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Biomedical subjects

J Duan

Publications and source records attributed to J Duan.

At least 37 records · Page 2Linked to original sources
PubMed2001

Development of an indirect competitive ELISA for ciprofloxacin residues in food animal edible tissues.

An indirect competitive enzyme-linked immunosorbent assay (ELISA) was developed to detect ciprofloxacin (CPFX) in food animal edible tissues. CPFX was converted by an active ester method into conjugates CPFX-bovine serum albumin (CPFX-BSA) and CPFX-human serum albumin (CPFX-HSA), which both allowed production of CPFX-specific rabbit antisera. In the ELISA, CPFX-HSA was coated onto the microtiter plate, followed by incubation with standard CPFX and anti-CPFX antibody. The indirect competitive ELISA revealed that the antisera have no cross-reactivity with penicillin, gentamicin, neomycin, sulfadiazine, and chlortetracycline. The antisera cross-reacted with enrofloxacin and norfloxacin about 69.8 and 44.6% as much as they did with CPFX. This ELISA was highly sensitive (0.32 ng/mL) to CPFX determination. Recovery of CPFX at 40 microg/kg was 75.58% in pork, 81.29% in chicken, and 84.30% in milk. The coefficients of variation varied from 3.7 to 9.2% over the range of CPFX concentrations studied. The linear detection range was between 1.6 and 1000 ng/mL. The results suggest that this ELISA is a specific, accurate, and convenient method for the detection of CPFX residues in food animal edible tissues.

Animals↗
PubMed2001

Real-time monitoring and verification of in vivo high dose rate brachytherapy using a pinhole camera.

We investigated a pinhole imaging system for independent in vivo monitoring and verification of high dose rate (HDR) brachytherapy treatment. The system consists of a high-resolution pinhole collimator, an x-ray fluoroscope, and a standard radiographic screen-film combination. Autofluoroscopy provides real-time images of the in vivo Ir-192 HDR source for monitoring the source location and movement, whereas autoradiography generates a permanent record of source positions on film. Dual-pinhole autoradiographs render stereo-shifted source images that can be used to reconstruct the source dwell positions in three dimensions. The dynamic range and spatial resolution of the system were studied with a polystyrene phantom using a range of source strengths and dwell times. For the range of source activity used in HDR brachytherapy, a 0.5 mm diameter pinhole produced sharp fluoroscopic images of the source within the dynamic range of the fluoroscope. With a source-to-film distance of 35 cm and a 400 speed screen-film combination, the same pinhole yielded well recognizable images of a 281.2 GBq (7.60 Ci) Ir-192 source for dwell times in the typical clinical range of 2 to 400 s. This 0.5 mm diameter pinhole could clearly resolve source positions separated by lateral displacements as small as 1 mm. Using a simple reconstruction algorithm, dwell positions in a phantom were derived from stereo-shifted dual-pinhole images and compared to the known positions. The agreement was better than 1 mm. A preliminary study of a patient undergoing HDR treatment for cervical cancer suggests that the imaging method is clinically feasible. Based on these studies we believe that the pinhole imaging method is capable of providing independent and reliable real-time monitoring and verification for HDR brachytherapy.

Biophysical Phenomena↗
PubMed2001

A self-correcting method for improving the precision of beam blocks.

A technique for manufacturing precise custom blocks is described. Using the tracing stylus of the mold making machine, reference markers are cut into the lateral borders of the polystyrene mold after the cavities for the blocks have been made. These markers are aligned with the central ray cross hair of the shadow tray when the blocks are mounted on the tray. The ability of the technique to enhance precision has been verified in laboratory tests by intentionally introducing small imperfections into a mold making machine and checking the positional accuracy of the mounted blocks. The clinical performance has been tested by evaluating 47 check films of blocks for 16 randomly selected patients. The average positional error of individual blocks, projected to the isocenter, was less than one mm. The average time needed to cut the reference markers was 25 seconds. Implementing the technique required only minor modifications of a commercial mold making machine.

Computer Simulation↗
PubMed2001

[Studies on chemical constituents of Maackia amurensis Rupr. et. Maxim].

OBJECTIVE: To study the chemical constituents of EtOH extract from heartwood of Maackia amurensis. METHOD: Silica gel column chromatography and Sephadex LH-20 were employed to separate, and the compounds obtainedere elucidated by means of UV, IR, MS, 1H NMR, 13C NMR. RESULT: 4', 8-dihydroxyl-7-methoxylisoflavone (I), tectorigenin(II), glycitein(III) and resveratrol (IV) were isolated and identified. CONCLUSION: Among them, Compound I was a new isoflavone and compound III was obtained from M. amurensis for the first time.

Isoflavones↗
PubMed2000

Hypercholesterolemia inhibits angiogenesis in response to hindlimb ischemia: nitric oxide-dependent mechanism.

BACKGROUND: Endothelium-derived nitric oxide (EDNO) plays an important role in the regulation of angiogenesis, whereas hypercholesterolemia (HC) impairs EDNO release. We examined the hypothesis that HC may inhibit ischemia-induced angiogenesis by inhibition of EDNO in a rat model of unilateral hindlimb ischemia and that oral L-arginine supplementation, a substrate for NO synthase, may prevent HC-related impairment of angiogenesis. METHODS AND RESULTS: Male Sprague-Dawley rats were fed (A) standard diet (control), (B) 2% high-cholesterol diet (HC group), or (C) high-cholesterol diet with oral L-arginine (2.25% in drinking water) (HC+L-arg group). At 2 weeks of the dietary intervention, unilateral limb ischemia was surgically induced in all animals. Dietary HC groups (B and C) revealed elevated total and LDL cholesterol levels compared with control animals. Laser Doppler blood flow analyses showed significant decreases in the ischemic/normal limb blood flow ratio in the HC group compared with controls (P:<0.05) when followed up until 4 weeks after surgery. Selective angiography and immunohistochemical analyses in the ischemic limb at postoperative day 14 revealed significantly lower angiographic scores (P:<0.01) and capillary densities (P:<0.01) in the HC group than controls, which were associated with decreased tissue contents of NO(x) and cGMP. Oral L-arginine supplementation (HC+L-arg) significantly improved all parameters of the laser Doppler blood perfusion ratio, angiographic scores, and capillary densities (P:<0.01 versus HC group), which were accompanied by significant elevations in serum L-arginine levels and tissue NO(x) and cGMP contents. CONCLUSIONS: Collateral vessel formation and angiogenesis in response to hindlimb ischemia were significantly attenuated in rats with dietary HC. The mechanism may be related to the reduced NO bioactivity in the ischemic tissues. Augmentation of the tissue NO activity by oral L-arginine supplementation restored the impaired angiogenesis in HC.

Administration, Oral↗
PubMed2000

Polyglycylation of tubulin is essential and affects cell motility and division in Tetrahymena thermophila.

We analyzed the role of tubulin polyglycylation in Tetrahymena thermophila using in vivo mutagenesis and immunochemical analysis with modification-specific antibodies. Three and five polyglycylation sites were identified at glutamic acids near the COOH termini of alpha- and beta-tubulin, respectively. Mutants lacking all polyglycylation sites on alpha-tubulin have normal phenotype, whereas similar sites on beta-tubulin are essential. A viable mutant with three mutated sites in beta-tubulin showed reduced tubulin glycylation, slow growth and motility, and defects in cytokinesis. Cells in which all five polyglycylation sites on beta-tubulin were mutated were viable if they were cotransformed with an alpha-tubulin gene whose COOH terminus was replaced by the wild-type COOH terminus of beta-tubulin. In this double mutant, beta-tubulin lacked detectable polyglycylation, while the alpha-beta tubulin chimera was hyperglycylated compared with alpha-tubulin in wild-type cells. Thus, the essential function of polyglycylation of the COOH terminus of beta-tubulin can be transferred to alpha-tubulin, indicating it is the total amount of polyglycylation on both alpha- and beta-tubulin that is essential for survival.

Amino Acid Sequence↗
PubMed2000

Topical effects of cidofovir on cutaneous rabbit warts: treatment regimen and inoculum dependence.

The present study examined topical effects of cidofovir on cutaneous rabbit warts. Based on an inoculum-dependency study, each New Zealand White rabbit was inoculated with a high and low titer of cottontail rabbit papillomavirus (CRPV) at four sites on each dorsolateral area. Inoculation with 50 ID(50) induced papillomas at 100% of the inoculation sites within 16+/-1 days, and the wart growth curve plateaued within approximately 7 weeks. With an inoculum of 5 ID(50), 80% of the inoculated sites developed papillomas within 21+/-1 days and their size plateaued at a later time. Cidofovir was applied topically twice daily on the inoculated sites at a concentration of 1% for 18 days, starting at three different time points. In the first experiment, treatment was initiated 7 days post-inoculation. One of the inoculated sides received cidofovir or the vehicle, PBS, while the other side was left untreated. With this treatment regimen, cidofovir significantly delayed the time of onset and the growth rate of papillomas induced with the high titer of inoculum. It completely prevented papilloma-induction on the sites inoculated with the low titer of CRPV. Reversible side-effects of cidofovir were observed on the directly treated area including erythema, necrosis, and flaking. Both therapeutic and side-effects were limited to the sites of direct exposure. In the second experiment, one of the two sides in each group of rabbits received cidofovir or vehicle starting on day 29 post-inoculation. With this treatment regimen, cidofovir significantly reduced wart growth against the low titer only. Topical treatment initiated on day 49 post-inoculation was not effective on warts initiated with either viral titer. These results demonstrated that topical cidofovir could be very effective against papillomavirus-induced wart growth if it is initiated early during the infection, especially against low titers of inoculum.

Administration, Topical↗
PubMed2000

Study on the growth inhibition of human multiple myeloma cells by an IL-6Ralpha mutant.

DM650, a soluble human IL-6Ralpha mutant with mutation of C277D/H280I, was previously shown to exhibit an antagonism to IL-6, which resulted in growth-inhibition of human multiple myeloma cell line AF-10 autocrining as the growth-stimulating factor. We investigated here the nature of the growth inhibition by examining cell apoptosis. Flow-cytometric analysis of the DNA fragmentation demonstrated that 7.2% of the AF-10 cells were apoptotic after 24 h of treatment with DM650. The constitutive gene expression of bcl-2 in AF-10 cells indicated that apoptosis suppressed by IL-6 was independent of bcl-2 regulation. The altered gene expression of c-myc and p53 suggested that a novel apoptosis pathway, other than that suppressed by IL-6, might be triggered by a complex of DM650 and IL-6.

Apoptosis↗
PubMed2000

In vivo urethral dose measurements: a method to verify high dose rate prostate treatments.

Radiation doses delivered in high dose rate (HDR) brachytherapy are susceptible to many inaccuracies and errors, including imaging, planning and delivery. Consequently, the dose delivered to the patient may deviate substantially from the treatment plan. We investigated the feasibility of using TLD measurements in the urethra to estimate the discrepancy in treatments for prostate cancer. The dose response of the 1 mm diam, 6 mm long LiF rods that we used for the in vivo measurements was calibrated with the 192Ir HDR source, as well as a 60Co teletherapy unit. A train of 20 rods contained in a sterile plastic tube was inserted into the urethral (Foley) catheter for the duration of a treatment fraction, and the measured doses were compared to the treatment plan. Initial results from a total of seven treatments in four patients show good agreement between theory and experiment. Analysis of any one treatment showed agreement within 11.7% +/- 6.2% for the highest dose encountered in the central prostatic urethra, and within 10.4% +/- 4.4% for the mean dose. Taking the average over all seven treatments shows agreement within 1.7% for the maximum urethral dose, and within 1.5% for the mean urethral dose. Based on these initial findings it seems that planned prostate doses can be accurately reproduced in the clinic.

Brachytherapy↗
PubMed2000

Hyperhomocysteinemia impairs angiogenesis in response to hindlimb ischemia.

Hyperhomocysteinemia (HH) is an independent risk factor for atherosclerosis, including peripheral arterial occlusive disease (PAOD). Because angiogenesis and collateral vessel formation are important self-salvage mechanisms for ischemic PAOD, we examined whether HH modulates angiogenesis in vivo in a rat model of hindlimb ischemia. Rats were divided into 3 groups: the control group was given tap water, the HH group was given water containing L-methionine (1 g x kg(-1) x d(-1)), and the HH+L-arg group was given water containing methionine (1 g x kg(-1) x d(-1)) and l-arginine (2.25 vol%). At day 14 of the dietary modifications, the left femoral artery and vein were excised, and the extent of angiogenesis and collateral vessels in the ischemic limb were examined for 4 weeks. Plasma homocysteine levels significantly increased (P:<0.001), and plasma and tissue contents of nitrite+nitrate as well as tissue cGMP levels significantly decreased in the HH group compared with the control group (P:<0.01). Laser Doppler blood flowmetry (LDBF) revealed a significant decrease in the ischemic/normal limb LDBF ratio in the HH group at days 7, 14, 21, and 28 (P:<0.01 versus control). Angiography revealed a significant decrease in the angiographic score in the HH group at day 14 (P:<0.001 versus control). Immunohistochemistry of ischemic tissue sections showed a significant reduction in the capillary density in the HH group (P:<0. 001 versus control). Oral l-arginine supplementation in rats with HH (HH+L-arg) restored the decreased plasma and tissue nitrite+nitrate and cGMP contents (P:<0.05) as well as angiogenesis, as assessed by LDBF (P:<0.05 versus HH), angiographic score (P:<0.01 versus HH), and capillary density (P:<0.001 versus HH). In summary, HH impaired ischemia-induced angiogenesis and collateral vessel formation in a rat model of hindlimb ischemia in vivo. The mechanism of the HH-induced impairment of angiogenesis might be mediated in part by a reduced bioactivity of endogenous NO in the HH state.

Angiography↗
PubMed2000

Transplanted cord blood-derived endothelial precursor cells augment postnatal neovascularization.

Endothelial precursor cells (EPCs) have been identified in adult peripheral blood. We examined whether EPCs could be isolated from umbilical cord blood, a rich source for hematopoietic progenitors, and whether in vivo transplantation of EPCs could modulate postnatal neovascularization. Numerous cell clusters, spindle-shaped and attaching (AT) cells, and cord-like structures developed from culture of cord blood mononuclear cells (MNCs). Fluorescence-trace experiments revealed that cell clusters, AT cells, and cord-like structures predominantly were derived from CD34-positive MNCs (MNC(CD34+)). AT cells and cell clusters could be generated more efficiently from cord blood MNCs than from adult peripheral blood MNCs. AT cells incorporated acetylated-LDL, released nitric oxide, and expressed KDR, VE-cadherin, CD31, and von Willebrand factor but not CD45. Locally transplanted AT cells survived and participated in capillary networks in the ischemic tissues of immunodeficient nude rats in vivo. AT cells thus had multiple endothelial phenotypes and were defined as a major population of EPCs. Furthermore, laser Doppler and immunohistochemical analyses revealed that EPC transplantation quantitatively augmented neovascularization and blood flow in the ischemic hindlimb. In conclusion, umbilical cord blood is a valuable source of EPCs, and transplantation of cord blood-derived EPCs represents a promising strategy for modulating postnatal neovascularization.

Animals↗
PubMed2000

Morphometric analysis of the human ophthalmic nerve and the aging process.

In the present study, the morphometric changes that occur in the human ophthalmic nerve fibers during the aging process were analyzed with the use of new discriminative staining method, which permits simultaneous observation of the axon and surrounding myelin sheath. Morphometric data on axons were collected in 45 human cadavers. A significant reversed correlation was observed between those data and the age of the subject. Our results indicate that definite changes occur in the ophthalmic nerve during the aging process.

Aged↗
PubMed2000

[Effects of estrogen on serum lipids, plasma endothelin-1, atherosclerosis in ovariectomized rabbits].

OBJECTIVE: To investigate the effects of estrogen on serum lipids, plasma endothelin-1(ET-1) and atherosclerosis in ovariectomized(OVX) rabbits. METHODS: Forty-five female rabbits were randomly divided into 5 groups, there are 9 in each: group A: normal control; group B: sham operation + cholesterol feeding; group C: OVX + cholesterol feeding; group D: OVX + cholesterol feeding + estradiol benzoate; group E: OVX + cholesterol feeding + estradiol valerate. The OVX rabbits fed with cholesterol were used as a model for atherosclerosis. After fed for 12 weeks, all rabbits were sacrificed, and the levels of serum lipids, plasma ET-1, atherosclerosis plaque of aorta were measured. RESULTS: (1) Similar with group B, the total cholesterol (TC) of group D and E [(24.95 +/- 5.31) mmol/L and (27.53 +/- 13.18) mmol/L respectively], were significantly decreased as compared with group C which was (37.69 +/- 4.16) mmol/L. (2) The plasma ET-1 level of group C, which was (343.37 +/- 106.10) ng/L, was significantly higher as compared with group D and E, which were (262.19 +/- 36.45) ng/L [symbol: see text] (245.37 +/- 35.76) ng/L respectively. (3) There were no statistically differences of lipidic sedimentation area among group D, E, and B, which were (17.30 +/- 5.44)% and (36.99 +/- 20.29)% and (29.03 +/- 9.67)% respectively. All of them were significantly decreased as compared with group C, which was (74.83 +/- 12.58)%. CONCLUSION: Estrogen may improve the serum lipids, decrease the plasma ET-1 level, and prevent the atherosclerosis of ovariectomized rabbits.

Animals↗
PubMed2000

[Phenotypic features and genetic diversity of strains of Rhodopseudomonas].

14 strains of purple non-sulfur bacteria and 3 type strains of Rhodopseudomonas were investigated by phenotypic characterizing, DNA-DNA hybridizing and DGGE analyzing. The characteristics of their morphology, structure and physiology show that 14 strains of isolates have the features of the genus Rhodopseudomonas: dividing asymmetrically by budding, lamellar intracytoplasmic membranes, presence of bacteriochlorophyll a and carotenoids of the normal spirilloxanthin series. On the base of their differences in morphology, growth, carbon sources 14 strains can be divided into 2 groups: g-c group, T group. Parts of 16S rRNA gene were amplified by using a pair of primers: 341f-906r. Denaturing gradient gel electrophoresis(DGGE) of PCR-amplified fragment of rDNA indicated that they have 3 genetic types: 1 of them, including 6 of 8 strains of T groups is similar to that of Rps. rutila R1, the other 2 types, represented separately by 2 of T group or all the g-c group, were different from that of either of 3 type strains The Data of the DNA-DNA hybridization of 8 representative strains indicated that the differences between different types were enough to separate them into different species including 2 possible new species.

DNA, Bacterial↗
PubMed2000

[The monomer electronic spectra and fluorescence spectra of some metal phthalocyanines].

The monomer electronic absorption spectra of the ZnPcS2P2 (disulfonated diphthalimidomethyl phthalocyanine zinc) in 11 kinds of solvents and 5 kinds of unsubstituted metal phthalocyanines in DMF were investigated. The monomer electronic absorption spectra of some substituted phthalocyanine zinc including ZnPcS4 (tetrasulfonated phthalocyanine zinc), ZnPcS4 (tetraphthalimidomethyl phthalocyanine zinc), ZnPc(NO2)4 (tetranitro phthalocyanine zinc) and ZnPcS2P2 in the same solvent were also studied. The result showed that (1) with the strengthening of coordination ability of the solvent, the maximum absorption wavelength of ZnPcS2P2 increased slightly. (2) with the increasing of electronegativity of central ion, the maximum absorption wavelength of MPcs had a little blue shift. (3) the electron-donating substituting group caused slightly blue shift. The monomer fluorescence spectra of ZnPcS4, ZnPcP4, and ZnPcS2P2 in different solvents were determined. The result showed that (1) the electron-withdrawing substituting group caused slightly red shift of the fluorescence spectra. (2) with the strenghtening of coordination ability of the solvent, the maximum emission wavelength increased slightly. (3) the fluorescence intensity of ZnPcS2P2 in the solution which contains Cremophor EL was remarkable stronger than that in other solvents. This is an important suggest to the development of photodynamic diagnose agent. The effect of solvents, central ions and substituents on spectra were partly explained by means of the quantrum chemistry.

Electrochemistry↗