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Biomedical subjects

N Wang

Publications and source records attributed to N Wang.

At least 127 records · Page 7Linked to original sources
PubMed2000

Synthesis, characterization, biodegradation, and drug delivery application of biodegradable lactic/glycolic acid polymers: I. Synthesis and characterization.

A series of lactic/glycolic acid polymers with various molar ratios of lactic to glycolic acid and various molecular weights were synthesized using the ring-opening polymerization method. The polymerization conditions for the lactic/glycolic acid polymer synthesis were as follows: 150 degrees C, 700 microm Hg, 3 h, 0.03 wt% of catalyst (stannous 2-ethyl-hexanoate) concentration. The molecular weight of these polymers was controlled by using a molecular weight controller, lauryl alcohol. The synthesized polymers have been characterized with respect to polymer composition, molecular weight, inherent viscosity, and glass transition temperature. The characterization experiments show a good correlation between the polymer compositions and the feed ratios of lactic to glycolic acid. The molecular weight of the lactic/glycolic polymers, ranging from 10,876 to 166,630 D and the intrinsic viscosity of the polymers, ranging from 0.16 to 0.86 dl g(-1), are controlled by the amount of molecular weight controller used. The effect of the amount of the molecular weight controller on the polymer molecular weight and the polymer inherent viscosity was studied. Results indicate that the molecular weight and inherent viscosity of the polymers have a log-log linear relationship with the amount of molecular weight controller used. The lactic/glycolic acid polymers are amorphous, glassy, and transparent. The glass transition temperature of the polymers range from 21.95 to 51.29 degrees C, depending on the polymer molecular weight and the composition.

Biocompatible Materials↗
PubMed2000

Defective HDL particle uptake in ob/ob hepatocytes causes decreased recycling, degradation, and selective lipid uptake.

Levels of plasma HDL are determined in part by catabolism in the liver. However, it is unclear how the hepatic catabolism of holo-HDL is regulated or mediated. Recently, we found that ob/ob mice have defective liver catabolism of HDL apoproteins in vivo that can be reversed by low-dose leptin treatment. Here we examined HDL catabolism and trafficking at the cellular level using isolated hepatocytes. We demonstrate that ob/ob hepatocytes have reduced binding, association, degradation, and resecretion of HDL apoproteins and 50% less selective lipid uptake relative to wild-type hepatocytes. In addition, HDL apoproteins were found to colocalize with transferrin in the general endosomal recycling compartment (ERC) in wild-type hepatocytes. However, the localization to the ERC was markedly reduced in ob/ob hepatocytes. Filipin staining of cellular cholesterol revealed decreased cholesterol in the ERC in ob/ob hepatocytes. Defects in HDL cell association and cholesterol distribution were reversed by leptin administration. The findings show a major defect in HDL uptake and recycling in ob/ob hepatocytes and suggest that HDL recycling through the ERC plays a role in the determination of plasma HDL protein and cholesterol levels.

Animals↗
PubMed2000

Selective activation of endothelial cells by the antioxidant pyrrolidine dithiocarbamate: involvement of C-jun N-terminal kinase and AP-1 activation.

The antioxidant agent pyrrolidine dithiocarbamate (PDTC) has been shown to protect endothelial cells (EC) from pro-inflammatory-induced and pro-oxidant-induced NF-kappaB activation. It also perturbs EC by altering activator protein-1 (AP-1) status and inducing ICAM-1. Experiments were performed to investigate the upstream mechanism by which PDTC produces these effects. We have demonstrated that PDTC not only induced AP-1 binding and ICAM-1 expression by itself, but it also augmented AP-1 activation and ICAM-1 induction in low-dose IL-1alpha treated cells. To dissect the mechanism of these effects, we measured c-Jun and c-Fos expression, and the activity of c-Jun NH2-terminal kinase (JNK) and extracellular signal regulated kinase (ERK) in human umbilical vein endothelial cells (HUVEC). We detected an increase in JNK activity in PDTC-treated HUVEC. Following cotransfection with JNK[K-M], a kinase-deficient JNK1, the PDTC-increased AP-1-driven-luciferase activity was attenuated. Utilizing a specific trans-reporting system we confirmed c-Jun activation by upstream signaling mechanisms. The results show that c-Jun activity was increased 9-fold after PDTC treatment. In addition, PDTC promoted more transient activation in ERK-c-fos. In contrast, PDTC produced sustained JNK-c-Jun activation, which translated into long-lasting ICAM-1 production. These results suggest that an antioxidant may contribute to chronic vascular endothelial activation.

Antioxidants↗
PubMed2000

Expression of adenylate cyclase subtypes II and IV in the human outflow pathway.

PURPOSE: It has been demonstrated that low doses of pilocarpine and other muscarinics substantially increase outflow facility in the isolated human outflow system devoid of ciliary muscle. These cholinergic-induced facility responses were thought possibly to be due to elevation of cAMP as a result of the presence of adenylate cyclases II (AC-II) and IV (AC-IV). Therefore, whether these isoforms are present in outflow tissues was examined. METHODS: Human anterior segments were perfused with carbachol (10(-9)-10(-5) M), and outflow facility and cAMP levels in the perfusate were measured simultaneously. Isolated trabecular meshwork (TM) were incubated with carbachol (10(-7) M), and the subsequent changes in cAMP were measured by radioimmunoassay. AC-II and AC-IV were characterized in ocular tissue with reverse transcription-polymerase chain reaction and in situ hybridization. RESULTS: Outflow facility increased, in a dose-dependent manner, by 10%, 16%, and 27% in response to 10(-9), 10(-7), and 10(-5) M carbachol, respectively. Similarly, cAMP increased by 9%, 70%, and 210% in response to 10(-9), 10(-7), and 10(-5) M carbachol, respectively. In addition, cAMP levels significantly increased by 39% in isolated TM strips incubated with 10(-7) M carbachol. AC-II was detected in most normal tissue examined, but not in any cultured cell lines or any glaucomatous tissue. AC-IV was also widely expressed in most normal tissues, faintly detected in some glaucoma tissue, but not detected in most cultured cells. CONCLUSIONS: The presence of AC-II and AC-IV in outflow tissues supports the hypothesis that cholinergics may indeed exert an effect on outflow facility, mediated by cAMP, which is independent of muscle contraction.

Adenylyl Cyclases↗
PubMed2000

Morphodensitometric analysis of protein kinase C beta(II) expression in rat colon: modulation by diet and relation to in situ cell proliferation and apoptosis.

We have recently demonstrated that overexpression of PKC beta(II) renders transgenic mice more susceptible to carcinogen-induced colonic hyperproliferation and aberrant crypt foci formation. In order to further investigate the ability of PKC beta(II) to modulate colonocyte cytokinetics, we determined the localization of PKC beta(II) with respect to cell proliferation and apoptosis along the entire colonic crypt axis following carcinogen and diet manipulation. Rats were provided diets containing either corn oil [containing n-6 polyunsaturated fatty acids (PUFA)] or fish oil (containing n-3 PUFA), cellulose (non-fermentable fiber) or pectin (fermentable fiber) and injected with azoxymethane (AOM) or saline. After 16 weeks, an intermediate time point when no macroscopic tumors are detected, colonic sections were utilized for immunohistochemical image analysis and immunoblotting. Cell proliferation was measured by incorporation of bromodeoxyuridine into DNA and apoptosis by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling. In the distal colon, PKC beta(II) staining was localized to the upper portion of the crypt. In comparison, proximal crypts had more (P < 0.05) staining in the lower tertile. AOM enhanced (P < 0.05) PKC beta(II) expression in all regions of the distal colonic crypt (upper, middle and lower tertiles). There was also an interaction (P < 0.05) between dietary fat and fiber on PKC beta(II) expression (corn/pectin > fish/cellulose, fish/pectin > corn/cellulose) in all regions of the distal colonic crypt. With respect to colonic cell kinetics, proliferation paralleled the increase in PKC beta(II) expression in carcinogen-treated animals. In contrast, apoptosis at the lumenal surface was inversely proportional to PKC beta(II) expression in the upper tertile. These results suggest that an elevation in PKC beta(II) expression along the crypt axis in the distal colon is linked to enhancement of cell proliferation and suppression of apoptosis, predictive intermediate biomarkers of tumor development. Therefore, select dietary factors may confer protection against colon carcinogenesis in part by blocking carcinogen-induced PKC beta(II) expression.

Animals↗
PubMed2000

Dietary fish oil reduces O6-methylguanine DNA adduct levels in rat colon in part by increasing apoptosis during tumor initiation.

There is epidemiological, clinical, and experimental evidence that dietary fish oil, containing n-3 polyunsaturated fatty acids, protects against colon tumor development. However, its effects on colonocytes in vivo remain poorly understood. Therefore, we investigated the ability of fish oil to modulate colonic methylation-induced DNA damage, repair, and deletion. Sprague Dawley rats were provided with complete diets containing either corn oil or fish oil (15% by weight). Animals were injected with azoxymethane, and the distal colon was removed 3, 6, 9, or 12 h later. Targeted apoptosis and DNA damage were assessed by cell position within the crypt using the terminal deoxynucleotidyl transferase-mediated nick end labeling assay and quantitative immunohistochemical analysis of O6-methylguanine adducts, respectively. Localization and expression of the alkyl group acceptor, O6-methylguanine-DNA-methyltransferase, was also determined. Lower levels of adducts were detected at 6, 9, and 12 h in fish oil- versus corn oil-fed animals (P < 0.05). In addition, fish oil supplementation had the greatest effect on apoptosis in the top one-third of the crypt, increasing the apoptotic index compared with corn oil-fed rats (P < 0.05). In the top one-third of the crypt, fish oil feeding caused an incremental stimulation of apoptosis as adduct level increased. In contrast, a negative correlation between apoptosis and adduct incidence occurred with corn oil feeding (P < 0.05). Diet had no main effect (all tertiles combined) on O6-methylguanine-DNA-methyltransferase expression over the time frame of the experiment. The enhancement of targeted apoptosis combined with the reduced formation of O6-methylguanine adducts may account, in part, for the observed protective effect of n-3 polyunsaturated fatty acids against experimentally induced colon cancer.

Analysis of Variance↗
PubMed2000

[Distribution patterns of root systems of main planting tree species in Weibei Loess Plateau].

The vertical patterns of root systems of Pinus tabulaeformis, Robinia pseudoacacia, Platycladus orientalis, Pinus sylvestris var. mongolica, Pinus armandi, Prunus armeniacia var. ansu planted in the Weibei Loess Plateau were studied with soil auger. Site conditions had a significant effect on the vertical root distribution of R. pseudoacacia, of which, soil moisture is the key factor. Soil species and soil structure also had great effect on the distribution. P. tabulaeformis had a maximum rooting depth at its young stage(8 years old), but the root density increased with age. There was a great difference in vertical root distribution among the tree species, of them, R. pseudoaccia rooted deepest, which negated the opinion that R. pseudoacacia is a shallow rooted tree species. According to the vertical root distribution of the tree species, the productivity of these species in the south-facing site of yellow loess soil would be in order of R. pseudoacacia > Prunus armeniacia var. ansu > P. tabulaeformis > P. sylvestris var. mongolica > P. armandi > Platycladus orientalis.

China↗
PubMed2000

Identification and analysis of mutations of the Wilson disease gene in Chinese population.

OBJECTIVE: To investigate the characteristics of mutations in exon 3-20 of Wilson disease (WD) gene and their consequences in Chinese population. METHODS: Sixty unrelated normal Chinese and forty-four unrelated WD patients were studied. Genomic DNA was prepared from peripheral blood leukocytes by a salt-out method. Polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) and subsequently direct sequencing were used to identify the mutations and polymorphisms of WD gene. RESULTS: Ten different mutations have been found, accounting for 52% of the mutant genes. Five of them are identified as novel missense mutations. Mutations Arg778Leu, Thr935Met and Ala874Val were represented respectively in 28.4%, 6.8% and 3.4% of WD chromosomes. The remaining mutations were found rare and limited to one or two patients. A total of 11 patients were homozygous for a single mutation, and 17 patients were in a compound heterozygous state with or without a known mutation. CONCLUSION: In Chinese, WD seems to result from two or three relatively common mutations and a large number of rare mutations. Arg778Leu and Thr935Met might be hotspots of mutation in Chinese population. The results indicated that the feature of mutations of WD gene is different between Chinese and the Western. Instead of exon 14 and exon 18, we had to select exon 8 and exon 12 first to detect mutations of WD gene in Chinese. It is of great importance to establish a direct diagnostic method for WD. This study improves our knowledge on functional domains of the WD gene, and helps elucidate the wide spectrum of manifestations of the disease as well.

Adenosine Triphosphatases↗
PubMed2000

[Some geographical features of the location and gene mutation of cancers occurring in Nantong City, China].

OBJECTIVE: To detect the location and geographical features of gene mutation of the cancer based on 30,709 clinical tumor biopsies. METHODS: Thirty thousand seven hundred and nine cases of tumor biopsy materials were collected from the Department of Pathology of Nantong Cancer Hospital between June 1974 and December 1987. The address of the village and county of patients was collected and statistical analysis was performed on data from lab examination. DNA sequencing of 31 cases of hepatocellular carcinoma (HCC) was performed at the Department of Pathology of the Medical College of Tokyo University, Japan. RESULTS: The data suggested that different carcinomas occurred predominantly in some districts and the frequency and type of mutation of the P53 gene in the HCC were different in different districts. CONCLUSION: It seems that based on the clinical biopsy materials, carcinomas of the uterus cervix (CC) and nasopharynx tend to occur in some districts of Nantong City and the frequency and type of mutation of the gene P53 of the HCC were different in different districts. The reason for this is not understood and further study will be done.

China↗
PubMed2000

[Multiple patterns of angle closure mechanisms in primary angle closure glaucoma in Chinese].

OBJECTIVE: The mechanism of primary angle closure glaucoma (PACG) in Chinese is studied to establish a new classification system based on the etiology and mechanism of angle closure. METHODS: The anterior chamber angle's configuration and the anatomic structures related to the angle in 126 cases with PACG were observed with ultrasound biomicroscope (UBM), and the mechanisms of angle closure were analyzed by diagnostic treatment. RESULTS: Based on the configuration of the angle and anatomic structures related to the angle as well as the mechanisms of angle closure, PACG could be divided into following subtypes: pure pupillary block angle closure glaucoma [PPB, 48 cases (38.1%)]; pure non-pupillary angle closure glaucoma [PNP, 9 cases (7.1%)]; multiple mechanism angle closure glaucoma [MM, 69 cases (54.8%)]. PPB manifested that the relative position of pupillary margin was located anteriorly, the peripheral iris bombé was due to the pupillary block, and the angle closure was not related to the location and shape of the peripheral iris and ciliary body. PNP showed that the relative position of pupil margin was located posteriorly, the angle closure was not caused by the pupillary block, but caused by anterior located ciliary body and/or thick and anterior located peripheral iris. MM pattern was caused by both pupillary block and non-pupilary block, and most of the cases manifested creeping angle closure. CONCLUSIONS: The angle closure mechanisms of PACG in Chinese are of multiple patterns. Based on the different mechanisms of angle closure in PACG, a new classification system should be established to improve the diagnosis and treatment of PACG.

Adult↗
PubMed2000

[Hostility behavior as risk factor of coronary heart disease].

OBJECTIVE: To explore the relationships between hostility, and the risks of coronary-prone behavior and the clusters of unhealthy behaviors in individuals with different levels of hostility. METHODS: A cross-sectional study was carried out among 1 010 male employees from two factories in Beijing Capital Steel and Iron Company in 1997. Data on major risks of cardiovascular, other social-demographic factors and levels of hostility by Cook-Medley Scales were collected. RESULTS: Body mass index, amounts of cigarette smoking and alcohol drinking were significantly increased (P < 0.01) with a characteristic of reduced social support from one's colleagues, when individual's level of hostility increased. In addition, less years of education, higher prevalence of other chronic diseases (P < 0.05) and clustering of various unhealthy behaviors were found related to the increase of individual's hostility. The odds ratio in the group with highest hostility was 2.37 times higher than in the lowest one, after confounding effects from age, blood pressure, education level, status of chronic disease and social support being adjusted. No significant differences on both systolic and diastolic blood pressures among groups with different levels of hostility were discovered. CONCLUSION: The association between hostility, coronary-prone risk behavior and cluster of unhealthy behaviors suggested that hostility might increase the risk of coronary heart diseases through affecting individual's behavior.

Adolescent↗
PubMed2000

[Cloning and sequence analysis of E0 gene of hog cholera virus lapinized Chinese strain and virulent shimen strain].

According to the published nucleotide sequences of genome of hog cholera virus, one pair of specific primers were designed and synthesized. From the spleen of rabbits which were infected with HCLV and HCV Shimen strain infected pig blood, the two E0 genes were amplified by RT-PCR. The amplified fragments were cloned into pGEM-T vector and sequenced. Sequence analysis showed nucleotide sequence and deduced amino acid sequence homologies of the E0 gene between HCLV and Shimen strain were 95.0% and 94.3%. There was 13 amino acid substitutions between them. One N-glycosylation site was missing from E0 gene of the Shimen strain. The nucleotide sequence homologies of the Shimen strain with the ALD, GPE-, Brescia and Alfort strains were 97.4%, 96.5%, 92.2% and 86.5%, respectively, the deduced amino acid sequence homologies were 97.4%, 96.0%, 95.2% and 92.5%, respectively. The nucleotide sequence homologies of E0 gene of the HCLV strain with the ALD, GPE-, Brescia and Alfort strains were 95.6%, 94.9%, 91.3% and 85.5%, respectively, the deduced amino acid sequence homologies were 93.4%, 92.5%, 91.6% and 90.7%, respectively. E0 gene from HCV was shown to be similar to a family of fungal and plant ribonuclease. The catalytically important residues were 28 to 40 and 71 to 89 of HCV E0 gene.

Amino Acid Sequence↗
PubMed2000

[Study on the pharmacologic effect of propolis].

Pharmacologic effects of propolis were investigated in this article. The results suggested that propolis has pharmacologic functions in many aspects. It is a new-type medicine derived from animal in pharmacology and food both. To small mouse, propolis showed the functions of anti-fatigue and endurance to lack of oxygen. To high-blood-lipid-model mouse, it prevented increase of blood-mucus and blood lipid(TC, TG, LDL-C) (P < 0.05-0.01), but there were insignificant changes to red-blood-cell proportion (HCT) and high-density lipoprotein chelesteral (HDC-C). To small immunosuppessive-model mouse, propolis could strengthen macrophagocyte phagocytosis in the abdominal-cavity (P < 0.05), and increase the thymus-index (P < 0.05), but there were insignificant changes to the spleen-index. The LD50 > 7500 mg/kg to small mouse.

Adjuvants, Immunologic↗
PubMed2000

[An evaluation of human hair homogeneity by inductively coupled plasma mass spectrometry].

Human hair certified reference material(GBW09101) homogeneity was evaluated by determining 10(-6) quantity Cu, Zn, Mg, K, Pb, Fe, Ca, Na and S on sample weight from 100 mg to 300 mg by neutron activation analysis, atomic absorption spectrometry and X-ray fluorescence analysis. Using variance F test, the results(F < F alpha) is not differ significantly and this material could be considered homogeneous. In this paper, an evaluation of homogeneity was made by Inductively Coupled Plasma Mass Spectrometry through the determination of 10(9) quantity La, Sm, Y in 0.2000 g samples. Using t test and F test, the results (magnitude of t < t alpha, F < F alpha) were satisfactory.

Copper↗
PubMed1999

Deafening alters neuron turnover within the telencephalic motor pathway for song control in adult zebra finches.

In the telencephalon of adult songbirds, projection neurons are lost and replaced within the efferent pathway controlling learned vocal behavior. We examined the potential role of auditory experience in regulating the addition and long-term survival of vocal control neurons in adult male zebra finches. Deafened and control birds were injected with the cell birth marker [(3)H]thymidine and then killed 1 or 4 months later. At the 1 month survival time, the number of [(3)H]-labeled neurons present in the high vocal center (HVC) was 70% lower in deafened birds compared with controls. This was true for all [(3)H]-labeled HVC neurons, as well as the subset that projected to the robust nucleus of the archistriatum. Over the next 3 months, two-thirds of the [(3)H]-labeled HVC neurons in control birds were lost, presumably through cell death. Surprisingly, deafened birds showed no loss over this interval. The total number of HVC neurons did not differ between control and deafened birds at either survival time. Nuclear diameters of [(3)H]-labeled HVC neurons decreased with cell age in both control and deafened birds, a process that may relate to the eventual death and replacement of these cells. These results suggest that experience influences the addition and also the longer-term fate of neurons formed in adulthood. We propose that auditory deprivation decreases the incorporation of new neurons and prolongs their life span. Alterations in the neuronal replacement cycle may relate to the gradual deterioration in song that occurs after deafening in adult zebra finches.

Animals↗
PubMed1999

Hepatic scavenger receptor BI promotes rapid clearance of high density lipoprotein free cholesterol and its transport into bile.

The clearance of free cholesterol from plasma lipoproteins by tissues is of major quantitative importance, but it is not known whether this is passive or receptor-mediated. Based on our finding that scavenger receptor BI (SR-BI) promotes free cholesterol (FC) exchange between high density lipoprotein (HDL) and cells, we tested whether SR-BI would effect FC movement in vivo using [(14)C]FC- and [(3)H]cholesteryl ester (CE)-labeled HDL in mice with increased (SR-BI transgenic (Tg)) or decreased (SR-BI attenuated (att)) hepatic SR-BI expression. The initial clearance of HDL FC was increased in SR-BI Tg mice by 72% and decreased in SR-BI att mice by 53%, but was unchanged in apoA-I knockout mice compared with wild-type mice. Transfer of FC to non-HDL and esterification of FC were minor and could not explain differences. The hepatic uptake of FC was increased in SR-BI Tg mice by 34% and decreased in SR-BI att mice by 22%. CE clearance and uptake gave similar results, but with much slower rates. The uptake of HDL FC and CE by SR-BI Tg primary hepatocytes was increased by 2.2- and 2.6-fold (1-h incubation), respectively, compared with control hepatocytes. In SR-BI Tg mice, the initial biliary secretion of [(14)C]FC was markedly increased, whereas increased [(3)H]FC appeared after a slight delay. Thus, in the mouse, a major portion of the clearance of HDL FC from plasma is mediated by SR-BI.

Animals↗
PubMed1999

Early repair treatment of electrical burns and recovery of tendons and nerves. Report of 194 operations.

A new approach to treatment of electrically burned tendons and nerves by primarily covering with skin or myocutaneous flaps is recommended. Between 1964 and 1989, 194 operations using the new approach were performed on 147 patients, of which 179 operations were successful and only 15 procedures resulted in infection. Among 42 cases involving the wrist, the rate of functional recovery of the electrically burned tendons was 97.6%; the rate of recovery in 21 cases of electrically burned peripheral nerves was 80.9%.

Burns, Electric↗