Biomedical subjects

Mei Sun

Publications and source records attributed to Mei Sun.

At least 37 records · Page 2Linked to original sources

PubMed2005

Phenolic antioxidants (hydrolyzable tannins, flavonols, and anthocyanins) identified by LC-ESI-MS and MALDI-QIT-TOF MS from Rosa chinensis flowers.

Rosa chinensis (Yuejihua) is a well-known ornamental plant, and its flowers are commonly used in traditional Chinese medicine. Methanolic crude extracts of dried R. chinensis flowers were used for simultaneous determination of phenolic constituents by liquid chromatography-mass spectrometry (LC-MS) and matrix-assisted laser desorption/ionization quadrupole ion trap time-of-flight mass spectrometry (MALDI-QIT-TOF MS). A total of 36 known and unknown phenolics were identified as hydrolyzable tannins, flavonols, and anthocyanins, mainly including gallotannins (mono-, di-, or trigalloylglucopyranosides), ellagitannins, quercetin, quercetin/kaempferol mono- and diglycosides, and cyanidin/pelargonidin diglycosides. MALDI-QIT-TOF MS was applied not only to verify most phenolics isolated and identified by LC-MS but also to tentatively identify two ellagitannins (rugosins B and C) not isolated and unidentified by LC-MS. This study is the first to demonstrate the rapid and successful use of MALDI-QIT-TOF MS and LC-MS to directly and simultaneously identify phenolics in the crude extracts of R. chinensis flowers without any purification. The antioxidant activity of the crude extracts from R. chinensis flowers was also measured with three assay methods. The results showed that the phenolic antioxidants from R. chinensis flowers exhibited very strong radical scavenging effect and antioxidant power. High levels of flavonols and hydrolyzable tannins might be important bioactive principles in the dried R. chinensis flowers.

Anthocyanins↗

PubMed2005

Structure-radical scavenging activity relationships of phenolic compounds from traditional Chinese medicinal plants.

Traditional Chinese medicinal plants associated with anticancer contain a wide variety of natural phenolic compounds with various structural features and possessing widely differing antioxidant activity. The structure-radical scavenging activity relationships of a large number of representative phenolic compounds (e.g., flavanols, flavonols, chalcones, flavones, flavanones, isoflavones, tannins, stilbenes, curcuminoids, phenolic acids, coumarins, lignans, and quinones) identified in the traditional Chinese medicinal plants were evaluated using the improved ABTS*+ and DPPH methods. Different categories of tested phenolics showed significant mean differences in radical scavenging activity. Tannins demonstrated the strongest activity, while most quinones, isoflavones, and lignans tested showed the weakest activity. This study confirmed that the number and position of hydroxyl groups and the related glycosylation and other substitutions largely determined radical scavenging activity of the tested phenolic compounds. The differences in radical scavenging activity were attributed to structural differences in hydroxylation, glycosylation and methoxylation. The ortho-dihydroxy groups were the most important structural feature of high activity for all tested phenolic compounds. Other structural features played a modified role in enhancing or reducing the activity. Within each class of phenolic compounds, the structure-activity relationship was elucidated and discussed. This study reveals the structure-activity relationships of a large series of representative natural phenolic compounds more systematically and fully than previous work. Structure-radical scavenging activity relationships of some natural phenolics identified in the medicinal plants were evaluated for the first time.

Drugs, Chinese Herbal↗

PubMed2005

Antioxidant capacity of 26 spice extracts and characterization of their phenolic constituents.

Total equivalent antioxidant capacity (TEAC) and phenolic content of 26 common spice extracts from 12 botanical families were investigated. Qualitative and quantitative analyses of major phenolics in the spice extracts were systematically conducted by reversed-phase high-performance liquid chromatography (RP-HPLC). Many spices contained high levels of phenolics and demonstrated high antioxidant capacity. Wide variation in TEAC values (0.55-168.7 mmol/100 g) and total phenolic content (0.04-14.38 g of gallic acid equivalent/100 g) was observed. A highly positive linear relationship (R2= 0.95) obtained between TEAC values and total phenolic content showed that phenolic compounds in the tested spices contributed significantly to their antioxidant capacity. Major types of phenolic constituents identified in the spice extracts were phenolic acids, phenolic diterpenes, flavonoids, and volatile oils (e.g., aromatic compounds). Rosmarinic acid was the dominant phenolic compound in the six spices of the family Labiatae. Phenolic volatile oils were the principal active ingredients in most spices. The spices and related families with the highest antioxidant capacity were screened, e.g., clove in the Myrtaceae, cinnamon in the Lauraceae, oregano in the Labiatae, etc., representing potential sources of potent natural antioxidants for commercial exploitation. This study provides direct comparative data on antioxidant capacity and total and individual phenolics contents of the 26 spice extracts.

Antioxidants↗

PubMed2005

Genetic enhancement of visual learning by activation of protein kinase C pathways in small groups of rat cortical neurons.

Although learning and memory theories hypothesize that memories are encoded by specific circuits, it has proven difficult to localize learning within a cortical area. Neural network theories predict that activation of a small fraction of the neurons in a circuit can activate that circuit. Consequently, altering the physiology of a small group of neurons might potentiate a specific circuit and enhance learning, thereby localizing learning to that circuit. In this study, we activated protein kinase C (PKC) pathways in small groups of neurons in rat postrhinal (POR) cortex. We microinjected helper virus-free herpes simplex virus vectors that expressed a constitutively active PKC into POR cortex. This PKC was expressed predominantly in glutamatergic and GABAergic neurons in POR cortex. This intervention increased phosphorylation of five PKC substrates that play critical roles in neurotransmitter release (GAP-43 and dynamin) or glutamatergic neurotransmission (specific subunits of AMPA or NMDA receptors and myristoylated alanine-rich C kinase substrate). Additionally, activation of PKC pathways in cultured cortical neurons supported activation-dependent increases in release of glutamate and GABA. This intervention enhanced the learning rate and accuracy of visual object discriminations. In individual rats, the numbers of transfected neurons positively correlated with this learning. During learning, neuronal activity was increased in neurons proximal to the transfected neurons. These results demonstrate that potentiating small groups of glutamatergic and GABAergic neurons in POR cortex enhances visual object learning. More generally, these results suggest that learning can be mediated by specific cortical circuits.

Animals↗

PubMed2005

Targeted gene transfer to nigrostriatal neurons in the rat brain by helper virus-free HSV-1 vector particles that contain either a chimeric HSV-1 glycoprotein C-GDNF or a gC-BDNF protein.

Direct gene transfer into neurons has potential for both studying neuronal physiology and for developing gene therapy treatments for specific neurological conditions. Due to the heterogeneous cellular composition of the brain, cell-type-specific recombinant gene expression is required for many potential applications of neuronal gene transfer. The two prevalent approaches for achieving cell-type-specific expression are to use a cell-type-specific promoter to control recombinant gene expression or to modify a virus vector particle to target gene transfer to a specific cell type. Targeted gene transfer to multiple peripheral cell types has been described, but targeted gene transfer to a specific type of neuron in the brain has yet to be reported. Targeted gene transfer approaches with Herpes Simplex Virus (HSV-1) vectors have focused on modifying glycoprotein C (gC) to remove the heparin binding domain and add a binding activity for a specific protein on the cell surface. This study was designed to develop HSV-1 vectors that target gene transfer to cells that contain receptors for either glial-cell-line-derived neurotrophic factor (GDNF) or brain-derived neurotrophic factor (BDNF), such as nigrostriatal neurons. We isolated chimeric gC-GDNF or chimeric gC-BDNF constructs, and the resulting proteins were incorporated into HSV-1 virus particles. We performed helper virus-free HSV-1 vector packaging in the presence of each chimeric protein. The resulting vector stocks supported 2.2- to 5.0-fold targeted gene transfer to nigrostriatal neurons in the rat brain, compared to vector particles that contained wild-type (wt) gC. Gene transfer to nigrostriatal neurons by vector particles that contained chimeric gC-BDNF was reduced by preincubation with an anti-BDNF antibody. Targeted gene transfer to neurons that contain specific neurotrophic factor receptors may benefit specific physiological and gene therapy studies.

Animals↗

PubMed2005

Comparison of the capability of GDNF, BDNF, or both, to protect nigrostriatal neurons in a rat model of Parkinson's disease.

Both glial cell line-derived neurotrophic factor (GDNF) and brain-derived neurotrophic factor (BDNF) can protect nigrostriatal dopaminergic neurons from neurotoxins in rodent and monkey models of Parkinson's disease (PD). These two neurotrophic factors are usually tested individually. This study was designed to compare GDNF, BDNF, or both, for their capabilities to correct behavioral deficits and protect nigrostriatal dopaminergic neurons in a rat model of PD. Gene transfer used a helper virus-free Herpes Simplex Virus (HSV-1) vector system and a modified neurofilament heavy gene promoter that supports long-term expression in forebrain neurons. Rats received unilateral intrastriatal injections of HSV-1 vectors that express either GDNF or BDNF, or both vectors, followed by intrastriatal injections of 6-hydroxydopamine (6-OHDA). Recombinant GDNF or BDNF was detected in striatal neurons in rats sacrificed at 7 months after gene transfer. Of note, GDNF was significantly more effective than BDNF for both correcting behavioral deficits and protecting nigrostriatal dopaminergic neurons. Expression of both neurotrophic factors was no more effective than expression of only GDNF. These results suggest that GDNF is more effective than BDNF for correcting the rat model of PD, and that there are no detectable benefits from expressing both of these neurotrophic factors.

Adrenergic Agents↗

PubMed2005

Expression of intestinal trefoil factor, proliferating cell nuclear antigen and histological changes in intestine of rats after intrauterine asphyxia.

AIM: To study the expressions of intestinal trefoil factor (ITF) and proliferating cell nuclear antigen (PCNA) and histologic changes in intestine, to investigate the relationship between ITF and intestinal damage and repair after intrauterine hypoxia so as to understand the mechanism of intestinal injury and to find a new way to prevent and treat gastrointestinal diseases. METHODS: Wistar rats, pregnant for 21 d, were used to establish animal models of intrauterine asphyxia by clamping one side of vessels supplying blood to uterus for 20 min, another side was regarded as sham operation group. Intestinal tissues were taken away at 0, 24, 48 and 72 h after birth and stored in different styles. ITF mRNA was detected by RT-PCR. PCNA expression was measured by immunohistochemistry. Intestinal tissues were studied histologically by HE staining in order to observe the areas and degree of injury and to value the intestinal mucosa injury index (IMDI). RESULTS: ITF mRNA appeared in full-term rats and increased with age. After ischemia, ITF mRNA was decreased to the minimum (0.59+/-0.032) 24 h after birth, then began to increase higher after 72 h than it was in the control group (P<0.01). PCNA positive staining located in goblet cell nuclei. The PCNA level had a remarkable decline (53.29+/-1.97) 48 h after ischemia. Structure changes were obvious in 48-h group, IMDI (3.40+/-0.16) was significantly increased. Correlation analyses showed that IMDI had a negative correlation with ITF mRNA and PCNA (r = -0.543, P<0.05; r = -0.794, P<0.01, respectively). CONCLUSION: Intrauterine ischemia can result in an early decrease of ITF mRNA expression. ITF and PCNA may play an important role in the damage and repair of intestinal mucosa.

Animals↗

PubMed2005

Anthocyanins, flavonols, and free radical scavenging activity of Chinese bayberry (Myrica rubra) extracts and their color properties and stability.

Characterization of anthocyanins and flavonols and radical scavenging activity assays of extracts from four Chinese bayberry (Myrica rubra) varieties with different fruit colors were carried out. One dominant anthocyanin and three major flavonols were isolated by HPLC, and cyanidin-3-O-glucoside and two of three flavonols, myricetin and quercetin-3-O-rutinoside, were identified by cochromatography with authentic standards. Both DPPH* and ABTS*(+) cation assays indicated that the black varieties (Biji and Hunan) demonstrated much higher radical scavenging activities than the pink (Fenhong) and yellow (Shuijing) varieties, which may be attributed to much higher levels of anthocyanins, flavonoids, and total phenolics in the black varieties. Biji and Hunan had 6.49 and 6.52 mM Trolox equivalent antioxidant capacity (TEAC) per 100 g of fresh weight, whereas the pink (Fenhong) and yellow (Shuijing) bayberries had 1.32 and 1.31 mM TEAC/100 g. Different fruit color was reflected by the surface color and pigment extract color. Color stability of the pigment was dependent on pH, and the pigment was more stable at low pH (pH approximately 1.5). The lightness (L) increased while the chroma (C value) decreased with increase of pH until pH 5, but higher pH caused a small decrease for L and an increase for C.

Anthocyanins↗

PubMed2005

AKT/PKB signaling mechanisms in cancer and chemoresistance.

During the past decade, Akt (also known as protein kinase B, PKB) has been extensively studied. It regulates a variety of cellular processes by mediating extracellular (mitogenic growth factor, insulin and stress) and intracellular (altered tyrosine receptor kinases, Ras and Src) signals. Activation of Akt by these signals is via its pleckstrin homology (PH) domain binding to products of phosphatidylinositol 3-kinase (PI3K). This process is negatively regulated by a dual phosphatase PTEN tumor suppressor. Today, more than 30 Akt substrates have been identified. These phosphorylation events mediate the effects of Akt on cell survival, growth, differentiation, angiogenesis, migration and metabolism. Further, PI3K/PTEN/Akt pathway is frequently altered in many human malignancies and overexpression of Akt induces malignant transformation and chemoresistance. Thus, the Akt pathway is a major target for anti-cancer drug development. This review focuses on Akt signaling mechanism in oncogenesis and chemoresistance, and ongoing translational efforts to therapeutically target Akt.

Animals↗

PubMed2005

HPLC characterization of betalains from plants in the amaranthaceae.

HPLC characterization of reversed-phase (RP) high-performance liquid chromatography (HPLC) has been widely used in separation and identification of plant pigments. An effective RP-HPLC-based method is established to systematically isolate, identify, and quantitate the betalain pigments in the plants of 37 species of eight genera in the Amaranthaceae. A total of 16 betacyanins and three betaxanthins are characterized mainly using the RP-HPLC method and also with the aid of mass spectroscopy. The identified betacyanins include eight amaranthine-types, six gomphrenin-types, and two betanin-types. They are also divided into six simple (nonacylated) betacyanins and 10 acylated betacyanins. Acylated betacyanins are identified as betanidin 5-O-beta-glucuronosylglucoside or betanidin 6-O-beta-glucoside acylated with ferulic, p-coumaric, or 3-hydroxy-3-methylglutaric acids. Three betaxanthins were separated from Celosia species in the Amaranthaceae and identified to be immonium conjugates of betalamic acid with dopamine, 3-methoxytyramine, and (S)-tryptophan; the latter two are found to be new betaxanthins from plants.

Amaranthaceae↗

PubMed2005

[Study on the role of angiogenesis and related factors in leukemias].

OBJECTIVE: To observe the bone marrow angiogenesis in leukemia and evaluate the expression and role of endostatin (ES), vascular endothelial growth factor (VEGF) and its receptor (VEGFR) in leukemia patients. METHODS: Bone marrow angiogenesis was assayed by vWF immunohistochemical method. The ES and VEGF concentrations in plasma were detected by ELISA. The expression of VEGFR in leukemia cells was determined by flow cytometry (FCM). RESULTS: The bone marrow microvessel density (MVD) in 26 cases of acute leukemia (AL) [(20.78 +/- 7.75)/high-power field (HP)] and 5 chronic myelogenous leukemia (CML) [(28.67 +/- 7.32)/HP] at newly diagnosed stage was significantly higher than that in the control group [(9.29 +/- 3.53)/HP, P < 0.01]. The bone marrow MVD in the complete remission (CR) groups, (11.33 +/- 5.66)/HP for AL and (17.00 +/- 8.04)/HP for CML, was significantly lower than that of newly diagnosed groups (P < 0.05 and < 0.01). No significant difference was found between the remission groups and the control group (P > 0.05). The plasma ES and VEGF concentrations of newly diagnosed AL and CML groups were significantly higher than those of the control group (P < 0.05). The levels of plasma ES and VEGF in AL CR group and plasma ES in CML CR group decreased to levels comparable to normal values (P > 0.05), but the plasma VEGF in CML CR group was still higher than that in control (P < 0.01). AL bone marrow mononuclear cells had higher expression of VEGFR at various levels whereas CML and control samples had lower levels of VEGFR. CONCLUSIONS: Leukemia patients at newly diagnosed stage had remarkable angiogenesis in bone marrow and elevated plasma ES and VEGF concentrations. VEGFR was expressed at different levels in AL cells.

Acute Disease↗

PubMed2005

[Reform steps of reestablishing disease prevention and control system of China].

OBJECTIVE: To develop and demonstrate the reform steps of reestablishing disease prevention and control system of China. METHODS: A model named "strategies of fulfilling public functions of disease prevention and control system of China" has been employed to develop reform steps. 154 centers for disease prevention and control (CDC) have been sampled to consult the opinions about the reform steps developed by research team. RESULTS: To reestablish the disease prevention and control system of China, the following reform steps should be kept to: (1) increase government's attention to disease prevention and control, (2) insure feasible government investment to disease prevention and control, (3) increase the stability and efficiency of government financing, (4) reform management system to enhance the operation efficiency of the CDC, (5) revise labor regulation to attract and stabilize specialists, (6) be carefully to dispose the non-public-service now delivered by the CDC. The consent percent of all sampling CDC was 98.7%.

China↗

PubMed2005

[A study on the cause of public health service delivery insufficiency of disease prevention and control system of China].

OBJECTIVE: To demonstrate the cause of public health service delivery insufficiency of disease prevention and control system of China. METHODS: 205 literatures in 8 national academic journals concerning health service management have been reviewed. The method of boundary analysis has been employed to conclude the various causes of public health service delivery insufficiency of disease prevention and control system of China. RESULTS: Literatures review demonstrated that the financing from government to disease prevention and control system of China was insufficiency and show lower efficiency, which has been agreed by 99.3% of CDC. Literatures review demonstrated that the financing administration idea of permitting charging service caused the fee-for-service played a key role in the economic reimbursement of various levels of CDC, which has been agreed by 96.0% of CDC. CONCLUSION: The causes of public health service delivery insufficiency of disease prevention and control system of China were the government financing insufficiency and the defective administration strategies.

China↗

PubMed2005

[Fundamental strategies to address the problem of public health service delivery insufficiency of disease prevention and control system of China].

OBJECTIVE: To develop and demonstrate the strategies to solve the problem of public health service delivery insufficiency of disease prevention and control system of China. METHODS: 205 literatures in 8 national academic journals concerning health service management have been reviewed. The method of boundary analysis has been employed to conclude the various reform strategies. Based on the causes and mechanism of public health service delivery insufficiency of disease prevention and control system, the logic analysis has been employed to develop fundamental strategies, which has been demonstrated by 154 CDC using intention questionnaires. RESULTS: There are fundamental strategies to which the agreeing rate for sampling CDC was over 95%: to make sure government should afford the financing function of disease prevention and control and secure the feasible investment for centers of disease prevention and control. Meanwhile, the working efficiency of CDC should be improved through strengthening management and reforming government investing manner.

China↗

PubMed2005

[Implementation analysis of public functions of centers of disease prevention and control of China].

OBJECTIVE: To evaluate the implementation of public function and items of the centers of disease prevention and control(CDC). METHODS: 161 centers of disease prevention and control have been investigated by two-stage stratified sampling. The implementation analysis of public function and items of CDC is measured by multiplying average operational proportion and average operational degree. RESULTS: 1. For investigated centers, the average rate of function implementation is 42.9% ,with 56.0% at provincial level and 43.7% at city level, 41.3% for the county level; while 49.3% in east areas, 45.4% in middle areas and 35.3% in west areas. 2. Among all 7 functional items, the implemented rate of disease prevention and control is 54.3%, 65.8% for emergency treatment, 35.0% for epidemic situation report and information management of health relative factors, 31.3% for inspection and control of health risk factors, 39.1% for the laboratory examination and evaluation, 36.4% for health education and health promotion, and 56.7% for technological guidance and application study. CONCLUSION: The implemented degree of public function of CDC was generally lower, varied with regions and levels. Among 7 public functional items, the emergency treatment function had the highest implementation, with the lowest for the inspection and control of health relative factors.

China↗

PubMed2005

[Operational proportion of the public function and items of 161 centers of disease prevention and control in 7 provinces].

OBJECTIVE: To explicate the operational proportion of public function and items of the centers of disease prevention and control (CDC). METHODS: 161 CDC have been investigated by two-stage stratified sampling to provide the information about the operation of the public function and items of CDC. RESULTS: (1) The average operational proportion investigated CDC is 71.7%, the province level 92.0%, the city level 73.7%, the county level 68.5%. East areas 76.5%, middle areas 71.5%, west areas 68.1%. (2) The operational proportion of disease prevention and control function and emergency treatment function were higher, but that of epidemic situation report and information management of health relative factor, inspection and control of health relative factor, and the laboratory examination and evaluation were lower. CONCLUSION: Public function and items were rather poorly carried out by the centers of prevention and control in China, especially those in middle and west areas, and those in counties.

China↗

PubMed2005

[Implementation analysis of public functions of 161 centers of disease prevention and control in 7 provinces].

OBJECTIVE: To evaluate the implementation of public function and items of the centers of disease prevention and control (CDC). METHODS: 161 centers of disease prevention and control have been investigated by two-stage stratified sampling. The implementation analysis of public function and items of CDC is measured by multiplying average operational proportion and average operational degree. RESULTS: (1) For investigated centers, the average rate of function implementation is 42.9%, with 56.0% at provincial level and 43.7% at city level, 41.3% for the county level, while 49.3% in east areas, 45.4% in middle areas and 35.3% in west areas. (2) Among all 7 functional items, the implemented rate of disease prevention and control is 54.3%, 65.8% for emergency treatment, 35.0% for epidemic situation report and information management of health relative factors, 31.3% for inspection and control of health risk factors, 39.1% for the laboratory examination and evaluation, 36.4% for health education and health promotion, and 56.7% for technological guidance and application study. CONCLUSION: The implemented degree of public function of CDC was generally lower, varied with regions and levels. Among 7 public functional items, the emergency treatment function had the highest implementation, with the lowest for the inspection and control of health relative factors.

China↗

PubMed2005

[Human resources allocation in centers of disease prevention and control in China].

OBJECTIVE: To compare the human resources allocation of CDC in different areas and different levels. METHODS: By stratified cluster sampling we get 70 CDC's manpower data, which come from different areas(east, middle part, west)and different levels (province, city, county). RESULTS: (1) The average number of CDC's staff is 62. (2)CDC of province level are understaffed by 15%, while CDC of county level are overstaffed by 3%, and CDC of county level are overstaffed by 12%. (3) Structure of age: The average age of CDC's staff is 62, people under 35 years old in CDC is 39.4%, people above 55 years old is 3.5% (4) Structure of education: People with graduate degree are only 0.8%, and people come from technicalsecondary school are 57.0%. (5) Structure of specialty: A majority of people's majors are clinical medicine, and the percent of people having a non-medical-major are 36.6%. (6) Area distributing. Distribution of average quality score of staff are imbalance in different areas, the average quality score of staff in east area are 1.07 times than that in middle area, and 1.12 times than that in west area.

China↗