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Biomedical subjects

B Li

Publications and source records attributed to B Li.

At least 145 records · Page 8Linked to original sources
PubMed2001

Vascular endothelial cell growth factor-driven endothelial tube formation is mediated by vascular endothelial cell growth factor receptor-2, a kinase insert domain-containing receptor.

Vascular endothelial cell growth factor (VEGF) binds to 2 related receptor tyrosine kinases, known as kinase insert domain-containing receptor (KDR) and fms-like tyrosine kinase (Flt-1). The KDR has been shown to mediate VEGF-stimulated endothelial cell mitogenesis, migration, and permeability. The Flt-1 receptor has been suggested to mediate VEGF-stimulated endothelial branching morphogenesis, a process whereby endothelial cells, in the presence of a 3D milieu composed of extracellular matrix components and a mixture of growth factors, undergo a morphological transition into a tubular network with many lumina. In the present study, we have used 2 independent endothelial cell tube formation models and highly selective VEGF mutants for the KDR and Flt-1 receptors. We demonstrate that KDR, not Flt-1, stimulation is responsible for the induction of endothelial tubulogenesis. In addition, we demonstrate a modulatory role for Flt-1 in VEGF-mediated tube formation. We also report that VEGF-driven endothelial tube formation is inhibited by selective inhibitors of mitogen-activated protein kinase activation and p38 protein kinase.

Blood Vessels↗
PubMed2001

Rapid fabrication of three-dimensional porous films with biomimetic patterns by natural evaporation of amphiphilic polyacetylene solutions under ambient conditions.

A simple process for fast fabrication of thin films with biomimetic morphological structures from a group of linear homopolymers is developed. Natural evaporation of tetrahydrofuran, chloroform, and hexane-dichloromethane solutions of poly(phenylacetylene)s that contain amino acid and ethylene glycol moieties under ambient conditions instantly produces three-dimensional porous films with structural patterns reminiscent of honeycombs and radiolarian shells. Morphological analysis by optical and electronic microscopy suggests that vesicles of the amphiphilic polymers serve as building blocks in the self-organization to the biomimetic structures.

Acetylene↗
PubMed2001

A COL1A1 Sp1 binding site polymorphism predisposes to osteoporotic fracture by affecting bone density and quality.

Osteoporosis is a common disease with a strong genetic component. We previously described a polymorphic Sp1 binding site in the COL1A1 gene that has been associated with osteoporosis in several populations. Here we explore the molecular mechanisms underlying this association. A meta-analysis showed significant associations between COL1A1 "s" alleles and bone mineral density (BMD), body mass index (BMI), and osteoporotic fractures. The association with fracture was stronger than expected on the basis of the observed differences in BMD and BMI, suggesting an additional effect on bone strength. Gel shift assays showed increased binding affinity of the "s" allele for Sp1 protein, and primary RNA transcripts derived from the "s" allele were approximately three times more abundant than "S" allele--derived transcripts in "Ss" heterozygotes. Collagen produced from osteoblasts cultured from "Ss" heterozygotes had an increased ratio of alpha 1(I) protein relative to alpha 2(I), and this was accompanied by an increased ratio of COL1A1 mRNA relative to COL1A2. Finally, the yield strength of bone derived from "Ss" individuals was reduced when compared with bone derived from "SS" subjects. We conclude that the COL1A1 Sp1 polymorphism is a functional genetic variant that predisposes to osteoporosis by complex mechanisms involving changes in bone mass and bone quality.

Aged↗
PubMed2001

L-type Ca(2+) channel regulation by pituitary adenylate cyclase-activating polypeptide in vascular myocytes from spontaneously hypertensive rats.

Pituitary adenylate cyclase-activating polypeptide (PACAP), a vasoactive peptide, modulates the L-type Ca(2+) channel current (L channel current) in vascular smooth muscle cells (VSMC) through activation and integration of two intracellular pathways, protein kinase A and protein kinase C (PKC). In the present study we compared the effects of PACAP on the L channel current in VSMC from the spontaneously hypertensive rats (SHR) and normotensive controls, Wistar Kyoto rats (WKY). We found that compared with WKY, VSMC from SHR had a higher L channel current density. Stimulation by PACAP (10 nM) caused an increase in the amplitude of the whole cell current and prolonged open time in VSMC from SHR and WKY, with the increase greater in SHR. These effects of PACAP on the L channel current was mimicked by an activator of PKC. In contrast, PACAP caused a smaller increase in cAMP accumulation in VSMC from SHR than WKY, and there was no difference in the inhibitory effect of 8-bromo-cAMP on the L channel current from both type of cells. The greater increase in amplitude of the L channel current by PACAP in VSMC from SHR persisted in the presence of adenosine cyclic 3',5'-monophosphothioate, Rp-isomer, a cAMP antagonist, but not calphostin C, a PKC inhibitor. Taken together, our results show an increase in L channel current density and an enhanced PACAP effect on the L channel current in VSMC from SHR compared with WKY. This difference in PACAP response appears to be predominately secondary to an increased PKC sensitivity.

Animals↗
PubMed2001

SRYand architectural gene regulation: the kinetic stability of a bent protein-DNA complex can regulate its transcriptional potency.

Protein-directed DNA bending is proposed to regulate assembly of higher-order DNA-multiprotein complexes (enhanceosomes and repressosomes). Because transcriptional initiation is a nonequilibrium process, gene expression may be modulated by the lifetime of such complexes. The human testis-determining factor SRY contains a specific DNA-bending motif, the high-mobility group (HMG) box, and is thus proposed to function as an architectural factor. Here, we test the hypothesis that the kinetic stability of a bent HMG box-DNA complex can in itself modulate transcriptional potency. Our studies employ a cotransfection assay in a mammalian gonadal cell line as a model for SRY-dependent transcriptional activation. Whereas sex-reversal mutations impair SRY-dependent gene expression, an activating substitution is identified that enhances SRY's potency by 4-fold. The substitution (I13F in the HMG box; fortuitously occurring in chimpanzees) affects the motif's cantilever side chain, which inserts between base pairs to disrupt base pairing. An aromatic F13 cantilever prolongs the lifetime of the DNA complex to an extent similar to its enhanced function. By contrast, equilibrium properties (specific DNA affinity, specificity, and bending; thermodynamic stability and cellular expression) are essentially unchanged. This correlation between potency and lifetime suggests a mechanism of kinetic control. We propose that a locked DNA bend enables multiple additional rounds of transcriptional initiation per promoter. This model predicts the occurrence of a novel class of clinical variants: bent but unlocked HMG box-DNA complexes with native affinity and decreased lifetime. Aromatic DNA-intercalating agents exhibit analogous kinetic control of transcriptional elongation whereby chemotherapeutic potencies correlate with drug-DNA dissociation rates.

Amino Acid Sequence↗
PubMed2001

Face verification through tracking facial features.

We propose an algorithm for face verification through tracking facial features by using sequential importance sampling. Specifically, we first formulate tracking as a Bayesian inference problem and propose to use Markov chain Monte Carlo techniques for obtaining an empirical solution. A reparameterization is introduced under parametric motion assumption, which facilitates the empirical estimation and also allows verification to be addressed along with tracking. The facial features to be tracked are defined on a grid with Gabor attributes (jets). The motion of facial feature points is modeled as a global two-dimensional (2-D) affine transformation (accounting for head motion) plus a local deformation (accounting for residual motion that is due to inaccuracies in 2-D affine modeling and other factors such as facial expression). Motion of both types is processed simultaneously by the tracker: The global motion is estimated by importance sampling, and the residual motion is handled by incorporating local deformation into the measurement likelihood in computing the weight of a sample. Experiments with a real database of face image sequences are presented.

Journal Article↗
PubMed2001

IGF-1 overexpression inhibits the development of diabetic cardiomyopathy and angiotensin II-mediated oxidative stress.

Stimulation of the local renin-angiotensin system and apoptosis characterize the diabetic heart. Because IGF-1 reduces angiotensin (Ang) II and apoptosis, we tested whether streptozotocin-induced diabetic cardiomyopathy was attenuated in IGF-1 transgenic mice (TGM). Diabetes progressively depressed ventricular performance in wild-type mice (WTM) but had no hemodynamic effect on TGM. Myocyte apoptosis measured at 7 and 30 days after the onset of diabetes was twofold higher in WTM than in TGM. Myocyte necrosis was apparent only at 30 days and was more severe in WTM. Diabetic nontransgenic mice lost 24% of their ventricular myocytes and showed a 28% myocyte hypertrophy; both phenomena were prevented by IGF-1. In diabetic WTM, p53 was increased in myocytes, and this activation of p53 was characterized by upregulation of Bax, angiotensinogen, Ang type 1 (AT(1)) receptors, and Ang II. IGF-1 overexpression decreased these biochemical responses. In vivo accumulation of the reactive O(2) product nitrotyrosine and the in vitro formation of H(2)O(2)-(.)OH in myocytes were higher in diabetic WTM than TGM. Apoptosis in vitro was detected in myocytes exhibiting high H(2)O(2)-(.)OH fluorescence, and apoptosis in vivo was linked to the presence of nitrotyrosine. H(2)O(2)-(.)OH generation and myocyte apoptosis in vitro were inhibited by the AT(1) blocker losartan and the O(2) scavenger TIRON: In conclusion, IGF-1 interferes with the development of diabetic myopathy by attenuating p53 function and Ang II production and thus AT(1) activation. This latter event might be responsible for the decrease in oxidative stress and myocyte death by IGF-1.

Angiotensin II↗
PubMed2001

In vivo effects of IL-4, IL-10, and amifostine on cytokine production in patients with acute myelogenous leukemia.

Both IL-4 and IL-10 have been shown in vitro to inhibit leukemia cell secretion of IL-1beta, GM-CSF, and TNFalpha, and increase leukemia cell release of IL-1ra. In this study, we have investigated the in vivo effects of IL-4, IL-10, and amifostine on cytokine production in patients with acute myelogenous leukemia (AML). Serum IL-1ra, IL-1beta, TNFalpha, GM-CSF, and SCF levels were measured in AML patients who received IL-4, IL-10, or amifostine. No significant changes in the serum levels of IL-1ra, IL-1beta, TNFalpha, GM-CSF, and SCF were found in AML patients who received amifostine. Both IL-4 and IL-10 were found to increase serum IL-1ra. This data is in accord with the in vitro studies. However, IL-4 increased serum GM-CSF levels and IL-10 increased serum IL-1beta and TNFalpha levels. These in vivo effects of the two cytokines differ from their in vitro effects. Despite the similar effects of IL-4 and IL-10 on cytokine production by AML cells in vitro, different effects were observed in AML patients in vivo. IL-4 increased serum SCF levels, whereas IL-10 decreased serum SCF levels. IL-4 increased serum GM-CSF levels, whereas IL-10 had no effect on them. Although IL-10 increased serum IL-1beta and TNFalpha levels, IL-4 had no effect on them. These findings indicate that the in vitro effects of IL-4 and IL-10 do not necessarily reflect their in vivo effects, and that the complex effects of the two cytokines on serum cytokine levels make it difficult to predict their therapeutic potential.

Amifostine↗
PubMed2001

Blocking L-selectin and alpha4-integrin changes donor cell homing pattern and ameliorates murine acute graft versus host disease.

L-selectin, LFA-1 and alpha(4) integrins play important roles in the homing of naïve T cells into peripheral lymphoid tissues. L-selectin- or LFA-1-deficient lymphocytes cannot effectively home to lymph nodes (LN), and antibody blockade of alpha(4) integrins also hinders lymphocytes homing. The present study was initiated to explore whether it is feasible to ameliorate acute graft-versus-host disease (aGVHD) by modulating the homing process of donor cells in the recipient in a mouse model. Using a fluorescence labeling method, we found that two monoclonal antibodies directed at L-selectin and alpha(4) integrins, respectively, when used in combination, could delay half of the donor C57BL/6J mouse spleen cells homing into the LN of recipient BALB/c mouse 15 h after injection. Spleen cells (1 x 10(7)) derived from C57BL/6J (H-2(b)) mice were injected into each C.B-17 SCID recipient mouse (H-2(d)) with or without prior incubation with 10 microg each of the two antibodies. T cell repopulation in the blood was observed in both groups of mice at a comparable level 14 days after injection of the donor cells. Eight control mice started to show aGVHD signs 7 - 14 days after the injection, and all died by day 31. However, among the ten mice that received the antibody-treated donor cells, two died before day 29, four survived between 36 and 78 days, and the remaining four survived more than 150 days, with two of them aGVHD free. It is apparent that the temporarily reduced lymphocyte homing into LN reduced the alloreactivity of the donor T cells, thus providing a simple way of modifying aGVHD. This novel approach may shed light on the prevention of aGVHD associated with clinical bone marrow transplantation.

Acute Disease↗
PubMed2001

Study of iron metabolism abnormality in the hepatocyte damage of hepatitis B.

OBJECTIVE: To study the effect of iron metabolism on patients with hepatitis B. METHODS: Hemoglobin (Hb), serum ferritin (SF), transferritin (TRF), serum iron (SI), and total iron binding capacity (TIBC) were detected in 103 patients with hepatitis B and 20 healthy adults. RESULTS: The severer the hepatocyte damage was, the higher the SF, SI and the lower the Hb, TRF, and TIBC were. Furthermore, it seems more obvious among fulminant hepatitis and liver cirrhosis. CONCLUSIONS: The overload of iron may enhance the hepatocyte damage induced by HBV. Therefore, to detect serum markers of iron metabolism is helpful to evaluate curative effect and prognosis of hepatitis B.

Adolescent↗
PubMed2001

[Effects of heat shock protein 70 overexpression on apoptosis of K562 cell caused by hyperthermia].

In order to observe the effects of heat shock protein 70(HSP70) on the apoptosis of K562 cell caused by hyperthermia, HSP70 was induced by pre-heating K562 cells at 40 degrees C and the levels of HSP70 were detected by RT-PCR. Cell apoptosis caused by hyperthermia at 43 degrees C was observed by Fluid cytometry (FCM) DNA content analyses. The results showed that HSP70 increased with the prolong of pre-heating time and reached the top level on pre-heating for 120 min and lasted for several hours. A lower apoptosis rate and less DNA ladder forming in the pre-heated cells than those not pre-heated. It is concluded that the higher expression of HSP70 induced by pre-heating treatment could inhibited the apoptosis caused by hyperthermia.

Apoptosis↗
PubMed2001

[The numerical simulation of the dynamic stress field from impacting head].

In order to study the mechanism of impact injury to the head, we have simulated the development of the stress field by using the numerical simulation method. The process of the head having been impacted vertically by an impactor can be described as a 2D problem, and the reactions of the head subjected to impacted force can be simulated and analyzed by the method based on the finite difference method (FDM). The model is subjected to applied force by an impactor with the initial velocity of 25 m/s (90 km/h). The pre-processing for the model is done on the microcomputer software. Once imported to the software, the nodes and elements are generated and material characteristics are assigned. The results demonstrate that the high resolution computer graphics can provide the dynamic distribution of the stress field, which can clearly show how the stress is developed, and how many its value is. The results are helpful to understanding the mechanism of impact injury to head.

Craniocerebral Trauma↗
PubMed2001

Correlation between the expression of cyclin A protein and p53 activity in oral squamous cell carcinomas.

Cyclins and wild-type p53 protein are prime cell cycle regulators and may be involved in tumorigenesis. Cyclin A is a late S cyclin and its abnormalities have been reported in several cancers, including oral squamous cell carcinomas. To explore whether aberrant G1/S in p53 mutant tumours leads to increased cyclin A protein in oral squamous cell carcinomas (OSCC), a total of 39 samples were evaluated for the expression of cyclin A and p53 protein by an immunohistochemical method using a labelled polymer assay. These samples comprised two hyperkeratotic and three oral premalignant lesions (two moderate and one severe dysplastic lesions), and 27 OSCC, together with seven healthy controls. The results demonstrated that the cyclin A protein was localized and highly expressed in the nuclei of the tumour cells. Although there was no correlation between cyclin A detection and the local lymph node involvement, a positive correlation was noted between the positivity of cyclin A and p53 protein (p <0.05). The results suggested that cyclin A may contribute to the progression of oral cancer and correlated to some degree with that of the p53 gene activity.

Carcinoma, Squamous Cell↗
PubMed2001

Evidence for nonacetylcholinesterase targets of organophosphorus nerve agent: supersensitivity of acetylcholinesterase knockout mouse to VX lethality.

The possibility that organophosphate toxicity is due to inhibition of targets other than acetylcholinesterase (AChE, EC 3.1.1.7) was examined in AChE knockout mice. Mice (34-55 days old) were grouped for this study, after it was determined that AChE, butyrylcholinesterase (BChE), and carboxylesterase activities had reached stable values by this age. Mice with 0, 50, or 100% AChE activity were treated subcutaneously with the nerve agent VX. The LD50 for VX was 10 to 12 microg/kg in AChE-/-, 17 microg/kg in AChE+/-, and 24 microg/kg in AChE+/+ mice. The same cholinergic signs of toxicity were present in AChE-/- mice as in wild-type mice, even though AChE-/- mice have no AChE whose inhibition could lead to cholinergic signs. Wild-type mice, but not AChE-/- mice, were protected by pretreatment with atropine. Tissues were extracted from VX-treated and untreated animals and tested for AChE, BChE, and acylpeptide hydrolase activity. VX treatment inhibited 50% of the AChE activity in brain and muscle of AChE+/+ and +/- mice, 50% of the BChE activity in all three AChE genotypes, but did not significantly inhibit acylpeptide hydrolase activity. It was concluded that the toxicity of VX must be attributed to inhibition of nonacetylcholinesterase targets in the AChE-/- mouse. Organophosphorus ester toxicity in wild-type mice is probably due to inhibition or binding to several proteins, only one of which is AChE.

Acetylcholinesterase↗
PubMed2001

[Study on preparation and properties of moisture permeable polyurethane membrane used for dressings].

A new hydrophilic polyurethane(PU) performed-polymer has been developed with polyethylene glycol(PEG) instead of general polyether. The solution of performed-polymer is poured casting a permeable membrane used for the outer layer of the bilayer dressings. The effects of molecular weigh (Mn) of PEG, the usage of cross-link agents, solvents and water in the solution on the moisture permeation of PU membrane have been studied. It has been shown that the membrane prepared is a porous moisture permeable membrane. The optimum conditions of preparing membrane are: Mn of PEG is 2,000-4,000, the mixture of acetone and N,N-dimethylformamide (DMF) is used as solvents, and the temperature of performance membrane is 50 degrees C-80 degrees C. The moisture permeability of the PU membrane is 49-60 g/m2.h at 35 degrees C, which can meet the requirement of the wound dressings. In addition, the mechanism of the moisture permeation of PU membrane has been discussed.

Bandages↗
PubMed2001

Analysis of normal epithelial cell specific-1 (NES1)/kallikrein 10 mRNA expression by in situ hybridization, a novel marker for breast cancer.

PURPOSE: Normal epithelial cell specific-1 (NES1)/kallikrein 10 gene is expressed in normal mammary and prostate epithelial cells, but the expression of NES1 mRNA and protein is markedly reduced in established breast and prostate cancer cell lines although the NES1 gene is intact. Here, we wished to assess whether NES1 expression is down-regulated in primary breast cancers. EXPERIMENTAL DESIGN: We developed and used an in situ hybridization technique with an antisense NES1 probe to detect NES1 mRNA in sections of normal breast specimens, typical and atypical ductal hyperplasia, ductal carcinoma in situ, and infiltrating ductal carcinoma. RESULTS: All of the 30 normal breast specimens showed high NES1 expression. Notably, 18 (75%) of 24 typical and atypical breast hyperplasia specimens showed high NES1 expression, with weak-to-moderate expression in 6 (25%). Significantly, 13 (46%) of 28 ductal carcinoma in situ specimens lacked NES1 expression, and the remaining 15 (54%) showed weak-to-moderate expression. Finally, 29 of 30 (97%) infiltrating ductal carcinoma grades I-III samples lacked NES1 mRNA, with weak expression in the remaining one sample. CONCLUSIONS: Our results demonstrate that NES1 mRNA is expressed in normal breast tissue and benign lesions, with loss of NES1 expression during tumor progression. We suggest that NES1 expression may serve as a molecular tool in the study of breast cancer progression. Studies with larger series of specimens should help assess whether NES1 expression can be a diagnostic and/or prognostic marker in breast and other cancers.

Biomarkers, Tumor↗
PubMed2001

[Clinical study: the effects of inhaling nitrous oxide for analgesia labor on pregnant women and fetus].

OBJECTIVE: To investigate the effect of the inhalation of nitrous oxide premixed with oxygen (50%:50%) for analgesia labor on maternal and fetus. METHODS: A total of 100 cases of pregnant women were provided with nitrous oxide premixed with oxygen (50%:50%) (control group); Another 100 cases were provided only with oxygen (comparison group). Recording duration of the Labor, way of delivery, bleeding volume, Apgars score, blood gas analysis to maternal radius artery and fetal umbilical blood among all patients. RESULTS: The effect for analgesia labor of the premixed gas was much better than that of control group, but there were no significant differences in time of labor, bleeding volume, Apgars score between the two groups. CONCLUSIONS: The inhalation of nitrous oxide premixed with oxygen (50%:50%) for analgesia labor benefits pregnant women because of keeping them being a good mental and physical condition. The inhalation of nitrous oxide for analgesia labor is a safe, effective and easy method.

Adult↗