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Biomedical subjects

Y Xu

Publications and source records attributed to Y Xu.

At least 559 records · Page 31Linked to original sources
PubMed1999

Zebrafish tbx-c functions during formation of midline structures.

Several genes containing the conserved T-box region in invertebrates and vertebrates have been reported recently. Here, we describe three novel members of the T-box gene family in zebrafish. One of these genes, tbx-c, is studied in detail. It is expressed in the axial mesoderm, notably, in the notochordal precursor cells immediately before formation of the notochord and in the chordoneural hinge of the tail bud, after the notochord is formed. In addition, its expression is detected in the ventral forebrain, sensory neurons, fin buds and excretory system. The expression pattern of tbx-c differs from that of the other two related genes, tbx-a and tbx-b. The developmental role of tbx-c has been analysed by overexpression of the full-length tbx-c mRNA and a truncated form of tbx-c mRNA, which encodes the dominant-negative Tbx-c. Overexpression of tbx-c causes expansion of the midline mesoderm and formation of ectopic midline structures at the expense of lateral mesodermal cells. In dominant-negative experiments, the midline mesoderm is reduced with the expansion of lateral mesoderm to the midline. These results suggest that tbx-c plays a role in formation of the midline mesoderm, particularly, the notochord. Moreover, modulation of tbx-c activity alters the development of primary motor neurons. Results of in vitro analysis in zebrafish animal caps suggest that tbx-c acts downstream of early mesodermal inducers (activin and ntl) and reveal an autoregulatory feedback loop between ntl and tbx-c. These data and analysis of midline (ntl-/- and flh-/-) and lateral mesoderm (spt-/-) mutants suggest that tbx-c may function during formation of the notochord.

Amino Acid Sequence↗
PubMed1999

Is hepatitis G/GB virus-C virus hepatotropic? Detection of hepatitis G/GB virus-C viral RNA in liver and serum.

The recently identified hepatitis G virus (HGV, also named GB virus-C, GBV-C) appears to have similarities to hepatitis C virus and other flaviviridae. To better understand its clinical significance and hepatotropism, we collected liver tissue and matched serum samples from 56 patients undergoing liver transplantation. HGV/GBV-C RNA was detected by reverse transcription-nested PCR, using primers from the relatively conserved 5' noncoding region of the genome to detect HGV/GBV-C RNA and the amount was semiquantitatively estimated by serial 10-fold endpoint dilution. The presence and amount of HCV RNA was estimated by the same methodology. Seventeen patients (30%) had HGV/GBV-C RNA detectable either in liver or in serum, including two of three with cryptogenic liver disease. Interestingly, 5 of 17 (29%) patients had HGV/GBV-C RNA in serum but not liver, even with repeated testing of hepatic RNA from different portions of the liver. Furthermore, the titer of HGV/GBV-C RNA was significantly lower in liver than in serum in most samples (mean log titer, 1.33 vs. 2.56, P < 0.05). In contrast, all 21 patients with HCV RNA in serum also had the virus detectable in liver. In five patients coinfected with HCV and HGV/GBV-C, the mean titer of HCV RNA in liver was higher than that in serum (log titer, 2.8 vs. 3.0, P > 0.05). Thus, our results suggest that HGV/GBV-C is probably not hepatotropic and may replicate predominantly in sites other than the liver. These findings brings into question the role of HGV in causing significant liver disease.

5' Untranslated Regions↗
PubMed1999

[An investigation of the polymorphism of HLA class II alleles in the Han population in Hubei Province of China].

OBJECTIVE: To investigate the polymorphism of HLA class II alleles in the Han population in Hubei province. METHODS: The alleles of DRB1*(n=168), DQB1*(n=160) and DPB1*(n=93) were typed by using the polymerase chain reaction/sequence specific primer(PCR/SSP) and polymerase chain reaction/restriction fragment length polymorphism (PCR/RFLP) techniques. RESULTS: 39 HLA-DRB1, 15 DQB1 and 17 DPB1 alleles were found. Alleles with higher frequencies are DRB1*0901 (GF=14%), *1501(GF=11.3%), *0301(GF=7.1%), *0803(GF=4.8%); DQB1*0301(GF=18.8%), *0303(GF=18.4%), *0201(GF=10%), *0302(GF=8.4%); DPB1*0501(GF=31.2%), *0401(GF=15.1%), *0201(GF=14%), *0402(GF=11.8%), respectively. As compared with Caucasians, the Han people in Hubei province have higher gene frequencies of DRB1*0901, *1001, *0803; DQB1*0303, *0502 and DPB1*0501, *0202; and lower gene frequencies of DRB1*0301, *0401, *1301; DQB1*0201, *0603 and DPB1*0401, suggesting that Hubei Hans have their own layout of HLA class II allele frequencies. CONCLUSION: These data may serve as normal reference values for the Han population in south China.

Alleles↗
PubMed1999

Inhibitory effects of captopril on hypoxia-induced proliferation and collagen synthesis in pulmonary vascular smooth muscle cells.

AIM: To study the effect of captopril (Cap) on hypoxia-induced proliferation and collagen synthesis in vascular smooth muscle cells (VSMC). METHODS: VSMC were isolated from rabbit pulmonary artery. Cultured VSMC were evaluated by incorporation of [3H]thymidine and [3H]proline, cell number, and intracellular calcium concentration ([Ca2+]i). RESULTS: Pretreatment of pulmonary VSMC with Cap 1 mumol.L-1 blocked hypoxia-induced increase in cell number and incorporation of [3H]proline and [3H]thymidine, which were decreased 25%, 21%, and 36%, respectively, as compared with hypoxic control. It also inhibited the increase of intracellular Ca2+ concentration under hypoxic condition. Addition of nifedipine inhibited hypoxia-stimulated increase in the collagen, DNA synthesis, and [Ca2+]i. Bay-K-8644 increased cell number (35%), DNA (55%), collagen synthesis (36%), and [Ca2+]i (33%) in pulmonary VSMC, that was completely abolished by Cap 1 mumol.L-1. CONCLUSION: Cap inhibited hypoxia-induced proliferation and collagen synthesis in VSMC.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1999

Crystal structure of human mitochondrial NAD(P)(+)-dependent malic enzyme: a new class of oxidative decarboxylases.

Background: Malic enzymes catalyze the oxidative decarboxylation of malate to pyruvate and CO(2) with the concomitant reduction of NAD(P)(+) to NAD(P)H. They are widely distributed in nature and have important biological functions. Human mitochondrial NAD(P)(+)-dependent malic enzyme (mNAD-ME) may have a crucial role in the metabolism of glutamine for energy production in rapidly dividing cells and tumors. Moreover, this isoform is unique among malic enzymes in that it is a cooperative enzyme, and its activity is controlled allosterically. Results: The crystal structure of human mNAD-ME has been determined at 2.5 Å resolution by the selenomethionyl multiwavelength anomalous diffraction method and refined to 2.1 Å resolution. The structure of the monomer can be divided into four domains; the active site of the enzyme is located in a deep cleft at the interface between three of the domains. Three acidic residues (Glu255, Asp256 and Asp279) were identified as ligands for the divalent cation that is required for catalysis by malic enzymes. Conclusions: The structure reveals that malic enzymes belong to a new class of oxidative decarboxylases. The tetramer of the enzyme appears to be a dimer of dimers. The active site of each monomer is located far from the tetramer interface. The structure also shows the binding of a second NAD(+) molecule in a pocket 35 Å away from the active site. The natural ligand for this second binding site may be ATP, an allosteric inhibitor of the enzyme.

Journal Article↗
PubMed1999

[Current status of cord blood banks in the world].

Since the first successful transplantation of placental/umbilical cord blood (PCB) in 1988 at St. Louis Hospital in Paris, the effort has been made to establish large scale cord blood banks for allogeneic transplantation around the world. Recent reports from New York Blood Center which stocks 9000 units and shipped 700 units to US and other countries indicates that PCB transplantation is as effective as bone marrow transplantation. There are many cord blood banks in the world now and the number of PCB units stocked in the world are increasing rapidly. The methods for collection and processing of PCB, and test items for screening for viral infections, etc. differ greatly among banks. Therefore, the quality of PCB units stocked worldwide has become an important issue and some major banks are trying to introduce GMP or ISO system for the quality assurance of PCB. In this chapter, we introduce the activities of major cord blood banks in the world. Guidelines or regulation for hematopoietic stem cell processing including PCB has been enacted in some countries though the situation of support from their governments differ. International registry for PCB transplantation have been developed by EUROCORD. The international network of cord blood banks, NETCORD, has been established recently with major banks in Europe, United States and Japan to ensure the rapid supply of safe and efficient PCB units to the patients throughout the world. Obtaining information of international activities of cord blood banks in the world and cooperation with them should bring the National Cord Blood Bank in Japan into concordance with a developing world standards.

Blood Banks↗
PubMed1999

Assessment of functional MR imaging in neurosurgical planning.

BACKGROUND AND PURPOSE: Presurgical sensorimotor mapping with functional MR imaging is gaining acceptance in clinical practice; however, to our knowledge, its therapeutic efficacy has not been assessed in a sizable group of patients. Our goal was to identify how preoperative sensorimotor functional studies were used to guide the treatment of neuro-oncologic and epilepsy surgery patients. METHODS: We retrospectively reviewed the medical records of 46 patients who had undergone preoperative sensorimotor functional MR imaging to document how often and in what ways the imaging studies had influenced their management. Clinical management decisions were grouped into three categories: for assessing the feasibility of surgical resection, for surgical planning, and for selecting patients for invasive functional mapping procedures. RESULTS: Functional MR imaging studies successfully identified the functional central sulcus ipsilateral to the abnormality in 32 of the 46 patients, and these 32 patients are the focus of this report. In epilepsy surgery candidates, the functional MR imaging results were used to determine in part the feasibility of a proposed surgical resection in 70% of patients, to aid in surgical planning in 43%, and to select patients for invasive surgical functional mapping in 52%. In tumor patients, the functional MR imaging results were used to determine in part the feasibility of surgical resection in 55%, to aid in surgical planning in 22%, and to select patients for invasive surgical functional mapping in 78%. Overall, functional MR imaging studies were used in one or more of the three clinical decision-making categories in 89% of tumor patients and 91% of epilepsy surgery patients. CONCLUSION: Preoperative functional MR imaging is useful to clinicians at three key stages in the preoperative clinical management paradigm of a substantial percentage of patients who are being considered for resective tumor or epilepsy surgery.

Adolescent↗
PubMed1999

Calcium-dependent cleavage of striatal enriched tyrosine phosphatase (STEP).

Striatal enriched phosphatase (STEP) is a family of protein tyrosine phosphatases enriched within the CNS. A member of this family, STEP61, is a membrane-associated protein located in postsynaptic densities of striatal neurons. In this study, we demonstrate that STEP61, is cleaved into smaller isoforms. To clarify the mechanism of cleavage, STEP61 was transiently expressed in NT2/D1 neuronal precursor cells. Exposure of transfected cells to the calcium ionophore, A23187, or to thapsigargin resulted in the rapid cleavage of STEP61. Pretreatment with the calpain inhibitor, calpeptin, or EGTA prevented proteolysis. One of the cleavage products has a relative molecular mass of 33 kDa (STEP33). A protein with the identical mobility is detected following calpain treatment of STEP61 fusion protein or postsynaptic densities purified from rat striatum. Exposure of primary neuronal cultures to glutamate also led to a significant increase in the concentration of a low molecular weight form of STEP. Taken together, these results suggest that in response to a rapid influx of calcium, STEP61, is proteolytically cleaved by calpain, leading to the release of a smaller isoform. This model may explain the rapid appearance of STEP33 in response to transient hypoxia-ischemia in the brain as cells attempt to counter the increase in tyrosine phosphorylation levels following neuronal insults.

Animals↗
PubMed1999

[Cloning and sequence analysis of ATCase genes from Psychrophilic vibrio].

The gene encoding for aspartate transcarbamoylase (ATCase) from Psychrophilic vibrio, strain 2693 was cloned and sequenced. The sequence revealed the existence of two gene encoding respectively for a catalytic chain (pyrB) and a regulatory chain (pyr I). The catalytic and regulatory polypeptide chains of Vibrio 2693 ATCase are encoded by a single pyrBI bicistronic operon, and appear to be transcribed under the control of the same promoter. The 3'-terminus of the catalytic cistron (pyrB) is adjacent to the 5'-terminus of the regulatory cistron, these is only a 4 bp space between the two coding regions.

Amino Acid Sequence↗
PubMed1999

[The use of risk factors scoring method in screening for undiagnosed diabetes in general population].

OBJECTIVE: Based on an epidemiological survey of NIDDM in the general population, two sub-population groups were selected to develop a screening method on risk factors to identify people at increased risk for undiagnosed diabetes. METHODS: Logistic regression analysis on the original data of population A was carried out to screen the main risk factors of diabetes. The score of the variable was determined based on the OR value and the aggregate score was used to predict the risk of undiagnosed diabetes. Both validity and effectiveness of the method were evaluated in population B. RESULTS: Results showed that the risk of having diabetes in the population increased along with aggregate scores of the method. Trend chi 2 test showed statistical significance (P < 0.01). When the threshold value was set up at 7, both sensitivity and specificity for identifying undiagnosed diabetes were 74.3% and 63.2%, respectively making the positive predictive value 4.2% and negative predictive value 99.2%. CONCLUSION: The benefits of this screen method seemed to be simple, economical and helpful to obtain a satisfactory response rate. The method could be used for health education and to identify people (community) at high risk for potential diabetes. It was predicted that this screening method could serve as an effective and useful tool for mass screening of NIDDM.

Adult↗
PubMed1999

The "mediator service", a component to ease the integration of medical applications in the SynEx framework.

Interoperability is a key issue and a long-term domain of research for distributed healthcare information systems. The European project SynEx provides an open and standard integration platform for both new and legacy medical applications. It allows the collaboration of distributed and heterogeneous healthcare records and services. It aims to provide access to Hospital Information Services, to remote sources of medical data and to medical knowledge, in a seamless way, hiding the distribution aspects and the heterogeneity of systems. In this project, the Medical Informatics Department of the Broussais University Hospital is responsible for the development of the "Mediator Service". It is a software component of the SynEx platform which is used as a "glue" mechanism to provide a flexible way to facilitate the interchange between any pair of systems, with different nomenclatures and data structures. The Mediator Service uses a generic model of mediators to create, through specialization, specific mediators for practical cases. Based on this model, it offers a C++ library to be used as the tool case by the programmers, to reduce the development effort. The use of XML as a powerful data interchange format and as a data structure descriptor is proposed and evaluated.

Computer Communication Networks↗
PubMed1999

Effects of tripchlorolide on the epididymides and testes of rats.

AIM: To further evaluate the antifertility effects of tripchlorolide, a derivative of triptolide produced at the extraction procedure of Tripterygium wilfordii Hook. f., in male rats and to investigate its sites and possible mechanisms of action. METHODS: In male rats, tripchlorolide was given by oral garage at a dose of 50 micrograms.kg-1.d-1 for 5 weeks, fertility was assessed by mating tests, and biochemical indices and light microscopic observation of the epididymides and testes were also performed. RESULTS: Administration of tripchlorolide at 50 micrograms.kg-1.d-1 for 3 weeks did not influence the fertility of male rats, but 5-week treatment rendered the rats infertile. The density and motility of spermatozoa collected from cauda epididymides were reduced significantly. The epididymal weights, as well as the L-carnitine concentration and alpha-glucosidase content in the epididymal fluid were decreased. There were no significant differences in alpha-glucosidase and acid phosphatase (ACP) in caput epididymal homogenates between the control and the experimental rats. Obvious morphological changes were observed in the epididymal spermatozoa, mainly including head and tail separation or acrosome curving. Sloughed spermatids were found in the seminifeous and epididymal tubules. In testicular homogenates, tripchlorolide had no influence on the lactate dehydrogenase-C4 (LDH-C4) and hyaluronidase activities. No apparent lesions were observed in the seminiferous and epididymal epithelium. CONCLUSION: At the dose level employed, tripchlorolide has a significant effect on the fertility in male rats and the primary sites of action may be spermatids and testicular and epididymal spermatozoa.

Animals↗
PubMed1999

[The effect of inhibition of nitric oxide synthesis on vasoregulatory factors in pregnant rats].

OBJECTIVE: To study the effect of the inhibition of nitric oxide(NO) synthesis on plasma endothelin (ET), prostaglandlin I2(PGI2), thromboxane (TXA2) and angiotensin (ANGII) in pregnant rats, and to investigate the role of these factors in the pathogenesis of pregnancy-induced hypertension(PIH). METHODS: Pregnant rats were divided into two groups randomly. Saline solution or L-nitro arginine methyl ester (L-NAME) 125 mg/day was given subcutaneously from day 14 of gestation till delivery. Systolic blood pressure, urine protein, platelet count, and weight of pups and placentae were determined. Plasma NO, ET, PGI2, TXA2 and ANGII were measured by RIA. RESULTS: Pregnant rats which were given L-NAME produced physical signs similar to those of PIH, such as increase in systolic blood pressure (140.6 +/- 3.8) mmHg and urine protein (801.38 +/- 57.12) mg/L, and decrease in platelet count (533 +/- 42) x 10(9)/L and weight of pups and placentae. Compared with controls, plasma NO, PGI2 and ANG II were decreased significantly while plasma ET and TXA2 were increased significantly in rats given L-NAME. CONCLUSION: Inhibition of NO synthesis can cause imbalance of several vaso-regulatory factors, which may be responsible for the pathogenesis of PIH.

6-Ketoprostaglandin F1 alpha↗
PubMed1999

[Dual color fluorescent in-situ hybridization detects sex chromosome mosaicism in human embryos].

OBJECTIVE: Using dual color fluorescent in-situ hybridization (FISH) to detect sex chromosome mosaicism in human embryos and perform preimplantation gender diagnosis. METHODS: Three abnormal fertilized embryos and 18 normal fertilized embryos which were not suitable for embryo transfer and cryopreservation were analyzed by dual color fluorescent in-situ hybridization. RESULTS: Mosaicism analysis was performed on 14 normal fertilized embryos, which had more than two cells. Nine embryos had sex chromosome mosaicism. XO in male and female embryos cells were 12% and 14% respectively. CONCLUSION: Identification of sex by FISH analysis of a single cleavage cell is accurate, and sex chromosome mosaicism will not affect preimplantation gender diagnosis.

Embryo Transfer↗
PubMed1999

[Cisplatin-induced apoptosis in laryngeal squamous cell carcinoma strain and the influence on cell cycle].

OBJECTIVE: To find more effective chemotherapeutic agents and treatment regimens, we studied the cytotoxicity of cisplatin to human laryngeal squamous cell carcinoma strain Hep2. METHODS: Using flow cytometry, fluorescence microscopy, and DNA agarose gel electrophoresis technique, we investigated in vitro Hep2 cells in different conditions. RESULTS: Hep2 was adherent cells in normal survival condition. Cisplatin affected Hep2 cell growth apparently. Under fluorescence microscope, necrotic cells were red, apoptotic cells were blue with condensed and fragmented nuclei, and normal cells were evenly blue. Adherent cells were 86%-96% viable. But nonadherent cells were 6%-13% viable. Death cells increased with the increase of drug concentration and time elapsing. Death cells were mainly apoptotic cells. The latter appeared to be time- and dose-dependent. DNA "ladder" was observed for nonadherent cells in agarose gel electrophoresis, but adherent cells were not. "Sub-G1" phase peak occurred in flow cytometry. After cisplatin treatment, the volume of adherent cells increased with dose- and time dependence. Cisplatin could cause Hep2 cell cycle to change. At first, G1 phase cell percentage reduced, while S phase increased. With time elapsing, G2/M phase increased. Cells experienced a slow-down in S-phase followed by a G2 block. CONCLUSION: Apoptosis is a major way of Hep2 cell death after cisplatin treatment and appeared to be time- and dose-dependent. In clinical chemotherapy, cisplatin should be used in high concentration. Inducing apoptosis is one of the characteristics of chemotherapeutic agents. Cisplatin should be taken a combination regimen with cell cycle-special agents.

Antineoplastic Agents↗