PubMed Health⌕ Search

Biomedical subjects

Lei Xu

Publications and source records attributed to Lei Xu.

At least 91 records · Page 5Linked to original sources
PubMed2004

[Comparison of habitats and seasonally differentiated distribution patterns of fig wasp populations associated with Ficus racemosa in Xishuangbanna].

The population distribution patterns of fig wasps associated with Ficus racemosa in Xishuangbanna were studied by using several indexes. The results indicated that the distribution patterns of 6 fig wasp species were all clump. The aggregative intensity of pollinating wasp (Ceratosolen fusciceps) population at primeval rain forest was nearly equal to that at seriously disturbed site, whereas they were both much higher than that at moderately disturbed site. In the meanwhile, the population aggregative intensity for the same wasp species was higher in rainy season than in dry-hot season, and the lowest was occurred in foggy-cool season. Non-pollinating wasp (Platyneura testacea, Platyneura mayri, Platyneura agraensis, Apocrypta westwoodi, Apocrypta sp.) population and each of their sex group were varied significantly in aggregative intensity, responding to the habitat change and seasonal alteration. The protection of original habitat should be focused on the protection of the mutualism of Ficus racemosa and fig wasps.

Algorithms↗
PubMed2004

[Altered expression of PTEN gene and LOH of its epigenetic microsatellite in gastric carcinoma].

OBJECTIVE: To investigate the expression of PTEN and loss of heterozygosity (LOH) of its epigenetic microsatellite in gastric carcinoma and explore their roles in progression of gastric carcinoma. METHODS: LOH of epigenetic microsatellites of PTEN (D10S541, D10S583 and D10S1687) in advanced gastric cancer was detected by PCR-SSCP. Expression of PTEN mRNA and protein in normal gastric mucosa and gastric cancer was evaluated by RT-PCR and SABC immunohistochemistry, respectively. The relationship between expression of PTEN mRNA and protein and lymph node metastasis or LOH of microsatellites was discussed. RESULTS: LOH of D10S541, D10S583 and D10S1687 was found in 37.5% (21/56) of advanced gastric cancers. The positive rates of PTEN mRNA expression were 80.4% (45/56), 45.5% (5/11) and 32.1% (18/56) in normal mucosa, early and advanced gastric carcinomas, respectively, while 78.6% (44/56), 44.5% (5/11) and 28.6% (16/56) at the protein level. PTEN mRNA and protein were less frequently expressed in early and advanced gastric carcinomas than that in normal gastric mucosa (P < 0.05). There was positive correlation between PTEN mRNA expression and LOH of microsatellites in advanced gastric carcinomas. PTEN protein expression paralleled with its mRNA expression (P < 0.05). The expression of PTEN mRNA and protein was negatively correlated with lymph node metastasis of advanced gastric carcinomas (P < 0.05). CONCLUSION: Down-regulated expression of PTEN gene is found in different stages of gastric carcinoma, and is closely correlated with LOH of its epigenetic microsatellites, which probably is its underlying molecular mechanisms. It suggests that altered PTEN gene contributes to tumorigenesis and progression of gastric carcinomas.

Gastric Mucosa↗
PubMed2003

Paracrine regulation of angiogenesis and adipocyte differentiation during in vivo adipogenesis.

With an increasing incidence of obesity worldwide, rational strategies are needed to control adipogenesis. Growth of any tissue requires the formation of a functional and mature vasculature. To gain mechanistic insight into the link between active adipogenesis and angiogenesis, we developed a model to visualize noninvasively and in real time both angiogenesis and adipogenesis using intravital microscopy. Implanted murine preadipocytes induced vigorous angiogenesis and formed fat pads in a mouse dorsal skin-fold chamber. The newly formed vessels subsequently remodeled into a mature network consisting of arterioles, capillaries, and venules, whereas the preadipocytes differentiated into adipocytes as confirmed by increased aP2 expression. Inhibition of adipocyte differentiation by transfection of preadipocytes with a peroxisome proliferator-activated receptor gamma dominant-negative construct not only abrogated fat tissue formation but also reduced angiogenesis. Surprisingly, inhibition of angiogenesis by vascular endothelial growth factor receptor-2 (VEGFR2) blocking antibody not only reduced angiogenesis and tissue growth but also inhibited preadipocyte differentiation. We found that part of this inhibition stems from the paracrine interaction between endothelial cells and preadipocytes and that VEGF-VEGFR2 signaling in endothelial cells, but not preadipocytes, mediates this process. These findings reveal a reciprocal regulation of adipogenesis and angiogenesis, and suggest that blockade of VEGF signaling can inhibit in vivo adipose tissue formation. The full text of this article is available online at http://www.circresaha.org.

3T3 Cells↗
PubMed2003

Obesity, tamoxifen use, and outcomes in women with estrogen receptor-positive early-stage breast cancer.

BACKGROUND: Obesity is associated with both increased breast cancer risk and poorer prognosis after disease onset. However, little is known about the effect of obesity on treatment efficacy. We evaluated the association of obesity with outcomes and with tamoxifen efficacy in women with early-stage, hormone-responsive breast cancer participating in a multicenter cancer cooperative group clinical trial. METHODS: The cohort consisted of 3385 women enrolled in National Surgical Adjuvant Breast and Bowel Project (NSABP) protocol B-14, a randomized, placebo-controlled trial evaluating tamoxifen for lymph node-negative, estrogen receptor (ER)-positive breast cancer. Hazards of breast cancer recurrence, contralateral breast tumors, other new primary cancers, and several mortality endpoints were evaluated in relation to body mass index (BMI), using statistical modeling to adjust for other prognostic factors. Median follow-up time was 166 months. All statistical tests were two-sided. RESULTS: The hazard of breast cancer recurrence was the same among obese (BMI > or =30.0 kg/m2) women as compared with underweight and normal-weight women (BMI <25.0; hazard ratio [HR] = 0.98, 95% confidence interval [CI] = 0.80 to 1.18). Contralateral breast cancer hazard was higher in obese women than in underweight/normal-weight women (HR = 1.58, 95% CI = 1.10 to 2.25), as was the risk of other primary cancers (HR = 1.62, 95% CI = 1.16 to 2.24). Compared with normal-weight women, obese women had greater all-cause mortality (HR = 1.31, 95% CI = 1.12 to 1.54) and greater risk of deaths due to causes unrelated to breast cancer (HR = 1.49, 95% CI = 1.15 to 1.92). Breast cancer mortality was not statistically significantly increased for obese women (HR = 1.20, 95% CI = 0.97 to 1.49). Tamoxifen reduced breast cancer recurrence and mortality, regardless of BMI. CONCLUSIONS: For women with lymph node-negative, ER-positive breast cancer, obesity was not associated with a material increase in recurrence risk or a change in tamoxifen efficacy. However, because obesity was associated with increased risks of contralateral breast cancer, of other primary cancers, and of overall mortality, it may influence long-term outcomes for breast cancer survivors.

Adult↗
PubMed2003

Intense directional lasing from a deformed square-shaped organic-inorganic hybrid glass microring cavity.

Intense directional light emission from a deformed square-shaped organic light-emitting microring cavity was observed. The ring cavity was a dye-doped organic-inorganic hybrid glass film coated upon a square-shaped fiber. From the near-field and far-field emission patterns and their emission spectra we found, for the first time to our knowledge, the simultaneous existence of chaotic whispering-gallery modes and four-bounce reflection modes. The two types of mode have different emission directions, different lasing thresholds, and different spectral linewidths. High-contrast angle-modulated light emission was also observed. We could control modulation and angular spread of emission by controlling the deformation of the cavity.

Journal Article↗
PubMed2003

Differential vascular and transcriptional responses to anti-vascular endothelial growth factor antibody in orthotopic human pancreatic cancer xenografts.

PURPOSE: The objectives of this study were to investigate the effects of anti-vascular endothelial growth factor (VEGF) treatment on various vascular functions, gene expression, and growth of orthotopic human pancreatic cancer xenografts and thus to provide useful preclinical data for novel cancer treatments. EXPERIMENTAL DESIGN: Small pieces of a human pancreatic carcinoma, PANC-1, were implanted into the pancreas of male severe combined immunodeficient mice. The animals were treated with anti-human VEGF antibody A.4.6.1 (300 micro g, every 3 days i.p.) or a nonspecific IgG between 4 and 8 weeks after tumor implantation. Then, vascular density, diameter, permeability, and tumor growth were determined by intravital microscopy. Subsequently, tumors were harvested, and angiogenic gene expression profile was determined by a microarray kit including 96 genes involved in tumor angiogenesis. RESULTS: Anti-VEGF antibody significantly reduced angiogenesis and growth of orthotopic PANC-1 tumors. In the anti-VEGF treatment group, the vessel density was significantly smaller (67.8 +/- 10.6 cm/cm(2)) than that seen in the control group (146.7 +/- 10.0 cm/cm(2)). However, vessel diameter and permeability were not altered significantly by anti-VEGF antibody treatment. The pancreatic tumors in the treated group were significantly smaller than those in the control group. Microarray and subsequent Northern blot and semiquantitative reverse transcription-PCR analyses revealed both a decrease (fibroblast growth factor 1, transforming growth factor beta1, platelet-derived growth factor alpha, erbB2, and c-ets1,) and an increase (placenta growth factor, hypoxia-inducible factor alpha, and endoglin) in expression of angiogenesis-related genes in the PANC-1 tumors by anti-VEGF treatment. CONCLUSIONS: Anti-VEGF antibody treatment has differential effects on vessel functions as well as angiogenic gene expression and inhibitory effects on angiogenesis and growth of the orthotopic pancreatic tumor. Anti-VEGF strategy appears promising for pancreatic cancer treatment.

Animals↗
PubMed2003

Early dynamics of guest-host interaction in dye-doped liquid crystalline materials.

We have studied in detail the early dynamics of laser-induced molecular reorientation in a dye-doped liquid crystalline (LC) medium that exhibits a significant enhancement of the optical Kerr nonlinearity due to guest-host interaction. Experimental results agree quantitatively with theory based on a model in which the anisotropic dye excitation helps reorient the LC molecules through a mean-field intermolecular interaction.

Journal Article↗
PubMed2003

Suppression of beating noise of narrow-linewidth erbium-doped fiber ring lasers by use of a semiconductor optical amplifier.

Beating noise in narrow-linewidth erbium-doped fiber ring lasers puts severe limitations on applications of the lasers. We demonstrate the suppression of beating noise in fiber ring lasers by using a semiconductor optical amplifier in the laser cavity, which acts as a high-pass filter. Two different ring structures are presented as examples to demonstrate this beating noise suppression.

Journal Article↗
PubMed2003

Microsurgical treatment for bilateral thumb defect: five case reports.

The authors present a new and efficient treatment for reconstruction of bilateral defective thumbs by different configured toe-tissues transplantations in a single stage, including bilateral second-toe transfer in 2 cases, bilateral hallux wrap-around flap transfer in 1 case, bilateral modified hallux wrap-around flap transfer in 1 case, and combined second toe with island flap with neurovascular pedicles from the proximal and dorsal aspect of the index finger transfer in 1 case. In total, eight transferred tissues survived uneventfully after circulation monitor and medicine administration according to the rules of microsurgery, and in two other transferred toe tissues, temporary circulation crises occurred. Over a 1-year follow-up, the satisfactory appearance and excellent function of the reconstructed bilateral thumbs were noted. For ensuring the success of the procedure, the authors emphasize the establishment of a double artery supply and venous return-flow systems and the modification of the hallux wrap-around flap dissection and tendon repair. Meanwhile, three-stage systemically functional rehabilitations also improved functional restoration of reconstructed thumbs.

Accidents, Occupational↗
PubMed2003

Repair of avulsion injury of the whole hand with single-stage transfer of five combined tissues: case report.

The authors present a 32-year-old man with an entire left hand avulsion injury. This was repaired in one stage with five free-tissue transfers, a combination of a left hallux wrap-around flap for thumb reconstruction, bilateral second toes for middle and ring finger reconstruction, and bilateral femoral anterolateral flaps for coverage of the injured hand at the palmar and dorsal aspects. All the transfers survived uneventfully. Due to enlargement of the flaps and narrowness of the first web space, three further surgical procedures were subsequently carried out. Over a 2-year follow-up, a satisfactory appearance of the reconstructed hand and functional restoration were obtained.

Accidents, Occupational↗
PubMed2003

The temporal-spatial expression of VEGF, angiopoietins-1 and 2, and Tie-2 during tumor angiogenesis and their functional correlation with tumor neovascular architecture.

Angiopoietins play a pivotal role in tumor angiogenesis by modulating vascular endothelial proliferation and survival. The expression of angiopoietins 1 and 2 (Ang-1 and Ang-2) and vascular endothelial growth factor (VEGF) has been documented in human malignant glioma. The expression of Ang-1, Ang-2, VEGF, and Tie-2, a member of the receptor tyrosine kinases and the natural receptor for both Ang-1 and Ang-2, follows a distinct transcriptional profile in vivo. Ang-2 and VEGF were expressed early in tumor formation and their levels increased throughout tumor growth. Their expression coincided with the expansion of the tumor mass and the formation of the vascular tree. There was no significant change in the expression of Tie-2 and Ang-1. The expression of Ang-1 and Tie-2 was more noticeable at the periphery of the tumor. The expression of Ang-2 was more robust at the periphery and within the tumor mass, and VEGF was more concentrated within the center of the tumor. This distinct expression profile may explain the morphology of the newly formed vessels at various times and regions of the tumor. The lack of concomitant expression of Ang-1 may underscore the unopposed endovascular induction by Ang-2 and VEGF resulting in the chaotic appearance and fragility of tumor vessels.

Angiopoietin-1↗
PubMed2003

A role for advanced glycation end products in diminished bone healing in type 1 diabetes.

The effect of type 1 diabetes on bone healing and bone formation in standardized craniotomy defects created in BALB/cByJ mice was determined. The hypothesis that advanced glycation end products (AGEs) contribute to diminished bone healing in diabetes was evaluated by assessing for the presence of the receptor for advanced glycation end products (RAGE) by immunohistochemistry in healing craniotomy defects in diabetic animals. The effect of local application of a known RAGE protein ligand, N(epsilon)-(carboxymethyl)lysine (CML)-mouse serum albumin (MSA), on craniotomy defect healing in normal animals was then assessed and compared to the effects of control MSA. Finally, evidence in support of the expression of RAGE mRNA and protein in osteoblastic cells was obtained. The results indicated that craniotomy defects in diabetic animals healed approximately 40% of the degree to which they healed in nondiabetic animals (P < 0.05). RAGE was expressed at higher levels in healing bone tissues in diabetic compared to control animals. Further studies in nondiabetic animals indicated that bone healing was reduced by 63 and 42% in lesions treated with 900 and 90 micro g CML-MSA, respectively, compared to in animals treated with MSA alone (P < 0.05). Evidence for the expression of RAGE was obtained in mouse and rat osteoblastic cultures. These results support the contribution of AGEs to diminished bone healing in type 1 diabetes, possibly mediated by RAGE.

3T3 Cells↗
PubMed2002

Induction of angiogenesis in a mouse model using engineered transcription factors.

The relationship between the structure of zinc-finger protein (ZFP) transcription factors and DNA sequence binding specificity has been extensively studied. Advances in this field have made it possible to design ZFPs de novo that will bind to specific targeted DNA sequences. It has been proposed that such designed ZFPs may eventually be useful in gene therapy. A principal advantage of this approach is that activation of an endogenous gene ensures expression of the natural array of splice variants. Preliminary studies in tissue culture have validated the feasibility of this approach. The studies reported here were intended to test whether engineered transcription factors are effective in a whole-organism model. ZFPs were designed to regulate the endogenous gene encoding vascular endothelial growth factor-A (Vegfa). Expression of these new ZFPs in vivo led to induced expression of the protein VEGF-A, stimulation of angiogenesis and acceleration of experimental wound healing. In addition, the neovasculature resulting from ZFP-induced expression of Vegfa was not hyperpermeable as was that produced by expression of murine Vegfa(164) cDNA. These data establish, for the first time, that specifically designed transcription factors can regulate an endogenous gene in vivo and evoke a potentially therapeutic biophysiologic effect.

3T3 Cells↗
PubMed2002

Tumour biology: herceptin acts as an anti-angiogenic cocktail.

Malignant tumours secrete factors that enable them to commandeer their own blood supply (angiogenesis), and blocking the action of these factors can inhibit tumour growth. But because tumours may become resistant to treatments that target individual angiogenic factors by switching over to other angiogenic molecules, a cocktail of multiple anti-angiogenic agents should be more effective. Here we show that herceptin, a monoclonal antibody against the cell-surface receptor HER2 (for human epidermal growth factor receptor-2; ref. 4), induces normalization and regression of the vasculature in an experimental human breast tumour that overexpresses HER2 in mice, and that it works by modulating the effects of different pro- and anti-angiogenic factors. As a single agent that acts against multiple targets, herceptin, or drugs like it, may offer a simple alternative to combination anti-angiogenic treatments.

Angiogenesis Inhibitors↗