Biomedical subjects

Lei Zhao

Publications and source records attributed to Lei Zhao.

At least 37 records · Page 2Linked to original sources

PubMed2006

Structure and effective interactions in polymer nanocomposite melts: an integral equation theory study.

The polymer reference interaction site model from integral equation theory is used to investigate the structure and effective interactions in polymer nanocomposite melts where strong nanoparticle-monomer interactions are principally considered in this work. For finite particle volume fraction, the compromise for the interference between polymers and nanoparticles results in an optimum particle volume fraction for nanoparticle dispersion in polymer melts. At constant particle volume fraction, the effects of degree of polymerization become insignificant when it reaches a threshold value, below which quantitative effects on the organization states of polymer nanocomposite melts are found and help nanoparticles to well disperse in polymer. The aggregation of large nanoparticles decreases with the increase of the nanoparticle-monomer attraction strength. These observations may provide useful information for the development of new polymer materials.

Journal Article↗

PubMed2006

Efficient synthesis of highly functionalized dihydropyrido[2,3-d]pyrimidines by a double annulation strategy from alpha-alkenoyl-alpha-carbamoyl ketene-(S,S)-acetals.

A convenient and efficient synthesis of highly functionalized dihydropyrido[2,3-d]pyrimidines via a double [5 + 1] annulation strategy starting from easily available alpha-alkenoyl-alpha-carbamoyl ketene-(S,S)-acetals 1 and cheap reagents (NH4OAc, DMF, and POCl3) has been developed. In the first step of the double annulation route, 2-amino-3-carbamoyl-5,6-dihydro-4-pyridones 2 were created in high to excellent yields by a formal [5C + 1N] annulation reaction of ketene-(S,S)-acetals 1 with ammonia (from ammonium acetate). In the second step of the double annulation strategy, the highly functionalized dihydropyrido[2,3-d]pyrimidine derivatives, 7,8-dihydropyrido[2,3-d]pyrimidin-4(3H)-ones 3 (when R1 = aryl) and 7,8-dihydropyrido[2,3-d]pyrimidines 4 (when R1 = H), were constructed, respectively, in fair to good yields by reacting 2 with excessive Vilsmeier reagent (DMF/POCl3). A mechanism involved in the second [5 + 1] annulation step, including a formal [5 + 1] annulation and accompanied chlorovinylation, chloroformylation, amination, and aromatization reactions, is proposed.

Acetals↗

PubMed2006

Effect of estradiol and dihydrotestosterone on hypergravity-induced MAPK signaling and occludin expression in human umbilical vein endothelial cells.

Female astronauts have been reported to have a higher incidence of post-flight orthostatic intolerance (POI) compared with that of their male counterparts. POI may result from increased permeability of the endothelial cell (EC) layer in the vasculature. The goal of this study has been to determine whether estradiol (E(2)) and dihydrotesterone (DHT) alter human umbilical vein ECs (HUVECs) responses to short term (10 min) hypergravity (1-3 g) mimicking the g force experienced by astronauts during liftoff. E(2) and DHT rapidly (within 5 min) activated MAPK (mitogen-activated protein kinase) in HUVEC at 1 g in a receptor-dependent manner. Liftoff inhibited MAPK phosphorylation, and rapid E(2) and DHT activation of MAPK was blocked. Liftoff simulation or brief (5-90 min) treatment with E(2) or DHT at 1 g had no effect on the expression of the EC tight-junction protein occludin. However, 24-h pre-treatment of HUVECs with E(2) and DHT prior to liftoff simulation significantly increased occludin expression, and hypergravity exposure did not alter this increase. These data provide evidence for a possible protective effect of E(2) and DHT on EC function as indicated by increased occludin; this may help maintain the integrity of EC tight junction and could thus retard or reduce the incidence of POI.

Base Sequence↗

PubMed2006

A dual effect of N-acetylcysteine on acute ethanol-induced liver damage in mice.

Reactive oxygen species (ROS) have been associated with acute ethanol-induced liver damage. N-acetylcysteine (NAC) is a glutathione (GSH) precursor and direct antioxidant. In this study, we investigated the effects of NAC on acute ethanol-induced liver damage. Female ICR mice were administered by gavage with a single dose of ethanol (6g/kg). NAC was administered in two different modes. In mode A, mice were injected with different doses of NAC at 30min before ethanol. In mode B, mice were injected with different doses of NAC at 4h after ethanol. Acute ethanol-induced liver damage was estimated by measuring serum alanine aminotransferase (ALT) activity and histopathological changes. Result showed that a single dose of ethanol (6g/kg) caused a significant increase in serum ALT activity, followed by microvesicular steatosis and necrosis in mouse liver. Pretreatment with NAC significantly protected against acute ethanol-induced liver damage in a dose-independent manner. Correspondingly, pretreatment with NAC significantly attenuated acute ethanol-induced lipid peroxidation and GSH depletion and inhibited hepatic TNF-alpha mRNA expression. By contrast, post-treatment with NAC aggravated ethanol-induced hepatic lipid peroxidation and worsened acute ethanol-induced liver damage in a dose-dependent manner. Taken together, NAC has a dual effect on acute ethanol-induced liver damage. Pretreatment with NAC prevent from acute ethanol-induced liver damage via counteracting ethanol-induced oxidative stress. When administered after ethanol, NAC might behave as a pro-oxidant and aggravate acute ethanol-induced liver damage.

Journal Article↗

PubMed2006

Variation of mitochondrial gene and the association with type 2 diabetes mellitus in a Chinese population.

Mitochondrial DNA (mtDNA) variants have been implicated in many diseases including diabetes mellitus. To explore whether these genetic variants contribute to the susceptibility for type 2 diabetes mellitus (T2DM) in a Chinese population, a total of 184 T2DM cases and 279 matched healthy controls were recruited. PCR restriction fragment length polymorphism (PCR-RFLP) analysis and DNA sequencing were used to determine the variants of mtDNA (including T16189C, G3316A, T3394C, A14693G, A3243G and C1310T). Some of them were further analyzed by mfold or tRNA-scan-SE software. A homoplastic A14693G, for the first time, was found in 4 of 184 Chinese cases, the frequency of A14693G and T3394C was 2.17% and 2.72%, respectively, in patients but not in the controls. Secondary structure prediction revealed that there were obvious conformational changes in T3394C mutant ND1 versus wild type and A14693G mutant tRNA(Glu) protein versus wild type, providing additional clues to the disease pathogenesis although A3243G and C1310T mutations were not detected in any patients in the two groups. The 16189 variant among type 2 diabetes was more prevalent than in controls (36.9% versus 28.7%, P=0.039), and stepwise multiple regression analysis showed that the 16189 variant was an independent factor contributing to HOMA-IR (R(2)=0.043, P=0.037). Our results suggest that the mutations of T3394C and A14693G may contribute to genetic predisposition to T2DM, with the T16189C variant being associated with insulin resistance.

Asian People↗

PubMed2006

Arterial baroreflex function does not influence telomere length in kidney of rats.

AIM: To investigate the relationship between arterial baroreflex (ABR) function and telomere length in kidney of rats. METHODS: Stroke-prone spontaneously hypertensive rats (SHR-SP) and sinoaortic denervated rats (SAD) were used as models with depressed arterial baroreflex. In the first experiments, SHR-SP rats were examined at the age of 24 weeks for both sexes and 40 weeks for female rats. In the second experiments, SAD rats were studied 4 and 35 weeks after SAD operation. Blood pressure was continuously recorded for 4 h in a conscious state. After the determination of baroreflex sensitivity (BRS), the terminal restriction fragment (TRF) of rat kidney was analyzed using Southern blot. RESULTS: The TRF length was found shorter in: a) male SHR-SP compared with age-matched female SHR-SP; b) female SHR-SP 40 weeks of age compared with 24 weeks of age; c) in rats 35 weeks after operation compared with rats 4 weeks post operation in both sham-operated and SAD rats. CONCLUSION: In SHR-SP, the TRF length did not correlate with BRS. In addition, SAD did not affect TRF length at either 4 or 35 weeks post-surgery. It may be concluded that baroreflex function does not influence the terminal restriction fragment (TRF) length in rats.

Animals↗

PubMed2006

Is there a role for the macrophage 5-lipoxygenase pathway in aortic aneurysm development in apolipoprotein E-deficient mice?

Activation of the 5-lipoxygenase (5-LO) pathway leads to the biosynthesis of proinflammatory leukotriene (LT) lipid mediators in macrophages, mast cells, and other inflammatory cell types. A recent surge in interest in this pathway within the cardiovascular system has arisen from a variety of exciting findings using genetic, pathological specimen, and biochemical approaches in humans and mice. We found that a subset of CD68-positive macrophages, localized within the adventitial layer of apolipoprotein E (apo E)-deficient mice, expressed 5-LO and that these cells represented a significant cellular component of aortic aneurysms induced by an atherogenic diet containing cholate. Surprisingly, almost no 5-LO-expressing cells were observed in atherosclerotic lesions in the same mice. Correspondingly, lesion size in the fat-fed mice did not depend on 5-LO gene expression but aneurysm incidence was reduced in the absence of the 5-LO pathway. We are currently exploring the potential mechanisms for 5-LO/LT involvement in aneurysm pathogenesis and if this pathway might come into play in other models such as induction by angiotensin II.

Animals↗

PubMed2006

[Methylation status of the 5' CpG islands in FHIT gene in the plasma and tissues of cervical cancer patients].

To evaluate the methylation status of the 5' CpG islands in FHIT gene using plasma and tissue samples from cervical cancer patients and find a novel marker for non-invasive diagnosis of cervical cancer, methylation-specific PCR (MSP) was employed to examine CpG island methylation in FHIT gene in 151 pretreatment plasma samples and 30 tumor tissue samples obtained from cervical cancer patients. MSP product was cloned and sequenced directly. CpG island methylation of FHIT was detected in 31.13% of the plasma samples, and in 53.33% of the tissue samples. The total concordant rate of methylation status between plasma and tissue samples in FHIT gene was 80.00%. We found a strong positive correlation between FHIT methylation in the plasma and the clinical stage and histological grade of the tumor. The data showed that CpG island methylation of the FHIT gene is prevalent in the plasma and tissue samples from cervical cancer patients. FHIT detection may be used as a non-invasive marker for diagnosis of cervical cancer and prognostic treatment evaluation.

Acid Anhydride Hydrolases↗

PubMed2006

[Assessment of the characteristics of echocardiography in pediatric patients with total anomalous pulmonary venous connection].

OBJECTIVE: To assess the accuracy of echocardiography in diagnosis of total anomalous pulmonary venous connection (TAPVC). METHODS: A combination of suprasternal, parasternal, subcostal and apical views were employed to diagnose TAPVC and to trace the course of the anomalous pulmonary venous connection, the direction of the inter-atrial shunt, enlargement of right atrium (RA) and right ventricle (RV), superior and inferior vena cava. All pediatric patients underwent surgical repair. The results of echocardiography were compared with surgical findings. RESULT: A total of 28 consecutive pediatric patients with suspected TAPVC were included in this study. The TAPVC diagnosis was confirmed in 26 cases after surgery, partial anomalous pulmonary venous connection (PAPVC) in one case, and Cor Triatriatum and possible TAPVC in another. The diagnostic accuracy of TAPVC by echocardiography in the study was 92.86%. There were 17 supracardiac TAPVC, 11 intracardiac TAPVC. In all patients, enlargement of the RA and RV, inter-atrial right-to-left shunt via atrial septal defects were documented in parasternal and subcostal views. Common pulmonary vein or four pulmonary vein direct to RA or via coronary sinus to RA were the draining sites of intracardiac TAPVC. The enlargement of left innominate vein-right superior vena cava draining to RA was seen in supracardiac TAPVC. CONCLUSION: A combination of suprasternal and subcostal multi-views in echocardiography can increase the diagnostic accuracy of TAPVC in pediatric patients.

Abnormalities, Multiple↗

PubMed2006

[Distribution of fimA genotype of Porphyromonas gingivalis in Chinese periodontitis patients and its relationship with chronic periodontitis].

OBJECTIVE: To investigate the distribution of fimA genotype of Porphyromonas gingivalis in Chinese periodontitis patients and try to find the relationship between fimA genotype and chronic periodontitis. METHODS: Subgingival plaque samples were collected from 101 periodontitis patients. P. gingivalis 16S rRNA primer and fimA type-specific primer were designed. The distribution of fimA genotype in periodontitis patients was detected by PCR. Clinical periodontal indices (PPD, CAL and BOP) were measured at the sample tooth's six points; namely, the mesio-, mid-, distobuccal and mesio-, mid-, distolingual points. RESULTS: P. gingivalis was detected in 89 periodontitis patients (88.1%). Among them, a single fimA genotype was detected in most subgingival plaque samples (65.1%), and the most prevalent fimA genotype was type II (43.8%), followed by type IV (40.4%); Type II fimA and IV fimA were more frequently detected in mild/moderate periodontitis group and severe periodontitis group. CONCLUSION: The findings indicate that P. gingivalis with type II fimA and IV fimA are more predominant in Chinese periodontitis, and the organisms are involved in the destructive progression of periodontitis in Chinese.

Adult↗

PubMed2006

[Effect of fibrinogen on the adherence of Porphyromonas gingivalis to human oral epithelial cells].

OBJECTIVE: To study the role of fibrinogen molecule in the pathogenesis of periodontal diseases. METHODS: An in vitro cell culture model was used. Methyl-(3)H Thymidine radiolabeled Porphyromonas gingivalis (Pg) ATCC 33277 were examined for their ability to adhere to and invade the confluent monolayers of human oral epithelial KB cells with or without exogenous human fibrinogens by scintillation spectrometry. RESULTS: The addition of exogenous fibrinogens made more amount of and higher ratios of adhesive and invasive Pg, in contrast to the group without exogenous fibrinogen (P < 0.001). At different concentrations of exogenous fibrinogen, the amount and ratios of adhesive and invasive Pg varied significantly (P < or = 0.007). The higher concentrations of exogenous fibrinogen was added, the greater amount and ratios of adhesive and invasive Pg were found. CONCLUSIONS: Fibrinogen promotes the adherence of Pg to human oral epithelial cells and may play an important role in the pathogenesis of periodontal diseases.

Bacterial Adhesion↗

PubMed2006

[Effect of background constituents on the degradation of trace nitrobenzene in aqueous solution by catalytic ozonation].

Effect of background constituents on the catalytic ozonation of nitrobenzene was investigated. Degradation rates of ozonation alone, ceramic honeycomb and modified ceramic honeycomb-catalyzed ozonation in tap water increased by 4.90%, 2.47% and 5.12% than those in distilled water respectively. The removal rate of ozonation alone increased by 6.25% with the increase of the concentration of magnesium ion (0 to approximately 8 x mg x L(-1)), but those of other two processes decreased by 11.41% and 17.64%, respectively, under the same experimental condition. Degradation efficiency of ozonation alone, ceramic honeycomb and modified ceramic honeycomb-catalyzed ozonation decreased by 4.42%, 9.38% and 12.24%, respectively, with the increase of the concentration of chloride ion (0 to approximately 40 mg x L(-1)). At the lower concentration, humic acid could accelerate the degradation of nitrobenzene, however, the reaction was retarded at higher concentrations of humic acid. The experiment also studied the influences of the applied ozone and initial concentration of nitrobenzene.

Catalysis↗

PubMed2006

[Effect of inorganic ions on degradation of trace nitrobenzene in aqueous solution by catalytic ozonation].

The experiment investigated the effects of general inorganic ions in natural source water on the three processes of ozonation alone, ceramic honeycomb and modified ceramic honeycomb-catalyzed ozonation for degradation of trace nitrobenzene in aqueous solution. The removal rate of ozonation alone and modified ceramic honeycomb-catalyzed ozonation increased by 5.0% and 8.6% with the increase of the concentration of calcium ion (0-4 mg x L(-1)), and that of ceramic honeycomb-catalyzed ozonation reached the climax at the concentration of calcium ion 0.5 mg x L(-1) under the same experimental condition. The degradation efficiency of ozonation alone, ceramic honeycomb and modified ceramic honeycomb-catalyzed ozonation enhanced by 10.9%, 11.6% and 9.6% with the increase of the concentration of manganese ion (0-4 mg x L(-1)), respectively, and decreased by 8.6%, 11.5% and 8.9% with the increase of the concentration of bicarbonate ion (0-200 mg x L(-1)). The concentration of nitrate and sulfate ion had no remarkable effect on ozonation alone, but the removal rate of other two processes decreased with the increase of the concentration of nitrate and sulfate ion.

Calcium↗

PubMed2006

[Study on in-plane optical anisotropy of semiconductor materials by reflectance difference spectroscopy].

In the present review, the measuring principle of reflectance difference spectroscopy (RDS) is given. As a powerful tool in the surface and interface analysis technologies, the application of RDS to the research on semiconductor materials is summarized along with the origins of the in-plane optical anisotropy of semiconductors. And it is believed that RDS will play an important role in the electrooptic modification of Si-based semiconductor materials.

English Abstract↗

PubMed2006

[Methylation status of FHIT gene in plasma and expression of FHIT gene in cancer tissue of cervical cancer patients].

OBJECTIVE: To explore the methylation status of 5' CpG island of fragile histidine triad (FHIT) gene in plasma and the expression of FHIT protein in cancer tissue of cervical cancer patients. METHODS: Methylation-specific PCR (MS-PCR) was employed to examine methylation of FHIT gene in 151 plasma samples before treatment. The immunohistochemistry was used to the expression of FHIT protein in cancer tissues. RESULTS: CpG island methylation of FHIT was detected in 31.13% of plasma samples. The expression of FHIT protein was decreased or discarded in 59.60% of cervical cancer tissues. Among them 47.78% was included in methylation positive samples. CONCLUSION: CpG island methylation of FHIT gene in plasma plays an important role on cervical cancer, which results in decreased expression of FHIT protein. It can be used to diagnose and evaluate the effect of treatment to cervical cancers.

Acid Anhydride Hydrolases↗

PubMed2006

[A clinical analysis of 9 cases of Gitelman syndrome].

OBJECTIVE: To analyze the clinical characteristics of Gitelman syndrome. METHODS: Clinical data of 9 cases of Gitelman syndrome seen in the past 25 years in Chinese PLA General Hospital were analyzed retrospectively. RESULTS: The age of onset of Gitelman syndrome was 14 - 33 years. Main symptoms included weakness, tetany, polydipsia, polyuria, nocturia and paralysis. All patients had normal blood pressure. The biochemical tests showed hypokalemic alkalosis (9/9), hypocalciuria and hypomagnesaemia (9/9), low urine Ca/Cr ratio (<0.2, 5/5) and hyperreninemia (9/9). Renal pathological examination showed juxtaglomerular apparatus hyperplasia (2/2). All the patients' symptoms were relieved after treatment with potassium and magnesium supplementation or with combined spironolactone and indomethacin. However, serum potassium and magnesium levels were still lower than normal range (8/9); only one patient's serum potassium recovered to normal level. CONCLUSION: When clinical features such as weakness, hypokalemic alkalosis with normotension were encountered, Gitelman syndrome should be suspected. Serum magnesium as well as urine magnesium and calcium should be measured for confirmation of diagnosis. The treatment of choice included potassium and magnesium supplementation, or combination with anti-aldosterone medications, prostaglandin inhibitors and angiotensin-converting enzyme inhibitor. Generally, these patients have good prognosis.

Adolescent↗

PubMed2006

Effects of multidrug resistance, antisense RNA on the chemosensitivity of hepatocellular carcinoma cells.

BACKGROUND: Multidrug resistance is a major obstacle in cancer chemotherapy. We examined whether the antisense RNA of multidrug resistance gene 1 (mdr1) could reverse multidrug resistance in the human hepatocellular carcinoma (HCC) cell line SMMC7721/ADM. METHODS: The recombinant adenoviruses pAdEasy-GFP-ASmdr1 product was produced by the adenoviral vector AdEasy system, which can express antisense RNA against the mdr1 gene. Following that, the recombinant adenovirus was transfected into the P-glycoprotein-producing multidrug resistance cell line, SMMC7721/ADM human HCC cells resistant to adriamycin (ADM) and daunorubicin (DNR). In order to investigate the reversal of multidrug resistance phenotype, we measured the expression of mdr1 mRNA by RT-PCR and the production of P-glycoprotein by flow cytometry. The sensitivities for ADM and DNR SMMC7721/ADM cells were examined by [3-(4, 5-dimethylthi-azol-2-yl)-2,5 diphenyl-terazolium bromide] (MTT) analysis. RESULTS: The low-level expression of mdr1 mRNA and P-glycoprotein production were observed in parental sensitive cells SMMC/7721 in addition to the overexpression of mdr1 mRNA and P-glycoprotein in SMMC7721/ADM cells. The transfection of antisense-RNA into SMMC7721/ADM cells resulted in decreases of mdr1 mRNA and P-glycoprotein, but increase of drug sensitivities. The sensitivities of transfected SMMC7721/ADM cells to ADM and DNR in IC50 reduced by 31.25% and 62.96% respectively. CONCLUSIONS: Mdr1 antisense RNA can increase the sensitivities of SMMC7721/ADM cells to anticancer drug by decreasing the expression of the mdr1 gene and inhibiting P-glycoprotein expression. This strategy may be applicable to cancer patients with P-glycoprotein mediated multidrug resistance.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed2005

Enhancement of specific absorption rate in lossy dielectric objects using a slab of left-handed material.

An enhancement of the specific absorption rate (SAR) inside a lossy dielectric object has been investigated theoretically based on a slab of left-handed medium (LHM). In order to make an accurate analysis of SAR distribution, a proper Green's function involved in the LHM slab is proposed, from which an integral equation for the electric field inside the dielectric object is derived. Such an integral equation has been solved accurately and efficiently using the conjugate gradient method and the fast Fourier transform. We have made a lot of numerical experiments on the SAR distributions inside the dielectric object excited by a line source with and without the LHM slab. Numerical experiments show that SAR can be enhanced tremendously when the LHM slab is involved due to the proper usage of strong surface waves, which will be helpful in the potential biomedical applications for hyperthermia. The physical insight for such a phenomenon has also been discussed.

Absorption↗