Biomedical subjects

Rong Chen

Publications and source records attributed to Rong Chen.

89 records · Page 5Linked to original sources

PubMed2002

Renal organic cation and nucleoside transport.

We previously reported that the rat organic cation transporter rOCT1 could transport the nucleoside analog deoxytubercidin (dTub) (Chen R, Nelson JA. Biochem Pharmacol 2000;60:215-9). The cationic form of dTub (dTub(+)) appeared to be the true substrate of rOCT1. We also reported that although rOCT2 is similar to rOCT1, it does not transport dTub at pH 7.4. In this study, we measured the K(m) and V(max) values of dTub(+) uptake at a reduced pH (pH 5.4) for both rOCT1 and rOCT2. The difference in substrate activity appears due, in large part, to a poor affinity of rOCT2 for dTub(+). The transport efficiency estimated by V(max)/K(m) values for rOCT2 was only 6% that of rOCT1. Chimeras constructed between rOCT1 and rOCT2 revealed that the difference in dTub binding lies within transmembrane domains 2-7. To evaluate the potential of OCT1 in the renal secretion of dTub, tissue distribution and urinary excretion of dTub in OCT1 knockout mice were measured. No significant difference was observed in renal elimination, plasma level, and tissue distribution of dTub between the knockout and the wild-type mice. Therefore, dTub is a good substrate for OCT1; however, OCT1 does not appear to be necessary for its renal secretion.

Animals↗

PubMed2002

Docking unbound proteins using shape complementarity, desolvation, and electrostatics.

A comprehensive docking study was performed on 27 distinct protein-protein complexes. For 13 test systems, docking was performed with the unbound X-ray structures of both the receptor and the ligand. For the remaining systems, the unbound X-ray structure of only molecule was available; therefore the bound structure for the other molecule was used. Our method optimizes desolvation, shape complementarity, and electrostatics using a Fast Fourier Transform algorithm. A global search in the rotational and translational space without any knowledge of the binding sites was performed for all proteins except nine antibodies recognizing antigens. For these antibodies, we docked their well-characterized binding site-the complementarity-determining region defined without information of the antigen-to the entire surface of the antigen. For 24 systems, we were able to find near-native ligand orientations (interface C(alpha) root mean square deviation less than 2.5 A from the crystal complex) among the top 2,000 choices. For three systems, our algorithm could identify the correct complex structure unambiguously. For 13 other complexes, we either ranked a near-native structure in the top 20 or obtained 20 or more near-native structures in the top 2,000 or both. The key feature of our algorithm is the use of target functions that are highly tolerant to conformational changes upon binding. If combined with a post-processing method, our algorithm may provide a general solution to the unbound docking problem. Our program, called ZDOCK, is freely available to academic users (http://zlab.bu.edu/~rong/dock/).

Algorithms↗

PubMed2002

Activated, but not resting human Th2 cells, in contrast to Th1 and T regulatory cells, produce soluble ST2 and express low levels of ST2L at the cell surface.

The T1/ST2 gene encodes, as a result of differential splicing, a cell surface protein (transmembrane form of T1/ST2, ST2L) and a soluble, secreted, protein (ST2). Here, we show that transcripts for both ST2L and ST2 are present in activated human Th2 clones, but not in Th1 and T regulatory clones. This activation-dependent expression of ST2L/ST2 transcripts was also found in short-term in vitro differentiated, activated CD4(+) Th2 cells. No expression of ST2L or ST2 mRNA was detected in any of the resting T cell subsets. Low cell surface expression of ST2L was detected on activated Th2 clones, and on freshly isolated non-IFN-gamma-producing CD4(+) peripheral blood T cells, activated with anti-CD3 and anti-CD28 mAb. Finally, ST2 could be detected in the culture supernatants of activated, but not resting, Th2 clones. Taken together, these results show that the T1/ST2 gene products are inducible proteins and that human Th2 cells, in addition to expressing ST2L at their cell surface, secrete ST2 following activation.

Animals↗

PubMed2002

Efferent tube suspension as a continent diversion mechanism: a preliminary report of a clinical study.

PURPOSE: We constructed a reliable continent tube that is surgically simple. MATERIALS AND METHODS: In 12 patients with malignant bladder tumor we performed radical cystectomy with isolation of a 50 cm. ileal loop with pedicle. The proximal segment (8 to 10 cm.) was tapered over a 16Fr catheter as an efferent tube, the remaining segment was detubularized to create a W-shape pouch and the tapered ileum was fixed to the back surface of the rectus muscle with 2 polyester tapers 1 cm. wide with a suspension tension of 500 g. The external orifice of the tapered ileum was anastomosed to the umbilicus. In 2 patients with neuropathic bladder a 15 cm. ileal loop with pedicle was isolated, the proximal segment (8 cm.) was tapered as an efferent tube with 500 g. suspension tension, and the remaining segment was detubularized and anastomosed to the bladder. RESULTS: The patients were followed for 6 to 17 months (mean 11.4) and were completely continent day and night. The stoma was easily catheterized with a 16Fr catheter in all cases. Urodynamic study of the efferent tubes revealed maximum pressure of 84 to 159 cm. water (mean 114). Retrograde radiography of the efferent tubes demonstrated perfect canalization without stenosis. CONCLUSIONS: This study suggests that the continent mechanism of the tapered ileum can be greatly enhanced by a suspension technique. This maneuver also provides easy catheterization and surgical simplicity.

Adolescent↗

PubMed2002

Pregnancy-induced changes in renin gene expression in mice.

A puzzling feature of the renin-angiotensin system during pregnancy is the appearance in the maternal circulation of a large increase in the concentration of prorenin and renin. The physiologic role of these changes is not understood. We determined that high levels of renin protein occur in the circulation of pregnant mice, thereby establishing the mouse as a valuable model for understanding gestation-induced changes in the renin-angiotensin system. We used the murine model to show that high levels of renin gene expression occur at the mother-fetus interface, first in maternal decidua and subsequently in placentas. These results were obtained using ICR mice that have 2 related renin genes, Ren1 and Ren2. We also examined renin gene expression in C57Bl/6 mice that have only the Ren1 gene. In these mice, very little renin gene expression was observed in placentas but instead was upregulated in kidneys during pregnancy. In both ICR and C57Bl/6 mice, there is an increase in renin protein in the maternal circulation during pregnancy. However, these mice differ with regard to gestation-induced sites of increased renin gene expression. These studies suggest that mice are a convenient and valuable model for studying renin gene expression during pregnancy.

Animals↗

PubMed2002

Simultaneous detection of Anaplasma marginale and a new Ehrlichia species closely related to Ehrlichia chaffeensis by sequence analyses of 16S ribosomal DNA in Boophilus microplus ticks from Tibet.

To identify ehrlichial agents in Boophilus microplus ticks, DNA samples of B. microplus collected from the Tibet Autonomous Region and Sichuan Province of China were screened by a nested PCR. Sixteen of 43 (37%) DNA samples of B. microplus from Tibet were positive in nested PCR analysis. All 27 samples from Sichuan were negative. The screen identified two ehrlichial agents based on different 16S rRNA genes that were found after amplifying and sequencing the 5'-end fragments of the 16S rRNA genes. One sequence was identical to that of the gene of Anaplasma marginale, an etiological agent of animal anaplasmosis. The other sequence was most similar to that of the gene of Ehrlichia chaffeensis, an etiological agent of human monocytic ehrlichiosis. The sequence of 1,501 bases from the novel ehrlichial agent was obtained and showed the greatest levels of sequence similarity (97 to 98%) to 16S rRNA gene sequences of the members of the E. canis group of the genus EHRLICHIA: Sequence comparison of the 16S rRNA gene with the members of the genus Ehrlichia reveals that the novel ehrlichial agent detected in B. microplus ticks is a new species of the genus Ehrlichia and is most closely related to E. chaffeensis.

Anaplasma↗

PubMed2002

Structural requirements for the assembly of Norwalk virus-like particles.

Norwalk virus (NV) is the prototype strain of a group of human caliciviruses responsible for epidemic outbreaks of acute gastroenteritis. While these viruses do not grow in tissue culture cells or animal models, expression of the capsid protein in insect cells results in the self-assembly of recombinant NV virus-like particles (rNV VLPs) that are morphologically and antigenically similar to native NV. The X-ray structure of the rNV VLPs has revealed that the capsid protein folds into two principal domains: a shell (S) domain and a protruding (P) domain (B. V. V. Prasad, M. E. Hardy, T. Dokland, J. Bella, M. G. Rossmann, and M. K. Estes, Science 286:287-290, 1999). To investigate the structural requirements for the assembly of rNV VLPs, we performed mutational analyses of the capsid protein. We examined the ability of 10 deletion mutants of the capsid protein to assemble into VLPs in insect cell cultures. Deletion of the N-terminal 20 residues, suggested by the X-ray structure to be involved in a switching mechanism during assembly, did not affect the ability of the mutant capsid protein to self-assemble into 38-nm VLPs with a T=3 icosahedral symmetry. Further deletions in the N-terminal region affected particle assembly. Deletions in the C-terminal regions of the P domain, involved in the interactions between the P and S domains, did not block the assembly process, but they affected the size and stability of the particles. Mutants carrying three internal deletion mutations in the P domain, involved in maintaining dimeric interactions, produced significantly larger 45-nm particles, albeit in low yields. The complete removal of the protruding domain resulted in the formation of smooth particles with a diameter that is slightly smaller than the 30-nm diameter expected from the rNV structure. These studies indicate that the shell domain of the NV capsid protein contains everything required to initiate the assembly of the capsid, whereas the entire protruding domain contributes to the increased stability of the capsid by adding intermolecular contacts between the dimeric subunits and may control the size of the capsid.

Animals↗

PubMed2002

An experimental study of colonic mucosal graft for urethral reconstruction.

OBJECTIVE: To investigate the possibility of urethral reconstruction with a free colonic mucosal graft. METHODS: Ten female dogs underwent a procedure in which the urethral mucosa was totally removed and replaced with a free graft of colic mucosa. A urodynamic study was performed before the operation and sacrifice. The dogs were sacrificed 8 to 16 weeks after the operation for histological examination of the urethra. RESULTS: Urethral stricture developed in 1 dog. The results of urody namic studies showed that the difference in maximum urethral pressure between pre-operation and pre-sacrifice in the remaining 9 dogs was not of significance (P > 0.05). Histological examination revealed that the colonic free mucosa survived inside the urethral lumen of the 9 dogs. Plicae surface and unilaminar cylindric epithelium of the colonic mucosa was observed in dogs sacrificed 8 weeks after the operation. Plicae surface and unilaminar cylindric epithelium of the colonic mucosa was not observed and metaplastic transitional epithelium covered a large proportion of the urethral mucosa in dogs sacrificed 12 weeks after the operation. CONCLUSIONS: Urethral mucosa can be replaced by colonic mucosa without damaging the continence mechanism in female dogs. This technique is useful when local or preputial skin and buccal or bladder mucosa are not available.

Animals↗

PubMed2002

[Bulbourethral suspension in treatment of male incontinence].

OBJECTIVE: To explore whether bulbourethral suspension procedure is effective for the treatment of male urinary incontinence of post-prostatectomy and posterior urethroplasty. METHODS: Twelve male patients with urinary incontinence undergone bulbourethral suspensive operation were reviewed and analyzed with regard to the operation method, postoperative urinary dynamics and clinical results. RESULTS: Ten patients resumed complete control of urination and 1 was improved. In one patient, postoperative difficulty occurred in voiding but corrected by transurethral bladder neck revision for free passage of urine and continence. Urodynamic study showed that the maximum urethral pressure ranged from 85 to 115 cm H(2)O (mean 98 cm H(2)O, 1 cm H(2)O = 0.098 kPa). The functional urethral length ranged from 3.5 to 4.5 cm (mean 3.75 cm). CONCLUSION: Bulbourethral suspension procedure is effective in the treatment of male urinary incontinence after prostatectomy and posterior urethroplasty.

Adult↗

PubMed2002

Urethral reconstruction with colonic mucosa in treatment of complex urethral stricture.

OBJECTIVE: To investigate the possibility of urethral reconstruction with colonic mucosa for the treatment of complex longer urethral stricture (>/= 10 cm). METHODS: From October 2000 to September 2001, 6 patients with complex longer urethral stricture were treated with colonic mucosal graft urethroplasty. They had under gone 3 previous unsuccessful urethral repairs on average. Urethral reconstruction with a free graft of colonic mucosa ranged from 10 to 15 cm (mean 12.17 cm). Follow-up included retrograde urethrography, urethroscopy, and uroflowmetry. RESULTS: The patients were followed up 3 - 14 months postoperatively (mean 7.8 months). Meatal stenosis developed in one patient 3 months after operation needed reoperation. The patient voided very well with urinary peak flow 28.7 ml per second duing follow-up for 12 months postoperatively. The other patients voided well with urinary peak flow greater than 15 ml per second. At urethroscopy, colonic mucosa was macroscopically difficult to distinguish from normal original urethral mucosa in 4 patients over 6 months after the operation. CONCLUSIONS: Colonic mucosa graft urethroplasty is feasible for the treatment of complex longer anterior urethral stricture. The technique is useful for urethral reconstruction when penial skin and bladder mucosa are not available.

Colon↗

PubMed2002

[Interventional therapy for the chronic seminal vesiculitis].

OBJECTIVES: To investigate the efficacy of transperineal seminal vesicle puncture under ultrasound guidance and continuous transcatheter antibiotic drugs instillation for the treatment of chronic seminal vesiculitis. METHODS: Forty-two patients with hemospermia were treated from April 1988 to January 2001. Of them 35 patients with urogenital inflammation were treated by transperineal seminal vesicle puncture under ultrasound guidance and continuous transcatheter antibiotic drugs instillation. RESULTS: Transperineal seminal vesicle puncture and continuous transcatheter antibiotic drugs instillation therapy was adopted for 35 patients with urogenital inflammation and the cure rate was 91.43%. CONCLUSIONS: Transperineal seminal vesicle puncture under ultrasound guidance and continuous transcatheter antibiotic drugs instillation was an effective method for diagnosis and treatment of chronic seminal vesiculitis.

Adult↗

PubMed2002

Urodynamic study of enhanced continent mechanism using tapered ileum as continent urinary reservoir.

OBJECTIVE: To investigate the effect of extramural support from the pouch and abdominal wall to enhance the continent mechanism of tapered ileum. METHODS: A total of 24 patients underwent a procedure in which an ileal segment was tapered into an efferent tube, of which a part was placed between the back surface of the rectus muscle and the ileal pouch wall. The internal orifice of the tapered ileum was anastomosed to the ileal pouch and its external orifice was anastomosed to the umbilicus. A urodynamic study of the efferent tubes and pouch was done 1.5 to 3 months and 6 to 24 months postoperatively. RESULTS: One patient died of heart disease 55 days postoperatively, while 22 of the remaining 23 were completely continent day and night. At 1.5 to 3 months, the urodynamic study of the efferent tubes demonstrated that the maximum closure pressure with a full pouch was 46 - 124 cmH(2)O (91.26 +/- 15.71 cmH(2)O) and with an empty pouch was 34 - 84 cmH(2)O (67 +/- 10.60 cmH(2)O). The difference in mean maximum closure pressure in the full and empty pouches was statistically significant (t = -11.78 and P = 0.00001). At 6 to 24 months, a second urodynamic study was performed on 18 cases, demonstrating a reservoir capacity of 420 to 750 ml (481.67 +/- 78.83 ml). Reservoir pressure was 6 to 9 cmH(2)O (7.17 +/- 1.17 cmH(2)O) when the pouch was filled to 50 ml, and 16 to 35 cmH(2)O (24.12 +/- 5.61 cmH(2)O) when it was filled to maximum capacity. There was no contractive wave during the filling in any patient. Maximum closure pressure in the efferent tube was 80 to 194 cm H(2)O (98.89 +/- 26.34 cmH(2)O) when the pouch was filled with saline, and 64 to 128 cmH(2)O (74.78 +/- 14.54 cmH(2)O) when the pouch was empty. The difference in mean maximum closure pressure in the full and empty pouches was statistically significant (t = -7.58 and P = 0.00003). CONCLUSIONS: This study indicates that the continent mechanism of tapered ileum may be greatly enhanced by extramural support from the abdominal and pouch walls.

Adult↗

PubMed2002

[Application of artificial neural network to simultaneous spectro-fluorimetric determination of phenol and resorcinol].

By the means of artificial neural network and Levenberg-Marquardt back-propagation train algorithm, the two components of phenol, resorcinol were determined simultaneously, in which the fluorescence spectra overlapped. In 290-345 nm, the fluorescence intensity at 14 wavelengths were taken as character of artificial neural network, and samples were arranged by method of equality design. The mean recovery of phenol and resorcinol were 100.2%, 99.99% respectively. The RSD of the results were 0.4% and 1.3%.

Algorithms↗

PubMedDate not supplied

The nonpolar resonance effects and the non-Hammett behaviors.

In the study we tried to unify the observed non-Hammett behaviors in various fields by proposing the nonpolar resonance effect. This effect was shown to be important not only for carbon radicals but also for some closed-shell systems. Therefore, the odd electron or spin is not the essential cause of the effect. The real origin of the non-Hammett effect should be the HOMO(reaction-center)-LUMO(acceptor) and LUMO(reaction-center)-HOMO(donor) interactions. This means that the nonpolar resonance effect is a universal effect. However, we found that the nonpolar resonance effect could not be well exhibited in many systems because of the serious competition from the polar Hammett effect. Finally, we showed that our proposal of the nonpolar resonance effect was valuable from a practical point of view, because using it we could perform much better correlation studies on some "tough" problems such as radical and multiple bond stabilities, UV and IR spectra, and molecular structures.

Journal Article↗

PubMedDate not supplied

A new method to evaluate the similarity of chromatographic fingerprints: weighted pearson product-moment correlation coefficient.

The Pearson product-moment correlation coefficient is being used to evaluate the similarity of the high-performance liquid chromatographic fingerprints of traditional Chinese medicine (TCM) in China. It is confirmed that a large range of peak areas produced the wrong results. A new algorithm concerning weighted Pearson product-moment correlation coefficient is proposed in this article. The results for both real cases and simulated data sets show that the weighted Pearson product-moment correlation coefficients allow relatively larger differences for large values, smaller differences for small values, and more reliable results than the unweighted Pearson product-moment correlation coefficients. Weight selection depends on the specific scientific problem.

Journal Article↗

PubMedDate not supplied

Demonstration of functional coupling between dopamine synthesis and its packaging into synaptic vesicles.

We have previously shown that the membrane-associated form of the GABA-synthesizing enzyme, glutamate decarboxylase 65 (GAD(65)), is activated by synaptic vesicle proton gradient-mediated protein phosphorylation. We now report that the rate-limiting enzyme in dopamine (DA) biosynthesis, tyrosine hydroxylase (TH), is regulated similarly to GAD(65). The membrane-associated form of TH (MTH) was activated by conditions favoring protein phosphorylation (e.g. ATP) and was inhibited by phosphatase (e.g. calf intestine phosphatase). Furthermore, the ATP-mediated activation of MTH was abolished by conditions that disrupted the proton gradient of synaptic vesicles, e.g. the presence of carbonyl cyanide M-chorophenylhydrazone, gramicidin, or the V-type ATPase inhibitor (bafilomycin), but not the P-type ATPase inhibitor (vanadate). Moreover, DA newly synthesized from tyrosine by MTH and membrane-associated aromatic amino acid decarboxylase was taken up preferentially rather than pre-existing DA. Therefore, the previously proposed model showing close coupling between GABA synthesis and GABA packaging into synaptic vesicles by vesicular GABA transporters is also applicable to the DA system. Hence, it is concluded that there is a general coupling mechanism between neurotransmitter synthesis and packaging of transmitter into synaptic vesicles.

Adenosine Triphosphate↗

PubMedDate not supplied

[Oxidase gene from sweetpotato].

Polyphenol oxidase is the enzyme responsible for enzymatic browning in sweetpotato that decreases the commercial value of sweetpotato products. Here we reported the cloning and characterization of a new cDNA encoding PPO from sweetpotato, designated as IbPPO (GeneBank accession number: AY822711). The full-length cDNA of IbPPO is 1984 bp with a 1767 bp open reading frame (ORF) encoding a 588 amino acid polypeptide with calculated molecular weight of 65.7 kDa and theoretical pI of 6.28. The coding sequence of IbPPO was also directly amplified from the genomic DNA of sweetpotato that demonstrated that IbPPO was an intron-free gene. The computational comparative analysis revealed that IbPPO showed homology to other PPOs of plant origin and contained a 50 amino acid plastidial transit peptides at its N-terminal and the two conserved CuA and CuB copper-binding motifs in the catalytic region of IbPPO. A highly conserved serine-rich motif was firstly found in the transit peptides of plant PPO enzymes. Then the homology-based structural modeling of IbPPO showed that IbPPO had the typical structure of PPO: the catalytic copper center was accommodated in a central four-helix bundle located in a hydrophobic pocket close to the surface. Finally, the results of the semi-quantitative RT-PCR analysis of IbPPO in different tissues demonstrated that IbPPO could express in all the organs of sweetpotato including: mature leaves, young leaves, the stems of mature leaves (petioles), the storage roots and the veins but at different levels. The highest-level expression of IbPPO was found in veins, followed by storage roots, young leaves and mature leaves; and the lowest-level expression of IbPPO was found in petioles. The present researches will facilitate the development of anti-brown sweetpotato by genetic engineering.

Amino Acid Motifs↗