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Lei Xu

Publications and source records attributed to Lei Xu.

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

[Effects of soil compactness stress on root activity and leaf photosynthesis of cucumber].

Responses of root activity and leaf photosynthesis to soil compactness stress were studied in cucumber plants grown in pots. Soil compaction was expressed by soil bulk density. There were three compactness treatments with soil bulk densities, 1.2, 1.4 and 1.6 g/cm(3). The results showed that when the soil compactness increased, the dry weight and activity of roots reduced (Fig. 1); the relative electrical conductivity and malondialdehyde (MDA) content of cucumber leaf (Fig. 2) increased; the soluble protein content decreased (Fig. 3); the activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) increased (Fig. 4); net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (E) and specific leaf weight (SLW) decreased, but intercellular CO(2) concentration (Ci) increased (Fig. 5). These results mean that high soil compaction brings stress to cucumber plants.

Catalase↗
PubMed2005

[Effects of different levels of positive end expiratory pressure on lung recruitment and hemodynamics after sustained inflation in acute respiratory distress syndrome in sheep].

OBJECTIVE: To study the effects of different levels of positive end expiratory pressure (PEEP) on recruitment and hemodynamics after sustained inflation in acute respiratory distress syndrome (ARDS) in sheep. METHODS: Twelve adult sheep were anaesthetized and ARDS was induced by lung lavage with warm normal saline. Pressure-volume (P-V) curves were traced using the low flow technique and the upper inflection point (UIP) was determined. Sustained inflation was exercised at the pressure of 5 cm H(2)O (1 cm H(2)O=0.098 kPa) below UIP, and the sheep were divided into groups according to different PEEP levels (PEEP5, PEEP10, PEEP15, PEEP20). Hemodynamics and lung mechanics values were recorded during the 2 hours of recruitment, and biopsy was performed at the end of the trial. RESULTS: There was no effect on hemodynamics and recruitment in 2 hours in PEEP5 and PEEP10 groups, but oxygenation was found to be decreased in PEEP5 group, and focal alveolar collapse was found in pathological examination. When the PEEP level reached 15 cm H(2)O, there was significant elevation in central venous pressure (CVP), and cardiac index (CI) fell remarkably, but oxygenation index and lung mechanics were improved and stable in 2 hours. CONCLUSION: Our study demonstrates that it can obviously improve oxygenation when PEEP is set at 10-20 cm H(2)O, oxygenation can be obviously improved, with little disturbance to hemodynamics in case cardiac function is normal.

Animals↗
PubMed2005

[Establishment of a mathematical model of static pressure-volume curve in acute respiratory distress syndrome].

OBJECTIVE: To explore the use of second derivate in seeking the inflection points of pressure-volume (P-V) curves and compare it with the step-by-step regression method. METHODS: Under general anesthesia, tracheotomy was done in 6 adult sheep, warm physiological saline was used to lavage the respiratory, followed by alveolar lavaged via tract through bronchofiberscope to reproduce acute respiratory distress syndrome (ARDS). The low flow technique was used to trace the P-V curves before and after the saline lavage, and features of the curves were analyzed with the software of Findgraph. RESULTS: The above two methods fit the P-V data well with good accuracy both in inflation and deflation limbs in normal and ARDS animals. From the graph of second derivate, the characteristic points of the P-V curves could be exactly obtained, and the low inflection points obtained by this method were well correlated with lower inflection point (LIP) +2 cm H(2)O (1 cm H(2)O=0.098 kPa) obtained by step-by-step regression method. CONCLUSION: The graph of second derivate gained from P-V curves is useful to describe the inflection points, so that it can be helpful in instructing in setting the required parameters of the ventilator in the treatment of ARDS.

Animals↗
PubMed2004

Molecular cloning and characterization of rat karyopherin alpha 1 gene: structure and expression.

Dopamine denervation in the striata of patients with Parkinson's disease (PD) leads to changes in neural plasticity. However, the mechanisms leading to the changes are still poorly understood. In an effort to study the molecular events in the denervated striatum, we identified and cloned rat karyopherin alpha 1 (KPNA1), a member of the importin/karyopherin alpha (KPNA) family. DNA sequence analysis revealed that the full-length cDNA, encoding rat KPNA1, was 4975 bp with a short 5'-untranslated region (UTR) of 70 bp, a putative coding sequence of 1617 bp, and an unusually long 3'-UTR of 3266 bp. The gene shared a high degree of similarity with its mouse and human homologs at both cDNA and protein levels. By computational analysis of its genomic sequence, the transcription unit was shown to span a 44-kb region and consist of 13 exons varying in size from 89 (6th exon) to 3454 bp (13th exon), and 12 introns varying in size from 0.3 to 8.9 kb. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis demonstrated that KPNA1 transcript existed in various adult tissues. Both Northern blot and semi-quantitative RT-PCR analysis showed that the expression level of KPNA1 mRNA was altered in the denervated striatum post-lesion in a time-dependent manner, reaching the maximum at 2 weeks post-lesion. Our results suggest involvement of KPNA1 in the striatal responses to denervation following 6-hydroxydopamine (6-OHDA)-induced lesion.

3' Flanking Region↗
PubMed2004

The candidate tumour suppressor protein ING4 regulates brain tumour growth and angiogenesis.

Gliomas are the most common primary tumours of the central nervous system, with nearly 15,000 diagnosed annually in the United States and a lethality approaching 80% within the first year of glioblastoma diagnosis. The marked induction of angiogenesis in glioblastomas suggests that it is a necessary part of malignant progression; however, the precise molecular mechanisms underlying the regulation of brain tumour growth and angiogenesis remain unresolved. Here we report that a candidate tumour suppressor gene, ING4, is involved in regulating brain tumour growth and angiogenesis. Expression of ING4 is significantly reduced in gliomas as compared with normal human brain tissue, and the extent of reduction correlates with the progression from lower to higher grades of tumours. In mice, xenografts of human glioblastoma U87MG, which has decreased expression of ING4, grow significantly faster and have higher vascular volume fractions than control tumours. We show that ING4 physically interacts with p65 (RelA) subunit of nuclear factor NF-kappaB, and that ING4 regulates brain tumour angiogenesis through transcriptional repression of NF-kappaB-responsive genes. These results indicate that ING4 has an important role in brain tumour pathogenesis.

Animals↗
PubMed2004

Hypoxia-induced activation of p38 mitogen-activated protein kinase and phosphatidylinositol 3'-kinase signaling pathways contributes to expression of interleukin 8 in human ovarian carcinoma cells.

PURPOSE: Overexpression of interleukin 8 (IL-8) is associated with disease progression in human ovarian cancer. Hypoxia, a common feature in solid tumors, induces IL-8 expression in human ovarian carcinoma cells through activation of nuclear factor-kappa B and activating protein-1. Here we show the upstream components of these signal transduction pathways that lead to IL-8 expression under hypoxia. EXPERIMENTAL DESIGN: We incubated Hey-A8 human ovarian carcinoma cells under hypoxic condition (1% O(2)) and determined hypoxia regulation of phosphatidylinositol 3'-kinase (PI3K)/Akt pathway, mitogen-activated protein kinases (MAPKs), and effects of ras and vascular endothelial growth factor by Western and Northern blots, the use of specific inhibitors, in vitro kinase assays, luciferase reporter genes, and ELISA. RESULTS: While investigating the upstream signaling pathways, we found that Akt kinase and p38 MAPK are activated by hypoxia. Both hypoxia-induced Akt and p38 MAPK functional activity, and IL-8 mRNA and protein expression were reduced with the inhibition of PI3K and p38 MAPK. Oncogenic ras overexpression resulted in an increase in the hypoxia-induced IL-8 expression, whereas the inhibition of ras by transfection of dominant-negative ras inhibited the hypoxia-induced IL-8 expression. CONCLUSIONS: These results show that hypoxia activates ras, PI3K/Akt pathway, and p38 MAPK pathway to enhance IL-8 gene transcription under hypoxia, and suggest these signaling pathways as potential targets for controlling IL-8 expression and angiogenesis by human ovarian carcinoma cells.

Blotting, Northern↗
PubMed2004

Combined free-tissue transfer for primary reconstruction of radial part of the hand.

This paper presents 14 cases of primary reconstruction of radial-part hand defect by combined free-tissue transfer. The thumb was reconstructed by wraparound flap or second-toe transfer, while a lateral upper-arm flap or anterolateral thigh flap was transferred to cover the soft-tissue defect of the radial part of the hand. The arteries of the toe and flap were anastomosed and cascaded with the radial artery in an anatomical "snuffbox." Fourteen toes and 13 flaps survived in 14 cases. Only one flap was lost. Two-point discrimination of thumb tips was between 4-8 mm. The results suggest that combined free-tissue transfer appears to be a promising way of reconstructing a defect of the radial part of the hand.

Adult↗
PubMed2004

Kinetics of vascular normalization by VEGFR2 blockade governs brain tumor response to radiation: role of oxygenation, angiopoietin-1, and matrix metalloproteinases.

The recent landmark Phase III clinical trial with a VEGF-specific antibody suggests that antiangiogenic therapy must be combined with cytotoxic therapy for the treatment of solid tumors. However, there are no guidelines for optimal scheduling of these therapies. Here we show that VEGFR2 blockade creates a "normalization window"--a period during which combined radiation therapy gives the best outcome. This window is characterized by an increase in tumor oxygenation, which is known to enhance radiation response. During the normalization window, but not before or after it, VEGFR2 blockade increases pericyte coverage of brain tumor vessels via upregulation of Ang1 and degrades their pathologically thick basement membrane via MMP activation.

Angiogenesis Inhibitors↗
PubMed2004

The effect of premolar extractions on tooth size discrepancies.

The purpose of this study is to investigate the effect of premolar extractions on tooth size discrepancy. A total of 213 plaster casts were divided into a Bolton big (BB), a Bolton normal (BN) and a Bolton small (BS) group according to the Bolton normal value plus or minus one standard deviation. The Bolton overall ratio of each group was measured and compared before and after hypothetical premolar extractions. The Bolton overall ratios after premolar extractions were smaller than those before extraction in each group. Some of the patients in the BN group and BB group were moved into the BS group and BN group after premolar extractions. A tooth size discrepancy occurred in some patients with normal overall ratios after premolar extractions, but a tooth size discrepancy might be corrected in some patients with big overall ratios after premolar extraction.

Adolescent↗
PubMed2004

Advances on BYY harmony learning: information theoretic perspective, generalized projection geometry, and independent factor autodetermination.

The nature of Bayesian Ying-Yang harmony learning is reexamined from an information theoretic perspective. Not only its ability for model selection and regularization is explained with new insights, but also discussions are made on its relations and differences from the studies of minimum description length (MDL), Bayesian approach, the bit-back based MDL, Akaike information criterion (AIC), maximum likelihood, information geometry, Helmholtz machines, and variational approximation. Moreover, a generalized projection geometry is introduced for further understanding such a new mechanism. Furthermore, new algorithms are also developed for implementing Gaussian factor analysis (FA) and non-Gaussian factor analysis (NFA) such that selecting appropriate factors is automatically made during parameter learning.

Algorithms↗
PubMed2004

Bystin as a novel marker for reactive astrocytes in the adult rat brain following injury.

Bystin has been identified as a protein which mediates cellular interactions between trophoblastic and endometrial epithelial cells by forming complexes with two partners, trophinin and tastin, during embryo implantation. However, the presence of bystin in the central nervous system has not been demonstrated. Here, we report the cloning of the full-length cDNA of the rat bystin gene from adult brain. Immunohistochemical and RT-PCR analysis showed that the levels of bystin expression were markedly up-regulated in the both 6-hydrodopamine-lesioned rat nigrostriatum and stab-lesioned cerebral cortex in adult rats. Double immunofluorescence staining revealed that most bystin-expressing glial cells were astrocytes (immature or mature). To determine the mechanisms for the up-regulation of bystin expression in glial cells, primary cultures of postnatal cortical astrocytes were employed. Western blot analysis showed that the expression of bystin was elevated by treatment with pro-inflammatory mediators lipopolysaccharide and interleukin-1 beta. Nerve growth factor known to be released after brain injury also induced bystin expression in the cultures. Exposure of astrocyte cultures to the differentiating agent forskolin resulted in up-regulation of bystin followed by a pronounced astrocytic stellation. The results suggest that the injury in the adult brain induces spatiotemporal up-regulation of bystin and it could be influenced, at least in part, by elevation of intracellular cAMP level. Bystin expressed by reactive astrocytes may be involved in their differentiation during the inflammatory processes following brain injury. The reappearance of bystin may also indicate that some reactive astrocytes have the capacity to recapitulate early developmental stages.

Animals↗
PubMed2004

One-bit-matching conjecture for independent component analysis.

The one-bit-matching conjecture for independent component analysis (ICA) could be understood from different perspectives but is basically stated as "all the sources can be separated as long as there is a one-to-one same-sign-correspondence between the kurtosis signs of all source probability density functions (pdf's) and the kurtosis signs of all model pdf's" (Xu, Cheung, & Amari, 1998a). This conjecture has been widely believed in the ICA community and implicitly supported by many ICA studies, such as the Extended Infomax (Lee, Girolami, & Sejnowski, 1999) and the soft switching algorithm (Welling & Weber, 2001). However, there is no mathematical proof to confirm the conjecture theoretically. In this article, only skewness and kurtosis are considered, and such a mathematical proof is given under the assumption that the skewness of the model densities vanishes. Moreover, empirical experiments are demonstrated on the robustness of the conjecture as the vanishing skewness assumption breaks. As a by-product, we also show that the kurtosis maximization criterion (Moreau & Macchi, 1996) is actually a special case of the minimum mutual information criterion for ICA.

Algorithms↗
PubMed2004

[Molecular cloning, purification, and serological characterization of four specific antigens of Mycobacterium tuberculosis].

OBJECTIVE: To express the 14,000, 37,000, and 6,000 early secretory antigenic target (ESAT-6) and mtb81 antigen genes in bacteria, and to purify the product and determine their activity. METHODS: The 14,000, 37,000 , ESAT-6, and mtb81 antigen genes were amplified from Mycobacterium tuberculosis genomic DNA by polymerase chain reactions and cloned into pGEX 4T-1 expression vector. BL21 strain of Escherichia coli was transformed with the recombinant vectors and induced to express recombinant proteins. The proteins were purified by affinity chromatography. The biological activity of purified proteins were estimated by enzyme-linked immunoabsorbant assay (ELISA). RESULTS: The BL21 strains of Escherichia coli with recombinant vectors showed high level of 14,000, 37,000, ESAT-6, and mtb81 gene expressions after induction. The products were purified successfully and showed high antigenicity and specificity. The sensitivity of 38,000, 14,000, ESAT-6, and mtb81 were 54%, 60%, 44%, and 36%, respectively. CONCLUSION: The expressions and purifications of recombinant 14,000, 37,000, ESAT-6, and mtb81 antigens with natural activity facilitate their research and application.

Antigens, Bacterial↗
PubMed2004

[Adjustment methods of proportional pressure support on weaning during acute aggravation in chronic respiratory failure patients with chronic obstructive pulmonary disease].

OBJECTIVE: To study the effects of two adjustment methods of proportional pressure support (PPS) on patients with acute aggravation in chronic respiratory failure of chronic obstructive pulmonary disease. METHODS: Seventy-five patients were randomized to two groups, 30 in proportional adjustment group and 45 in target adjustment group, respectively. Suitable flow assist (FA) and volume assist (VA) were adjusted with proportional adjustment and target adjustment methods respectively according to the ventilation parameters until the weaning of ventilation. RESULTS: There were no significant differences in resistance, elastic, FA as well as VA on weaning point, duration of mechanical ventilation, and successful weaning rate between the two groups (all P>0.05). CONCLUSION: The same aim and successful weaning rate could be gained in the target adjustment group compared with the proportional adjustment group. More clinical experience and more intensive care would be needed in the target adjustment group.

Female↗
PubMed2004

Clinical application of axonal repair technique for treatment of peripheral nerve injury.

OBJECTIVE: To evaluate the efficacy of axonal repair technique for treatment of peripheral nerve injury clinically. METHODS: In 1998, the authors applied axonal repair technique to treat peripheral nerve injuries in 12 patients with 13 nerves. It consists of four steps, ie, stumps of the nerve being soaked in a modified Collins fluid, freezed, trimmed, and coapted with glue, making the injured nerve repaired at the axonal level. RESULTS: The patients were followed up for an average of 13 months. Results showed that in 4 cases of first-stage contralateral C7 transfer, regenerating axons reached to the sternoclavicular joint or axilla at 4 to 7 months, offering the timing for performing the second-stage contralateral C7 transfer. In 5 cases of accessory nerve transferred to the suprascapular nerve, the abduction of the shoulder was 40 degree on average. In the other 3 patients with four different nerves repaired, results were also satisfactory. CONCLUSIONS: This technique is promising in the treatment of peripheral nerve injury.

Adult↗