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Liang Chen

Publications and source records attributed to Liang Chen.

At least 73 records · Page 4Linked to original sources
PubMed2005

Negative correlation between compositional symmetries and local recombination rates.

Although still not much understood, the universal reverse complement symmetry in genomes may contain much information about the genome. In this article, under the hypothesis that recombination rate variations may be related to the high order DNA structure, we studied the association between local recombination rates and local symmetry levels in mouse, rat and human. We found significant negative correlations between recombination rates and reverse complement compositional symmetries in these three organisms. This negative correlation pattern also held at individual chromosome levels when data only from each individual chromosome was analyzed.

Animals↗
PubMed2005

Subpeaks in the Brillouin loss spectra of distributed fiber-optic sensors.

Subpeaks in the Brillouin loss spectra of distributed fiber-optic sensors were observed for what is believed to be the first time and studied. We discovered that the Fourier spectrum of the pulsed signal and the off-resonance oscillation both contributed to subpeaks. The off-resonance oscillation at frequency /v - vB/ is the oscillation in the Brillouin time domain when beat frequency v of the two counterpropagating laser beams does not match local Brillouin frequency vB. This study is important in differentiating the subpeaks from actual strain-temperature peaks.

Journal Article↗
PubMed2005

Effect of optical phase on a distributed Brillouin sensor at centimeter spatial resolution.

Because of the power imbalance between the two arms of an interferometer in an electro-optic modulator (EOM), the output of the EOM is combined amplitude modulation (AM) and phase modulation (PM) for the probe signal consisting of the pulse and the dc component. Because of this PM, the Brillouin gain-loss spectrum becomes asymmetric. The central Brillouin frequency is shifted from that of an AM pulse. The maximum extinction ratio of the EOM is limited to approximately 29 dB for a power-splitting ratio of 51% to 49%. The asymmetric property induced by PM is not pulse shape dependent; for both Gaussian- and super-Gaussian-shaped pulses the Brillouin loss spectrum is symmetric for AM and asymmetric for combined AM and PM (power imbalance).

Journal Article↗
PubMed2005

Brillouin spectral deconvolution method for centimeter spatial resolution and high-accuracy strain measurement in Brillouin sensors.

Combining a dc and a short pulse (approximately 1 ns) as the probe beam in the pump-probe configuration of Brillouin-based distributed sensors allows us to represent the Brillouin spectrum as a top Lorentzian-like portion and a bottom Gaussian-like portion. Because of the interaction of these two parts, the Lorentzian-like portion carries spatial information that can be extracted within centimeter spatial resolution. Using this information, we develop a spectrum deconvolution method, which considers the location correlation of the strain distribution, to find the number of Brillouin peaks and their frequencies in the top Lorentzian-like portion and hence achieve accurate strain information. An optimum level of dc to pulse power for the best signal and position detection capability is discussed.

Journal Article↗
PubMed2005

Formation of odd-numbered clusters of CO2 adsorbed on nanotube bundles.

Simulations show that CO2 adsorbed in the groove sites of carbon nanotubes displays unique quasi-one-dimensional behavior. Clusters containing only odd numbers of molecules are formed at finite CO2 coverages and low temperatures. The molecules are orientationally ordered with respect to the nanotube groove axis and azimuthally ordered in the plane perpendicular to the groove axis. This ordering is a result of a delicate balance between solid-fluid and fluid-fluid forces; the CO2 quadrupole plays a critical role in the cluster formation and orientational ordering.

Journal Article↗
PubMed2005

Gene expression analysis reveals that histone deacetylation sites may serve as partitions of chromatin gene expression domains.

BACKGROUND: It has been a long-term puzzle whether chromatin can be further divided into distinct gene expression domains. Because histone deacetylation affects chromatin structure, that in turn may affect the expression of nearby genes, histone deacetylation sites may act to partition chromatin into different gene expression domains. In this article, we explore the relationship between histone deacetylation sites and gene expression patterns on the genome scale using different data sources, including microarray data measuring gene expression levels, microarray data measuring histone deacetylation sites, and information on regulatory targets of transcription factors. RESULTS: Using 269 Saccharomyces cerevisiae microarray datasets, histone deacetylation datasets, and regulatory targets of transcription factors assembled from the Yeast Proteome Database and ChIP-chip data, we found that histone deacetylation sites can reduce the level of co-expression of neighboring genes. CONCLUSION: Histone deacetylation sites may serve as possible partition sites for chromatin domains and affect gene expression.

Binding Sites↗
PubMed2005

[The clinical effect of bipolar long-stem prosthetic replacement on the treatment of comminuted intertrochanteric fracture of hip in the elderly osteoporotic patients].

OBJECTIVE: To evaluate the clinical effect of bipolar long-stem prosthetic replacement on the treatment of comminuted intertrochanteric fracture of hip in the elderly osteoporotic patients. METHODS: From March 2000 to August 2003, 18 patients who were more than 72 years old with comminuted intertrochanteric fracture were treated with bipolar long-stem prosthetic replacement. There were 8 males and 10 females (aged from 72 to 91). Fractured fragments of large trochanter and minor trochanter should be preserved during the operation so that the fragments can be fixed with steel wires and insertion of artificial femoral head. The surgical approach and operative technique, the average course of treatment in hospital, the average time to ambulate with full-weight bearing on the operated limb after the operation, complication, and mortality were observed. RESULTS: All patients were followed up 6 to 28 months (16.2 months on average). The average course of stay at hospital was 16 days. The average time to ambulate was 32 days. The incidence of the pain of the hip joint was one-eighteenth, and one patient due to another disease was unable to walk without using two crutches one month after the surgery. The mortality of the patients was one-eighteenth one year after the surgery. CONCLUSION: Bipolar long-stem prosthetic replacement for the treatment of comminuted intertrochanteric fractures in the elderly osteoporotic patients proves to be a suitable alternative. Patients have better prognosis, early full-weight bearing, rapid rehabilitation, and fewer complications.

Aged↗
PubMed2005

A stronger bicortical sacral pedicle screw fixation through the s1 endplate: an in vitro cyclic loading and pull-out force evaluation.

STUDY DESIGN: The insertion torque and pull-out force after cyclic loading of the bicortical sacral pedicle screw through the S1 endplate were tested using human cadaveric specimens. OBJECTIVES: The purpose of this study was to (1) evaluate the effect of cyclic loading on the pull-out force of two different techniques of bicortical sacral pedicle screw fixation and (2) to correlate the pull-out force after cyclic loading with the screw insertion torque. SUMMARY OF BACKGROUND DATA: Biomechanical studies using conventional sacral pedicle screw fixation techniques have demonstrated reduction in stiffness and strength after cyclic loading. Technical difficulties with anterior sacral cortex penetration and frequent screw loosening have been reported in clinical studies. In the authors' center, a new method of sacral pedicle screw fixation bicortically through the S1 endplate has been used successfully in the clinical setting. However, the mechanical stability of this new technique after undergoing cyclic loading has not been documented in the literature. METHODS: Seven-millimeter compact Cotrel-Dubousset sacral screws were randomly assigned by side (left vs. right) and inserted bicortically either anteromedially through the anterior sacral cortex or superiorly through the S1 endplate of 17 fresh frozen human sacrum. The tk;4maximum insertion torque for each screw was measured. Cyclic loading from 40 N to 400 N was applied to each screw at a frequency of 2 Hz for 20,000 cycles. Pull-out tests were conducted after completion of the cyclic tests. RESULTS: The mean maximum insertion torque and mean pull-out force following cyclic loading were significantly higher for bicortical fixation through the S1 endplate (mean 3.17 N.m and 1457 N) than bicortical fixation through the anterior sacral cortex (mean 1.98 N.m and 1122 N). Both S1 endplate and anterior cortical fixation techniques demonstrated significant correlations between insertion torque and pull-out force following cyclic loading. CONCLUSIONS: In sacral pedicle screw fixation, screw trajectory through the S1 endplate was significantly stronger than screws penetrating the anterior sacral cortex. Insertion torque was a good intraoperative indicator of screw pull-out force after cyclic loading.

Adult↗
PubMed2005

[Diagnosis and treatment of tentorial dural arteriovenous fistulae].

OBJECTIVE: Tentorial dural arteriovenous fistulae are uncommon but life-threatened lesions. We present our experience of 5 cases with tentorial dural arteriovenous fistulae, review the relevant literature and present the rationale of our current management strategy. METHODS: The data of five patients with tentorial DAVF treated in Huashan Hospital between June 2002 and May 2003 were reviewed retrospectively, including their ill history, neuroimagings, operation records and follow-up data. RESULTS: There were 3 females and 2 males with age from 25 to 52 years (average, 42.6 years). Clinical manifestations were acute subarachnoid hemorrhage in 2 cases, progressing neurological deficits in 3 cases. MRI and DSA were major diagnostic and follow-up modalities. Borden classification type II was in 1 case, type III in 4 cases. According to DAVF location, tentorial marginal type were in 3 cases, tentorial lateral type 1 case, tentorial medial type 1 case. Two patients had transarterial embolization preoperatively. All patients underwent craniotomy with the coagulation of the nidus and tentorium, disconnection of leptomeningeal venous drainage. The surgical approaches were via trans-anterior-petrous approach in 3 cases, transpterional subdural approach 1 case, transoccipital and transtentorial approach 1 case. All patients had clinical improvement, there was no surgical mortality and morbidity. Postoperative DSA confirmed obliteration of DAVF in 3 cases, MRI demonstrated the thrombosis of venous aneurysm and the disappearance of previous brainstem edema, partial thrombosis of venous aneurysm in 1 case. Follow-up study ranging from 1 to 2 year showed no recurrence and all patients resume their full activities. CONCLUSIONS: Tentorial DAVF is an aggressive vascular lesion, causing subarachnoid hemorrhage and progressive neurological deficits. Prompt diagnosis and definite treatment for tentorial DAVF are mandatory. Obliteration of the nidus and/or leptomeningeal venous drainage should be the goal of treatment. Microsurgical procedures with/without endovascular intervention are the best choice of treatment.

Adult↗
PubMed2005

Coherent probe-pump-based Brillouin sensor for centimeter-crack detection.

We provide a theoretical explanation for a coherent probe-pump-based Brillouin sensor system that achieves centimeter spatial resolution with high-frequency resolution. It was recently discovered that, when a combination of cw and pulsed light (the probe beam) interacts with a cw laser (the pump beam), centimeter spatial resolution with high-frequency resolution can be achieved even though the probe-pulse duration is 1.5 ns [Opt. Lett. 29, 1485 (2004)]. Our study reveals that the coherent portion inside the pulse length of these two interactions caused by the same phase is responsible for this behavior. It allows us to detect 1.5-cm outer-layer cracks on an optical ground-wire cable.

Journal Article↗
PubMed2005

Central nervous system injury-induced repulsive guidance molecule expression in the adult human brain.

BACKGROUND: The repulsive guidance molecule (RGM) is involved in formation of the central nervous system during development by moderating the repulsion of growing axons. However, the role of RGM in adult central nervous system lesions remains to be clarified. OBJECTIVE: To identify and determine RGM expression in adult brains with focal cerebral ischemia or traumatic brain injury and in neuropathologically unaffected control brains. Patients Twenty-one brains of patients with focal cerebral ischemia, 25 brains after traumatic brain injury, and 4 control brains. Main Outcome Measure Expression of RGM as assessed by immunohistochemical analysis. RESULTS: In normal brains, RGM expression was detected on the perikarya of some neurons, choroid plexus, smooth muscle and endothelial cells, oligodendrocytes, and myelinated white matter fibers. After focal cerebral ischemia and traumatic brain injury, RGM-immunopositive cells accumulated in lesional and perilesional areas. In hemorrhagic lesions, a massive accumulation of RGM-immunopositive cells was observed. During the first week after insult, RGM expression remained confined to neurons, smooth muscle and endothelial cells, and leukocytes infiltrating the lesion. Thereafter, with maturation of the lesion, we observed RGM expression by components of the developing scar tissue, such as fibroblastoid cells, reactive astrocytes, and a pronounced extracellular RGM deposition resembling neo-laminae. CONCLUSIONS: This is the first study of RGM in the human central nervous system. Following central nervous system injury, RGM, a novel, potent axonal growth inhibitor, is present in axonal growth impediments: the mature myelin, choroid plexus, and components of the developing scar.

Adult↗
PubMed2005

Variations of main quality components of tea genetic resources [Camellia sinensis (L.) O. Kuntze] preserved in the China National Germplasm Tea Repository.

The variations of the main quality components of tea, tea polyphenols, catechins, amino acids, caffeine, and water extract of 596 accessions Chinese tea genetic resources, preserved in the China National Germplasm Tea Repository (CNGTR), were analyzed. Tea polyphenols content on a dry weight basis varied from 13.6 to 47.8%, averaging 28.4%. The tea polyphenols content increases gradually from northern and eastern provinces to southern provinces, the highest is in Yunnan tea resources. The content of catechins ranged from 81.9 g/kg to 262.7 g/kg, averaging 144.6 g/kg. The genetic resources from Hunan province had the highest catechins content, inconsistent with the tea polyphenols, which were highest in Yunnan tea resources. The amino acids content ranged from 1.1 to 6.5%, with an average of 3.3%. It was much lower in the southern provinces compared with northern and eastern provinces. The average caffeine content was 4.2%, varying from 1.2 to 5.9%. Yunnan province has plentiful high caffeine genetic resources, next is Fujian province. Caffeine content of Chinese and Japanese tea genetic resources were very similar. The average of water extract content was 44.7%, varying from 24.4 to 57.0%. The variation pattern was similar to that of tea polyphenols. Tea genetic resources of transnormal components are valuable and they could be used directly or indirectly for commercial functional components extract, breeding, and production.

Amino Acids↗
PubMed2005

PKA independent and cell type specific activation of the expression of caudal homeobox gene Cdx-2 by cyclic AMP.

Cdx-2 is a transactivator for the proglucagon gene in pancreatic and intestinal endocrine cells. Cdx-2 is also expressed in differentiated intestinal epithelia of nonendocrine origin. Cdx-2-/- mice are embryonic lethal, while Cdx-2+/- mutants show multiple malfunctions including the formation of intestinal polyps. Within the polyps, the remaining wild type Cdx-2 allele ceases its expression, while the expression of both Cdx-2 and proglucagon in the endocrine cells remains unaltered, indicating that Cdx-2 could be haplo-insufficient for nonendocrine cells, but not for proglucagon producing endocrine cells. We propose that mechanisms underlying Cdx-2 expression and auto-regulation [Xu F, Li H & Jin T (1999), J Biol Chem274, 34310-34316] differ in these two types of cells. We show here that forskolin and cAMP upregulate Cdx-2 expression in proglucagon producing cells, but not in colon cancer cells and primary intestinal cell cultures. It is unlikely that the activation is mainly mediated by PKA, because the activation was observed in a PKA deficient cell line. Co-transfecting a dominant negative Ras expression plasmid substantially repressed the Cdx-2 promoter, in contrast to a previous finding that Ras is a negative factor for Cdx-2 expression in colon cancer cells. Furthermore, forskolin activated ERK1/2 phosphorylation in the endocrine cells, and attenuation of ERK1/2 phosphorylation by its inhibitor is associated with attenuated Cdx-2 expression. Finally, an Epac pathway specific cAMP analogue stimulated both ERK1/2 phosphorylation and Cdx-2 expression. Taken together, our observations suggest that Cdx-2 expression is regulated by the second messenger cAMP, cell-type specifically, via the Epac pathway.

Animals↗
PubMed2005

Immune responses to foot-and-mouth disease DNA vaccines can be enhanced by coinjection with the Isatis indigotica extract.

The Isatis indigotica extract is widely used in clinical practice for the treatment of influenza, epidemic hepatitis, epidemic encephalitis B etc. The goal of this study was to investigate whether coinjection of the Isatis indigotica extract with foot-and-mouth disease virus (FMDV) DNA vaccine could increase the protective immune response. Mice were vaccinated twice with either FMDV DNA vaccine plus the Isatis indigotica extract or DNA vaccine alone. Compared with the group of DNA vaccine alone, in the group that received DNA vaccine plus the Isatis indigotica extract was observed a significant increase in not only FMDV-specific antibody response but also T cell proliferation assay. All swine immunized with either FMDV DNA vaccine plus the Isatis indigotica extract or DNA vaccine alone were partially protected from FMDV challenge, but the signs of DNA vaccine plus the Isatis indigotica extract group were less severe than that of DNA vaccine alone. Coinjection of the Isatis indigotica extract with DNA vaccine has adjuvant effect on the immune response against viral pathogens and its application provides an effective strategy to improve the efficacy of DNA vaccines.

Adjuvants, Immunologic↗
PubMed2005

Echovirus 30, Jiangsu Province, China.

An outbreak of aseptic meningitis occurred in the northern area of Jiangsu Province in China from January to July in 2003. A total of 1,681 cases were involved in this outbreak, and 99% of patients were <15 years of age. To identify the etiologic agent, 66 cerebrospinal fluid specimens were tested by cell culture. Eighteen showed an enteroviruslike cytopathic effect on MRC-5 human fetal diploid lung cells. An enterovirus primer-mediated reverse transcriptase-polymerase chain reaction, a standard neutralization assay, and sequencing of the complete capsid-encoding (VP1) gene identified the 18 isolates (FDJS03) as echovirus 30. At least a 10% difference was seen in nucleotide sequences of VP1 between FDJS03 isolates and other global strains of echovirus 30. Phylogenetic analysis based on complete sequences of VP1 was performed to further characterize the FDJS03 isolates. This report is the first to identify a distinct lineage of echovirus 30 as a probable cause of this outbreak.

Base Sequence↗
PubMed2005

[Selectivity and individualization of transpedicular balloon kyphoplasty for aged osteoporotic spinal fractures].

OBJECTIVE: To investigate the selectivity and individualization of transpedicular balloon kyphoplasty for aged osteoporotic spinal fracture. METHODS: Twenty-two consecutive procedures were performed in 17 aged patients with osteoporotic spinal compression fractures from April 2002 to June 2004. The signal changes in different sequences were confirmed by magnetic resonance imaging before the procedures. This operation involved the percutaneous insertion of two inflatable bone tamps into a fractured vertebral body transpedicularly under fluoroscopic guidance. Every patient was treated individually, according to the results of radiography and CT scan before operation. Preoperative and postoperative complications, visual analogue scale, and radiographic findings such as vertebral height and Cobb angle were recorded and analyzed. RESULTS: All patients tolerated the procedure well with immediate relief of their back pain in 24 hours. There was no leakage of cement into the epidura. The mean loss percent of the anterior and middle vertebral heights were (35.32 +/- 13.15)% and (27.53 +/- 12.61)% before operation, and (14.21 +/- 12.43)% and (16.2 +/- 7.5)% after operation. The height restoration of vertebra was confirmed by X-ray after the procedure (P < 0.01). The mean kyphosis was improved from (25.3 +/- 4.2) degrees to (8.6 +/- 5.1) degrees. No complications occurred. No patient had nerve injury. The patients were allowed to walk next day after the procedure. CONCLUSION: The selectivity and individualization of transpedicular balloon kyphoplasty for aged osteoporotic spinal fractures has satisfactory short-term clinical efficacy. It is also an effective way to prevent complications.

Aged↗
PubMed2005

[Cloning, expression, purification of protein kinase Cdelta and its preliminary application in drug lead compounds screening].

Protein kinase Cdelta (PKCdelta) is a member of protein kinase C family, which possess phospholipid-dependent serine and threonine kinase activity. PKCdelta is a potential drug target of diabetes and some cancers. The abnormal activation of PKCdelta can arouse diabetes and some cancers. Therefore the specific inhibitors of PKCdelta can be applied in the research and development of the drug candidate of these diseases. The present aim is to obtain active recombinant PKCdelta from COS1 cells. For cloning of mouse PKCdelta a pair of specific primers were designed based on the published sequence of this gene. The cDNA of full coding region was obtained by RT-PCR. The amplified cDNA was subsequently cloned into FLAG-tagged pcDNA3.0 and its sequence was confirmed by DNA sequencing analysis. FLAG-tagged pcDNA3.0-PKCdelta was transfected into COS1 cells. A cell strain which can stably express PKCdelta was obtained by G418 screening. FLAG-tagged PKCdelta in the supernant of COS1 cells extracts was absorbed by anti-FLAG resin and eluted by FLAG peptide. The purified protein appeared as a single band on both SDS-PAGE and western blotting, indicating that it was chemical and antigenic pure. By kinase assay, the recombinant PKCdelta was active. Positive inhibitor, staurosporine, was used to prove the enzyme could be greatly inhibited. Several compounds have been found to inhibit the enzyme, which indicates the preliminary application in drug lead compounds screening.

Animals↗