Biomedical subjects

Li-Xin Zhang

Publications and source records attributed to Li-Xin Zhang.

8 recordsLinked to original sources

PubMed2004

Theoretical modeling study of the necrotic field during high-intensity focused ultrasound surgery.

BACKGROUND: High-intensity focused ultrasound (HIFU) is a type of micro-invasive treatment of tumor. It is important to create a guideline for the volume and position of the necrotic field by means of a theoretical model, this being one of the key problems in the clinic application of HIFU. MATERIAL/METHODS: Based on cellular thermo-necrotic theory, a computational model of temperature distribution and, therefore, the necrotic field was developed. A multi-transducer system with non-interferential and self-focused property was devised to provide experimental verification of the theoretical model. RESULTS: The necrotic field resulting from the modeling simulation did not show any evident difference from that of the experiment. The necrotic field of the same heating duration (4 seconds) was found with both modeling and experiment to be spheroid, with its center at the system's geometric focus and a volume of 1x1x2 cm3. CONCLUSIONS: The model of this study may predict the practical volume of the necrotic field as well as the time needed for it to form.

Computer Simulation↗

PubMed2004

[Screening and identification of ovarian carcinomas related genes].

BACKGROUND & OBJECTIVE: Ovarian cancer is the leading cause of death among gynecological malignancies. Up to now, little is known about specific tumor-suppressor genes or oncogenes involved in the ovarian cancer genesis. Thus isolation of new candidate genes and characterization of their role in ovarian cancer genesis will be helpful for understanding the molecular mechanisms and developing protocols for early diagnosis and therapy of ovarian carcinomas. This study was developed to screen and identify genes related to ovarian carcinomas. METHODS: Modified mRNA differential display PCR and reverse Northern dot blot analysis were used to screen and identify different displayed genes between ovarian carcinoma tissue and normal ovarian tissue. The genes were sequenced and analyzed by bioinformatics software. With these gene fragments as probes, in situ hybridization was used to characterize specific gene expression difference between ovarian cancer tissues and normal ovarian tissues. RESULTS: Of 12 differentially expressed genes, 5 were novel genes, 3 were chromosome genomic repeat sequences and the other 4 were known human genes. Furthermore, in situ hybridization analysis indicated that four genes, ZNF361, PSMA2, OCRC13 (a novel gene on chromosome 1) and OCRC4 (a novel gene on chromosome 9) were highly expressed in 36 samples of ovarian cancer tissues but not in 16 samples of normal ovarian tissues (P< 0.05). More interestingly, the gene OCRC4, with 99% sequence homology to mouse spindlin, a member of gene family specially expressed during gametogenesis, was highly expressed in 19 samples of ovarian cancer from total 36 cases (53%), but not expressed in control samples. CONCLUSION: Our observations indicate that the four genes ZNF361, PSMA2, OCRC4, and OCRC13 may be ovarian cancer related genes. It is speculated that novel gene OCRC4 might also be a member of specific gene family, which plays roles during early period of embryo development and tumorigenesis.

Blotting, Northern↗

PubMed2004

[Comparative genomic hybridization analysis of nasopharyngeal carcinoma drug-resistant cell CNE2/DDP and its parent cell CNE2].

BACKGROUND & OBJECTIVE: Developed from fluorescence in situ hybridization (FISH), comparative genomic hybridization (CGH) is a new molecular and cellular technique,used to examine the genomic imbalances,especially the loss and amplification of chromosomes,and to locate these alterations in certain chromosome regions. For a comprehensive understanding of the possible differences in genomic DNA between nasopharyngeal carcinoma drug-resistant and drug-sensitive cells, we analyzed the genomic DNA of a nasopharyngeal carcinoma drug-resistant cell line CNE2/DDP and its parent cell line CNE2 with CGH. METHODS: Genomic DNA was extracted from CNE2/DDP and CNE2 cells, as well as from normal placenta tissue. Fluorescent random primed labeling method was used to label the DNA probes (CNE2 and CNE2/DDP cells with green fluorescein-12-dUTP and normal placenta tissue with red tetramethylrhodamine-5-dUTP). The labeled DNA probes were then co-hybridized with normal lymphocyte metaphase chromosomes. Signals were taken by charge coupled device (CCD) and processed with Quips CGH Program after fluorescent hybridization. The green-to-red fluorescent ratio was calculated automatically and showed with graphs. RESULTS: There were extensive chromosome changes in CNE2, mainly the gain of 1q, 3q, 5p, 6p, 7p, 8q, 9q, 11p, 12q and 19q, and the loss of 4q, 12p, 13p, 14p, 15p, 18, 20q, 21p and 22. However, the CNE2/DDP cells, which come from the CNE2, showed a relatively normal karyotype except loss of 8p and gain of 8q and 19q. Consistent result was achieved after the CNE2/DDP cells were cultured in the medium free of any drugs for over one month. It appears that the CNE2/DDP cell has relative normal and much more stable chromosome constitution than its parent CNE2 cell. CONCLUSION: The CNE2/DDP is a single drug-resistant clone selected from CNE2,which is a blend of sub-clones that have different sorts of chromosome number and structure. It strongly suggests that the appearance of tumor drug-resistance is mainly a select process in which the would-be drug-resistant cell clone be selected from unfavorable survival condition.

Cell Line, Tumor↗

PubMed2003

[Establishment of a human nasopharyngeal carcinoma drug-resistant cell line CNE2/DDP and screening of drug-resistant genes].

BACKGROUND & OBJECTIVE: Chemotherapy constitutes one of the chief supplementary methods in the treatment of nasopharyngeal carcinoma (NPC). However, the appearance of drug resistance often causes failure of chemotherapy. For overcoming drug resistance, it is of great importance to screen drug-resistant associated genes so as to identify potential molecular targets. This study was designed to establish a drug-resistant cell line from a human nasopharyngeal carcinoma cell line CNE2, and to screen human nasopharyngeal carcinoma drug-resistant genes by a new strategy based on improved subtractive hybridization. METHODS: The drug-resistant cell line was established by a program of treating the human nasopharyngeal carcinoma cells CNE2 in the medium with repeated sharp high and then low but gradually increasing concentration of cisplatin. Drug sensitivity was measured by MTT assay. Fluorescence activated cell analysis(FACS) was employed for determining the concentration of fluorescence dye rhodamine 123 within the cells. Cell growth curve, doubling time, and cell morphology were measured and observed. The drug-resistant genes were screened by a new strategy of PCR-based subtractive hybridization. Sequencing and blast analysis were performed after the differentially expressed genes had been verified by reverse dot blotting. The result was further confirmed by RT-PCR. RESULTS: The resistance indexes of CNE2/DDP to cisplatin (DDP), 5-fluorouracil (5-FU), and vincristine (VCR) were 27.9, 227.9, and 55.5, respectively, indicating its multi-drug resistant property. FACS analysis showed that the concentration of rhodamine 123 was much lower in CNE2/DDP cells than in CNE2 cells (12.98 vs. 243.62). The CNE2/DDP cells appeared smaller, more regularly round, and longer doubling time (26 hours vs. 19 hours) than CNE2 cells. Six differentially expressed sequences were discovered using improved subtractive hybridization; all of them were found to be homologous to known genes after sequencing analysis. Three of them were highly expressed in CNE2/DDP cells. Among them, one sequence, which encodes a 79 amino acid protein,known as DC13 protein (DC13), was a function unknown gene which has certain relationship with malignancy. The other two sequences were ubiquitin C gene and NADH dehydrogenase subunit 2 (ND2) gene, respectively. The other three of the six sequences, whose expression were inhibited in CNE2/DDP cells, were cytochrome C oxidase subunit I(COX1), ribosomal protein L27(RPL27),and ribosomal protein S27 (RPS27) genes, respectively. CONCLUSION: A drug- resistant cell line CNE2/DDP, which showed a typical resistant phenotype to anti-cancer drugs was established. The PCR-based improved subtractive hybridization is an effective approach to identify differentially expressed genes. Many genes, both known and unknown, might contribute to the existence of drug-resistant phenotype, through increasing or decreasing their expression.

Antineoplastic Agents↗

PubMed2002

Decreased calcium-dependent constitutive nitric oxide synthase (cNOS) activity in prefrontal cortex in schizophrenia and depression.

To further understand the potential role of nitric oxide synthase (NOS) in schizophrenia and affective disorders, we determined the calcium-dependent constitutive NOS (cNOS) enzymatic activity and protein levels in the prefrontal cortex of postmortem brains of patients with unipolar, bipolar, and schizophrenic disorders and non-psychiatric controls (n = 15 for each group). Protein levels of two NOS isoforms, nNOS and eNOS, were not significantly different from the non-psychiatric controls in any of the patient groups. However, cNOS activity was significantly lower in schizophrenic patients (mean +/- S.E. = 19.1 +/- 3.2 cpm/microg/45 min) than in the control group (28.5 +/- 3.4, P < 0.05). Trends of lower cNOS activity were found in unipolar (20.3 +/- 2.6, P = 0.062) and bipolar patients (20.8 +/- 3.0, P = 0.079). Males had significantly higher NOS activity (25.4 +/- 2, n = 36, P = 0.01) than females (17.3 +/- 1.9, n = 24), but no significant diagnosis and gender interactions were found. To minimize potential effects of extended postmortem interval (PMI) on NOS activity and proteins, the PMI was limited to 30 h and the data (n = 38) were re-analyzed. cNOS activity was significantly (P < 0.05) lower in patients with schizophrenia (15.8 +/- 5.6, P = 0.026) and unipolar depression (18.8 +/- 3.2, P = 0.042) but not in patients with bipolar illness (22.9 +/- 3.4, P = 0.21) than in the control group (29.5 +/- 3.7). cNOS activity was significantly correlated with brain pH in the total sample (r = 0.28, P < 0.05, n = 60) and in the PMI controlled subgroup (r = 0.43, P < 0.01, n = 38). Our data provide evidence of reduced cNOS activity in the postmortem brains of patients with schizophrenia and depression.

Adult↗

PubMed2002

Decreased prefrontal CaMKII alpha mRNA in bipolar illness.

Ca2+/calmodulin-dependent protein kinase II (CaMKII) plays critical roles in neurotransmission, synaptic plasticity, learning and memory. The aim of this study was to examine, by in situ hybridization, prefrontal cortical expression of CaMKII alpha mRNA in postmortem brains of unipolar, bipolar, schizophrenic, and control subjects. Compared to controls, bipolar patients had significantly lower levels of CaMKII alpha mRNA in laminae I-VI of Brodmann's area 9 and laminae I-III and VI of area 46. Unipolar patients also exhibited significantly lower levels of CaMKII alpha mRNA in laminae I-IV of area 9 than did controls. The significant decrease in CaMKII alpha mRNA in bipolar patients could be associated with some of the affective and cognitive alterations that have been linked to prefrontal cortical dysfunction in bipolar disorder, although this requires further direct examination.

Analysis of Variance↗

PubMed1996

Purification and Characterization of a DTT-sensitive Protease Associated with PS II Particles.

A DTT-sensitive protease was purified by hydrophobic chromatography on butyl-Toyopearl 650 M and anion-exchange chromatography on DEAE-Sephadex A-50 from the 1 M NaCl extract of PS II particles. The results of SDS-PAGE and gel-filtration chromatography on Superose 12 Have showed that it is a monomeric protease with a MW of 37 000. The protease generated polypeptides of 13.2 kD, 12 kD and 10.5 kD fragments from 18 kD protein, and those of 23 kD, 22 kD and 20 kD fragments from 24 kD protein, respectively. The protease had maximum activity at pH 8.0, and showed to be sensitive to DTT and beta-Me but insensitive to the ionic strength of NaCl. Studies with protease inhibitors suggested that this enzyme is not a serine-protease.

Journal Article↗

PubMedDate not supplied

Adaptive designs for sequential experiments.

Various adaptive designs have been proposed and applied to clinical trials, bioassay, psychophysics, etc. Adaptive designs are also useful in high cost engineering trials. More and more people have been paying attention to these design methods. This paper introduces several broad families of designs, such asthe play-the-winner rule, randomized play-the-winner rule and its generalization to the multi-arm case, doubly biased coin adaptive design, Markov chain model.

Clinical Trials as Topic↗