Biomedical subjects

J Duan

Publications and source records attributed to J Duan.

At least 19 recordsLinked to original sources

PubMed2001

Haplotype variation and linkage disequilibrium in 313 human genes.

Variation within genes has important implications for all biological traits. We identified 3899 single nucleotide polymorphisms (SNPs) that were present within 313 genes from 82 unrelated individuals of diverse ancestry, and we organized the SNPs into 4304 different haplotypes. Each gene had several variable SNPs and haplotypes that were present in all populations, as well as a number that were population-specific. Pairs of SNPs exhibited variability in the degree of linkage disequilibrium that was a function of their location within a gene, distance from each other, population distribution, and population frequency. Haplotypes generally had more information content (heterozygosity) than did individual SNPs. Our analysis of the pattern of variation strongly supports the recent expansion of the human population.

Alleles↗

PubMed2001

Proposed lipocalin fold for apolipoprotein M based on bioinformatics and site-directed mutagenesis.

Apolipoprotein M (apoM) is a novel apolipoprotein that is predominantly present in high-density lipoprotein. Sensitive sequence searches, threading and comparative model building experiments revealed apoM to be structurally related to the lipocalin protein family. In a 3D model, characterized by an eight-stranded anti-parallel beta-barrel, a segment including Asn135 could adopt a closed or open conformation. Using site-directed mutagenesis, we demonstrated Asn135 in wild-type apoM to be glycosylated, suggesting that the segment is solvent exposed. ApoM displays two strong acidic patches of potential functional importance, one around the N-terminus and the other next to the opening of the beta-barrel.

Amino Acid Sequence↗

PubMed2001

Effect of Foley catheters on seed positions and urethral dose in (125)I and (103)Pd prostate implants.

PURPOSE: To estimate the perturbation of seed position and urethral dose, subsequent to withdrawal of urethral catheters. METHODS AND MATERIALS: A mathematical model based on the volume incompressibility of tissues was used to compute seed positions and doses following removal of the Foley. The model assumed that the central axis of the urethra remains stationary, and that prostate tissue and seeds move radially toward the center of the urethra to fill the void left by the catheter. Seed motion has also been measured using transrectal ultrasound. RESULTS: Based on the computations, seeds located originally close to the urethra travel relatively large distances toward the urethra upon Foley removal, whereas seeds located further away move substantially less. This seed motion leads to higher urethral doses than shown in a standard treatment plan. Dose enhancements increase with catheter size, decrease with increasing prostate volume, are more pronounced for (103)Pd than for (125)I, and range between 3.5% and 32.4%. Postimplant dosimetry is equally affected if images are taken with urethral catheters in place, showing lower urethral doses than actually delivered. Preliminary ultrasound based measurements of seed motion agree with the theory. CONCLUSION: During the implantation procedure, 12 fr or smaller urethral catheters are preferable to larger diameter catheters if urine drainage is sufficient. Treatment planners should avoid planning seeds at 5 mm or closer from the urethra. Special caution is indicated in prostates having about 20 cm(3) or smaller volumes, and when (103)Pd is used. Postimplant dosimetry is susceptible to the same errors.

Brachytherapy↗

PubMed2001

Augmentation of postnatal neovascularization with autologous bone marrow transplantation.

BACKGROUND: Endothelial progenitor cells (EPCs) have been identified in adult human peripheral blood. Because circulating EPCs should originate from bone marrow (BM), we examined whether BM mononuclear cells (BM-MNCs) can give rise to functional EPCs and whether transplantation of autologous BM-MNCs might augment angiogenesis and collateral vessel formation in a rabbit model of hindlimb ischemia. METHODS AND RESULTS: Rabbit BM-MNCs were isolated by centrifugation through a Histopaque density gradient and cultured on fibronectin. EPCs developed from BM-MNCs in vitro, as assessed by acetylated LDL incorporation, nitric oxide (NO) release, and expression of von Willebrand factor and lectin binding. Unilateral hindlimb ischemia was surgically induced in rabbits (n=8), and fluorescence-labeled autologous BM-MNCs were transplanted into the ischemic tissues. Two weeks after transplantation, fluorescence microscopy revealed that transplanted cells were incorporated into the capillary network among preserved skeletal myocytes. In contrast, transplanted autologous BM-fibroblasts did not participate in EC capillary network formation (n=5). Then, in an additional 27 rabbits, saline (control; n=8), autologous BM-MNCs (n=13; 6.9+/-2.2x10(6) cells/animal), or BM-fibroblasts (n=6; 6.5+/-1.5x10(6) cells/animal) were injected into the ischemic tissues at postoperative day 7. Four weeks after transplantation, the BM-MNC-transplanted group had more angiographically detectable collateral vessels (angiographic score: 1.5+/-0.34 versus 0.94+/-0.26 and 1.1+/-0.14; P:<0.05), a higher capillary density (23+/-5.8 versus 10+/-1.9 and 11+/-0.8 per field; P:<0.001), and a greater laser Doppler blood perfusion index (505+/-155 versus 361+/-35 and 358+/-22 U; P:<0.05) than the control and BM-fibroblast-transplanted groups. CONCLUSIONS: Direct local transplantation of autologous BM-MNCs seems to be a useful strategy for therapeutic neovascularization in ischemic tissues in adults, consistent with "therapeutic vasculogenesis."

Angiography↗

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↗

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↗

PubMed1998

Dose and duration-dependence of ganciclovir treatment against murine cytomegalovirus infection in severe combined immunodeficient mice.

The present study investigates the full dose-response curve and treatment duration dependence of ganciclovir (GCV) against murine cytomegalovirus (MCMV) infection in severe combined immunodeficiency (SCID) mice. Animals inoculated intraperitoneally with 6.3 x 10(3) pfu of MCMV per mouse developed typical wasting syndrome rapidly and died around day 12 post-inoculation. Once-daily treatment with subcutaneous GCV for 5 days dose dependently delayed MCMV-induced wasting syndrome and mortality at a dose range of 1-80 mg/kg per day, whereas a dose of 160 mg/kg per day induced reversible side-effects. The effect of GCV treatment on mean death day (MDD) was significantly correlated to reductions of viral titers in the lung (r = 0.969, P < 0.05). Treatment duration dependence was examined at the dose of GCV at 80 mg/kg per day for 1, 5, 8 and 12 days. The protective duration, over vehicle-treated mice, was constantly 3-4 days plus the duration of GCV treatment, as evidenced by the delay of viral replication, wasting syndrome and death. At a sub-optimally effective dose of 10 mg/kg per day of GCV, maximum protection was achieved with a 8-day treatment regimen. Prolongation of this treatment to 12 days failed to further delay mean death day and wasting syndrome that started on day 10, indicative of insufficient suppression of viral replication. Treatment with a single dose of GCV failed to show a complete dose-response curve since only minimal protective effects were observed at the dose of 80 mg/kg while side-effects were associated with the dose of 160 mg/kg. The treatment duration dependence and requirement for sufficient dosage of GCV against CMV infection observed in the current model are consistent with clinical observations. It also suggests that 5 8 days treatment duration may be a good balance considering the opportunity for identifying active compounds and speeding up the turnaround time in drug evaluations.

Analysis of Variance↗

PubMed1998

A human B cell line AF10 expressing HIL-17.

AF10, a human B cell line, is a mycoplasma-free variant cloned from the human IgE myeloma cell line U266. Total RNA isolated from the AF10 cells was used as template for RT-PCR, and a specific product of about 411bp corresponding to the coding region of hIL-17 lack of a leading sequence obtained. The sequence of the RT-PCR product is the same to that reported in the literature. The expressed rhIL-17 in E. coli can induce 10- to 15-fold increase of IL-6 secretion by mouse fibroblast 3T3 cells. It is for the first time until now that hIL-17 messager has been detected in B cell. There may exist some potential relationship between hIL-17 and myeloma cells.

3T3 Cells↗

PubMed1998

High-level expression of human interleukin-17 in the yeast Pichia pastoris.

Human interleukin-17 (hIL-17) gene without the signal sequence was isolated from activated peripheral blood lymphocytes by RT-PCR, then highly expressed in the yeast Pichia pastoris in the form of the glycosylated monomer. The monomer of rhIL-17 stimulated mouse fibroblast 3T3 cells to secrete IL-6 and was specifically bound to its receptors on 3T3 cells.

3T3 Cells↗

PubMed1998

Antiviral activity of a selective ribonucleotide reductase inhibitor against acyclovir-resistant herpes simplex virus type 1 in vivo.

The present study reports the activity of BILD 1633 SE against acyclovir (ACV)-resistant herpes simplex virus (HSV) infections in athymic nude (nu/nu) mice. BILD 1633 SE is a novel peptidomimetic inhibitor of HSV ribonucleotide reductase (RR). In vitro, it is more potent than ACV against several strains of wild-type as well as ACV-resistant HSV mutants. Its in vivo activity was tested against cutaneous viral infections in athymic nude mice infected with the ACV-resistant isolates HSV type 1 (HSV-1) dlsptk and PAAr5, which contain mutations in the viral thymidine kinase gene and the polymerase gene, respectively. Following cutaneous infection of athymic nude mice, both HSV-1 dlsptk and PAAr5 induced significant, reproducible, and persistent cutaneous lesions that lasted for more than 2 weeks. A 10-day treatment regimen with ACV given topically four times a day as a 5% cream or orally at up to 5 mg/ml in drinking water was partially effective against HSV-1 PAAr5 infection with a reduction of the area under the concentration-time curve (AUC) of 34 to 48%. The effects of ACV against HSV-1 dlsptk infection were not significant when it was administered topically and were only marginal when it was given in drinking water. Treatment under identical conditions with 5% topical BILD 1633 SE significantly reduced the cutaneous lesions caused by both HSV-1 dlsptk and PAAr5 infections. The effect of BILD 1633 SE against HSV-1 PAAr5 infections was more prominent and was inoculum and dose dependent, with AUC reductions of 96 and 67% against infections with 10(6) and 10(7) PFU per inoculation site, respectively. BILD 1633 SE also significantly decreased the lesions caused by HSV-1 dlsptk infection (28 to 51% AUC reduction). Combination therapy with topical BILD 1633 SE (5%) and ACV in drinking water (5 mg/ml) produced an antiviral effect against HSV-1 dlsptk and PAAr5 infections that was more than the sum of the effects of both drugs. This is the first report that a selective HSV RR subunit association inhibitor can be effective against ACV-resistant HSV infections in vivo.

Acyclovir↗