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Biomedical subjects

Mei Li

Publications and source records attributed to Mei Li.

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

Visual evoked potential changes related to illusory perception in normal human subjects.

To study the human brain activity correlated with illusory perception, we chose a physically flat plane figure which looks like a convex figure. We studied visual evoked potential (VEP) changes, which reflect perceptual properties of illusory perception. We defined two paradigms, an illusory paradigm (IP) and a control paradigm (CP). Two stimuli, A and B, were randomly presented in the IP, while stimuli C and D were randomly presented in the CP. Stimulus A was the only figure which looked like a convex figure. A three-way analysis of variance was applied to the VEP components in each paradigm, with three factors: figures, electrodes, and sessions. Different configuration patterns between the two paradigms explained different grand mean VEP waveforms between the two paradigms; a greater N1 for the CP, a greater P1 for the IP, and marked attenuation of the N3 and P3 components for the IP. Significant main effects of figures only for the IP were found on P1 and P1N2 amplitude and P2 latency, which are assumed to reflect perceptual properties of stereoscopical illusory perception.

Adult↗
PubMed2004

Activation of gene expression by triplex-directed psoralen crosslinks.

Psoralen-conjugated triplex-forming oligonucleotides (pso-TFOs) can target photochemical adducts to specific DNA sequences. Here, we have used pso-TFOs to activate gene expression on a plasmid. We designed a pso-TFO adapter, consisting of a single-stranded TFO for targeting DNA, linked to a double-stranded hairpin segment that contains a hybrid ecdysone response element (E/GRE) enhancer for binding activated ecdysone receptors. When targeted to the 5' flanking region of a minimal promoter, this pso-TFO adapter increased the expression of a downstream reporter gene three- to four-fold. Gene activation, however, was independent of both the E/GRE hairpin of the adapter and ecdysone receptors, suggesting it was due to an intrinsic effect of triplex. Gene activation was dependent on psoralen photo-crosslinking. Gene activation by pso-TFOs in which the psoralen was linked to the TFO via a disulfide bond was similar before and after detachment of the TFO and its release from the triplex. These results indicate that psoralen photo-crosslinks play a prominent role in activation. Gene activation was undiminished in XPA, XPD and XPG human cell lines, indicating that activation was not dependent on the complete nucleotide excision repair (NER) pathway. Collectively, these results demonstrate that TFOs can be used to direct psoralen crosslinks adjacent to a gene as a way of activating gene expression.

Binding Sites↗
PubMed2004

Tissue-specific and inducible Cre-mediated recombination in the gut epithelium.

We generated two complementary systems for Cre-mediated recombination of target genes in the mouse digestive epithelium and tested them with a Cre-reporter mouse strain. Cre was expressed under the control of a 9 kb regulatory region of the murine villin gene (vil-Cre). Genetic recombination was initiated at embryonic day (E) 9 in the visceral endoderm, and by E12.5 in the entire intestinal epithelium, but not in other tissues. Cre expression was maintained throughout adulthood. Furthermore, transgenic mice bearing a tamoxifen-dependent Cre recombinase (vil-Cre-ERT2) expressed under the control of the villin promoter were created to perform targeted spatiotemporally controlled somatic recombination. After tamoxifen treatment, recombination was detectable throughout the digestive epithelium. The recombined locus persisted for 60 days after tamoxifen administration, despite rapid intestinal cell renewal, indicating that epithelial progenitor cells had been targeted. The villin-Cre and villin-Cre-ERT2 mice provide valuable tools for studies of cell lineage allocation and gene function in the developing and adult intestine.

Animals↗
PubMed2004

S-adenosylmethionine and its metabolite induce apoptosis in HepG2 cells: Role of protein phosphatase 1 and Bcl-x(S).

S-adenosylmethionine (SAMe) and its metabolite 5'-methylthioadenosine (MTA) are proapoptotic in HepG2 cells. In microarray studies, we found SAMe treatment induced Bcl-x expression. Bcl-x is alternatively spliced to produce two distinct mRNAs and proteins, Bcl-x(L) and Bcl-x(S). Bcl-x(L) is antiapoptotic, while Bcl-x(S) is proapoptotic. In this study we showed that SAMe and MTA selectively induced Bcl-x(S) in a time- and dose-dependent manner in HepG2 cells. There are three transcription start sites in the human Bcl-x gene which yield only Bcl-x(L) in control HepG2 cells. SAMe and MTA treatment did not affect promoter usage, but while one promoter yielded only Bcl-x(L), the other two yielded both Bcl-x(L) and Bcl-x(S), with Bcl-x(S) as the predominant messenger RNA (mRNA) species. Trichostatin A, 3-deaza-adenosine, cycloleucine, and okadaic acid had no effect on Bcl-x(S) induction by SAMe or MTA. Calyculin A and tautomycin, on the other hand, blocked SAMe and MTA-mediated Bcl-x(S) induction and apoptosis in a dose-dependent manner. SAMe and MTA increased protein phosphatase 1 (PP1) catalytic subunit mRNA and protein levels and dephosphorylation of serine-arginine proteins, with the latter blocked by calyculin A. The effects of SAMe and MTA on Bcl-x(S), PP1 expression, and apoptosis were also seen in 293 cells, but not in primary hepatocytes. Induction of Bcl-x(S) by ceramide in HepG2 cells also resulted in apoptosis. In conclusion, we have uncovered a highly novel action of SAMe and MTA, namely the ability to affect the cellular phosphorylation state and alternative splicing of genes, in this case resulting in the induction of Bcl-x(S) leading to apoptosis.

Acetylation↗
PubMed2004

Short term outcome and risk factors for mortality in adults with critical severe acute respiratory syndrome (SARS).

The independent risk factors to predict mortality of critical severe acute respiratory syndrome (SARS) were investigated. One hundred and two patients diagnosed with critical SARS were admitted to hospitals of Shanxi Province, from March 7, 2003 to June 4, 2003. The patients were prospectively studied after admission to access their short term outcomes and the risk factors associated with adverse outcomes, defined as death. All the demographic and clinical characteristics were studied and univariate and multivariate Logistic regression were employed to access the risk factors. The results showed that of the 102 cases, 23 patients died, with a crude mortality rate of 22.5%. Multivariate Logistic regression revealed that age above 50 [odds ratio (OR) 1.10, 95% confidence internal (CI) 1.03 to 1.16, P=0.004], lymphopenia at early stage (OR 14.62, 95% CI 1.78 to 11.97, P=0.01) were independently associated with mortality. On the other side, psychotherapy (OR 0.01, 95 % CI 0.00 to 0.06, P<0.001) was independently associated with aliveness. It was concluded that critical SARS is a new disease entity that carries significant mortality and morbidity. Specific clinical and laboratory parameters predicting unfavorable and favorable outcomes have been identified.

Adult↗
PubMed2004

Peroxisome-proliferator-activated receptor (PPAR)-gamma activation stimulates keratinocyte differentiation.

Previous studies demonstrated that peroxisome-proliferator-activated receptor (PPAR)-alpha or PPAR-delta activation stimulates keratinocyte differentiation, is anti-inflammatory, and improves barrier homeostasis. Here we demonstrate that treatment of cultured human keratinocytes with ciglitazone, a PPAR-gamma activator, increases involucrin and transglutaminase 1 mRNA levels. Moreover, topical treatment of hairless mice with ciglitazone or troglitazone increases loricrin, involucrin, and filaggrin expression without altering epidermal morphology. These results indicate that PPAR-gamma activation stimulates keratinocyte differentiation. Additionally, PPAR-gamma activators accelerated barrier recovery following acute disruption by either tape stripping or acetone treatment, indicating an improvement in permeability barrier homeostasis. Treatment with PPAR-gamma activators also reduced the cutaneous inflammatory response that is induced by phorbol 12-myristate-13-acetate, a model of irritant contact dermatitis and oxazolone, a model of allergic contact dermatitis. To determine whether the effects of PPAR-gamma activators are mediated by PPAR-gamma, we next examined animals deficient in PPAR-gamma. Mice with a deficiency of PPAR-gamma specifically localized to the epidermis did not display any cutaneous abnormalites on inspection, but on light microscopy there was a modest increase in epidermal thickness associated with an increase in proliferating cell nuclear antigen (PCNA) staining. Key functions of the skin including permeability barrier homeostasis, stratum corneum surface pH, and water-holding capacity, and response to inflammatory stimuli were not altered in PPAR-gamma-deficient epidermis. Although PPAR-gamma activators stimulated loricrin and filaggrin expression in wild-type animals, however, in PPAR-gamma-deficient mice no effect was observed indicating that the stimulation of differentiation by PPAR-gamma activators is mediated by PPAR-gamma. In contrast, PPAR-gamma activators inhibited inflammation in both PPAR-gamma-deficient and wild-type mouse skin, indicating that the inhibition of cutaneous inflammation by these PPAR-gamma activators does not require PPAR-gamma in keratinocytes. These observations suggest that thiazolidindiones and perhaps other PPAR-gamma activators maybe useful in the treatment of cutaneous disorders.

Animals↗
PubMed2004

Fusobacterium nucleatum induces premature and term stillbirths in pregnant mice: implication of oral bacteria in preterm birth.

Fusobacterium nucleatum is a gram-negative anaerobe ubiquitous to the oral cavity. It is associated with periodontal disease. It is also associated with preterm birth and has been isolated from the amniotic fluid, placenta, and chorioamnionic membranes of women delivering prematurely. Periodontal disease is a newly recognized risk factor for preterm birth. This study examined the possible mechanism underlying the link between these two diseases. F. nucleatum strains isolated from amniotic fluids and placentas along with those isolated from orally related sources invaded both epithelial and endothelial cells. The invasive ability may enable F. nucleatum to colonize and infect the pregnant uterus. Transient bacteremia caused by periodontal infection may facilitate bacterial transmission from the oral cavity to the uterus. To test this hypothesis, we intravenously injected F. nucleatum into pregnant CF-1 mice. The injection resulted in premature delivery, stillbirths, and nonsustained live births. The bacterial infection was restricted inside the uterus, without spreading systemically. F. nucleatum was first detected in the blood vessels in murine placentas. Invasion of the endothelial cells lining the blood vessels was observed. The bacteria then crossed the endothelium, proliferated in surrounding tissues, and finally spread to the amniotic fluid. The pattern of infection paralleled that in humans. This study represents the first evidence that F. nucleatum may be transmitted hematogenously to the placenta and cause adverse pregnancy outcomes. The results strengthen the link between periodontal disease and preterm birth. Our study also indicates that invasion may be an important virulence mechanism for F. nucleatum to infect the placenta.

Amniotic Fluid↗
PubMed2004

[Effects of different human parathyroid hormone 1-34 administration on SaoS-2 cells].

OBJECTIVE: To observe the effects of different human parathyroid hormone 1-34 (hPTH1-34) administration on SaoS-2 cells, and explore the mechanism of bone formation improvement. METHODS: Each cycle covered 48 h. SaoS-2 cells were continuously or intermittently stimulated by 50 ng/ml hPTH1-34 for 1, 3, 6, 12, and 24 h in each cycle. Total RNA was extracted by Trizol kit. Alkaline phosphatase (ALP), osteocalcin or bone Gla-containing protein (BGP) and cyclic adenosine monophosphate (cAMP) levels were measured by chemical method, radioimmunoassay and competitive protein binding method, respectively. c-fos gene expression was semi-quantified by reverse transcription polymerase chain reaction (RT-PCR). RESULTS: ALP level was time-dependently increased in 1, 3 and 6 h stimulation, especially in 3 and 6 h (compared with control, P < 0.01; P < 0.05 or P < 0.01 compared with continuous stimulation). The cAMP level was time-dependently increased in 3 and 6 h incubation (P < 0.05 compared with control and continuous stimulation). Intermittent hPTH1-34 stimulation had more effects on cAMP level than continous action (P < 0.001). hPTH1-34 intermittent stimulation of 1, 3, and 6 h enhanced c-fos gene expression time-dependently. CONCLUSIONS: Intermittent hPTH1-34 stimulation has a stronger effect on osteoblast than continuous action, especially in 3, 6 h in each cycle intermittent stimulation. The synchronous responses of c-fos, ALP and cAMP to hPTH1-34 suggest that hPTH1-34 affect Saos-2 cells through cAMP dependent protein kinase A (PKA) pathway and c-fos gene paly an important role.

Alkaline Phosphatase↗
PubMed2004

[Bone mineral density and leptin receptor polymorphism Gln223Arg in Han women in Beijing].

OBJECTIVE: To investigate the association between bone mineral density (BMD) and leptin receptor (LEPR) polymorphism (Gln223 Arg) in young women and postmenopausl osteoporotic women. METHODS: BMD values were determined by dual energy X-ray absorptiometry. The Gln223 Arg genotypes of LEPR were analyzed by using polymerase chain reaction-restriction fragment length polymorphism method. RESULTS: Hardy-Weinberg equilibrium was evident for LEPR polymorphism. The subjects carrying the GG genotype of LEPR had significantly higher BMD at lumbar spine as compared with the subjects with GA and AA genotype in young women [(1.213 +/- 0.127) g/cm(2) vs (1.154 +/- 0.124) g/cm(2), P < 0.05]. There were no significant differences in BMD at the proximal femur among GG, GA and AA genotype in young women. No significant differences in BMD at all sites were observed among GG, GA and AA genotype in postmenopausl osteoporotic women. Correlation was found between BMD and leptin receptor polymorphism (Gln223 Arg) at lumbar spine (r = -0.151, P < 0.05). CONCLUSION: Leptin receptor polymorphism (Gln223 Arg) has association with peak bone mass in young women, which may be used as genetic marker in predicting the risk of developing osteoporosis in Chinese women of Han nationality.

Adult↗
PubMed2004

Sterilization of Escherichia coli cells by the application of pulsed magnetic field.

The inactivation of microorganisms by pulsed magnetic field was studied. It was improved that the application of electromagnetic pulses evidently causes a lethal effect on E. coli cells suspended in phosphate buffer solution Na2HPO4/NaH2PO4 (0.334/0.867 mmol/L). Experimental results indicated that the survivability (N/N0; where N0 and N are the number of cells survived per milliliter before and after electromagnetic pulses application, respectively) of E. coli decreased with magnetic field intensity B and treatment time t. It was also found that the medium temperatures, the frequencies of pulse f, and the initial bacterial cell concentrations have determinate influences in destruction of E. coli cells by the application of magnetic pulses. The application of an magnetic intensity B = 160 mT at pulses frequency f= 62 kHz and treatment time t = 16 h result in a considerable destruction levels of E. coli cells (N/N0 = 10(-4)). Possible mechanisms involved in sterilization of the magnetic field treatment were discussed. In order to shorten the treatment time, many groups of parallel inductive coil were used. The practicability test showed that the treatment time was shortened to 4 h with the application of three groups of parallel coil when the survivability of E. coli cells was less than 0.01%; and the power consumption was about 0.2 kWh/m3.

Colony Count, Microbial↗
PubMed2004

[Influence of epidermal growth factor and gonadotrophin on the in vitro maturation of human oocytes].

OBJECTIVE: To study the effect of epidermal growth factor(EGF) and different concentrations of gonadotrophin (Gn) on the in vitro maturation of human oocytes. METHODS: EGF was added to the vitro culture medium in order to observe the effect of Gn combined with or without EGF on the result of in vitro maturation. The concentrations of hCG and FSH were changed respectively to observe the difference between the results. RESULTS: Adding EGF to the culture medium improved the maturation rate of oocyte significantly (P < 0.05). There was no difference between the results with different concentrations of hCG and FSH in the culture medium. CONCLUSION: EGF can improve the results of the in vitro maturation of human oocytes by increasing the maturation rate significantly. Increasing the concentration of Gn does not influence the results of in vitro maturation.

Cells, Cultured↗
PubMed2004

[Effect of heat treatment on the electrocatalytic activity of SnO2/Ti anode in degradation of p-benzoquinone].

Sb-doped SnO2/Ti anode was prepared in our lab with thermal decomposition method, and in the same time, the effect of heat treatment on the properties of the electrode also was studied. Scanning electron microscopy (SEM) was used to study the surface characterization of the electrodes. X-ray photoelectro-spectroscopy (XPS) measurements were carried out to study the chemical state of elements, Sn and Sb. The potentiodynamic polarization behaviors of the two anodes in different solutions were performed. Galvanostatic electrolyses were carried out at 5 mA/cm2 to study the electrocatalytic activity of the two anodes in removing organic pollutant. SEM showed that the electrodes had the same well-known cracked-mud structure, while the electrode annealed in O2 [SnO2/Ti(O2)] had more larger surface area than the electrode annealed in the air [SnO2/Ti(air)]. XPS measurements showed that the binding energies of both Sn3d(5/2) and Sb3d(5/2) of SnO2/Ti(O2) were 0.15 eV smaller than what of the SnO2/Ti(air) film. Both of the electrochemical measurements and electrolyses results confirmed that SnO2/Ti(O2) was more active in the degradation of organic pollutant. The galvanostatic electrolyses lasted until the solutions were decoloured throughly, 76.3% of total organic carbon (TOC) was removed with SnO2/Ti(O2), compared with 63.3% of SnO2/Ti(air). The similar exponential rules were driven for the variations of residual TOC concentration with two anodes.

Benzoquinones↗
PubMed2004

[Dynamics and species-diversities of artificial Sonneratia apetala, Sonneratia caseolaris and Kandelia candel communities].

Studies on the dynamics and species-diversities of artificial Sonneratia apetala, Sonneratia caseolaris and Kandelia candel communities showed that the arbor layer of S. apetala and S. caseolaris communities contained two distinctive sub-layers. The upper layer was composed of S. apetala or S. caseolaris, and the medium layer was composed of K. candel and Aegiceras corniculatum. The dominant population S. apetala or S. caseolaris in S. apetala and S. caseolaris communities only had old-aged individuals but no regenerations appeared recently, while K. candel and A. corniculatum were actively progressive populations, which would possibly become dominant populations during the course of community development, showing that S. apetala and S. caseolaris were pioneer species for plantation, which could promote natural colonization of regional mangrove species when planted at open mudflat. K. candel was the actively progressive population in K. candel community, its natural regeneration and succession could be successful, while A. corniculatum and B. sexangula were initially progressive populations. The species composition and species-diversities of S. apetala and S. caseolaris communities were similar, both contained the main species in K. candel community, namely, K. candel, A. corniculatum and Bruguiera sexangula, showing that S. apetala and S. caseolaris could co-exist with these regional species. To introduce and plant them could help to form complicated and diversified mangrove communities. During the early stage of the development, the species-diversities of S. apetala and S. caseolaris communities were higher when their planting density was high. The species-diversities grew slightly higher when the communities became older.

Biodiversity↗
PubMed2004

[Research advance in cyclic hydroxamic acids, main allelochemicals of Zea mays].

The research advance in cyclic hydroxamic acids was reviewed in this paper. Cyclic hydroxamic acids are the important natural products of cereal crops. They and their respective derivatives are the constitutive compounds of a wide variety of gramineous plants and few dicot plants. They have structural diversity and different natural occurrences. Because of their phytotoxic properties, cyclic hydroxamic acids show a great variety of biological activities. They are the defensive agents against plant diseases, pests, nematodes and other plants. The distribution of cyclic hydroxamic acids in Zea mays and their variation in relation to the age were focused on in the paper. In Zea mays, there are structural diversity of cyclic hydroxamic acids and related benzoxazolinones. DIMBOA (1,4-benzoxazin-3(4H)-ones) is the most abundant derivative in Zea mays. The content of cyclic hydroxamic acids is strongly cultivar-dependent in Zea mays. Hydroxamic acids are not present in seeds. After germination, the level of DIMBOA increases, and the maximum level occurs in young seedlings a few days after germination. DIMBOA exists in all parts of plants, and its concentration is generally higher in shoots than in roots. In all stages, the young leaves of Zea mays have relatively high content of DIMBOA. The concentrations of these hydroxamic acids are highly dependent on environmental growth conditions. Under UV-light and water deficiencies, the levels of hydroxamic acids in plant increase rapidly. Cyclic hydroxamic acids exuded by Zea mays root can be quantitatively analyzed by HPLC. Supplying iron can significantly increase the exudation of DIMBOA from Zea mays root.

Benzoxazines↗
PubMed2004

[Clinical analysis of nosocomial pulmonary fungal infection in patients with cancer].

BACKGROUND & OBJECTIVE: Nosocomial fungal infection is an important complication of cancer patients. Among them, pulmonary fungal infection is over 20%. This study was designed to analyze and evaluate risk factors, and clinical features of nosocomial pulmonary fungal infection in patients with cancer. METHODS: In 1 229 patients with malignant tumor, clinical records of 78 patients with nosocomial pulmonary fungal infection were retrospectively analyzed. RESULTS: Pulmonary fungal infection rate was 6.35% (78/1 229). The major fungus was Candida albicans (68.18%). The main risk factors were age of > or =50 years (P< 0.005), primary site (lung cancer, P< 0.001), cancer stage (stage IV, P< 0.005), pulmonary radiotherapy (P< 0.001), chemotherapy (P< 0.001), and long-term hospitalization ( >2 weeks, P< 0.005). CONCLUSION: The effective methods to reduce nosocomial pulmonary fungal infection in patients with cancer are reducing risk factors, early diagnosis, and timely treatment.

Adult↗
PubMed2004

[The cryopreservation of human oocytes at different maturity stages].

OBJECTIVE: To examine the ultrastructure changes and the effects of different sucrose concentrations on the developmental potential of human frozen-thawed oocytes at different maturity stages. METHODS: Oocytes at different maturity stages collected from polycystic ovarian syndrome patients were involved in the study. Different sucrose concentrations (0.1, 0.2 or 0.3 mol/L) were used to study the developmental potential of the frozen-thawed oocytes. Non-frozen and frozen-thawed different maturity oocytes were processed for transmission electron microscopy observation. RESULTS: The results revealed that the mitochondria and the vesicles in the immature oocytes cytoplasm were fewer than those in the mature oocytes without regular distribution. Electron density of the mitochondria and distribution of the vesicles in the mature oocytes changed with the cryopreservation. No remarkable change was produced in the immature oocytes between non-frozen and frozen-thawed oocytes. Cryopreserving with 0.2 mol/L sucrose resulted in perfect development potential for both mature and immature oocytes than that with 0.1 mol/L. Study involving 0.3 mol/L sucrose in the cryoprotectant resulted in higher survival rate and clinical pregnancies. CONCLUSION: The results suggest that sucrose concentration of 0.3 mol/L in the cryoprotectant solution is efficient in freezing oocytes with slow-freezing method. Cryopreservation with slow-freezing method could produce ultrastructure changes in the human oocytes.

Cell Survival↗
PubMed2004

[The adverse reactions and treatment of fundus fluorescein angiography].

PURPOSE: To investigate the safety of fluorescein angiography and to evaluate the examination. METHODS: We retrospectively analyzed 8 344 patients who underwent fluorescein angiography in our hospital in the past four years. The rate of adverse events was calculated and the emergency management for severe cases was discussed. RESULTS: There were 693 cases (8.3%) of adverse events occurring in the patients. Many of them were mild or moderate ones, which were 664 cases in number and were 7.87% in rate. The other 29 cases (0.35%) were severe ones. No special treatment was needed for the mild or moderate adverse events, the symptoms can be relaxed by deep breathing or having a rest for a moment. The symptoms of the severe adverse events can be relieved through anti-hypersuscepibility treatments and no sequelae left. No case of death occurred. CONCLUSION: The adverse events could occur in fluorescein angiography examination. It suggests that we should pay attention to it and be aware of the system conditions of the patients. It is also important for us to grasp the indications and contraindications and to prepare for the emergent events. In summary, fluorescein angiography is generally a safe method for the examination of fundus disease.

Adolescent↗