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Based on product design systematic and modularization, aiming at an unknown working environment, the research of snake robot creates a new field for bionic robot research. Based on the requirements such as small size, multi-degree of freedom, light, simple, reliable, cheap and easy to install and maintain, we developed a small snake robot. The robot is made up of the same modules and able to complete various movement methods in their special connection ways. The robot can move by serpentine locomotion and cross obstacles. With the small snake robot technology matures, it will be smaller and may into the human body for some diagnosis or treatment work.

Heterologous expression of the rat 5-HT1A receptor in stably transfected GH4C1 rat pituitary cells (clone GH4ZD10) and mouse Ltk- fibroblast cells (clone LZD-7) (Albert, P.R., Zhou, Q.-Y., VanTol, H.H.M., Bunzow, J.R., and Civelli, O. (1990) J. Biol. Chem. 265, 5825-5832) was used to characterize the cellular specificity of signal transduction by the 5-HT1A receptor. We demonstrate that the 5-HT1A receptor, acting via pertussis toxin-sensitive G proteins, can change its inhibitory signaling phenotype and become a stimulatory receptor, depending on the cell type, differentiation state, or intracellular milieu of the cell in which it is expressed. When expressed in pituitary GH4ZD10 cells, activation of 5-HT1A receptors decreased both basal and vasoactive intestinal peptide-enhanced cAMP accumulation and blocked (+/-)-Bay K8644-induced influx of calcium, inhibitory responses which are typical of neurons which endogenously express this receptor. Similarly, 5-hydroxytryptamine (5-HT) also inhibited adenylyl cyclase in fibroblast LZD-7 cells, reducing the forskolin-induced enhancement of cAMP levels by 50%, but did not alter basal cAMP levels. In contrast to GH4ZD10 cells, where 5-HT had no effect on basal or thyrotropin-releasing hormone-induced phosphatidylinositol turnover, 5-HT enhanced the accumulation of inositol phosphates and induced a biphasic increase in [Ca2+]i in LZD-7 cells. These dominant stimulatory actions of 5-HT, as well as the inhibitory effects, were absent in untransfected cells and displayed the potency and pharmacological specificity of the 5-HT1A receptor, indicating that the 5-HT1A subtype coupled to both inhibitory and stimulatory pathways in the fibroblast cell. The actions of 5-HT in GH and L cells were blocked by 24-h pretreatment with pertussis toxin, suggesting that inhibitory G proteins (Gi/G(o)) mediate both inhibitory and stimulatory signal transduction of the 5-HT1A receptor. However, the 5-HT-induced stimulatory pathway in fibroblasts was blocked selectively by acute (2-min) pretreatment with TPA, an activator of protein kinase C. This action of protein kinase C was potentiated by activation of protein kinase A, indicating that the expression of the stimulatory pathway of the 5-HT1A receptor in LZD-7 cells is modulated by second messengers.

Neurokinin-1 (NK-1)/substance P (SP) receptors were solubilized using 10 mM 3-[( cholamidopropyl)-dimethylammonio]-1- propanesulfate from porcine striatal membranes (solubilization yield, 80%). In solubilized preparations, [3H]SP apparently bound to a single class of high-affinity sites (KD = 0.82 +/- 0.13 nM) as in membrane homogenates. The ligand selectivity pattern observed in both membrane and solubilized receptor preparations indicated that [Sar9,Met(O2)11]SP = SP much greater than senktide = [Nle10]neurokinin A. This suggests the selective labeling of the NK-1 receptor class in both assays. Solubilized receptors were retained on agarose-coupled lectins that bind N-acetylglucosamine-galactose and beta-galactose (Ricinus communis I and Ricinus communis II), mannose (concanavalin A and lentil), and N-acetylglucosamine (wheat germ agglutinin) but not on lectins binding fucose (Lotus A) and N-acetylgalactosamine (Doli-chos biflorus A). Thus, it appears that porcine brain NK-1/SP receptors are enriched with various carbohydrate moieties, beta-galactose and N-acetylglucosamine-galactose residues being especially abundant. This situation is rather different from that in various other members of the rhodopsin seven-transmembrane receptor superfamily.

Based on the critical role of actin in the maintenance of synaptic function, we examined whether expression of familial beta-amyloid precursor protein APP-V642I (IAPP) or mutant presenilin-1 L286V (mPS1) affects actin polymerization in rat septal neuronal cells. Expression of either IAPP or mPS1 but not wild-type amyloid precursor protein or presenilin-1induced formation of actin stress fibers in SN1 cells, a septal neuronal cell line. Treatment with beta-amyloid (Abeta) peptide also caused formation of actin stress fibers in SN1 cells and primary cultured hippocampal neurons. Treatment with a gamma-secretase inhibitor completely blocked formation of actin stress fibers, indicating that overproduction of Abeta peptide induces actin stress fibers. Because activation of the p38 mitogen-activated protein kinase (p38MAPK)-mitogen-associated protein kinase-associated protein kinase (MAPKAPK)-2-heat-shock protein 27 signaling pathway mediates actin polymerization, we explored whether Abeta peptide activates p38MAPK and MAPKAPK-2. Expression of IAPP or mPS1 induced activation of p38MAPK and MAPKAPK-2. Treatment with a p38MAPK inhibitor completely inhibited formation of actin stress fibers mediated by Abeta peptide, IAPP or mPS1. Moreover, treatment with a gamma-secretase inhibitor completely blocked activation of p38MAPK and MAPKAPK-2. In summary, our data suggest that overproduction of Abeta peptide induces formation of actin stress fibers through activation of the p38MAPK signaling pathway in septal neuronal cells.

We reported previously that normal Huntingtin is associated with epidermal growth factor receptor (EGF) signaling complex (Liu, Y. F., Deth, C. R., and Devys, D. (1997) J. Biol. Chem. 272, 8121-8124). To investigate the potential role of normal and polyglutamine-expanded Huntingtin in the regulation of growth factor receptor-mediated cellular signaling and biological function, we stably transfected full-length Huntingtin containing 16, 48, or 89 polyglutamine repeats into PC12 cells where cellular signaling mechanisms, mediated by nerve growth factor (NGF) or EGF receptors, are well characterized. Expression of polyglutamine-expanded Huntingtin, but not normal Huntingtin, leads to a dramatic morphological change. In clones carrying the mutated Huntingtin, both NGF and EGF receptor-mediated activation of mitogen-activated protein kinase, c-Jun N-terminal kinase, and Akt are significantly attenuated, and NGF receptor-mediated neurite outgrowth is blocked. Co-immunoprecipitation studies show that the associations of NGF or EGF receptors with growth factor receptor-binding protein 2 (Grb2) and phosphoinositide 3-kinase are significantly inhibited. NGF-induced tyrosine phosphorylation of NGF receptors (TrkA) is also consistently suppressed. Our data demonstrate that polyglutamine-expanded Huntingtin disrupts cellular signaling mediated by both EGF and NGF receptors in PC12 cells. It is known that Huntington's disease patients exhibit an extremely low incidence of a variety of cancers and are deficient in glucose metabolism. Thus, our results may reflect an important molecular mechanism for the pathogenesis of the disease.

Increased glutamate-mediated excitotoxicity seems to play an important role in the pathogenesis of Huntington's disease (Tabrizi, S. J., Cleeter, M. W., Xuereb, J., Taaman, J. W., Cooper, J. M., and Schapira, A. H. (1999) Ann. Neurol. 45, 25-32). However, how polyglutamine expansion in huntingtin promotes glutamate-mediated excitotoxicity remains a mystery. In this study we provide evidence that (i) normal huntingtin is associated with N-methyl-d-aspartate (NMDA) and kainate receptors via postsynaptic density 95 (PSD-95), (ii) the SH3 domain of PSD-95 mediates its binding to huntingtin, and (iii) polyglutamine expansion interferes with the ability of huntingtin to interact with PSD-95. The expression of polyglutamine-expanded huntingtin causes sensitization of NMDA receptors and promotes neuronal apoptosis induced by glutamate. The addition of the NMDA receptor antagonist significantly attenuates neuronal toxicity induced by glutamate and polyglutamine-expanded huntingtin. The overexpression of normal huntingtin significantly inhibits neuronal toxicity mediated by NMDA or kainate receptors. Our results demonstrate that polyglutamine expansion impairs the ability of huntingtin to bind PSD-95 and inhibits glutamate-mediated excitotoxicity. These changes may be essential for the pathogenesis of Huntington's disease.

We previously reported that expression of polyglutamine-expanded huntingtin induces apoptosis via c-Jun amino-terminal kinase (JNK) activation in HN33 cells (Liu, Y. F. (1998) J. Biol. Chem. 273, 28873-28822). Extending this study, we now demonstrate a role of mixed-lineage kinase 2 (MLK2), a JNK activator, in polyglutamine-expanded huntingtin-mediated neuronal toxicity. We find that normal huntingtin interacts with MLK2, whereas the polyglutamine expansion interferes with this interaction. Similar to the expression of polyglutamine-expanded huntingtin, expression of MLK2 also induces JNK activation and apoptosis in HN33 cells. Co-expression of dominant negative MLK2 significantly attenuates neuronal apoptosis induced by the mutated huntingtin. Furthermore, over-expression of the N terminus of normal huntingtin partially rescues the neuronal toxicity induced by MLK2. Our results suggest that activation of MLK2-mediated signaling cascades may be partially involved in neuronal death induced by polyglutamine-expanded huntingtin.

Huntington's disease is one of a growing number of hereditary neurodegenerative disorders caused by expansion of a polyglutamine stretch at the NH2 terminus of huntingtin. To explore whether polyglutamine-expanded huntingtin induces neuronal toxicity, I examined the expression of the full-length of huntingtin with 16, 48, or 89 polyglutamine repeats in a rat hippocampal neuronal cell (HN33). Expression of mutated huntingtin with 48 or 89 polyglutamine repeats stimulated c-Jun amino-terminal kinases (JNKs) activity and induced apoptotic cell death in HN33 cells while expression of normal huntingtin with 16 polyglutamine repeats had no toxic effect. The JNK activation precedes apoptotic cell death and co-expression of a dominant negative mutant form of stress-signaling kinase (SEK1) nearly completely blocked activation of JNKs and neuronal apoptosis mediated by mutated huntingtin. Taken together, my studies demonstrate that expression of polyglutamine-expanded huntingtin induces neuronal apoptosis via activation of the SEK1-JNK pathway.

The human dopamine D2L (long form) and D2S (short form) receptors were expressed separately in mouse Ltk- fibroblast cells to investigate whether there is a difference in transmembrane signaling of these D2 receptors. Both receptors induced two signals, a phosphatidylinositol-linked mobilization of intracellular calcium and an inhibition of cyclic adenosine 3'-5' monophosphate (cAMP) accumulation, each with similar response magnitudes and identical pharmacology. Both calcium and cAMP signals were sensitive to pretreatment with pertussis toxin (PTX), indicating mediation by coupling to Gi/Go proteins. However, the two forms of D2 receptor were distinguished by acute prior activation of protein kinase C (PKC) with 12-O-tetradecanoyl 4 beta-phorbol 13-acetate (TPA): TPA blocked the D2S-mediated increase in cytosolic free calcium concentration ([Ca2+]i) in a concentration-dependent manner (between 10 nM and 1 microM), whereas the D2L receptor-induced increase in [Ca2+]i was resistant to TPA and was only partially (60%) inhibited by 100 microM TPA. By contrast, TPA did not alter the inhibition of cAMP accumulation induced by activation of either D2S or D2L receptors. We conclude that, in the L cell system, prior activation of PKC differentially modulates the transmembrane signaling of the D2L and D2S receptors, preferentially inhibiting the D2S receptor-mediated calcium signal but not altering the dopamine-induced inhibitory cAMP signal of either receptor subtype.

The signal transduction pathways of the dopamine-D1 receptor were investigated in two cell types stably transfected with the human D1 receptor cDNA, rat pituitary GH4C1 cells (GH4-hD1), and mouse Ltk-fibroblast cells (L-hD1). In both GH4-hD1 and L-hD1 cell lines, stimulation of the dopamine-D1 receptor induced a marked increase in cAMP accumulation. In addition, dopamine potentiated activation of L-type voltage-dependent calcium channels in a cAMP-dependent manner in GH4-hD1 cells. However, in L-hD1 cells, dopamine increased cytosolic free calcium concentrations ([Ca++]i) by mobilization of intracellular calcium rather than by calcium influx. This effect was correlated with a dopamine-induced enhancement of phospholipase C activity in L-hD1 cells. Pretreatment (24 h) with cholera toxin (CTX) was used to maximally activate the GTP-binding protein (G protein) Gs, causing a maximal elevation of cAMP levels and uncoupling the D1 receptor from Gs. The described actions of dopamine in both cell lines were abolished by pretreatment with CTX, indicating that CTX substrates (e.g. Gs) may mediate these actions. The blockade by CTX was not due to CTX-induced elevation of cAMP, since pretreatment with forskolin or 8-bromo-cAMP to activate cAMP-dependent protein kinase did not inhibit dopamine actions nor alter basal [Ca++]i. Pretreatment (1-3 h) of L-hD1 cells with forskolin (10 microM) or 8-bromo-cAMP (5 mM) altered neither the basal activity of phospholipase C nor basal [Ca++]i in L-hD1 cells but greatly enhanced the dopamine-induced increase of phosphatidyl inositol turnover and [Ca++]i. From these results we conclude that: 1) the dopamine-D1 receptor induces multiple and cell-specific signals, including elevation of cAMP levels in both GH and L cells, cAMP-dependent activation and potentiation of opening of L-type voltage-dependent calcium channel in GH cells, and a novel phosphatidyl inositol-linked mobilization of cellular calcium in L cells; 2) coupling of the D1 receptor to these responses involves CTX-sensitive proteins, possibly Gs; and 3) acute preactivation of cAMP-dependent protein kinase can markedly enhance, rather than attenuate, certain pathways of dopamine-D1 transmembrane signaling.

Reduced glutathione (L-gamma-glutamyl-L-cysteinylglycine; GSH) is an endogenous tripeptide involved in the formation and maintenance of protein thiol groups as well as in various detoxification reactions. Because multiple receptor types contain thiol groups or disulfide bridges, effects of GSH treatments on mu-opioid, neurokinin-1/substance P, and kainic acid receptor binding sites were investigated and compared with those produced by dithiothreitol (DTT), a potent synthetic reducing agent. GSH inhibited binding more potently than did DTT at all three receptor types in porcine striatal membrane homogenates as well as in CHAPS-solubilized preparations of the mu and neurokinin-1 sites. GSH-induced inhibitory effects were associated with decreases in maximal binding capacity (Bmax) without significant alteration in apparent affinity (KD). Cysteine, the functional moiety of GSH, mimicked GSH effects albeit with lower potencies, whereas oxidized glutathione had no effects at similar concentrations. In CHAPS-solubilized preparations, the combination of low concentrations of GSH and guanylylimidodiphosphate markedly decreased the Bmax values of the binding of [3H][D-Ala2,Gly-ol5]enkephalin and [3H]substance P. This GSH-mediated mechanism may be important to prevent cell overstimulation by accelerating receptor uncoupling, desensitization, and/or internalization. This is in keeping with purported roles of GSH related to the maintenance of cellular integrity.