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Biomedical subjects

Y Zhao

Publications and source records attributed to Y Zhao.

At least 199 records · Page 11Linked to original sources
PubMed2001

Maturation and function of mouse T-cells with a transgenic TCR positively selected by highly disparate xenogeneic porcine MHC.

Remarkably normal cellular immune function, along with specific T-cell tolerance to highly disparate xenogeneic donors, can be achieved by grafting fetal pig thymus (FP THY) tissue to T and NK cell-depleted, thymectomized (ATX) mice. Porcine MHC can mediate positive selection of mouse CD4+ T-cells with a mouse MHC-restricted TCR in FP THY-grafted, T- and NK cell-depleted, ATX TCR-transgenic "AND" mice. However, functional studies were not performed on transgenic mouse T-cells selected in a FP THY graft. We have now performed further studies to confirm the ability of porcine MHC to mediate the positive selection of mouse T-cells with a mouse MHC-restricted TCR, and to exclude the possibility that the maturation of mouse T-cells with a mouse MHC-restricted TCR in FP THY grafts in ATX "AND" mice is a special case. For this purpose, TCR-transgenic mice with an unrelated transgenic TCR ["3A9", specific for hen egg lysozyme (HEL) peptide 46-61 presented by I-Ak] were employed. Similar to FP THY-grafted ATX "AND" mice, large numbers of mouse CD4 single positive thymocytes expressing the transgenic TCR (Vbeta8.2) and expressing a mature phenotype (Qa-2high and heat stable antigen, HSAlow) were detected in FP THY grafts. Porcine thymus grafting led to a high level of peripheral repopulation with mouse naive-type (CD44low CD45RBhigh CD62Lhigh) CD4+ cells expressing the transgenic TCR in T and NK cell-depleted ATX "3A9" mice, regardless of whether the recipients had a positive selecting or a non-selecting, class II deficient MHC background. The mouse CD4+ T-cells expressing the "3A9" TCR showed efficient primary proliferative responses to the protein antigen (HEL) when it was presented by mouse class II+ antigen presenting cells (APC) in vitro. These results, collectively, support the general conclusion that discordant xenogeneic porcine MHC can mediate positive selection of mouse T-cells with mouse MHC-restricted TCR. This study has implications for the potential clinical use of xenogeneic thymus transplantation to reconstitute cellular immunity in the setting of thymic insufficiency or thymectomy, and hence for its applicability to the induction of xenograft tolerance and in the treatment of immunodeficiency diseases.

Animals↗
PubMed2001

Computational fluid dynamics study of a protruded-hinge bileaflet mechanical heart valve.

BACKGROUND AND AIM OF THE STUDY: Following clinical experience with the Medtronic Parallel bileaflet mechanical heart valve, considerable interest has been shown in investigating fluid mechanics inside the hinge socket. Most of these studies involved hinges that are recessed into the valve housing, such as the St. Jude Medical (SJM), CarboMedics, Sorin and On-X bileaflet mechanical heart valves. The aim of this study was to investigate the flow fields of a protruded hinge under steady flow conditions, with the occluder in its fully open position. Computational fluid dynamics (CFD) simulation using the Fluent 4.4.7 commercial solver was applied in this investigation. This protruded hinge mechanism for pivoting the occluder is an in-house design from the Cardiovascular Dynamics Laboratory, Nanyang Technological University. METHODS: The Fluent 4.4.7 code was run on a Silicon Graphic Inc. computer (4-CPUx185 MHz) in the CFD simulation. A body-fitted coordinates (BFC) grid was generated to cover the entire valvular flow domain, including the interior of the hinge and leaflet. Clearance between the leaflet and pivot housing was 50-70 microm. In the vicinity of the protruded hinge, mesh cells were small compared with hinge dimensions. A power law distribution of grid points was applied to optimize the number of cells used to cluster the entire flow field. The overall computational flow domain of the valve channel, including the floating leaflet and immersed hinge, was approximately 170,000 cells in total. Inside the hinge socket, approximately 10,000 cells were generated. A comparative model with recessed hinge that resembled the SJM valve hinge design was modeled. Due to geometric difficulties, an unstructured grid scheme was applied. Great attention was focused within the hinge pocket, in particular to the clearance between the hinge pivot and leaflet. A total of 2 million cells was generated for the whole computational flow domain. RESULTS: Under steady flow conditions, with the leaflet fixed in an open position, the protruded hinge design yielded a pair of small vortices that formed behind the stoppers. A low-magnitude velocity was observed inside the hinge clearance. Vortices developed behind the protruded stopper. Migrating flow was noted beneath the leaflet clearance as a result of pressure difference across the leaflet. For the recessed hinge design, reverse flow dominated the inside of the hinge socket, and developed into a pair of vortices at high Reynolds number. CONCLUSION: The protruded hinge mechanism was designed to expose the overall hinge region to the mainstream flow for a positive washing effect. Flow in this protruded hinge design is, in general, found to be three-dimensional. Initial results under steady flow conditions showed low laminar and turbulent shear stress, while the hinge clearance was well washed.

Computer Simulation↗
PubMed2001

[Role of metallothionein in the resistance of rat osteoblasts to zinc excess and deficiency].

This study is expected to investigate the role of metallothionein(MT) in the resistance of osteoblasts to high or low zinc conditions. Antisense MT oligonucleotide was used to reduce the content of MT in osteoblast. Cellular MT content was determined by silver/hemolysate saturation method, and the cytotoxicity was measured by the activity of LDH releasing from damaged cells. The results showed that antisense MT oligonucleotide markedly decreased the resistance of osteoblast to zinc excess and zinc deficiency. It suggested that MT played an important role in the modulation and maintenance of intracellular zinc homeostasis of osteoblasts.

Animals↗
PubMed2001

[Geographical divisions of rat transmissible diseases].

In order to prevent rat transmissible diseases, it is necessary to know the geographical distribution of rats, their external parasitic arthropod and rat-borne disease in human, and to make a graph of geographical division. Stratified sampling was conducted by county to capture rats, and to sort out flea for identification of their genus and species. A total of 55,064 rats sorting as 6 families, 17 genera and 21 species were captured, and a total of 34,733 flea sorting as 4 families, 25 genera and 53 species were picked. Three kinds of rat-borne diseases, namely plague, leptospirosis and epidemic hemorrhagic fever have been occurred and epidemic in Shanxi Province. Following the general principles for geographical division, Shanxi Province was divided into 4 sub-regions: (1) basin among mountains and prairie in Yanbei; (2) loess plateau, hill and prairie with shrub in the west; (3) hill, shrub and basin, prairie with forest in the middle part; (4) hill, basin with forest and prairie in the southeast. When bubonic plague was epidemic, its transmissible mode was probably Meriones meridianus--Xenopsylla conformis--Mus musculus, Rattus norvegicus--Xenopsylla cheoopis--human. Bubonic plague has been occurred within Xingxian and Linxian conxian counties of the second sub-region. Leptospirosis has been occurred in Xiangfen county of the third sub-region, the source of infection was from pigs instead of rats. Epidemic hemorrhagic fever has been occurred in the third and fourth sub-regions, the source of infection was mainly from Ruttus norvegicus.

Animals↗
PubMed2001

Trinucleotide repeat analysis of Huntington's disease gene in Singapore.

INTRODUCTION: Huntington's disease (HD) is an inherited neurodegenerative disorder characterised by chorea and progressive dementia. The mutation causing the disease has been identified as an unstable expansion of a trinucleotide (CAG)n. We have assessed the (CAG)n repeats in the patients and controls in our population. MATERIALS AND METHODS: Polymerase chain reactions (PCRs) for the repeat region were carried out for 116 individuals: 10 were asymptomatic at-risk members from 5 families; 53 symptomatic patients from various hospitals; and 53 normal unrelated Singaporeans. Estimation of the number of repeats was based on Metaphor gel electrophoresis, sizing using the GeneScan on ABI 310 Genetic Analyzer, and sequencing using the same equipment. RESULTS: Metaphor gel sizing generally gives an over-estimation, and GeneScan gives an under-estimation of repeat numbers compared with sequencing which is the gold standard. Of the 63 patients and family members tested, 25 had one expanded allele of 40 to 54 CAG repeats and the other allele in the normal range of 15 to 30 repeats. One patient had an allele in the intermediate range (38). CONCLUSION: The range of CAG repeats in the normal and HD alleles in our population is similar to those reported elsewhere. An accurate sizing can only be obtained with sequencing. For allele sizes in the intermediate range (37-40), sequencing should be carried out to confirm the carrier status of a patient.

Adolescent↗
PubMed2001

[Rapid detection of the common alpha-thalassemia-2 determinants by PCR assay].

OBJECTIVE: Most frequent molecular lesions of alpha-thalassemia-2 determinants are deletions of one alpha-globin gene. Satisfactory PCR methodologies for detecting the deletions are required for molecular diagnosis and genetic screening since there was no internal control in most published PCR-based strategies. The purpose of this study is to develop a reliable PCR protocol specific for the two common alpha-thalassemia-2 determinants with internal control. METHODS: The multiple repeat elements and the high GC-content of the alpha-globin locus impose severe limitations on designing suitable primers and optimizing stable conditions for PCR. In this study, two multiplex PCR systems were successfully set up. One was designed to detect the rightward deletion (-alpha(3.7)/) with two pairs of primers including one newly optimized pair for amplification of the internal standard to indicate the success of failure of PCR amplification. The other, to the leftward deletion(-alpha(4.2)/) with three primers, which were designed according to the newly sequenced data of the -alpha(4.2) and HbQ-alpha(4.2) deletions in this lab(Genbank Accession No. AF221717). In the PCR system, one is used as a common upstream primer and the other two are used as specific downstream primers for typing the normal allele and the deletion one, respectively. RESULTS: Easily interpretable, unambiguous amplifications were observed by using the multiplex PCR systems for the detection of the two common alpha-thalassemia-2 determinants. The three or four primers were run in the same tube under the same condition and both of these two systems could be used at the same thermal cycle parameters. For typing the rightward deletion, a mutant-specific amplification of 1.7 kb and a 1140 bp amplified band as a normal and system control were produced. For typing the leftward deletion, two PCR-amplified bands, a 956 bp fragment specific for a -alpha(4.2) gene and a 1140 bp one for a normal allele were found. CONCLUSION: Two sets of PCR systems with internal controls for detecting the most common two alpha-thalassemia-2 determinants have been established and may be suitable for molecular diagnosis and population screening.

Base Sequence↗
PubMed2001

Imaging blood flow in human port-wine stain in situ and in real time using optical Doppler tomography.

BACKGROUND: Optical Doppler tomography (ODT) combines laser Doppler flowmetry with optical coherence tomography to obtain high-resolution images of blood flow in human skin in situ and in real time. OBSERVATIONS: We present a case in which ODT was used on a patient with a port-wine stain (PWS) birthmark to document the change of blood flow in response to laser therapy. It might be possible to use ODT blood flow measurements in situ to assist in assessing the efficacy of laser PWS therapy. If partial restoration of flow occurs immediately or shortly after laser exposure, indicative of reperfusion due to inadequate blood vessel injury, the PWS can be retreated using higher light dosages. Retreatment is continued until the measured Doppler shift is zero due to a permanent reduction in blood flow, indicative of irreversible microthrombus formation in the PWS vessels. CONCLUSIONS: We have demonstrated that ODT may be used for noninvasive imaging of blood vessels in PWS skin. Moreover, ODT will potentially allow laser therapy to be optimized on an individual patient basis by providing a fast, semiquantitative evaluation of the efficacy of PWS laser therapy in situ and in real time.

Humans↗
PubMed2001

[Study of the cytotoxity against human hepatocellular carcinoma cells induced by the MAGE-1 gene modified dendritic cells].

OBJECTIVE: To genetically modify dendritic cells (DC) with a tumor associated antigen gene MAGE-1 and to observe in vitro the cytotoxic effect induced by this genetically modified DC against human hepatocellular carcinoma (HCC) cell line SMMC7721, thus giving a primary verification of the possibility of this genetically modified DC to induce specific antitumor immunity against HCC and serving as a new type of vaccine. METHODS: The MAGE-1 gene was inserted into the retrovirus vector LXSN to construct the recombinant retrovirus LMSN. The monocyte-derived DCs were transfected by LMSN and control virus LXSN respectively as well as a third group was set up as non-transfected control. The MAGE-1 gene expression in LMSN transfected DC was identified by Western blot and the in vitro cytotoxities against SMMC7721 induced by three groups of DC were tested by MTT assay. RESULTS: A recombinant retrovirus LMSN containing the tumor rejection antigen gene MAGE-1 was successfully constructed and the MAGE-1 gene expression in LMSN transfected human monocyte-derived DC was induced. The LMSN transfected DC could induce very high lytic activity against SMMC7721 in vitro with the lytic activity of 78.9%+/-3.6%. Nevertheless, the LXSN transfected DC and non-transfected DC only induced relatively lower lytic activity as 34.7%+/-4.3% and 3.9%+/-2.0%, respectively. The difference of the lytic activities between those three groups as statistically significant (P<0.01). CONCLUSIONS: The MAGE-1 gene transfected DC can induce higher in vitro cytotoxicity against SMMC7721, suggesting the possibility of this genetically modified DC to induce specific antitumor activity and to serve as a new type of vaccine for HCC.

Animals↗
PubMed2001

[Effects of interferon-alpha on recurrence and metastasis of hepatocellular carcinoma after curative resection in nude mice].

OBJECTIVE: To study the effect of interferon-alpha (IFN-alpha) on the recurrence and metastasis of hepatocellular carcinoma (HCC) in nude mice, and to clarify if there is synergistic effect treated by combination of IFN-alpha and all-trans retinoic acid (ATRA). METHODS: The effect of IFN-alpha and/or ATRA on the proliferation of HCC cell lines was measured in vitro. The metastatic model of human HCC in nude mice LCI-D20 was used in present study. Curative resection was performed at 10th day after implantation in 44 nude mice. Drugs were given at the next day after resection. IFN-alpha was administered subcutaneously at doses of 3+/-10(5) U/day, 6+/-10(5) U/day, respectively. ATRA was administered p.o. at a dose of 20 mg/kg/day, and IFN-alpha 6+/-10(5)U/day combined with ATRA 20 mg/kg/day. The mice were sacrificed 35 days after treatment. The recurrent tumor size was measured and the presence of intrahepatic dissemination and lung metastases were recorded. RESULTS: The effect of IFN-alpha and/or ATRA on the proliferation of HCC cells SMMC7721, BEL-7402, BEL-7405, and MHCC97 was not obvious. The combination of IFN-alpha and ATRA had no synergistic effect in vitro. The lung metastatic rate, the liver recurrent rate, the size of main recurrent lesions, the number of intrahepatic disseminating nodules and the largest disseminating nodule of the controlled group was 100%(12/12), 100%(12/12), (1346.3+/-4.2 ) mm(3), 8.2+/-4.4, 864 mm(3), respectively; whereas it was 0, 87.5%(7/8), (8.7+/-2.9) mm(3), 2.3+/-0.6, and 7.8mm(3), respectively in the IFN-alpha 3+/-10(5) U/day treated group(P<0.05); 0, 12.5%(1/8), 0.5mm(3), 2, 0.5 mm(3) in the IFN-alpha 6+/-10(5)U/day treated group(P<0.05); 0, 12.5%(1/8), 1 mm(3), 2.5+/-0.7, 8 mm(3) in the IFN-alpha 3+/-10(5) U/day and ATRA treated group(P<0.05); 87.5%, 100%, (1472.6+/-5.6) mm(3), 7.3+/-3.8, 768.5 mm(3) in the ATRA treated group (P>0.05). CONCLUSIONS: IFN-alpha has an inhibitory effect on intrahepatic recurrence and lung metastasis of human HCC after curative resection in nude mice, and the effect is enhanced with increasing dose. IFN-alpha and ATRA have no synergistic effect according to in vivo and in vitro test. ATRA has no effect on recurrence and metastasis of HCC.

Animals↗
PubMed2001

[The sonochemical-degradation mechanism of toluene in aqueous solution].

The sonochemical degradation of toluene in the airproof aqueous solution was studied, and the mechanism and course of degradation was explored. It was found that the sonication time had great effect on the removal rate of toluene, and the degradation followed a pseudo-first-order kinetic law, and 90%-95% of toluene was removed only after being irradiated for 40 min, types of dissolved gas and pH also had some effects. After aqueous solution was analyzed pH and scanned UV-wavelength and identified components with SMPE-GC-MS, results confirmed that radical-oxidation controlled the sonochemical-oxidation of toluene, and main middle-products included benzaldehyde, bibenzyl, dibutyl phthalate, et al., final products were carbon dioxide and water.

Free Radicals↗
PubMed2001

[Degradation of methamidophos by Saccharomyces rouxii WY-3].

A strain of Yeast WY-3 was isolated from wastewater sample. It is capable of utilizing methamidophos as sole nitrogen and phosphorus sources, and also capable of utilizing methylamine, ethylamine and ammonium sulfate as nitrogen sources except nitrate and hydroxylamine. The yeast could grow in medinm containing 60% glucose and was identified as Saccharomyces rouxii WY-3. The strain contains a high active acid phosphatase. The crude enzyme was applied to a plate of polyacrylanide gel for electrophoresis, then activity was detected as white single band. Inhibiting test showed that sodium fluoride could seriously inhibit the activity of acid phosphatase to release phosphorus from methamidophos, wherease it make no effect on deamination of the strain WY-3 from methamidophos. After methamidophos was degraded by strain WY-3, toxity of the pesiticide reduced obviously, and its portion intermediate, methanol and inorganic phosphorus, were deteted.

Biodegradation, Environmental↗
PubMed2001

[Analysis of several genes using primer extension preamplification based on individual cell].

OBJECTIVE: To analyze several genes at the same time in one individual cell using primer extension preamplification (PEP). METHODS: The whole genome of individual cell was preamplified by PEP using 10 base random oligonucleotides. The aliquots(5 mu liter) from PEP were used to amplify SRY, ZP(3), RhCE, RhD and F VIII genes by nested PCR. RESULTS: The five genes could be amplified following PEP-PCR. Lymphocyte of four genotypes were diagnosed by PEP-PCR; correct diagnoses were obtained in 95.6%. CONCLUSION: At least five genes can be analyzed by PEP-PCR based on one individual cell in this laboratory. This method could be used in preimplantation genetic diagnosis and noninvasive prenatal diagnosis.

Female↗
PubMed2001

[Radiographic study of the development of the permanent teeth].

OBJECTIVE: To study the development of permanent teeth by radiographic methods. METHODS: The permanent teeth development of children ranging from 4-17 years was evaluated from 1709 panoramic radiographs by the Nolla's method. Each tooth was graded from 0 to 10 stage. The average developmental stage for girls and boys were calculated. RESULTS: The average developmental stage and development curves for girls and boys were obtained respectively. For the completion of crown and root development, girls are more advanced than boys by an average of 0.3 and 0.6 years. CONCLUSIONS: Girls are ahead of boys for the development of the permanent teeth. The norms of the maturation of permanent teeth can be used to evaluated the development of the individual teeth.

Adolescent↗
PubMed2001

[Analysis of inductive factors, diagnosis and treatment of 21 cases with pregnancy accompanied with pulmonary edema].

OBJECTIVE: To investigate the inductive factors, the prevention and treatment methods of pulmonary edema during pregnancy. METHODS: The clinical materials of 21 cases of pregnancy with pulmonary edema treated in our hospital from Jan. 1985 to Jan. 2000 were analysed retrospectively. RESULTS: Among 21 patients, 26 pulmonary edema attacked, 9 of them had upper have respiratory diseases, thirteen cases caused by improper infusion. Fourteen cases were well controlled quickly with antiplasm nifedipine, myocardial strength and diuretics. If the symptoms could not be controlled properly, vasodilators were applicated. We had 16 cesarean section under epidural anaesthesia, one vaginal birth, and the other one birth by forceps. CONCLUSIONS: Pulmonary edema in pregnancy usually followed with acute heart failure caused by sever pregnancy induced hypertension. We should pay more attention to the indications of it. During treatment, we should give vasodilators properly, so as to prevent pulmonary edema.

Adult↗