 play a role in the regulation of gene expression during T cell development.

The effect of papaine on the time course of the end-plate current.

Papaine is known to detach cholinesterases from the synaptic cleft. It could be expected that this would result in an increase of the amplitude and half-time of the end-plate current. Thus, the effect of papaine on the end-plate current. Thus, the effect of papaine on the end-plate current should be similar to the effect of anticholinesterase methanesulfonylfluoride. The end-plate current was recorded in frog skeletal muscle at various levels of membrane potential, before and after papaine was added to the bath. The effect of papaine was an increase of the half-time of the end-plate current, similarly as after treatment of the muscle by methanesulfonylfluoride. It seems that both papaine and methanesulfonylfluoride have a similar mechanism of action. In either experimental condition hydrolysis of transmitter is decreased or abolished, which results in an increase of the half-time of the end-plate current.