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Biomedical subjects

J Tan

Publications and source records attributed to J Tan.

At least 181 records · Page 10Linked to original sources
PubMed1997

Outcomes after cervical cold knife conization with complete and incomplete excision of abnormal epithelium: a review of 699 cases.

A retrospective analysis was undertaken of 699 cone biopsies performed at the Royal Women's Hospital in Melbourne from 1966 to 1992. In 572 cases (82%), abnormal epithelium was assessed as having been completely excised, and in 127 (18%) excision was incomplete. There were no significant differences in age, parity, cytology, histology, or indications for conization between patients in whom excision was incomplete and those in whom complete excision was achieved. Of the patients whose cone biopsy histology showed complete excision of abnormal epithelium, 96.7% were found to have been cured of disease on the basis of normal follow-up or normal histology of hysterectomy specimens. The overall cure rate after incomplete cone biopsy was found to be 77%, but was influenced by the site of incomplete excision. The cure rate for incomplete excision at the ectocervical margin was 86%; incomplete excision at the endocervix was 68% and only 40% if excision was incomplete at both edges. Cone biopsy undertaken for cervical intraepithelial neoplasia is likely to be curative when the lesion is completely excised, but recurrent disease may occur and adequate follow-up is an essential part of patient management after conization, regardless of histological findings in the conization specimen. Most cases of incompletely excised cervical intraepithelial neoplasia will also be cured, especially if the incomplete margin is ectocervical, and cytological and colposcopic follow-up may be an acceptable alternative to repeat cone biopsy or hysterectomy in the management of such cases.

Adolescent↗
PubMed1997

Applying epidemiological principles to ergonomics: a checklist for incorporating sound design and interpretation of studies.

The primary purpose of this paper is to provide a checklist of scientific requirements necessary for the design of sound ergonomics studies. Ergonomics researchers will be able to use the checklist when designing a study and preparing it for publication. Practitioners can use the checklist to critically appraise study results, thereby having greater confidence when applying ergonomic recommendations to the workplace. A secondary purpose of the paper is to pilot the checklist on a sample of papers in the ergonomics literature and to assess its reliability. While there are checklists to assess the epidemiological rigour of studies, none have been adapted to address methodological issues in ergonomics. Two epidemiologists independently searched five ergonomics journals (Applied Ergonomics, Ergonomics, Human Factors, International Journal of Human-Computer Interaction and Journal of Human Ergology) for research studies on VDT use and visual function published between 1990 and 1995. Twenty-one articles were reviewed. Each paper was scored according to the checklist. Overall, the reviewers found that the articles did not consistently fulfill some of the checklist criteria. An insufficient sample size was the most serious omission. Inter-rater reliability of the checklist was excellent for 11 of 14 items on the checklist (Kappa > 0.74), good for two items (Kappa between 0.40 and 0.74) and poor for one item. As ergonomics is gaining acceptance as an integral part of occupational health and safety, individuals in this field must be cognizant of the fact that study results are being applied directly to workplace procedures and design. It is incumbent upon ergonomists to base their work on a solid research foundation. The checklist can be used as a tool to improve study designs and so ultimately has implications for improving the fit between the worker and the work environment.

Computer Terminals↗
PubMed1997

Dehydroepiandrosterone activates mutant androgen receptors expressed in the androgen-dependent human prostate cancer xenograft CWR22 and LNCaP cells.

An androgen receptor (AR) gene mutation identified in the androgen-dependent human prostate cancer xenograft, CWR22, changed codon 874 in the ligand-binding domain (exon H) from CAT for histidine to TAT for tyrosine and abolished a restriction site for the endonuclease SfaNI. SfaNI digestion of AR exon H DNA from normal but not from prostate cancer tissue indicated H874Y is a somatic mutation that occurred before the initial tumor transplant. CWR22, an epithelial cell tumor, expresses a 9.6-kb AR mRNA similar in size to the AR mRNA in human benign prostatic hyperplasia. AR protein is present in cell nuclei by immunostaining as in other androgen-responsive tissues. Transcriptional activity of recombinant H874Y transiently expressed in CV1 cells in the presence of testosterone or dihydrotestosterone was similar to that of wild type AR. With dihydrotestosterone at a near physiological concentration (0.01 nM), H874Y and wild type AR induced 2-fold greater luciferase activity than did the LNCaP mutant AR T877A. The adrenal androgen, dehydroepiandrosterone (10 and 100 nM) with H874Y stimulated a 3- to 8-fold greater response than with wild type AR and at 100 nM the response was similar with the LNCaP mutant. H874Y, like the LNCaP cell mutant, was more responsive to estradiol and progesterone than was wild type AR. The antiandrogen hydroxyflutamide (10 nM) had greater agonist activity (4- to 7-fold) with both mutant ARs than with wild type AR. AR mutations that alter ligand specificity may influence tumor progression subsequent to androgen withdrawal by making the AR more responsive to adrenal androgens or antiandrogens.

Androgen Antagonists↗
PubMed1997

[Medicine S inhibits class II MHC expression of intragraft renal in rats].

The Purpose of this study was to address the mechanism of medicine S which has anti-rejection effects of renal allografts in rats. Kidney transplantations were performed from SD to Wistar strain (allogeneic) and from Wistar to Wistar (Isograft) using the same modified technigue described by Fabre and kamada. Experimental rats were divided into five groups. Group I (Isograft group) and group II (allograft group) as controls were not treated with medicine. The others were allograft groups which received medicine S, Cyclosporine A, and low-dose Cyclosporine combined with medicine S, respectively. Renal function and resultant morphology changes were assessed 2, 4 weeks after transplantation. All sections of kidney grafts were stained with monoclonal antibody class II MHC (OX6), and then the surface densities of positive staining were quantified by computer image analysis. The level of molecular expression in group II was significantly increased (7.61 +/- 0.57 vs 0.51 +/- 0.2 of group I, P < 0.01). In groups I and IV, the molecule of expression was reduced, compared with the groups II, III and V (P < 0.05). The results suggest that medicine S decreases the level of class II MHC expression and medicines combined with lowe-dose cyclosporine is more effective than cyclosporine alone.

Animals↗
PubMed1997

[Effect of haemorrheological changes on acute pancreatitis].

This study sought to determine the effect of the haemorrheological changes on the pathological damage to pancreas in acute pancreatitis. 96 Wistar rats, four months old, were allocated into three groups: group I (n = 32) received surgery for pancreatic duct obstruction (PDO) with secretion stimulation; group II (n = 32) for PDO with high molecular dextran (DX110) injection intravenously, and group III (n = 32) for PDO with secretion stimulation and DX110 injection intravenously. Ten other rats were used as controls (group IV) for laparotomy alone. The results showed that PDO with hypersecretion could induced edematous pancreastitis and PDO with DX110 injection induced only very lightly oedema in the pancreas which was similar to the result of PDO alone, although the haemorrheological changes were obvious in these rats. PDO with hypersecretion and DX110 injection induced acute necrotic pancreatitis, and the pathological lesion in the pancrease which changed gradually from edematous to necrotic could be observed. This result suggests that haemorrheological change may not be a causative factor of the acute necrotic pancreatitis, but it probably could exacerbate the damage to pancreas in acute pancreatitis and play an important role in the transformation from edematous to necrotic pancreatitis.

Animals↗
PubMed1997

[Bone histomorphometric changes in ovariectomized goat at different time courses].

Using histopatholoical method, we investigated the bone histomorphometric changes in ovariectomied goats at different time courses. Eight goats, female, aged one and a half years, were randomly divided into two groups, the control and the ovariectomy (OVX). Iliac crest biopsies were separately processed before ovariectomy and at 60 days, 120 days and 180 days after ovariectomy. The histomorphometric changes were observed. It was found that the bone structure in trabecular bone remained relatively constant in the control group throughout the whole study. In contrast, the trabecular quantity was slightly decreased and the trabeculae were disconnected in OVX at 60 days after ovariectomy. The bone structure was characterized by the thinning of the trabeculae, the further discontinuance and quantity loss of trabeculae, and the anlargement of marrow cavity at 120 days to 180 days after ovariectomy. Apparently, these bone structural changes manifested with typical osteopenia pathological changes. Our results may serve as a basis for the design of further studies using OVX goat as an animal model for postmenopausal osteoporosis.

Animals↗
PubMed1997

Changes of plasma tPA and PAI activities in patients with diabetic retinopathy.

PURPOSE: To investigate the relationship between the diabetic retinopathy (DR) and the activity of plasma tissue plasminogen activator (tPA) and plasminogen activator inhibitor (PAI). METHODS: tPA and PAI activities were measured by chromatogenous substrate assay in plasma samples obtained from patients with and without diabetic retinopathy (n = 42). Retinopathy was determined by stereoscopic color fundus photographs graded according to a modification of Chinese National Fundus Disease Academic Meeting. And 21 sex-age matched normal people were as controls. This study was in a masked fashion. RESULTS: 1. tPA activity was lower and PAI activity was higher in all of diabetic patients than those in controls (P < 0.001); 2. tPA activity was lower and PAI activity was higher in proliferative DR (PDR) subgroup than those in non-DR (NDR) and background-DR (BDR) subgroups (P < 0.01, respectively); 3. there was no significant difference between BDR and NDR subgroups (P > 0.05); and 4. the results also suggested that the severity of DR and duration of diabetes were correlated negatively with the activity of tPA but positively with that of PAI (r = -0.564, -0.416, 0.671, 0.442; P < 0.01, respectively). CONCLUSIONS: Reduced plasma tPA activity and enhanced PAI activity in diabetic patients, probably is one of the causes for thromboembolic diseases and are related to the severity of DR and duration of diabetes. Therefore, the change and imbalance between activities of plasma tPA and PAI might play a role in developing and progression of DR.

Adolescent↗
PubMed1997

[The development and application of computer assisted photogrammetric-system of facial soft tissue running under multiple facilities for taking image].

The photogrammetric-system was developed by using multimedia computer, colour television camera, SE100 video blaster, Newsketch 1212 HR digitizer and by using Visual Basic language. It ran under Windows 3.1 and Windows 95. The features of this system: 1. It had three kinds of functions: photogrammetric function for frontal and profile facial soft tissue, function for managing file and function for forming dynamic data base. 2. It ran under different facilities for taking image (television camera with video blaster, digitizer, scanner) speedily and specificly, and had very friendly interface, and was of multimedia. The application of this system: 1. assisting diagnosing, making plan for treatment and observing results of treatment in clinic of orthodontics, orthopedics and facial plastics, 2. assisting analysing the features of facial soft tissue about certain people, 3. assisting the multimedia teaching.

Adolescent↗
PubMed1997

[The analysis of frontal facial soft tissue of normal native adult of han race of Guangdong province by using the computer assisted photogrammetric-system].

UNLABELLED: The authors analysed the feature of frontal facial soft tissue of 150 native adults of Guangdong province by using the computer assisted photogrammetric-system made by the authors, which contained several new mode parameters planed by the authors. THE RESULTS: 1. The mean measurements of six parameters (Sn-Mes, Gs-Mes, Exr-Exl, Enr-Enl. [symbol: see text]Zyr-Rc-Mes, [symbol: see text]Zyl-Lc-Mes.) of the male subjects were larger than those of the female subjects, and the mean measurements of two parameters (Zyr-Zyl/Gs-Mes, Rc-Lc/Gs-Mes) of the male subjects were smaller than the ones of the female subjects. 2. The four measurements (Tr-Mes, Gs-Sn, Zyr-Zyl, Chr-Chl) in both male and female subjects of Guangdong province were smaller than the ones of Sichuan and Shandong provinces, and one measurement (Tr-Gs) of Guangdong male subjects was also smaller than the one of Sichuan or Shandong province, and one measurement of Guangdong female subjects smaller than the one of Shandong province. The conclusions: 1. The normal native adults of han race of Guangdong province show sex-difference and region-difference in the feature of frontal facial soft tissue. 2. The new-mode parameters (such as: [symbol: see text]Zyr-RC-Mes, [symbol: see text]Zyl-Lc-Mes, Zyr-Zyl/Gs-Mes, Rc-Lc/Gs-Mes) are helpful in studying the feature of frontal facial soft tissue.

Adolescent↗
PubMed1997

[Some YAC contig construction and long range physical mapping at human X chromosome Xp11.3-21.3].

Human X chromosome short arm Xp11.3-p21.3 is an area, where several genetic disease gene loci are located. In this work, the YAC conting construction, long range physical mapping were done for this region. Some DNA probes and STS markers were used for YAC screening. Totally 77 YACs were obtained from the YAC libraries of CEPH, ICRF and ours. The size determination, 26 pairs of microsatelite STS analysis, single copy probe hybridization, Alu-PCR finger printing and long range physical mapping were conducted with these YACs. These results allowed us to map these YACs, and finally 6 YAC contigs were obtained in Xp11.3-21.3, covering about 15.3 Mb. This work will greatly facilitate the positional cloning of disease genes or the genome sequencing in this important region.

Chromosome Mapping↗
PubMed1997

A model of human anti-T-cell monoclonal antibody therapy in SCID mice engrafted with human peripheral blood lymphocytes.

A chimeric severe combined immunodeficient mouse engrafted with human peripheral blood (hu-PBL-SCID) model has been developed to test anti-T-cell monoclonal antibody (mAb) effects on systemic symptoms of the host and the survival of human skin grafts. To obtain consistent engraftment without lethal acute graft-versus-host disease (GVHD), SCID mice were pretreated with a combination of total body irradiation (2.5 Gy, day 0) and anti-asialo GM1 (anti-mouse natural killer cell) antiserum (50 micrograms i.p., day 3) before the intraperitoneal injection of 40-50 X 10(6) human PBL on day 4. With this protocol, the engraftment rate was 82% with 5-98% human CD45-positive cells in the peripheral blood. Mortality at 30 days was 0% in the mice bearing 5-50% human cells compared with 70% in those with more than 50%. Using hu-PBL-SCID mice with 5-50% human cells in their peripheral blood, we demonstrated the following results: 1) Human T cells isolated from these mice proliferated in response to immobilized OKT3 stimulation in vitro. 2) Hu-PBL-SCID mice but not normal SCID mice were able to reject human skin grafts in vivo 16-21 days after grafting. 3) Both OKT3 (anti-human CD3 mAb) and T10B9 (anti-human alpha beta T-cell receptor mAb) treatment prevented human skin graft rejection in hu-PBL-SCID mice. 4) OKT3 but not T10B9 induced first dose reactions characterized by hypothermia and hypoactivity which were consistently observed within 90 min of intravenous injection into hu-PBL-SCID mice. 5) Human cytokines were detected in the serum of the hu-PBL-SCID mice treated with anti-T-cell mAbs. The close similarity of these responses to human clinical mAb immunosuppressive therapy suggests that the hu-PBL-SCID mouse model may be an excellent tool for investigating the immunosuppression, side effects, and mechanism of action of agents that are specific for human and higher apes and not reactive with lower animals.

Acute Disease↗
PubMed1997

Surgical excision of intracranial arteriovenous malformations after preoperative embolisation with N-butylcyanoacrylate.

The aim of this study was to determine the usefulness of preoperative embolisation of intracranial arteriovenous malformations (AVMs) with N-Butylcyanoacrylate (NBCA) since the introduction of this interventional neuroradiology technique in March 1994 at Tan Tock Seng Hospital, Singapore. Twenty-one patients who underwent complete surgical excision of their AVMs (proven on postoperative angiograms) were studied. Eight patients had preoperative embolisation with NBCA prior to surgical excision of their AVMs. Thirteen patients had excision of their AVMs without preoperative embolisation and these were used as the control group. The parameters studied were the patient's AVM characteristics, the amount of blood loss and the length of operative time. Statistically significant reduction in blood loss occurred in Spetzler and Martin Grade 3 and 4 AVMs but not in Grade 1 and 2 AVMs undergoing preoperative embolisation with NBCA. Operative time was reduced in Grade 3 and 4 AVMs but not in Grade 1 and 2 AVMs, although this was not statistically significant. Preoperative embolisation of AVMs is hence a useful and important adjunct in the management of patients with Grade 3 and 4 AVMs of the brain undergoing conventional open microneurosurgery.

Adolescent↗
PubMed1997

[HLA-DR typing by standard serology and PCR-amplification with sequence-specific primers: a comparative study].

OBJECTIVE: DNA typing for HLA-DR by polymerase chain reaction with sequence-specific primers (PCR-SSP) compared with standard serology to evaluate the reliability and clinical practicability. METHODS: Double-blind typing for HLA-DR alleles was carried out using DNA typing by PCR-SSP and standard serology by microlymphocytotoxicity technique in 61 donors and 101 recipients of cadaveric transplantation. Matching time, sensitivity, specificity and clinical practicability were compared according to typing results by both methods. RESULTS: All 162 samples were able to be typed by PCR-SSP. A total of 308 alleles were detected (16 DR "blank"). The results of matching were confirmed by analysis with restriction endonucleases and Southern hybridization. The specificity and reproducibility were 100%. HLA-DR typing was performed in 5 hours by PCR-SSP or 20 hours by serology. The discrepancy rate between PCR-SSP and serological HLA-DR typing was 30.2% (35.6% for kidney recipients, 21.3% for donors). The discrepancies consisted of 8 loci being doubtful, 29 antigens being incorrectly interpreted by serology and 20 of serological "blanks" turning out to be definable alleles by the DNA method. CONCLUSIONS: Genotyping for HLA-DR by PCR-SSP offers the advantages of better reagent and sample availability, more rapid and greater accuracy, all of which would warrant that this approach was suitable for clinical practice in organ transplantation.

DNA↗
PubMed1996

Construction of human factor IX expression vectors in retroviral vector frames optimized for muscle cells.

Development of a highly refined human factor IX (hFIX) expression vector system is critical for establishing a durable hemophilia B gene therapy. Here we report construction of a series of retroviral vectors and identification of an optimal basic structure and components for expressing hFIX in skeletal muscle cells. These vectors, which are derived from Moloney murine leukemia virus (MoMLV) with its enhancer sequence in the 3' long terminal repeat (LTR) deleted, contained internal hFIX expression units inserted in forward configuration without or with a viral vector intron sequence (pdL or pdLIn vector frame, respectively) or in inverted configuration without a viral vector intron sequence (pdLi frame). Internal expression units contained a hFIX cDNA or hFIX minigene (hIXm1 or hIXm2) derived from the hFIX cDNA by insertion of a shortened first intron sequence of the hFIX gene. Regardless of the promoter and vector frame used, both hIXm1 and hIXm2 gave 10- to 14-fold higher hFIX expression compared to those with hFIX cDNA. Internal hFIX transcriptional control units of these vectors were composed of various promoters linked with or without the muscle creatine kinase enhancer (Me) sequence. Promoters tested included those of alpha-actin (alpha A775), beta-actin (beta A280), cytochrome oxidase (CO1250 and CO650), myogenin (Mg1031 and Mg353), and Rous sarcoma virus (RSV). beta A200, which was derived from beta A280 by eliminating potential polyadenylation sites, was also tested. As extensively examined with the myogenin promoter, presence of one or multiple copies of Me in the vectors elevated the expression activity in myotubes by 4.5- to 19-fold over those without Me, but not significantly in myoblasts. Similar enhancements in expression activity with Me were also observed with other promoters, except those of RSV and CO. The latter two showed only modest enhancements in the presence of Me. As assayed with myotubes in culture, the general order of hFIX expression activity of various promoters with four copies of Me in the three different vector frames was beta A280 approximately beta A200 > Mg353 > Mg1031 approximately RSV approximately CO650 approximately alpha A775 > CO1250. One exception was that CO650 showed significantly less activity in pdLi-type vectors than in the pdLIn vectors. Based on the systematic analyses of various structural components, a group of pdLi vectors consisting of beta A200, two to four copies of Me, and hIXm2 was identified to have the optimal basic vector structure to be used in retrovirus for hFIX expression in differentiated skeletal muscle cells. The present studies provide the critical first step for establishing a highly refined hemophilia B gene therapy based on skeletal muscle-targeted hFIX gene transfer.

Animals↗
PubMed1996

Regulation of IgM and IgD heavy chain gene expression: effect of abrogation of intergenic transcriptional termination.

Early IgM+ B cells express little or no membrane IgD due to the low abundance of delta mRNA. Extensive transcriptional termination regulated by sequences in the intronic region between mu and delta heavy chain genes may be the primary reason for the lack of delta gene transcription. We have examined the effect of deletion of these sequences on the regulation of IgM and IgD heavy chain gene expression in transfectants as well as mice carrying this otherwise intact transgene. By run-on transcriptional measurement, we show that the delta exons are transcribed in bone marrow B cells from these transgenic mice. However, in spite of the induced premature synthesis of the full-length mu-delta transcript in pre-B cells, processing to delta mRNA does not occur until the lymphocytes express cell surface IgM. Therefore, during B cell development, synthesis of the full-length transcript is a necessary but not sufficient condition for initiation of delta mRNA synthesis. Furthermore, unexpectedly, the abrogation of transcriptional termination was found to also affect the processing of the primary transcript to microM mRNA. These results show that expression of IgD in primary B cells is stringently regulated and closely linked to IgM expression.

Animals↗
PubMed1996

Injection of complementary DNA encoding interleukin-12 inhibits tumor establishment at a distant site in a murine renal carcinoma model.

Interleukin (IL-12) protein has been shown to elicit diverse immunological responses and potent antitumor activity. We demonstrate here that intradermal injection of IL-12 cDNA induces systemic biological effects characteristic of the cytokine in vivo. Intradermal injection of IL-12 cDNA resulted in local expression of IL-12 mRNA, which correlated with a 10-fold increase in natural killer activity and a 3-4-fold increase in anti-CD3-induced IFN-gamma production in cultured splenocytes. Furthermore, when challenged with Renca tumor cells at a distant site, the day of tumor emergence was significantly delayed, and tumor growth was reduced in mice that received IL-12 cDNA, compared to mice given injections of plasmid vector alone. A number of the mice receiving IL-12 cDNA injections remained tumor free months after tumor challenge. In contrast to mice receiving recombinant IL-12 protein, no splenomegaly was detected when natural killer activity was significantly induced in mice receiving injections of IL-12 cDNA. Because purified plasmid DNA is more economical to prepare and has a longer shelf-life than recombinant proteins, and intradermal administration of cDNA encoding IL-12 did not cause splenomegaly, our findings suggest that the in vivo injection of cDNA encoding IL-12 may be a less toxic and more cost-effective alternative to IL-12 protein therapy in some clinical or experimental therapeutic applications.

Animals↗