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Biomedical subjects

Bo Liu

Publications and source records attributed to Bo Liu.

At least 91 records · Page 5Linked to original sources
PubMed2005

A potent transactivation domain mimic with activity in living cells.

Transcriptional coactivator-binding peptoids were isolated from a large combinatorial library. One of these molecules is shown to function as a potent activation domain surrogate in mammalian cells. Up to a 900-fold increase in expression of a Gal4-responsive reporter gene is observed when a steroid conjugate of the peptoid is incubated with HeLa cells expressing a Gal4 DNA-binding domain (DBD)-glucocorticoid receptor ligand-binding domain (GRLBD) fusion protein.

Animals↗
PubMed2005

[Cervical posterior laminoplasty operation using coralline hydroxyapatite].

OBJECTIVE: To study the results of using coralline hydroxyapatite (CHA) in cervical posterior laminoplasty operation. METHODS: Two hundred and fifty-six patients underwent cervical spinous process-splitting laminoplasty using CHA. All patients had been followed up over 3 months. One hundred and forty-two patients were followed up at least 2 years. All patients had spinal stenosis at least at 3 levels or OPLL. The average follow up time was 34.6 months. RESULTS: The CHA grafts were stable between the split spinous processes. The union rate of CHA was 83.5%. After operation, the spinal cord moved dorsally, and the anteroposterior compression ratio had been improved from 0.19 to 0.42. No apparent kyphosis occurred. The JOA score improvement rate was 58.3%. There were 24 patients (17%) with axial symptom. CONCLUSION: Cervical posterior laminoplasty operation using coralline hydroxyapatite may achieve good results.

Adult↗
PubMed2005

[Dynamic observation of the biomechanic properties of sciatic nerve at the suture site in rats following repairing].

OBJECTIVE: To observe the biomechanic properties of sciatic nerve at the suture site in rats following repairing. METHODS: The right sciatic nerves of 40 white Sprague-Dawley 300-350 gm rats were exposed, cut and then repaired with 10-0 nylon sutures, laced in the epineurium. 0, 1, 3, 6 weeks after operation, the tensile strength of the sciatic nerves were measured, the data analyzed statistically. RESULTS: The load-elongation curves for both the normal unoperated and operated nerves had the similar shape. The tensile strength of the 0 week was significant difference to 1, 3 and 6 weeks (P < 0.01). No significant difference was found among 1, 3 and 6 weeks. CONCLUSION: The tensile strength of the injured nerves are recovered in the first week and resistant in 6 weeks after repairing.

Animals↗
PubMed2005

Development of a unique system for spatiotemporal and lineage-specific gene expression in mice.

We have developed an advanced method for conditional gene expression in mice that integrates the Cre-mediated and tetracycline-dependent expression systems. An rtTA gene, preceded by a loxP-flanked STOP sequence, was inserted into the ROSA26 locus to create a R26STOPrtTA mouse strain. When the STOP sequence is excised by Cre-mediated recombination, the rtTA is expressed in the Cre-expressing cells and all of their derivatives. Therefore, cell type-, tissue-, or lineage-specific expression of rtTA is achieved by the use of an appropriate Cre transgenic strain. In mice also carrying a target gene under the control of the tetracycline response element, inducible expression of the target gene is temporally regulated by administration of doxycycline. Our results demonstrate that this universal system is uniquely suited for spatiotemporal and lineage-specific gene expression in an inducible fashion. Gene expression can be manipulated in specific cell types and lineages with a flexibility that is difficult to achieve with conventional methods.

Animals↗
PubMed2005

A high-throughput assay for assessing the cell permeability of combinatorial libraries.

There is great interest in the identification of synthetic molecules that are capable of manipulating protein-protein interactions in living cells. Peptides, unlike other classes of small molecules, have binding properties appropriate for this application, but most are poorly cell permeable and sensitive to proteases. Therefore, considerable effort has been expended in the development of libraries of oligomeric peptide-like molecules. However, there are no clear-cut rules to guide the design of libraries rich in cell permeable compounds. Furthermore, currently available empirical methods to assess permeability may not accurately reflect true permeability and/or are capable of only modest throughput. We describe here an assay for assessing the relative cell permeability of synthetic molecules in the context of steroid fusions that is capable of high throughput and can be used in any transfectable cell line.

Binding, Competitive↗
PubMed2005

Two microtubule-associated proteins of the Arabidopsis MAP65 family function differently on microtubules.

The organization and dynamics of microtubules are regulated by microtubule-associated proteins, or MAPs. In Arabidopsis (Arabidopsis thaliana), nine genes encode proteins of the evolutionarily conserved MAP65 family. We proposed that different MAP65s might have distinct roles in the interaction with microtubules. In this study, two AtMAP65 proteins, AtMAP65-1 and AtMAP65-6, were chosen to test this hypothesis in vitro. Although both fusion proteins were able to cosediment with microtubules in vitro, different properties on tubulin polymerization and microtubule bundling were observed. AtMAP65-1 was able to promote tubulin polymerization, enhance microtubule nucleation, and decrease the critical concentration for tubulin polymerization. It also induced the formation of large microtubule bundles by forming cross-bridges between microtubules evenly along the whole length of microtubules. In the presence of AtMAP65-1, microtubule bundles were more resistant to cold and dilution treatments. AtMAP65-6, however, demonstrated no activity in promoting tubulin polymerization and stabilizing preformed microtubules. AtMAP65-6 induced microtubules to form a mesh-like network with individual microtubules. Cross-bridge-like interactions were only found at regional sites between microtubules. The microtubule network induced by AtMAP65-6 was more resistant to high concentration of NaCl than the bundles induced by AtMAP65-1. Purified monospecific anti-AtMAP65-6 antibodies revealed that AtMAP65-6 was associated with mitochondria in Arabidopsis cells. It was concluded that these two MAP65 proteins were targeted to distinct sites, thus performing distinct functions in Arabidopsis cells.

Arabidopsis↗
PubMed2005

PDGF-BB regulates p27 expression through ERK-dependent RNA turn-over in vascular smooth muscle cells.

Cyclin-dependent kinase inhibitor p27, a critical determinant for cell cycle progression, is an important regulation target of mitogenic signals during arterial injury. In this study, we show in rat aortic smooth muscle cells that PDGF-BB down-regulated p27 protein and mRNA in an ERK-dependent mechanism. Inhibition of ERK, but not other subtypes of the mitogen-activated protein kinase family, prevented the reduction of p27 protein and mRNA. Conversely, direct activation of ERK via adenovirus-mediated expression of a constitutively active form of MEK led to a reduction of p27 protein and mRNA, further supporting the central role of ERK in regulation of p27 expression. Rapamycin, which potently inhibited PDGF-induced activation of p70 S6 kinase as well as proliferation of smooth muscle cells, did not alter the expression of p27. To delineate the molecular mechanism underlying the p27 down-regulation, we examined the effect of PDGF-BB on p27 promoter activity as well as mRNA stability. Stimulation with PDGF-BB significantly shortened the half-life of p27 mRNA without affecting its promoter activity. To further understand the PDGF-stimulated p27 mRNA turnover, we inserted the 5'- and/or 3'-untranslated regions of p27 cDNA into a non-PDGF-responsive luciferase gene. Only those chimeric genes that contained the 3'-untranslated region responded to PDGF-BB with reduced expression. Moreover, inhibition of ERK completely prevented the effect of PDGF on the chimera expression. In summary, our data suggest that p27 is down-regulated by PDGF-BB in vascular smooth muscle cells through an ERK-dependent posttranscriptional mechanism.

3' Untranslated Regions↗
PubMed2005

Oxytocin inhibits T-type calcium current of human decidual stromal cells.

CONTEXT: Little is known about the crosstalk between the decidua and myometrium in relation to human labor. The hormone oxytocin (OT) is considered to be a key mediator of uterine contractility during parturition, exerting some of its effects through calcium channels. OBJECTIVE: The objective was to characterize the effect of OT on the T-type calcium channel in human decidual stromal cells before and after the onset of labor. DESIGN: The nystatin-perforated patch-clamp technique was used to record inward T-type calcium current (I(Ca(T))) from acutely dispersed decidual stromal cells obtained from women at either elective cesarean section [CS (nonlabor)] or after normal spontaneous vaginal delivery [SVD (labor)]. SETTING: These studies took place at the University of Nottingham Medical School. RESULTS: I(Ca(T)) of both SVD and CS cells were blocked by nickel (IC(50) of 5.6 microm) and cobalt chloride (1 mm) but unaffected by nifedipine (10 microm). OT (1 nm to 3.5 microm) inhibited I(Ca(T)) of SVD cells in a concentration-dependent manner, with a maximal inhibition of 79.0% compared with 26.2% in decidual cells of the CS group. OT-evoked reduction of I(Ca(T)) was prevented by preincubation with the OT antagonist L371,257 in the SVD but not CS group. OT, in a concentration-dependent manner, displaced the steady-state inactivation curve for I(Ca(T)) to the left in the SVD group with no significant effect on curves of the CS group. CONCLUSION: Inhibition of I(Ca(T)) by OT in decidual cells obtained during labor may signify important functional remodeling of uterine signaling during this period.

Calcium Channel Blockers↗
PubMed2005

High-birefringence fiber loop mirrors and their applications as sensors.

The reflection and transmission characteristics of a high-birefringence fiber loop mirror (HiBi-FLM), which is composed of a standard fiber coupler and one-section or multisection high-birefringence fibers (HBFs), are analyzed and discussed in detail. Theoretical reflectivity and transmissivity expressions for HiBi-FLMs with one-, two-, and three-section HBFs were obtained. The procedure for calculating reflectivity and transmissivity for HiBi-FLMs with n-section HBFs is given. Experimental results have verified the theoretical model. The basic characteristics of the one-section HiBi-FLM when strain and high temperature are applied to HBFs were analyzed and investigated theoretically and experimentally. The experimental results are in good agreement with the theoretical analysis. Furthermore, a strain--temperature sensor that makes use of those characteristics, which is new for applications of HiBi-FLMs, has been proposed and demonstrated.

Journal Article↗
PubMed2005

Syntheses of quinolone hydrochloride enantiomers from synthons (R)- and (S)-2-methylpiperazine.

A series of R and S enantiomers of 7-(3-methylpiperazin-1-yl) quinolone derivatives were synthesized from (R)- and (S)-tert-butyl 2-methylpiperazine-1-carboxylate and tested for their antibacterial activities on 14 kinds of bacteria. Although no distinct difference in in vitro antibacterial activities was observed, 2-64-fold difference between R and S enantiomers was observed in approximately 52% of cases.

Molecular Structure↗
PubMed2005

Ionizing radiation-dependent gamma-H2AX focus formation requires ataxia telangiectasia mutated and ataxia telangiectasia mutated and Rad3-related.

The histone variant H2AX is rapidly phosphorylated at the sites of DNA double-strand breaks (DSBs). This phosphorylated H2AX (gamma-H2AX) is involved in the retention of repair and signaling factor complexes at sites of DNA damage. The dependency of this phosphorylation on the various PI3K-related protein kinases (in mammals, ataxia telangiectasia mutated and Rad3-related [ATR], ataxia telangiectasia mutated [ATM], and DNA-PKCs) has been a subject of debate; it has been suggested that ATM is required for the induction of foci at DSBs, whereas ATR is involved in the recognition of stalled replication forks. In this study, using Arabidopsis as a model system, we investigated the ATR and ATM dependency of the formation of gamma-H2AX foci in M-phase cells exposed to ionizing radiation (IR). We find that although the majority of these foci are ATM-dependent, approximately 10% of IR-induced gamma-H2AX foci require, instead, functional ATR. This indicates that even in the absence of DNA replication, a distinct subset of IR-induced damage is recognized by ATR. In addition, we find that in plants, gamma-H2AX foci are induced at only one-third the rate observed in yeasts and mammals. This result may partly account for the relatively high radioresistance of plants versus yeast and mammals.

Arabidopsis↗
PubMed2005

Methods for optical adjustment in lidar systems.

In a lidar system, both a well-adjusted receiving telescope and an accurate transmitter-receiver alignment are essential for obtaining reliable data, but usually these are time consuming and difficult to accomplish, especially when the optical axis of the telescope is fixed. To solve these problems, we present a novel method, to our knowledge, for the receiving telescope adjustment, which is carried out mainly with a commercial laser plummet. A simple, fast alignment procedure is also described. These are tested by adjustment of the Fe-resonance fluorescence lidar system of Wuhan University and proved to be effective and convenient. The lidar system is applied to monitor the Fe layer in the mesosphere, leading to continuous retrieval of the iron density profiles with fine spatiotemporal resolution.

Journal Article↗
PubMed2005

Rapamycin inhibits fibronectin-induced migration of the human arterial smooth muscle line (E47) through the mammalian target of rapamycin.

The matrix protein fibronectin (FN) is a potent agoinst of vascular smooth muscle cell (SMC) migration. The role of rapamycin and the mammalian target of rapamycin (mTOR) in matrix protein-induced migration has not yet been defined. In these studies, we found that rapamycin (10 nM) markedly diminished chemotaxis of E47 cells (a cell line derived from human atherosclerotic plaques) and rat aortic SMCs toward FN as well as type I collagen and laminin; however, a period of preincubation >20 h was required. Subsequently, we showed that treatment with FN induced a rapid activation of mTOR as well as its downstream effector, S6 kinase (S6K). Moreover, FN-induced activation of both proteins was inhibited by preincubation with rapamycin for only 30 min. We then explored the upstream signaling pathway through which FN might mediate mTOR activation. A blocking antibody to alpha(v)beta(3) inhibited FN-induced mTOR/S6K activation as well as E47 cell chemotaxis, implicating alpha(v)beta(3) as the integrin receptor responsible for initiating FN-induced migration. Moreover, preincubation of E47 cells with wortmannin or LY-294002 blocked FN-induced mTOR/S6K activation, demonstrating that phosphatidylinositol 3-kinase (PI3K) plays a critical role in this rapamycin-sensitive signaling pathway. It has been previously suggested that rapamycin's effect on migration maybe related to enhancement of p27(kip1). However, treatment of E47 cells with rapamycin did not alter the level of p27(kip1) in the presence or absence of FN. Taken together, our data demonstrate that rapamycin inhibits FN-induced SMC migration through a pathway that involves at least alpha(v)beta(3)-integrin, PI3K, mTOR, and S6K.

Androstadienes↗