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Biomedical subjects

Jun Li

Publications and source records attributed to Jun Li.

At least 109 records · Page 6Linked to original sources
PubMed2006

Self-assembled supramolecular hydrogels formed by biodegradable PEO-PHB-PEO triblock copolymers and alpha-cyclodextrin for controlled drug delivery.

A materials design of a new supramolecular hydrogel self-assembled between alpha-cyclodextrin and a biodegradable poly(ethylene oxide)-poly[(r)-3-hydroxybutyrate]-poly(ethylene oxide) (PEO-PHB-PEO) triblock copolymer was demonstrated. The cooperation effect of complexation of PEO segments with alpha-cyclodextrin and the hydrophobic interaction between PHB blocks resulted in the formation of the supramolecular hydrogel with a strong macromolecular network. The in vitro release kinetics studies of fluorescein isothiocyanate labeled dextran (dextran-FITC) model drug from the hydrogel showed that the hydrogel was suitable for relatively long-term sustained controlled release of macromolecular drugs, which many simple triblock copolymer hydrogel systems could not achieve. The hydrogel was found to be thixotropic and reversible, and can be applied as a promising injectable drug delivery system.

Biocompatible Materials↗
PubMed2006

Highly tunable large-core single-mode liquid-crystal photonic bandgap fiber.

We demonstrate a highly tunable photonic bandgap fiber, which has a large-core diameter of 25 microm and an effective mode area of 440 microm2. The tunability is achieved by infiltrating the air holes of a photonic crystal fiber with an optimized liquid-crystal mixture having a large temperature gradient of the refractive indices at room temperature. A bandgap tuning sensitivity of 27 nm/degrees C is achieved at room temperature. The insertion loss is estimated to be less than 0.5 dB and caused mainly by coupling loss between the index-guided mode and the bandgap-guided mode.

Journal Article↗
PubMed2006

Dynamic and static light scattering studies on self-aggregation behavior of biodegradable amphiphilic poly(ethylene oxide)-poly[(R)-3-hydroxybutyrate]-poly(ethylene oxide) triblock copolymers in aqueous solution.

The self-aggregation behavior of two amphiphilic poly(ethylene oxide)-poly[(R)-3-hydroxybutyrate]-poly(ethylene oxide) (PEO-PHB-PEO) triblock copolymer samples with nearly identical PHB block lengths but different PEO block lengths, PEO-PHB-PEO(2000-810-2000) and PEO-PHB-PEO(5000-780-5000), was studied with dynamic and static light scattering (DLS and SLS), in combination with fluorescence spectroscopy and transmission electron microscopy (TEM). The formation of polymeric micelles by the two PEO-PHB-PEO triblock copolymers was confirmed with fluorescence technique and TEM. DLS analysis showed that the hydrodynamic radius (R(h)) of the monodistributed polymeric micelles increased with an increase in PEO block length. The relative thermostability of the triblock copolymer micelles was studied by SLS and DLS at different temperatures. The aggregation number and the ratio of the radius of gyration over hydrodynamic radius were found to be independent of temperature, probably due to the strong hydrophobicity of the PHB block. The combination of DLS and SLS studies indicated that the polymeric micelles were composed of a densely packed core of hydrophobic PHB blocks and a corona shell formed by hydrophilic PEO blocks. The aggregation numbers were found to be approximately 53 for PEO-PHB-PEO(2000-810-2000) micelles and approximately 37 for PEO-PHB-PEO(5000-780-5000) micelles. The morphology of PEO-PHB-PEO spherical micelles determined by DLS and SLS measurements was further confirmed by TEM.

Biocompatible Materials↗
PubMed2006

Anopheles gambiae genome reannotation through synthesis of ab initio and comparative gene prediction algorithms.

BACKGROUND: Complete genome annotation is a necessary tool as Anopheles gambiae researchers probe the biology of this potent malaria vector. RESULTS: We reannotate the A. gambiae genome by synthesizing comparative and ab initio sets of predicted coding sequences (CDSs) into a single set using an exon-gene-union algorithm followed by an open-reading-frame-selection algorithm. The reannotation predicts 20,970 CDSs supported by at least two lines of evidence, and it lowers the proportion of CDSs lacking start and/or stop codons to only approximately 4%. The reannotated CDS set includes a set of 4,681 novel CDSs not represented in the Ensembl annotation but with EST support, and another set of 4,031 Ensembl-supported genes that undergo major structural and, therefore, probably functional changes in the reannotated set. The quality and accuracy of the reannotation was assessed by comparison with end sequences from 20,249 full-length cDNA clones, and evaluation of mass spectrometry peptide hit rates from an A. gambiae shotgun proteomic dataset confirms that the reannotated CDSs offer a high quality protein database for proteomics. We provide a functional proteomics annotation, ReAnoXcel, obtained by analysis of the new CDSs through the AnoXcel pipeline, which allows functional comparisons of the CDS sets within the same bioinformatic platform. CDS data are available for download. CONCLUSION: Comprehensive A. gambiae genome reannotation is achieved through a combination of comparative and ab initio gene prediction algorithms.

Algorithms↗
PubMed2006

High-fat emulsion-induced rat model of nonalcoholic steatohepatitis.

Non-alcoholic fatty liver disease (NAFLD) is emerging as a common medical problem. Nonalcoholic steatohepatitis (NASH) is the critical turning point at which NAFLD progresses to more advanced stages such as hepatic fibrosis, cirrhosis and even hepatocellular carcinoma. However, the study of the pathogenic or therapeutic factors involved in NASH has been hampered by the absence of a suitable experimental model. The aim of the present work was to establish a high-fat emulsion-induced rat model of NASH. Male Sprague-Dawley rats were fed a high-fat emulsion via gavage for 6 weeks. Animals were examined for weight gain, serum and hepatic biochemistry, insulin sensitivity, hepatic malondialdehyde (MDA), superoxide dismutase (SOD) and tissue morphology, as well as cytochrome P-450 2E1 (CYP2E1) and peroxisome proliferator-activated receptor alpha (PPARalpha) expression in the liver. The results showed that rats treated with high-fat emulsion became obese, demonstrated abnormal aminotransferase activity, hyperlipoidemia, hyperinsulinemia, hyperglycemia and insulin resistance. The model rats exhibited an increased concentration of serum TNF-alpha, total cholesterol (TC), triglyceride (TG), MDA and reduced SOD levels in the liver. Immunoblot analysis showed that the expression of CYP2E1 was increased, whereas PPARalpha was reduced in the NASH model rat liver. Moreover, morphological evaluation revealed that hepatic steatosis, inflammation and mitochondrial lesions were also reproduced in this model. In conclusion, a practical and repeatable new rat model of steatohepatitis was established by feeding with high-fat emulsion via gavage. This model provides a valuable research tool and reproduces many of the clinical indices of human NASH.

Animals↗
PubMed2006

Association of attention-deficit/hyperactivity disorder with serotonin 4 receptor gene polymorphisms in Han Chinese subjects.

Attention-deficit/hyperactivity disorder (ADHD) is an important public health problem. Although serotonin is believed to be an important neurotransmitter in the etiology of this disorder, it remains unclear which specific 5-HT receptors are involved in regulating the symptoms of ADHD. Previous studies have provided favorable evidence for the association of ADHD with both the serotonin transporter gene and serotonin 1B receptor gene. To further investigate the role of other genes of the serotonergic pathway in ADHD, the current study examined variants of the serotonin 4 receptor gene in a relatively large sample of ADHD nuclear families. The T allele of the 83097 C>T polymorphism of HTR4 showed a tendency of preferential transmission to probands with ADHD (chi(2)=2.699, P=0.100). When haplotype TDT analysis of HTR4 was performed, we further found that the C/G haplotype of the 83097 C>T and 83198 A>G polymorphisms (chi(2)=8.783, P=0.003) and the C/G/C haplotype of these and the -36 C>T polymorphism (chi(2)=5.762, P=0.016) were under-transmitted to probands with ADHD. These results suggest that the HTR4 gene may play a role in the genetic predisposition to ADHD.

Asian People↗
PubMed2006

Mallory body (cytokeratin aggresomes) formation is prevented in vitro by p38 inhibitor.

Microarray analysis of livers from mice fed diethyl-1,4-dihydro-2,4,6-trimethyl-3,5-pyridinedicarboxylate (DDC) to induce Mallory body (MB) cytokeratin aggresome formation showed that gene expression for cellular adhesion molecules, cytokeratins, kinases and aggresome forming proteins were upregulated, when MBs were formed in vivo. This response was enhanced when the DDC was refed (mice fed DDC for 10 weeks followed by DDC withdrawal for 1 month, then refed DDC for 7 days). Immunofluorescent antibody staining of the MBs that formed showed that MAPK p38 was colocalized with ubiquitin and p62 in the MBs. To investigate further the mechanisms of MB formation, primary cultures derived from DDC primed mice and their controls were incubated for 6 days. Liver cells cultured for 3 h and 6 days were used for microarray analysis. At 3 h, there were no MBs formed, but MBs were numerous after 6 days of culture. At 3 h, the expression of a large number of genes was different when the control, and the DDC primed hepatocytes were compared, which indicates that the primed hepatocytes were phenotypically changed. The gene expression of many kinases including p38 was upregulated after 6 days where the gene expression of cytokeratins, adhesion molecules and aggresome forming proteins were upregulated when MBs formed. An inhibitor of p38 phosphorylation (SB202190) completely prevented MB formation. Western blot showed that phosphorylated p38 MAPK and total p38 were absent in vitro after the p38 inhibitor treatment. Immunostaining of 6-day DDC-primed hepatocyte cultures stained with antibodies to p62 and phospho-p38 MAPK showed that phosphorylated p38 MAPK was concentrated within the MBs. Antibodies to specific serine phosphorylated sites 73 and 431, located in cytokeratin 8, localized to Mallory bodies in vivo, indicating that cytokeratin 8 was hyperphosphorylated. The data supported the concept that MBs form as the result of hyperphosphorylation of cytokeratin 8 by p38.

Animals↗
PubMed2006

Psc-AFP, an antifungal protein with trypsin inhibitor activity from Psoralea corylifolia seeds.

An antifungal protein designated as Psc-AFP, with an apparent molecular mass of 18kDa, was isolated from a traditional Chinese herb, malaytea scurfpea (Psoralea corylifolia L.). The isolation procedure entailed extraction, cation exchange chromatography on CM FF, gel filtration chromatography on Superdex 75 and reversed-phase high performance liquid chromatography on SOURCE 5RPC column. Automated Edman degradation determined the partial N-terminal sequence of Psc-AFP to be NH2-EWEPVQNGGSSYYMVPRIWA, which displayed homology with plant trypsin inhibitors. The protease inhibitor activity of Psc-AFP was then confirmed by the inhibition on trypsin. Psc-AFP at 10 microM inhibited the mycelial growth of Alternari brassicae, Aspergillus niger, Fusarium oxysporum and Rhizoctonia cerealis, suggesting that Psc-AFP has a role in the defense against pathogens.

Amino Acid Sequence↗
PubMed2006

Possible association of the alpha-2A adrenergic receptor gene (ADRA2A) with symptoms of attention-deficit/hyperactivity disorder.

A dysfunction of the central noradrenergic system has long been suggested to be involved in attention-deficit/hyperactivity disorder (ADHD). Pharmacological evidence from animal studies and clinical practice has identified the alpha-2A adrenergic receptor gene (ADRA2A) as a candidate gene in ADHD. Some findings from Caucasian populations seem to support a role for this gene in ADHD. The current study first examined the association of the ADRA2A MspI and DraI polymorphisms with ADHD in the Han Chinese population, which differs quite substantially from the Caucasian population in the frequencies of alleles at these polymorphisms. No biased transmission of alleles of either polymorphism was observed using transmission disequilibrium test (TDT) analysis in a sample of 268 nuclear families with an ADHD proband; however, haplotype analysis only identified a trend toward over-transmission of the M/C haplotype to probands with the combined subtype of ADHD (chi(2) = 3.233, P = 0.072). The mm genotype of the MspI polymorphism was also marginally related (P = 0.051) to lower ADHD symptom scores in a sample of 559 Chinese children with ADHD, which is inconsistent with data from Caucasian samples. Our results provide weak evidence for a possible role of ADRA2A in ADHD symptom expression.

Adolescent↗
PubMed2006

Association between tryptophan hydroxylase gene polymorphisms and attention deficit hyperactivity disorder in Chinese Han population.

Attention deficit hyperactivity disorder (ADHD) is a severe behavioral disorder in children known to have a substantial genetic component. Prior studies have implicated serotonin genes in the etiology of ADHD but have not examined tryptophan hydroxylase (TPH), which is a rate-limiting enzyme in serotonin biosynthesis. The current study examined the relationship between the A218C and A-6526G polymorphisms of the TPH gene and ADHD. Three hundred sixty-two unrelated ADHD probands and their biological parents were recruited to participate in this study. No biased transmission of any allele of the two polymorphisms was observed using TDT analysis. However, haplotype analyses found that the rare 218A/-6526G haplotype was significantly not transmitted to probands with ADHD (chi(2) = 4.4995, P = 0.034), regardless of subtype. Although this finding for ADHD in the Chinese Han population.

Adolescent↗
PubMed2006

Formation and characterization of the XeOO(+) cation in solid argon.

This report presents the preparation and characterization of a xenon-containing cationic radical species, XeOO+. The XeOO+ cation was produced either by co-deposition of the reactive species generated by laser ablation of different transition metals with dioxygen and xenon mixtures in excess argon or by condensation of high-frequency discharged O2/Xe/Ar mixtures at 12 K and is identified by infrared absorptions. High-level quantum chemical calculations indicate that XeOO+ has a bent structure with direct xenon-oxygen dative bonding, and the doublet ground state is much more stable than the Xe + O2+ reactants.

Journal Article↗
PubMed2006

Enterocyte TLR4 mediates phagocytosis and translocation of bacteria across the intestinal barrier.

Translocation of bacteria across the intestinal barrier is important in the pathogenesis of systemic sepsis, although the mechanisms by which bacterial translocation occurs remain largely unknown. We hypothesized that bacterial translocation across the intact barrier occurs after internalization of the bacteria by enterocytes in a process resembling phagocytosis and that TLR4 is required for this process. We now show that FcgammaRIIa-transfected enterocytes can internalize IgG-opsonized erythrocytes into actin-rich cups, confirming that these enterocytes have the molecular machinery required for phagocytosis. We further show that enterocytes can internalize Escherichia coli into phagosomes, that the bacteria remain viable intracellularly, and that TLR4 is required for this process to occur. TLR4 signaling was found to be necessary and sufficient for phagocytosis by epithelial cells, because IEC-6 intestinal epithelial cells were able to internalize LPS-coated, but not uncoated, latex particles and because MD2/TLR4-transfected human endothelial kidney (HEK)-293 cells acquired the capacity to internalize E. coli, whereas nontransfected HEK-293 cells and HEK-293 cells transfected with dominant-negative TLR4 bearing a P712H mutation did not. LPS did not induce membrane ruffling or macropinocytosis in enterocytes, excluding their role in bacterial internalization. Strikingly, the internalization of Gram-negative bacteria into enterocytes in vivo and the translocation of bacteria across the intestinal epithelium to mesenteric lymph nodes were significantly greater in wild-type mice as compared with mice having mutations in TLR4. These data suggest a novel mechanism by which bacterial translocation occurs and suggest a critical role for TLR4 in the phagocytosis of bacteria by enterocytes in this process.

Animals↗
PubMed2006

[Human natural infection of Plasmodium knowlesi].

A blood film slide taken from a patient previously diagnosed as vivax malaria in Mojiang County, Yunnan Province, showing atypical forms. The ring forms had multinuclei, and the late trophozoites trended to form band. The schizonts and gametocytes were somewhat alike to Plasmodium vivax. PCR amplification confirmed that the patient was infected by P. knowlesi.

Adult↗
PubMed2006

The effect of the JAK2 V617F mutation on PRV-1 expression.

JAK2(V617F)an acquired mutation of JAK2, is present in a majority of patients with polycythemia vera and to a lesser extent among patients with the other myeloproliferative disorders. We analyzed the effect of JAK2(V617F) on the expression of polycythemia rubra vera 1(PRV-1), using an in vitro model. Compared to wild-type JAK2, the presence of JAK2(V617F) increased both PRV-1 protein and mRNA levels in murine myeloid cells. A JAK2 inhibitor eliminated the V617F-induced increase in PRV-1 expression.

Amino Acid Substitution↗
PubMed2006

Hydrogen bond catalyzed direct reductive amination of ketones.

[reaction: see text] A novel, biomimetic concept for the direct reductive amination of ketones is described that relies on selective imine activation by hydrogen bond formation. The mild, acid- and metal-free process requires only catalytic amounts of thiourea as hydrogen bond donor and utilizes the Hantzsch ester for transfer hydrogenation. The method allows the efficient synthesis of structurally diverse amines.

Journal Article↗
PubMed2006

The pre-ischaemic neuroprotective effects of the polyamine analogues BU43b and BU36b in permanent and transient focal cerebral ischaemia models in mice.

The present study investigated the neuroprotective potential of two novel polyamine analogues, BU43b and BU36b, when administered 30 min prior to cerebral ischaemia. Neuroprotection in a permanent and a transient focal cerebral ischaemia mouse model (induced by intraluminal middle cerebral artery occlusion (MCAO)) was investigated using a range of histological and behavioural assessments. In the permanent ischaemia model, BU43b reduced oedema and showed a trend towards reduction in %HLV (percentage hemisphere lesion volume) when administered at a dose of 30 mg/kg i.p. Following transient ischaemia, treatment with BU43b decreased the %HLV and reduced oedema when administered at 30 mg/kg. BU43b also improved the locomotor activity (LMA) in MCAO mice at both 20 mg/kg and 30 mg/kg doses. BU36b was less effective than BU43b in both the permanent and the transient models, with its most pronounced effect being a trend towards reduction in oedema in both models. These results demonstrate that BU43b administered 30 min before ischaemia provided a good level of neuroprotection in the two models of cerebral ischaemia used and may have potential as a neuroprotective treatment for stroke.

Animals↗
PubMed2006

Structure-activity relationships in the induction of Phase II enzymes by derivatives of 3H-1,2-dithiole-3-thione in rats.

Derivatives of 3H-1,2-dithiole-3-thione (D3T) decrease the incidence and multiplicity of tumours in animals exposed to chemical carcinogens by a mechanism that is believed to involve their ability to increase tissue activities of Phase II detoxification enzymes. One D3T derivative, 4-methyl-5-pyrazinyl-3H-1,2-dithiole-3-thione (oltipraz) has been investigated as a chemopreventative agent in humans, although large-scale trials of this substance were abandoned because of toxicity problems. While detailed information on the inductive ability of oltipraz is available, little is known of the relative activity of other D3T derivatives in vivo. In the present study, the effects of 10 dithiolethiones on the activities of two Phase II enzymes, NAD(P)H:quinone acceptor oxidoreductase and glutathione S-transferase, have been determined in a number of rat tissues. In all tissues, oltipraz was a relatively weak inducer. D3T itself and 5-methyl-, 4-chloro-5-methyl-, 4-phenyl- and 5,6-dihydrocyclopenta[c]-1,2-dithiole-3-thione (cyclopenta) were the most active compounds, both in terms of degree of induction and the number of organs in which enzyme induction occurred. Cyclopenta was a potent enzyme inducer in the urinary bladder, whereas 4-chloro-5-methyl-3H-1,2-dithiole-3-thione was particularly effective in the liver and the 4-phenyl derivative showed high inductive activity in the lungs. Comparison of the inducer activities of selected dithiolethiones, including cyclopenta, in cultured bladder carcinoma cells in vitro showed strong correlation with the in vivo data, suggesting that the different inducer activity of the dithiolethiones in vivo, at least in the bladder, is an intrinsic property of these compounds. In view of the evidence that Phase II enzyme induction plays a major role in the chemoprotective action of dithiolethiones, evaluation of the anti-cancer activity of the more potent inducers identified in this study would be of interest.

Animals↗