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Biomedical subjects

Y Chen

Publications and source records attributed to Y Chen.

At least 1,189 records · Page 66Linked to original sources
PubMed1999

Shift in arm-pointing movements during gravity changes produced by aircraft parabolic flight.

It has been shown that target-pointing arm movements without visual feedback shift downward in space microgravity and upward in centrifuge hypergravity. Under gravity changes in aircraft parabolic flight, however, arm movements have been reported shifting upward in hypergravity as well, but a downward shift under microgravity is contradicted. In order to explain this discrepancy, we reexamined the pointing movements using an experimental design which was different from prior ones. Arm-pointing movements were measured by goniometry around the shoulder joint of subjects with and without eyes closed or with a weight in the hand, during hyper- and microgravity in parabolic flight. Subjects were fastened securely to the seat with the neck fixed and the elbow maintained in an extended position, and the eyes were kept closed for a period of time before each episode of parabolic flight. Under these new conditions, the arm consistently shifted downward during microgravity and mostly upward during hypergravity, as expected. We concluded that arm-pointing deviation induced by parabolic flight could be also be valid for studying the mechanism underlying disorientation under varying gravity conditions.

Adult↗
PubMed1999

Reversal of spontaneous progressive autoimmune encephalomyelitis by myelin basic protein-induced clonal deletion.

Autoimmune encephalomyelitis can be initiated spontaneously and developed progressively in TCR transgenic mice specific for myelin basic protein when exposed to non-sterile environment, thus more closely mimicking human multiple sclerosis. By intravenous administration of myelin basic protein, we succeeded in reversing the clinical and pathological signs of progressive spontaneous disease in these mice. Flow cytometry showed that the majority of transgenic T cells in lymph nodes and spleen as well as spinal cords of treated mice were deleted. Dramatically increased numbers of apoptotic cells were found in peripheral immune organs of treated animals. Proliferative responses of single transgenic T cell to autoantigen were significantly decreased in treated mice, indicating that the remaining T cells were anergic. Moreover, production of both Th1 and Th2 cytokines was suppressed. This study is the first demonstration of reversal of progressive, spontaneous autoimmune disease of the central nervous system, and provides direct evidence that apoptosis-induced clonal deletion, along with anergy of remaining cells, but not Th2 switch, play a major part in the reversal of this disease by intravenous administration of autoantigen.

Animals↗
PubMed1999

Daily exercise enhances acetylcholine-induced dilation in mesenteric and hindlimb vasculature of hypertensive rats.

The effect of daily spontaneous running (DSR) on endothelial function was examined in spontaneously hypertensive rats (SHR). Following 8-11 weeks of DSR (n=15) or sedentary control (SED, n=15), rats were instrumented with arterial and venous catheters and mesenteric and iliac Doppler ultrasonic flow probes. Hemodynamic responses to vasodilator-mediated substances were determined under two experimental conditions; 1) bolus injection of indomethacin (10 mg/kg) and 4 bolus doses of acetylcholine (0.5-2.0 microg/kg); 2) bolus injection of N(omega)-nitro-L-arginine (5 mg/kg) and 4 bolus doses of nitroglycerin (3-12 microg/kg). Hindlimb vascular conductance decreased more in response to indomethacin in DSR vs. SED rats (-18.3+/-2.8% vs. -10.4+/-2.5%). However, the mesenteric or hindlimb vascular conductance responses to N(omega)-nitro-L-arginine were not different between DSR and SED rats. DSR also enhanced mesenteric and hindlimb vascular conductance responses to acetylcholine. Results suggest that DSR enhances acetylcholine-induced vasodilation in SHR.

Acetylcholine↗
PubMed1999

Alpha-Gal oligosaccharides: chemistry and potential biomedical application.

This article focuses on the most recent research efforts by the Wang group in the field of alpha-Gal oligosaccharides. alpha-Gal oligosaccharides are carbohydrate structures bearing a Gal( alpha)1-3Gal(beta) terminus. This class of compounds are believed to act as xenoactive antigens that instigate the hyperacute rejection in xenotransplantation. Enzymatic methods using recombinant (alpha)1-3 galactosyltransferase were employed to synthesize several alpha-Gal oligosaccharides. In addition, a chemical synthetic scheme was devised in order to produce readily accessible amounts of alpha-Gal. Conformational analysis was done using both NMR techniques and molecular modeling protocols. These studies provide important information in the structure-function relationship of alpha-Gal and anti- alpha-Gal antibodies.

Animals↗
PubMed1999

[A comparative study of HLA-A locus in northern and southern Chinese bymeans of PCR/SSOP typing].

OBJECTIVE: To compare the HLA-A locus in a population selected from Beijing (northern group) with that in a population selected from Guangzhou (southern group). METHODS: HLA typing was performed by using PCR/SSOP method. A pair of primer and 54 probes were used. RESULTS: In 18 alleles identified, the differences in gene frequency between northern and southern Chinese were found. In northern group, A*0205, 0210 and 2901 were absent, and the frequencies of A*2601, 3001 and 3101 were higher than those of southern group; while in southern group, A*3103, 3201 and 6801 were absent, the frequencies of A*0203 and 1101 were higher than those of northern group; and in addition, six subtypes of A2 serological specificity, namely A*0201, 0203, 0205, 0206, 0207 and 0210, were found, in which A*0201 predominated. CONCLUSION: There are some differences in the genetic background of northern and southern Chinese. A2 subtypes have important implications for unrelated-donor transplantation.

Alleles↗
PubMed1999

[Inhibitory effect of triplex forming oligodeoxynucleotides on HBV replication and synthesis of antigen].

OBJECTIVE: To explore the inhibitory effect of triplex forming oligodeoxynucleotides(TFO) on replication of HBV and synthesis of antigen. METHODS: A 21 mer phosphorothioate triplex forming oligodeoxynucleotides (TFO21) directed at SP1 sites in HBV core promoter and a control of 21 mer phosphorothioate oligodeoxynucleotides (ODNcon) were synthesized. HepG 2.2.15 cells which can produce HBsAg, HBeAg, HBV DNA and HBV particle were treated with TFO21 and ODNcon. In HepG 2.2.15 cells treated with these oligodeoxynucleotides, the levels of HBsAg, HBeAg, and HBV DNA were examined by ELISA and dot hybridization method, respectively. RESULTS: The levels of HBsAg, HBeAg and HBV DNA in TFO21 group were lower than those in the bank control group. At concentration of 10 mumol/L, TFO21 inhibited synthesis of HBsAg and HBeAg by 57.5% and 77%. The inhibitory effect of TFO21 was dosage-dependent, and was related to time in which 2.2.15 cells were incubated with TFO21. No inhibition was observed in the ODNcon group. No toxicity was observed in the 2.2.15 cells treated with oligodeoxynucleotides. CONCLUSION: These results indicate that TFO is a potent inhibitor for HBV replication and synthesis of antigen, and also suggest that TFO is a therapeutic potential for the treatment of patients infected with HBV.

DNA, Viral↗
PubMed1999

Structural studies of initial lymphatics adjacent to gastric and colonic malignant neoplasms.

Invasion and metastases are the main causes of death from cancer, and prognosis is best correlated with invasion of malignant cells into initial lymphatics and dissemination to regional lymph nodes. Using both light and transmission electron microscopy, we examined human gastric and colonic cancers and their relation to initial lymphatics. Invasion of malignant tumor cells into the initial lymphatics was characterized by interdigitating and overlapping endothelium giving way to open junctions as lymphatic endothelial cells were apparently dissolved and destroyed. Cytoplasmic vesicles, mitochondria, and rough endoplasmic reticulum were qualitatively increased as demonstrated by image analysis.

Colonic Neoplasms↗
PubMed1999

[A study on polymorphism of mitochondrial DNA D loop in the Han nationality in China].

OBJECTIVE: To investigate the polymorphism of mitochondrial DNA D loop in the Han nationality in China and the mean nucleic acid substitute frequency on each site. METHODS: A 465bp-long DNA fragment in mtDNA D loop was amplified by PCR technique and the polymorphism was analyzed by restriction fragment length polymorphism (RFLP) using 6 restriction enzymes (on 10 sites). Some samples were analyzed by direct sequencing of PCR products. RESULTS: RFLP analyses with 6 restriction enzymes on the 10 sites generated 14 restriction types. The calculated mean nucleic acid substitute frequency (based on Nei formula) on each site of mtDNA D loop in the Han nationality in China was 0.029. CONCLUSION: The mean nucleic acid substitute frequency on each site in the D loop region was 10 times as high as that in mtDNA.

Asian People↗
PubMed1999

[Gene transfer efficiency enhancement by inactivated Coxsakie virus B1 in primary skeletal muscle cells].

OBJECTIVE: To study the effect of inactivated Coxsackie virus B1(CVB1), which was considered to have high affinity to skeletal muscle cell, on gene transfer efficiency of reporter gene, pCDNA3-LacZ, in primary muscle cells. METHODS: Viruses were purified by polyethylene sedimentation followed by sucrose supercentrifugation. Virus, transferrin-polylysine(TfpL) and LacZ were designed as different concentrations and groups, then positive cells contained beta-galactosidase were calculated as gene transfer efficiency. RESULTS: Inactivated CVB1 made an enhancement of gene transfer efficiency from less than 1% in TfpL+LacZ group to 15-20 per cent in CVB1+TfpL+LacZ group. CONCLUSION: Like adenovirus, inactivated CVB1 can also increase gene transfer efficiency in muscle cells, which provides experimental basis for constructing new vector targeting to muscle cells.

Cells, Cultured↗
PubMed1999

Tricyclic pyrone analogs: a new synthetic class of bifunctional anticancer drugs that inhibit nucleoside transport, microtubule assembly, the viability of leukemic cells in vitro and the growth of solid tumors in vivo.

Tricyclic pyrones (TPs) may represent a novel synthetic class of microtubule (MT) de-stabilizing anticancer drugs previously shown by us to inhibit macromolecule synthesis, tubulin polymerization, and the proliferation of leukemic and mammary tumor cells in vitro. A linear skeleton with a N-containing aromatic ring attached at C3 of the top A-ring, a central pyran B-ring and a six-membered bottom C-ring with no alkylation at C7 are required for the antitumor activities of the lead compounds, a 3-pyridyl benzopyran (code name H10) and its somewhat weaker 2-pyridyl regioisomer (code name H19). Increasing concentrations of H10 do not alter the binding of [3H]vinblastine and [3H]GTP to tubulin but mimic the ability of unlabeled colchicine (CLC) to reduce the amount of [3H]CLC bound to tubulin, suggesting that TPs may interact with the CLC binding site to inhibit tubulin polymerization. Exogenous Mg2+ cations absolutely required for the binding of GTP to tubulin and MT assembly cannot overcome the antitubulin action of H10. H10 reduces the viability of L1210 cells in vitro (IC50: 0.5 microM) but its antitumor activity may be related to its ability to inhibit tubulin polymerization and rapidly increase the mitotic index rather than to induce DNA cleavage and apoptosis. The anticancer potential of TPs in vivo is demonstrated by the fact that i.p. injections of the water-soluble H10-HCl decrease the growth of solid tumors in mice inoculated s.c. with Lewis lung carcinoma. A critical finding is that the antimitotic H10 is a bifunctional anticancer drug, which also blocks the cellular transport of nucleosides (IC50: 6 microM) to inhibit DNA synthesis. Since few CLC site-binding antimitotic agents are active in solid tumor models in vivo, the ability of these new MT destabilizing TPs to totally block nucleoside transport might be valuable in polychemotherapy to arrest tumor cells at several phases of their cycle, potentiate the action of antimetabolites and sensitize multidrug-resistant tumor cells.

Animals↗
PubMed1999

Application of the holmium yttrium-aluminum-garnet laser for complicated impacted ureteral stones: a preliminary report.

BACKGROUND: Minimally invasive surgery is a current trend in all kinds of surgical fields. Endoscopic stone manipulation with electrohydraulic lithotripsy (EHL) is the preferred method for treating lower ureteral stones or calculi which cannot be resolved with extracorporeal shock wave lithotripsy (SWL). We evaluated the efficiency and safety of holmium yttrium-aluminum-garnet (YAG) laser for treatment of large impacted ureteral stones. METHODS: In a clinical trial period including April and May 1998, 13 patients with ureteral stones underwent holmium YAG lasertripsy. Six patients had large impacted ureteral stones (1.3 to 3.8 cm). We conducted lasertripsy with a 6.5-Fr. rigid tapered ureteroscope and a 550-nm SlimLine laser fiber under the guidance of a 3-Fr. ureteral catheter. The irrigation pump was set at 300 mmHg to increase the surgeon's visual clearance and to help keep the operative field ston-free. RESULTS: The postoperative stone-free rate was 100%. There were no intraoperative complications, even in the treatment for a 3.8-cm steinstrasse in the upper ureter. All preoperative hydronephrosis improved. In general, the operative time, not including anesthesia, was less than 30 minutes. There was no intraoperative or postoperative flank pain or fever when the procedure was combined with pressure irrigation for visual clearance and keeping the area stone-free. CONCLUSION: Holmium YAG lasertripsy is an excellent treatment modality, especially for a large impacted ureteral stone or steinstrasse. The treatment is efficient and safe. Furthermore, there is no learning curve necessary for an experienced endo-urologist. It helps the urologist to carry out a minimally invasive lithotripsy instead of an open surgery for large impacted ureteral stones.

Adult↗
PubMed1999

Partial nephrectomy for incidental primary renal neuroendocrine carcinoma: case report.

Here we present an 83-year-old woman who was referred to our hospital and had had left flank pain and oligouria for 3 days. Plain abdominal film and ultrasonography revealed left ureteropelvic junction stone with obstructive uropathy. The serum level of creatinine fell to 3.1 mg/dl from 7.6 mg/dl after ureteral catheter drainage was given 5 days after admission. Then a left pyelolithotomy was performed and a tumor of 2 x 1 x 1 cm over the lower pole of the left kidney was found incidentally. Partial nephrectomy was performed in consideration of her age and poor renal function although the biopsy result showed it to be carcinoma. The final pathological report and immunohistochemical study results proved that it was neuroendocrine carcinoma. To our knowledge, this is the first case of primary renal neuroendocrine carcinoma to be treated using conservative surgery. The clinical course was acceptable, since she had been found to be free of disease during regular follow-up of 2.5 years with the creatinine level of about 2.5 mg/dl.

Aged↗
PubMed1999

[A preliminary study on the genetic susceptibility of asthma in a Chinese population].

OBJECTIVE: To study the asthma genetic susceptibility by way of ccandidate region so as to accumulate data on the related loci in Chinese population and determine whether genetic susceptibility to asthma is linked to the chromosome region. METHODS: One hundred ninety-two samples from 32 families were collected from Zhaoan county in Fujian province. Two Rsa I polymorphic sites within uncoded region of the high-affinity IgE receptor beta chain gene (Fc(epsilon) RI-beta) located on chromosome 11q13 were detected by PCR/Rsa I restriction endonuclease digestion. The polymorphic markers D5S436 and D5S393 within chromosome 5q31-33 were amplified by PCR incorporated with radioactive isotope. The asthma family samples were compared with unrelated samples randomly selected from general population. RESULTS: Genotypes containing A allele within intron 2 polymorphic site of Fc(epsilon) RI-beta gene were associated with asthma (P<0.05,OR = 2.039). Significant difference in the level of total serum IgE was noted among three genotypes of intron 2 polymorphic site of Fc(epsilon) RI-beta gene (P<0.05). The association between A allele and elevated total serum IgE was also significant (P<0.05, RR = 1.361). No relationship between exon 7 polymorphic site of Fc epsilonRI-beta gene and asthma was shown. By sib-pair analysis, significant evidence for linkage to asthma was observed with D5S436 (P<0.05) but not with D5S393. No significant linkage to total serum IgE was identified with both of these markers. CONCLUSION: The above-accumulated data suggested that both Fc epsilonRI-beta gene and chromosome 5q31-33 could be very attractive candidate gene and region for further studies in Chinese population, and to confirm these preliminary results, more markers within these regions merit testing in additional population samples.

Adolescent↗
PubMed1999

Epidemiology of contralateral breast cancer.

Two to 11% of women diagnosed with breast cancer will develop contralateral breast cancer in their lifetime. Women with a first primary are at a 2-6-fold increased risk of developing contralateral breast cancer compared with the risk in the general population of women developing a first primary cancer. The incidence rate of contralateral breast cancer varies from four to eight per 1000 person-years. To assess the risk factors associated with the development of contralateral breast cancer among women with a first primary breast cancer, the epidemiological literature concerning these factors was reviewed and summarized. Studies have shown that a family history of breast cancer, an early age at initial diagnosis, and a lobular histology of the first primary breast cancer increase the risk of developing contralateral breast cancer. Although chemotherapy and tamoxifen therapy may reduce this risk, there are inconsistent results regarding the effects of radiotherapy and the effects of reproductive, environmental and other factors. Additional analytical studies addressing all potential risk factors associated with the development of contralateral breast cancer are necessary in view of the increasing incidence and survival of women with a first primary.

Breast Neoplasms↗
PubMed1999

What makes the circadian clock tick: genes that keep time?

Intense activity in the field of circadian rhythms has led in recent years to a basic understanding of how an endogenous clock is generated. Oscillating products of the period (per) and timeless (tim) genes, which feed back to regulate their own synthesis, and transcription factors, which activate these genes, combine to generate a molecular loop that apparently drives behavioral and physiological rhythms. The best-characterized component of this system is the per gene, with considerable effort directed towards identifying the mechanisms that regulate cyclic expression of RNA and protein. Since the cycling of PER protein is controlled largely by post-transcriptional mechanisms, the relative importance of RNA versus protein cycling has been addressed in several studies that are discussed in this chapter. However, it now is clear that regulation of per cannot be dissociated from that of tim, since they are co-dependent components. The overt behavioral phenotype likely depends upon the effect that any perturbation has on both components, rather than on either alone. Major features of the feedback loop appear to be conserved, from fruit flies to mammals. One difference between the two systems is the manner in which the "molecular clock" responds to light. In flies, levels of TIM protein are reduced in response to light, while in mammals, per RNA is induced. The pathway that conducts light to the clock is poorly understood but there is increasing evidence in support of a dedicated pathway for circadian photoreception, as opposed to the sole use of the visual transduction system.

Animals↗
PubMed1999

Exploration of the association between apoptosis and cleft palate.

OBJECTIVE: To explore the significance and effect of apoptosis in the development of cleft palate induced by dexamethasone (DEX). METHODS: Various doses of DEX (10-50 mg/kg) were injected intraperitoneally into Kunming mice on gestation day (GD) 12. The cranio-maxillary sections of samples were labeled by HRP-avidin-biotin-dUTP in situ end-labeling (ISEL) and were observed morphologically and quantitatively under a light microscope and electron microscope. RESULTS: ISEL positive cells were found in treatment groups. The means of sums and cleft palate incidence have a positive correlation with the doses of DEX (r = 0.9911/0.9978). CONCLUSION: A relationship exists between an increased level of apoptosis and the development of cleft palate induced by DEX.

Animals↗
PubMed1999

[Taurine inhibits deposition of extracellular matrix in experimental liver fibrosis in rats].

OBJECTIVE: To study the effect of taurine on liver fibrosis and its mechanism. METHODS: Fibrosis was induced by the administration of carbon tertrachloride(CCl4) in rats. Some of the animals were treated with taurine. The rats were killed after 12 weeks of CCl4 treatment. Depositions of type I, III and IV collages, laminin and hyaluronic acid were studied in liver sections by immunohistochemical technique using specific antibody. The hepatic contents of type I, III procollage and tissue inhibitor of metalloproteinase-1(TIMP-1) mRNA were determined by Northern blot hybridization. RESULTS: A significant elevations of hepatic collagen I, III, IV, laminin and hyaluronic acid were observed after 12 weeks of liver injury in animals without taurine treatment, and a definite increase in the amounts of hepatic type I, III procollagen and TIMP-1 mRNA was noted. Taurine prevented increases in type I, III procollagen mRNA expression as well as the accumulation of the collagens, laminin and hyaluronic acid in the liver. CONCLUSION: The data indicate that taurine has a protective effect in CCl4-induced hepatic fibrosis. The results suggest taurine might be of potential value in clinical practice.

Animals↗