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Biomedical subjects

Jun Wu

Publications and source records attributed to Jun Wu.

At least 91 records · Page 5Linked to original sources
PubMed2005

An increase in telomere sister chromatid exchange in murine embryonic stem cells possessing critically shortened telomeres.

Telomerase deficiency leads to a progressive loss of telomeric DNA that eventually triggers cell apoptosis in human primary cells during prolonged growth in culture. Rare survivors can maintain telomere length through either activation of telomerase or recombination-based telomere lengthening, and thus proliferate indefinitely. We have explored the possibility that telomeres may be maintained through telomere sister chromatid exchange (T-SCE) in murine telomere reverse transcriptase-deficient (mTert-/-) splenocytes and ES cells. Because telomerase deficiency leads to gradual loss of telomeric DNA in mTert-/- splenocytes and ES cells and eventually to chromosomes with telomere signal-free ends (SFEs), we examined these cell types for evidence of sister chromatid exchange at telomeres, and observed an increase in T-SCEs only in a subset of mTert-/- splenocytes or ES cells that possessed multiple SFEs. Furthermore, T-SCEs were more often detected in ES cells than in splenocytes that harbored a similar frequency of SFEs. In mTert heterozygous (mTert+/-) ES cells or splenocytes, which are known to exhibit a decrease in average telomere length but no SFEs, no increase in T-SCE was observed. In addition to T-SCE, other genomic rearrangements (i.e., SCE) were also significantly increased in mTert-/- ES cells possessing critically short telomeres, but not in splenocytes. Our results suggest that animals and cell culture differ in their ability to carry out genomic rearrangements as a means of maintaining telomere integrity when telomeres become critically shortened.

Animals↗
PubMed2005

Acid sphingomyelinase is induced by butyrate but does not initiate the anticancer effect of butyrate in HT29 and HepG2 cells.

Butyric acid and sphingomyelin (SM) affect colonic tumorigenesis. We examined the potential link between butyrate stimulation and SM metabolism in colonic and hepatic cancer cell lines. After incubating HT29 and HepG2 cells with butyrate and other short-chain fatty acids, we found that butyrate increased acid but not neutral or alkaline sphingomyelinase (SMase) activity by 10- to 20-fold. The effects occurred after 16 h of incubation and were associated with reduced SM and phosphatidylcholine contents and increased ceramide levels. Northern blotting showed increased acid SMase mRNA levels in these cells after butyrate stimulation. Propionate was less potent, and acetate had no effect. No similar changes of acid phosphatase could be identified. At concentrations that increased acid SMase expression, butyrate inhibited cell proliferation, activated caspase 3, and induced apoptosis. However, the antiproliferative and apoptotic effects of butyrate preceded the changes of acid SMase and were not affected by knocking down acid SMase expression by small, interfering RNA. In addition, butyrate-induced acid SMase expression was not affected by blocking the caspase pathway. In conclusion, butyrate regulates SM metabolism by stimulating acid SMase expression in colon and liver cancer cells, but the increased acid SMase is not a critical mechanism for initiating the anticancer effects of butyrate.

Antineoplastic Agents↗
PubMed2005

Metal-ion adsorption on carboxyl-bearing self-assembled monolayers covalently bound to magnetic nanoparticles.

Hematite nanoparticles have been functionalized with a self-assembled monolayer of undecanoic acid (UA) by covalent attachment via siloxane groups. The number density of carboxylic/carboxylate groups on the surface was determined by titration, yielding values on the order of 10(14) UA molecules/cm(2) and thus consistent with a closed-packed monolayer. The ability of these functionalized particles to adsorb Cd(2+) in the ppm range was demonstrated using in situ anodic stripping voltammetry.

Adsorption↗
PubMed2005

The Drosophila acetylcholine receptor subunit D alpha5 is part of an alpha-bungarotoxin binding acetylcholine receptor.

The central nervous system of Drosophila melanogaster contains an alpha-bungarotoxin-binding protein with the properties expected of a nicotinic acetylcholine receptor. This protein was purified 5800-fold from membranes prepared from Drosophila heads. The protein was solubilized with 1% Triton X-100 and 0.5 M sodium chloride and then purified using an alpha-cobratoxin column followed by a lentil lectin affinity column. The purified protein had a specific activity of 3.9 micromol of 125I-alpha-bungarotoxin binding sites/g of protein. The subunit composition of the purified receptor was determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis. This subunit profile was identical with that revealed by in situ labeling of the membrane-bound protein using the photolyzable methyl-4-azidobenzoimidate derivative of 125I-alpha-bungarotoxin. The purified receptor reveals two different protein bands with molecular masses of 42 and 57 kDa. From sedimentation analysis of the purified protein complex in H2O and D2O and gel filtration, a mass of 270 kDa was calculated. The receptor has a s(20,w) of 9.4 and a Stoke's radius of 7.4 nm. The frictional coefficient was calculated to be 1.7 indicating a highly asymmetric protein complex compatible with a transmembrane protein forming an ion channel. The sequence of a peptide obtained after tryptic digestion of the 42-kDa protein allowed the specific identification of the Drosophila D alpha5 subunit by sequence comparison. A peptide-specific antibody raised against the D alpha5 subunit provides further evidence that this subunit is a component of an alpha-bungarotoxin binding nicotinic acetylcholine receptor from the central nervous system of Drosophila.

Acetylcholine↗
PubMed2005

Cloning of alkaline sphingomyelinase from rat intestinal mucosa and adjusting of the hypothetical protein XP_221184 in GenBank.

Intestinal alkaline sphingomyelinase (alk-SMase) digests sphingomyelin and the process may influence colonic tumorigenesis and cholesterol absorption. We recently identified the gene of human alk-SMase and cloned the cDNA. Cross-species screening of homology in GenBank found a hypothetical rat protein, XP_221184, with 491 amino acid residues, which shares 73% identity with human alk-SMase. Based on the cDNA sequence of this protein, we cloned a cDNA from rat intestinal mucosa by RT-PCR. The cloned cDNA encodes a protein with 439 amino acid residues and higher (85%) identity with human alk-SMase. The cloned cDNA differed from the XP_221184 cDNA in splice sites linking exons 2 and 3, and exons 3 and 4, respectively. In the sequence of the cloned protein, the predicted activity motif, sphingomyelin binding sites, and potential glycosylation sites in human alk-SMase are all conserved. To confirm the cloned protein is the real form of alk-SMase, native alk-SMase was purified from rat intestine and subjected to proteolytic digestion followed by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry and electrospray ionization (ESI) tandem mass spectrometry. Seven tryptic peptides were found to match the cloned protein sequence. Transient expression of the cloned cDNA linked with a myc tag in COS-7 cells demonstrated high SMase activity, with an optimal pH at 9.0 and a specific dependence on taurocholate and taurochenodeoxycholate. The expressed protein reacted with both anti-myc and anti-human alk-SMase antibodies. Northern blotting of rat tissues revealed high levels of mRNA in jejunum but not in other tissues. In conclusion, we cloned rat alk-SMase cDNA from rat intestine, adjusted the putative rat alk-SMase protein in GenBank, and confirmed the specific expression of the gene in the small intestine.

Amino Acid Sequence↗
PubMed2005

Functional studies of human intestinal alkaline sphingomyelinase by deglycosylation and mutagenesis.

Intestinal alk-SMase (alkaline sphingomyelinase) is an ectoenzyme related to the NPP (nucleotide phosphodiesterase) family. It has five potential N-glycosylation sites and predicated transmembrane domains at both the N- and C-termini. The amino acid residues forming the two metal-binding sites in NPP are conserved, and those of the active core are modified. We examined the functional changes of the enzyme induced by deglycosylation and mutagenesis. Treating alk-SMase cDNA-transfected COS-7 cells with tunicamycin rendered the expressed enzyme completely inactive. Mutations of the five potential N-glycosylation sites individually and in combination showed that these sites were all glycosylated and deficient glycosylation decreased the enzyme activity. Immunogold labelling showed that the wild-type enzyme was mainly located in the plasma membrane, whereas the C-terminal domain-truncated enzyme was released into the medium. Deglycosylation blocked the release of the enzyme that accumulated in endosome-like structures. The enzyme activity was also decreased by mutations of the residues forming the putative metal-binding sites and the active core. Substitution of the active core sequence with that of NPP or mutation of T75 in the core abolished the enzyme activity against sphingomyelin but failed to render the enzyme NPP active. Our results indicate that alk-SMase activity is severely affected by defective N-glycosylation and structural alterations of the putative metal-binding sites and the predicted active core.

Animals↗
PubMed2005

Complete 1H and 13C NMR assignments of four new steroidal glycosides from a gorgonian coral Junceella juncea.

Four new cholest-type steroidal glycosides, junceellosides A-D, isolated from the EtOH/CH(2)Cl(2) extracts of the South China Sea gorgonian coral Junceella juncea, were identified. Complete assignments of the (1)H and (13)C NMR chemical shifts for these compounds were achieved by means of one- and two-dimensional NMR techniques, including (1)H-(1)H COSY, HSQC, HMBC and NOESY spectra.

Animals↗
PubMed2005

A comparative study of 99mTc-YIGSR and 99mTc-MIBI uptake in tumor cells.

To investigate a new kind of tumor tracer 99mTc-YIGSR developed from a five amino structure (YIGSR) of the Laminin -chain, which can bind to the laminin receptors of tumor specifically, and radiolabeled with MAG3. (1) Preparation of the 99mTc-YIGSR probe: with S-Acetly-NH3-MAG3 as the chelator and with proper reductants YIGSR was labeled with 99mTc; (2) Cell culture and viability measurement: EAC was maintained in RPMI 1640 supplemented with calf serum; the trypan blue exclusion was applied to calculate the cell viability; (3) Study of the cell dynamic: The EAC's uptake of 99mTc-YIGSR and 99mTc-MIBI was observed at 37 degrees C and 22 degrees C, respectively. (1) The labeling efficiencies of 99mTc-YIGSR and 99mTc-MIBI were (62 +/- 3)% and (96 +/- 2)%, respectively; (2) The cell viability was declined with time of incubation; (3) At 37 degrees C, the EAC'S uptake of 99mTc-YIGSR and 99mTc-MIBI reached the peak of (43.16 +/- 2.4) % and (24.4 +/- 1.8) % at 60 min, respectively; and at 22 degrees C, the highest uptake was (26.5 +/- 2.1) % and (9.47 +/- 1.9) % at 60 min, respectively. The in vitro study suggests that 99mTc-YIGSR is superior to 99mTc-MIBI in cell uptake and has potential value in tumor imaging.

Animals↗
PubMed2005

A summary of the effects of antihypertensive medications on measured blood pressure.

BACKGROUND: Epidemiologic analysis of family data on blood pressure (BP) is often compromised by the effects of antihypertensive medications. A review of numerous clinical trials that investigated the effects of BP-lowering medications is summarized here. METHODS: Published clinical trials, including 137 clinical trials with monodrug therapies and 28 clinical trials of combination drug therapies with a total of 11,739 participants, were reviewed from PubMed. Six major classes/groups of antihypertensive medications were categorized by ethnicity, including angiotensin-converting enzyme (ACE) inhibitors, alpha1-blockers, cardioselective beta-blockers (beta1-blockers), calcium channel blockers, thiazide and thiazide-like diuretics, and loop diuretics. RESULTS: Using sitting or supine BP, for ethnic groups combined, monodrug therapy with ACE inhibitors showed a weighted average effect of lowering the systolic and diastolic BP by 12.5/9.5 mm Hg; alpha1-blockers by 15.5/11.7 mm Hg; beta1-blockers by 14.8/12.2 mm Hg; calcium channel blockers by 15.3/10.5 mm Hg; thiazide diuretics by 15.3/9.8 mm Hg; and loop diuretics by 15.8/8.2 mm Hg. However, ACE inhibitors, alpha1-blockers, and beta1-blockers were less effective in African Americans than in non-African Americans, whereas calcium channel blockers, thiazide diuretics, and loop diuretics were more effective in African Americans than in non-African Americans. For two-drug combination therapy with ethnic groups combined, the BP-lowering effect of the second medication, when compared to its effect as monodrug therapy, was 84% and 65% for systolic and diastolic BP, respectively. CONCLUSIONS: The BP-lowering effects reported here may be used to impute the pretreatment BP levels, which can improve the information content and hence the power of epidemiologic analysis in studies where use of antihypertensive medications is a confounding factor in the BP measurements.

Adult↗
PubMed2005

The role of NO in macrophage dysfunction at early stage after burn injury.

AIM: To explore the role of nitric oxide (NO) in macrophage dysfunction at early stage after burn injury. METHOD: Peritoneal macrophages were isolated and cultured from early stage burnt mice. NO production and inducible NO synthase (iNOS) expression in the macrophages were checked by the Greiss method and real-time PCR (TaqMan), respectively. l-Arginine, the substrate of NO producing, or N-monomethyl-l-arginine (l-NMMA), a competing blocker of NOS was administered to the culture, the changes of NO, TNF-alpha and PGE2 productions were measured, additionally the changes of the iNOS, TNF-alpha and COX-2 expression were assayed by real-time PCR. After that, the effects of l-arginine and l-NMMA were determined on burnt macrophage influencing the proliferation of normal splenic lymphocytes. RESULT: A large amount of NO was produced by macrophages from post burn hour 6 (6PBH) with a high level of iNOS expression. l-Arginine could increase NO production in a dosage-dependent manner, while l-NMMA attenuated NO production, but neither could affect iNOS expression. Moreover, l-arginine enhanced productions of both the latter produced TNF-alpha and PGE2 from burnt macrophages, and the expressions of TNF-alpha and COX-2 were improved significantly, while l-NMMA did reverse ways. It was found that macrophages from post burn hour 24 mice could inhibit Con A-stimulated normal splenic lymphocytes dramatically, l-NMMA could decrease this function significantly, but l-arginine could not influence the suppression. CONCLUSION: Our experiment indicated NO derived from burnt macrophage played a vital role in macrophage producing excessive TNF-alpha and PGE2, and suppressing lymphocyte function at early stage after burn injury.

Animals↗
PubMed2005

Assessment of the value of confirming responses in clinical trials in oncology.

The requirement for a second assessment to confirm initial tumour response is required by all response guidelines. Its rationale, however, is not clear. We have conducted this study to compare validity of response rate assessment determined with and without secondary confirmation. Using specified criteria, nine trials of one single cytotoxic drug including 416 patients were selected from a pharmaceutical database. Objective response rates were determined by a single determination and by two separate determinations. 81 responses (19.5%, [15.8-23.6%]) were scored by the confirmation method and 97 responses (23.3% [19.3-27.7%]) by the no-confirmation method. The Kappa (kappa) coefficient of 0.89 indicates good agreement between both methods. This is the first study that systematically compares response rates calculated with and without performing response confirmation. Results show good agreement between both methods. We suggest that assessing response without confirmation may be the preferred method. These results should be confirmed by additional studies in a variety of cancer settings.

Antineoplastic Agents↗
PubMed2005

Oleanane triterpenes from Aegiceras corniculatum.

A new oleanane triterpene, 16alpha-hydroxy-l3,28-epoxyoleanan-3-one 1, was isolated from the stem bark of Aegiceras corniculatum, together with protoprimulagenin, aegicerin, embelinone, syringic acid, gallic acid, isorhamnetin and isorhamnetin 3-O-alpha-L-rhamnofuranosyl-(1-->6)-beta-D-glucopyranoside. Their structures were determined by spectroscopic methods.

Humans↗
PubMed2005

Thermodynamics of the interaction of aluminum ions with DNA: implications for the biological function of aluminum.

Aluminum is a known neurotoxic agent and its neurotoxic effects may be due to its binding to DNA. However, the mechanism for the interaction of aluminum ions with DNA is not well understood. Here, we report the application of isothermal titration calorimetry (ITC), fluorescence spectroscopy, and UV spectroscopy to investigate the thermodynamics of the binding of aluminum ions to calf thymus DNA (CT DNA) under various pH and temperature conditions. The binding reaction is driven entirely by a large favorable entropy increase but with an unfavorable enthalpy increase in the pH range of 3.5-5.5 and at all temperatures examined. Aluminum ions show a strong and pH-dependent binding affinity to CT DNA, and a large positive molar heat capacity change for the binding, 1.57 kcal mol(-1) K(-1), demonstrates the burial of the polar surface of CT DNA upon groove binding. The fluorescence of ethidium bromide bound to CT DNA is quenched by aluminum ions in a dynamic way. Both Stern-Volmer quenching constant and the binding constant increase with the increase of the pH values, reaching a maximum at pH 4.5, and decline with further increasing the pH to 5.5. At pH 6.0 and 7.0, aluminum ions precipitate CT DNA completely and no binding of aluminum ions to CT DNA is observed by ITC. Combining the results from these three methods, we conclude that aluminum ions bind to CT DNA with high affinity through groove binding under aluminum toxicity pH conditions and precipitate CT DNA under physiological conditions.

Aluminum↗
PubMed2005

Visually perceived eye level and horizontal midline of the body trunk influenced by optic flow.

The eye level and the horizontal midline of the body trunk can serve, respectively, as references for judging the vertical and horizontal egocentric directions. We investigated whether the optic-flow pattern, which is the dynamic motion information generated when one moves in the visual world, can be used by the visual system to determine and calibrate these two references. Using a virtual-reality setup to generate the optic-flow pattern, we showed that judged elevation of the eye level and the azimuth of the horizontal midline of the body trunk are biased toward the positional placement of the focus of expansion (FOE) of the optic-flow pattern. Furthermore, for the vertical reference, prolonged viewing of an optic-flow pattern with lowered FOE not only causes a lowered judged eye level after removal of the optic-flow pattern, but also an overestimation of distance in the dark. This is equivalent to a reduction in the judged angular declination of the object after adaptation, indicating that the optic-flow information also plays a role in calibrating the extraretinal signals used to establish the vertical reference.

Adaptation, Psychological↗
PubMed2005

High-density lipoprotein cholesterol levels increase with age, body mass index, blood pressure and fasting blood glucose in a rural Uygur population in China.

OBJECTIVES: To investigate the distribution of the serum high-density lipoprotein cholesterol (HDLC) levels and its relationship with obesity, hypertension and diabetes in a Uygur case-control study on hypertension. DESIGN: A case-control (339 hypertensive cases, 272 normotensive controls) study on hypertension was conducted, and obesity, hypertension, lipid profiles and fasting blood glucose were analyzed. METHODS: The demographic data, history of disease and lifestyles, including diet, smoking and salt intake, were recorded and three measurements of blood pressure were obtained by trained observers. The fasting serum lipid profiles and glucose were determined. RESULTS: The HDLC levels of hypertensive participants were significantly higher than normotensive participants after adjustment for age and gender (1.145 versus 1.117 mmol/l, P = 0.001, power = 0.867). After adjustment for related variables, the HDLC levels slightly increased with age, body mass index and fasting glucose (all P = 0.001, power > 0.80) in normotensive participants and only increased with age among hypertensive participants (P = 0.0001, power = 0.971). CONCLUSIONS: The serum HDLC levels in Uygur normotensive participants increased with age, body mass index, blood pressure and fasting glucose levels. This was inconsistent with the previous studies and the reason remained unclear. Further study is needed to elucidate both the environmental and genetic determinants of the novel distribution of the HDLC levels and their association with coronary heart disease in the Uygur population.

Adolescent↗