Biomedical subjects

B Dai

Publications and source records attributed to B Dai.

At least 19 recordsLinked to original sources

PubMed2001

[Tumor targeted expression of adenovirus mediated CDglyTK gene regulated by irradiation via Egr-1 promoter].

OBJECTIVE: To construct adenoviral vecter of AdEgr-CD/TK in which CDglyTK gene was driven by Egr-1 promoter, and control the tumor targeted expression of CDglyTK gene by gamma irradiation so as to observe the effects of gene-radiotherapy of liver cancer. METHODS: Adenoviral vector of AdEgr-CD/TK was generated through homologous recombination in bacteria. The expression of CDglyTK gene in MM45T. Li cells infected with AdEgr-CD/TK and exposed to different doses of gamma irradiation were analyzed, and the relative survival rate of the cells in presence of prodrugs 5-FC and GCV was tested. In addition, the tumor suppression effects of different treatments were investigated in 64 mice bearing liver cancer by observing the size of tumor at interval of four days. RESULTS: In vitro experiment showed that gamma irradiation markedly and dose-dependently induced CDglyTK expression in MM45T. Li tumor cells, and significantly enhanced the sensitivity of MM45T. Li cells infected with AdEgr-CD/TK to prodrugs 5-FC or GCV resulting in cell being killed (P < 0.01). A synergetic cytotoxic effect was found when both 5-FC and GCV were added. In vivo experiment revealed that, compared with other control treatments, intratumoral injection of AdEgr-CD/TK combined with intraperitoneal injection of GCV + 5-FC and TLI obviously suppressed tumor growth (P < 0.01), with 30% of the tumor eradicated completely while without causing the increase of whole body cytotoxic effect. CONCLUSION: Tumor targeted expression of CDglyTK gene under the control of irradiation represents a novel strategy for safe and effective gene therapy of cancer and might have wide application in the future.

Adenoviridae↗

PubMed2001

Recording of spared motor evoked potentials and its augmentation by 4-aminopyridine in chronic spinal cord-injured rats.

OBJECTIVE: To research the direct electrophysiological evidence of discomplete spinal cord injury (SCI) and the effect of 4-aminopyridine on it. METHODS: Motor evoked potentials (MEPs), both spinal cord recorded MEPs (scMEPs) and extracellularly recorded MEPs (exMEPs) were recorded and characterized on a T13 epidural electrode (scMEPs) and an extracellular microelectrode (exMEPs) for 10 normal rats and 40 rats with lesions of various severity (sham, 35 g.cm force (gcf), 70 gcf, 100 gcf impact injury) at the T8-T9 cord using the Allen's drop model. The incline plane and Tarlov techniques were used to assess clinical neurological function. RESULTS: MEPs in the normal rats were elicited by applying transcortical suprathreshold stimulation consisting of 3-4 early negative peaks (N1, N2, N3 and N4) followed by several late waves. The N1 and N2 peaks were largest in the anterior and ventrolateral funiculus, respectively, which was indicative of extrapyramidal pathways. The 100 gcf impact injuries and the cord transection abolished the MEP distal to the lesion, whereas the 35 gcf injuries resulted in a latency shift and amplitude decrement of the MEP peaks. Eighteen of the 20 rats with 70 gcf-injuries showed clinical paraplegia. Among them, 7 rats had neurophysiological evidence of residual conduction pathways through the lesioned cord segment, such as the presence of N1 and N2 peaks in the scMEPs or exMEPs. After 4-aminopyridine (4-AP) administrations (1 mg/kg), the amplitude of the spared exMEP increased significantly and spread more widely. CONCLUSIONS: MEPs evoked by transcortical stimulation travel mostly in the extrapyramidal tract. MEP monitoring could provide an excellent method of detecting the functional integrity of the motor tracts after SCI, and could even detect spared motor fibers after discomplete SCI. Furthermore, the use of 4-AP or other K+ channel blocking agents may be a potential treatment for patients with chronic moderate to severe SCI.

4-Aminopyridine↗

PubMed2001

[Changes in cyclin expression during proliferation and differentiation of CD34(+) cells derived from fetal liver induced by thrombopoietin].

In order to elucidate the intrinsic mechanism underlying proliferation and differentiation of megakaryocytes during ontogenesis, CD34(+) cells were isolated from human fetal liver (FL) with a high-gradient magnetic sorting system (MACS) and were incubated in liquid suspension with 50 and 100 ng/ml of thrombopoietin (TPO) and in MegaCult(Tm) -C semi-solid culture system with 0, 12.5, 25, 50, 100, and 200 ng/ml of TPO. The cell number, colony number of CFU-Mk, platelet-associated antigen phenotype, and DNA ploidy of CD41(+) cells were examined from d 0 to d 12 in culture. The expression patterns of cyclins B1, D1, and D3 were also analyzed by using immunoblot and flow cytometry. TPO stimulated proliferation of CD34(+) cells of FL from 1 x 10(5)/ml to 13.12 +/-4.06 10(5)/ml with 95% of CD41a(+) cells and 3% of CD34(+) cells after 12 d of culture. Most of the megakaryocytes (MKs) derived from FL were in 2 N ploidy class, and few in 4 N ploidy class, but no megakaryocytes ploidy class was higher than 4 N. The effect of TPO on the formation of CFU-Mk colonies from FL derived CD34(+) cells is shown in a dose-response curve. The expression of cyclin B1 increased progressively and the high level of cyclin B1 was maintained in FL CD34(+) cells induced by TPO during 12 d of culture. A high level of cyclin B1 appeared on FL derived MKs of G1 phase at d 12. The expression of cy-of cyclins D1 and D3 gradually increased in FL CD34(+) cells, which was induced by TPO during the initial 6-day incubation. Afterwards, the level of cyclins D1 and D3 decreased progressively, particularly in MKs which were in G2+M phases. These data suggest that (1) TPO induced proliferation and differentiation of FL derived CD34(+) cells through upregulation of cyclin B1 in G2+M phases and cyclins D1 and D3 in all phases of cell cycle, and (2) Continuing high level of cyclin B1 and decreases of cyclins D1 and cyclin D3 on MKs in G2+M phases may contribute to a retardation of MK endoreduplication.

Antigens, CD34↗

PubMed2000

Identification of a novel cis element required for cell density-dependent down-regulation of insulin-like growth factor-2 P3 promoter activity in Caco2 cells.

The activity of the exogenous, full-length insulin-like growth factor-2 (IGF-2) P3 promoter is significantly up-regulated during the logarithmic growth phase but rapidly declines in confluent CaCo2 cells undergoing differentiation. Nuclear run-on assays confirmed cell density-dependent regulation of endogenous P3 promoter. To identify regulatory elements in the P3 promoter that may be required for regulating cell density-dependent transcriptional activity, we used the methods of promoter truncation, electrophoretic mobility shift assay, DNase footprinting, and mutation analysis. The relative activity of the full-length (-1229/+140) and truncated (-1090/+140) promoter was identical, being approximately 19, 27, 7, and 3% of pSV-luc activity on days 3, 5, 7, and 9 of cell culture, respectively. However, truncation to -1048 resulted in complete loss of cell density-dependent down-regulation of P3 promoter activity on days 7 and 9, suggesting the presence of regulatory elements between -1091 and -1048 sequence. Further stepwise truncation to -515 did not change promoter activity. Truncation to -138/+140 resulted in complete loss of promoter activity, suggesting that the core promoter was within the -515/-138 segment. A 14-base pair footprint (-1084/-1070) was identified by DNase footprinting within the distal -1091/-1048 segment. Electrophoretic mobility shift assay with wild type and mutant probes confirmed the presence of a novel 7-base pair (CGAGGGC) (-1084/-1078) cis element (P3-D); its mutation abolished binding. Functionality of P3-D cis element was confirmed by measuring the activity of core P3 promoter ligated to distal P3 segment containing either the mutant or wild type P3-D element. We have, therefore, identified a novel cis element, P3-D, that appears to play a critical role in regulating IGF-2 P3 promoter activity in a cell density/differentiation-dependent manner.

Base Sequence↗

PubMed2000

Autocrine gastrins in colon cancer cells Up-regulate cytochrome c oxidase Vb and down-regulate efflux of cytochrome c and activation of caspase-3.

Suppression of the gastrin gene in human colon cancer cells by stably expressing antisense (AS) gastrin RNA results in significant growth suppression of AS cells. To understand mechanisms mediating the growth effects of autocrine gastrins, differential expression of transcripts by AS and control (C) clones of a representative cell line (HCT-116) was analyzed to identify target genes of autocrine gastrins. Six differentially expressed transcripts were confirmed and sequenced. Of these, the RNA and protein levels of cytochrome c oxidase (COX) Vb were significantly higher in C versus AS cells. The expression of COX Vb by colon cancer cells was proportional to the expression of gastrin. Higher levels of COX Vb coprecipitated with cytochrome c in the mitochondria of C versus AS cells. Treatment of mitochondria with digitonin resulted in a 2-fold higher release of cytochrome c from AS versus C mitochondria. As a corollary, the cytosolic levels of cytochrome c were significantly higher in AS versus C cells, which correlated with approximately 2- and approximately 3-fold higher activation of caspase-9 and -3, respectively, in AS versus C cells in response to camptothecin. Thus, autocrine gastrins may support growth/survival of cells by up-regulating COX Vb, which may decrease the sensitivity of the cancer cells to apoptotic stimuli by increasing retention of cytochrome c in mitochondria.

Colonic Neoplasms↗

PubMed2000

Interactive software for generation and visualization of structured findings in radiology reports.

OBJECTIVE: Our objectives were to develop a user-friendly graphic interface for a module that integrates traditional radiology reporting, natural language processing, and editing capabilities; to facilitate the structuring of radiology reports as part of routine clinical practice; to use a commercial speech recognition module for online transcription; and to implement the module in a hardware-independent environment. CONCLUSION: After implementation, the module was tested with 150 chest radiology reports by two radiologists and assessed for ease of use and accuracy. Overall, accuracy was close to 90% and user satisfaction was high. When radiology reports are structured as a part of routine clinical practice, it is possible to accomplish intelligent indexing and retrieval to facilitate teaching and research.

Medical Records Systems, Computerized↗

PubMed2000

Evaluation of SNOMED3.5 in representing concepts in chest radiology reports: integration of a SNOMED mapper with a radiology reporting workstation.

Standardized medical terminologies are gaining importance in the representation of medical data. In this paper, we present the evaluation of the SNOMED3.5 medical terminology to code concepts routinely used in chest radiology reports. Integration of this terminology mapper into a radiology reporting workstation that incorporates a speech recognition system and a natural language processor is also discussed. A total of 700 anatomical location terms (including synonyms) were tested and 72% of the terms had corresponding SNOMED terms. Of the 28% that did not result in a match, 16% were either morphological variants of SNOMED terms or could be found from a combination of terms from two or more SNOMED axes. Only 12% of the terms (primarily specialized radiology terms) were concepts not actually included in the SNOMED terminology.

Humans↗

PubMed1999

Initial experiences with building a health care infrastructure based on Java and object-oriented database technology.

A multi-tiered telemedicine system based on Java and object-oriented database technology has yielded a number of practical insights and experiences on their effectiveness and suitability as implementation bases for a health care infrastructure. The advantages and drawbacks to their use, as seen within the context of the telemedicine system's development, are discussed. Overall, these technologies deliver on their early promise, with a few remaining issues that are due primarily to their relative newness.

Database Management Systems↗

PubMed1998

Differential activation of IGF-II promoters P3 and P4 in Caco-2 cells during growth and differentiation.

BACKGROUND & AIMS: Insulin-like growth factor (IGF)-II gene is overexpressed in colon cancers. Transcriptional up-regulation may be the major mechanism contributing to its overexpression. IGF-II messenger RNA (mRNA) levels are up-regulated during proliferation followed by a significant decline during differentiation of Caco-2 cells. Mechanisms underlying transcriptional regulation of the IGF-II gene promoters (P1-P4) have yet to be examined in colon cancers, which was the basis for this study. METHODS: Ribonuclease protection assay was used to measure IGF-II mRNA derived from P1-P4. To determine if changes in the IGF-II transcripts reflected differences in promoter activity, transient transfection assays with the full-length P1-P4-luciferase expression vectors were performed. RESULTS: Both P3- and P4-derived transcripts were significantly up-regulated during the proliferative phase of the cells (days 3-6 in culture) and declined rapidly in cells undergoing differentiation (days 7-10); conversely, P1- and P2-derived transcripts were not detected. Similarly, transcriptional activity of P3 and P4 promoters reached peak levels by days 4-6 and declined rapidly thereafter. P1 and P2 were relatively inactive on all days. CONCLUSIONS: The activity of the P3 and P4 promoters may play a selective role in regulating IGF-II mRNA levels during growth and differentiation of colon cancer cells.

Caco-2 Cells↗

PubMed1998

Design and development of an interactive medical teleconsultation system over the World Wide Web.

The objective of the medical teleconsultation system presented in this paper is to demonstrate the use of the World Wide Web (WWW) for telemedicine and interactive medical information exchange. The system, which is developed based on Java, could provide several basic Java tools to fulfill the requirements of medical applications, including a file manager, data tool, bulletin board, and digital audio tool. The digital audio tool uses point-to-point structure to enable two physicians to communicate directly through voice. The others use multipoint structure. The file manager manages the medical images stored in the WWW information server, which come from a hospital database. The data tool supports cooperative operations on the medical data between the participating physicians. The bulletin board enables the users to discuss special cases by writing text on the board, send their personal or group diagnostic reports on the cases, and reorganize the reports and store them in its report file for later use. The system provides a hardware-independent platform for physicians to interact with one another as well as to access medical information over the WWW.

Internet↗

PubMed1998

[Immunoprotection in guinea pigs using DNA recombinant plasmid rpDJt and expressed protein P68 in L. interrogans serovar lai].

Immunoprotection against the infection by Leptospira interrogans serogroup Icterohemorrhagiae serovar lai strain 017 was demonstrated in guinea pigs vaccinated with DNA recombinant plasmid rpDJt and expressed protein P68 derived from genomic library of Leptospira strain 017. Thirty days after active immunization, each group received intraperitoneally (1/2 dose) and subcutaneously (1/2 dose) inoculum of L. interrogans serovar lai stain 017; cultures were adjusted to 5 x 10(8) cells/ml. All guinea pigs were observed for 10 days after challenge. Survival (%) of P68 group was 100(7/7); P23 group was 75(3/4); group rpDJt was 77(10/13); group lack recombinant (control) pT7-7 was 25 (3/12), and group with whole-cell inactivated vaccine was 93(13/14). Although the protective antigen in the leptospires has yet to be determined, it is evident that expressed protein P68 conferred a high degree of immunoprotection in guinea pigs.

Animals↗

PubMed1998

[Nucleotide sequence analysis of a species specific probe by an inserted fragment from recombinant plasmid pCX7 of L. interrogans sensu stricto serovar lai].

The etiological agents of leptospirosis are the pathogenic leptospires (L. interrogans sensu lato) which can be divided into 223 serovars organized into 23 serogroups. The serovar remains the basic taxon, but serotyping may now be accomplished and recognized by acceptable methods. Complementary molecular approaches are being used extensively to assess genetic relatedness amongst leptospires with restriction endonuclese analysis (REA), pulse field gel electrophoresis (PFGE) and DNA-DNA hybridization as well established tools. However, the method is cumbersome and unsuitable for routine application. To develop a sensitive and specific method for identification of pathogenic leptospires, a genomic library of L. interrogans sensu stricto serovar lai was constructed with the plasmid vector pUC9. A recombinant plasmid, designated pCX7 which has homologous fragment of pathogenic leptospires was screened from the bank. pCX7 could recognize pathogenic leptospiral DNA fragment 1.7 kb of strain 017 without cross hybridization to nonpathogenic leptospiral DNA. Inserted fragment of pCX7 DNA sequencing was performed by Dr. Yan Zhengxin (Max-Plank-Institut fur Biology, Tubingen, Germany). Insert fragment was cloned into pBluescript and sequenced by using ABI(Applied Bio. Systems, Model 373A). Nucleotide sequences were analyzed by Dr. Xiao Jianguo (Texas University Medical School and School of Public Health, Center for Infectious Diseases) using a suit of computer program (NIH). One open reading frame of 306 nucleotids were identified. There were identifiable initiation codons, terminators, pribnow box and sextama box within the sequenced regions. These results further confirmed that the little homology between L. interrogans sensu strito and L. borgpeterseni serovar javanica, L. inadai serovar ranarun and serovar manhao (L. genomospecies 2), L. biflexa serovar patoc, L. illini. pCX7 DNA probe could provide a base for identification and classification of leptospires.

DNA, Bacterial↗

PubMed1998

[Cloning, characterization and expression in E. coli of the flagellin gene from Leptospira interrogans Serovar lai].

To obtain a large amount of recombinant endoflagellin protein of leptospsira, we have cloned the fla B gene from Leptospira interrogans serovar lai strain 017, which encodes the core flagellar protein. The entire open reading frame was amplified by polymerase chain reaction, which was digested with endonucleases Sal I and Cla I, then was orientationally cloned into the expression vector, pT7-7. The recombinant plasmid was transformed into Escherichia coli JM109 (DE3) for expression. After induction with IPTG, a 34 kd expression protein was detected by SDS-PAGE. The amount of recombinant protein was estimated as 11.8% of the whole bacterial lysate proteins. Probed with insert fragments, Southern blot analysis indicated that possibly two gene related to fla B were present in the genome of Leptospira interrogans serovar lai stain 017. Western blot analysis showed that the 34 kd expression protein reacting with rabbit polyclonal antiserum raised against leptospira endflagellin.

Cloning, Molecular↗

PubMed1998

[Analysis of molecular karyotype of Leishmania isolates from hilly foci and plain foci of China].

AIM: To analyse the molecular karyotypes of Leishmania isolates from hilly and plain foci of China. METHODS: Pulsed field gel electrophoresis(PFGE) was performed in 1% agarose at 6 V/cm in 0.5 x TBE at 14 degrees C with a pulse time of 60 s for 15 h and a pulse time 90 s for 9 h. RESULTS: Each isolate was resolved into 15 different EtBr-staining bands ranging in size from 200 to 2,200 kb, in which the karyotypes of 6 isolates from hilly foci were similar (including karyotypes of canine isolates similar with those of human isolates), and they were partly similar with those of L. infantum. The karyotypes of the two isolates from plain foci were similar, but the isolates from the two topographically different foci were different from each other. CONCLUSION: Homology exists between L. d. isolates from hilly foci and plain foci respectively, and exists in part between L. d. isolates from hilly foci and L. infantum; while heterogeneity exists between L. d. isolates from hilly foci and plain foci. The reservoir host, domestic dog, plays an important role as the infection source of leishmaniasis in the hilly foci of China.

Animals↗

PubMed1997

First trial of home ECG and blood pressure telemonitoring system in Macau.

OBJECTIVE: To determine the feasibility of home monitoring of patients with cardiac disease or hypertension. METHODS: An improved home electrocardiographic and blood pressure telemonitoring system linked to a central workstation was tested in 10 patients in Macau for 3 months. RESULTS: The total number of connections was 1377. Of the automatic alarm connections, 32.5% were false positive, with the percentage of false positives ranging from 7.6 to 54.6 for different patients. Both patients and physicians found the system easy to use. CONCLUSIONS: Further investigation is required to match the number of patients with the system capacity. A more robust dysrhythmia detection algorithm is needed to reduce the number of false alarms. Nevertheless, the results were sufficiently good that the trial is being expanded.

Blood Pressure Determination↗

PubMed1997

Cloning of the functional promoter for human insulin-like growth factor binding protein-4 gene: endogenous regulation.

The majority of the colon cancers analyzed to-date express insulin-like growth factor binding protein (IGFBP)-4, and antisense inhibition of IGFBP-4 messenger RNA (mRNA) confers a growth advantage to the cells in response to endogenous and exogenous IGFs. We recently reported a significant up-regulation of IGFBP-4 expression in a human colon cancer cell line (CaCo2) on spontaneous differentiation of the cells in culture. This suggests that the expression of IGFBP-4 may be related to growth and differentiation of colon cancer cells. To study the endogenous factors involved in the transcriptional regulation of IGFBP-4, we have isolated and sequenced the human (h) IGFBP-4 promoter. The approximately 1.3 kilobase pair (kb) 5' flanking region of the IGFBP-4 gene is GC rich and possesses several potential regulatory elements. These elements include a typical TATA box with sequence TATAA, located -299 nt from the initiation ATG codon. The cap site is located 14 nt downstream of the TATA box as determined by primer extension analysis. A 1.4-kb DNA fragment including the 1.254 kb 5' flanking region of the hIGFBP-4 gene was subcloned into a luciferase reporter vector (pGL-2 basic) either in the sense (BP-4-S-pGL) (S) or antisense (BP-4-AS-pGL) (AS) (negative control) orientation, relative to the luciferase coding sequence in the vector. CaCo2 cells were transfected with either the S or the AS vectors on days 2-10 of culture; cotransfection with the SV40-beta-Galactidose (Gal) vector was used to correct for transfection efficiency. The ratio of luciferase/beta-Gal expression by CaCo2 cells transfected with the S vectors increased significantly from days 3 and 4 to days 5 and 6 of culture, followed by a sharp decline on days 7-9, resembling the pattern of endogenous expression of IGFBP-4 by the cells; the expression of luciferase by the AS vectors remained low and insignificant. These results thus suggest that the approximately 1.4 kb 5' flanking region of the IGFBP-4 gene contains the cis elements required for regulation of the IGFBP-4 gene. Cloning and sequencing of the functional hIGFBP-4 promoter will enable us, for the first time, to study the endogenous factors/mechanisms responsible for the growth/differentiation (cell density) associated regulation of IGFBP-4 expression in colonic epithelial cells.

Base Sequence↗

PubMed1997

A home electrocardiography and blood pressure telemonitoring system.

A home electrocardiography (ECG) and blood pressure telemonitoring system for cardiac patients was installed in the Macau region. The monitoring centre was established in the emergency unit at the Government Hospital of Macau. The first users were 10 cardiovascular patients selected by a physician. The average age of these users was 61 years (range 30-78). The results of a three-month trial showed that the system was easy to operate and technically reliable. It was found to be helpful for cardiac patients. The most significant problem during the trial was electrical noise from the ECG electrodes.

Adult↗

PubMed1997

[Immunogenecity of expressed protein p68 from recombinant plasmid rpDJt in L. interrogans serovar lai].

There are two types of infection caused by pathogenic microorganisms, intracellular infection and intercellular infection. Infection of pathogenic leptospira is an intercellular infection. The immunological reaction of host to intercellular infection is unique. The potential immunogen of an expressed protein should meet three criteria: it can be degraded (by antigen-present cells in the host); it should have antigenic epitope which can be recognized by specific antibodies and have at least one epitope that can be recognized by an MHC II protein and T cell receptor. In this study we report the cloning of an L. interrogans protein in plasmid rpDJt and the immunogencity of the expressed protein derivative. A genomic library of L. interrogans serovar lai strain 017 was constructed with the plasmid vector pUC18. Recombinant plasmids, designated pDJH2 and pDJ8 were screened from the bank. EcoRI-inserted fragment of 1. 9 kb recombinant DNA of pDJH2 was ligated into T7 RNA polymerase/promoter vectors (pT7-7). Then they were transformed into E. coli JM109 (De3), one of subclones, designated rpDJt was achieved. SDS-PAGE showed that the molecular weights of expression proteins were 68 kd and 23 kd respectively, designated p68 and p23. Purifying and isolating p68 and p23, we separated them from SDS-Polyacrylamide gels by using Side-Strip method. After fragmenting and electroeluting, p68 and p23 were injected into guinea pigs and rabbits. An extremely strong immune response to p68 was obtained since an anti-p68 antibody response could be detected to a dilution 1:524,288 (guinea pigs) and 1:262,144 (rabbits) by ELISA while anti-P23 antibody being 1:1024 (the same to guinea pigs and rabbits). The results of improved MTT and conA 3HTdR transformation methods showed the activities and proliferation of Th-cells were increased in guinea pigs after p68 immunization (IL-6, 83.25 IU/ml, IL-2, 28.75 IU/ml; RPI, 2.04, SI, 65.62%) Thlymphocyte existed in two subclasses, the Th1- and Th2-cells. A major role of Th2-cells is to "help" B-cells differentiate, replicate, and secrete antibody. The properties of these interactions explain why p68 makes good antigen and p23 does not. The antigens responsible for eliciting the production of protective antibodies are not known; however, several outer membrane proteins on L. interrogans are candidates for vaccine. Our results suggest that expresion protein p68 from recombinants (rpDJt) may be a candidate for gene engineered subunit vaccine for Leptospirosis.

Animals↗