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Biomedical subjects

H Tan

Publications and source records attributed to H Tan.

At least 55 records · Page 3Linked to original sources
PubMed2000

[Clinical study of direct digital radiography in caries detection].

OBJECTIVE: Direct digital radiography is a computer-based image technique, the purpose of this paper is to investigate possible usage of direct digital radiography-radio visiography (RVG) in caries detection in clinic. METHODS: A human head model with teeth was used to establish the operative exposure time for RVG in vitro, then RVG images for normal and carious tooth were obtained in vivo and were compared with conventional E-speed film in image quality and diagnostic accuracy. RESULTS: The optimal exposure time for RVG image was obtained, and the exposure time was different in each tooth quarter. The acceptable rate of image quality and diagnostic accuracy of RVG was statistically equivalent to that of E-speed film (P > 0.05), however, the excellent rate of RVG was statistically superior to that of E-speed film (P < 0.05). CONCLUSION: The conventional X-ray will be substituted by RVG in caries detection in clinic.

Adolescent↗
PubMed2000

[Expression and activity analysis of the human glutathione-S-transferase in Lactococcus lactis].

The glutathione-S-transferase A1 cDNA was amplified from human liver total RNAs by RT-PCR and was cloned into a Escherichia coli expression vector pET23b, then the recombinant plasmid pET23bhgst was introduced into E. coli BL21 (DE3) and induced by IPTG, the high-level expression of hGSTA1 appeared in the E. coli cells. The cDNA encoding hGSTA1 was subcloned into pMG36e, a lactococcal expression vector, and introduced into Lactococcus lactis MG1363 by electroporation. In the positive transformants, the hGSTA1 was expressed as a fusion protein which was verified by SDS-PAGE and Western blot. The hGSTA1 from both E. coli and L. lactis was purified by affinity chromatography on glutathione-agarose and all showed enzymatic activity. The potential application of the recombinant Lactococcus lactis in functional food was also discussed.

Blotting, Western↗
PubMed2000

[Studies on sanH and sanI--genes related to nikkomycin biosynthesis of Streptomyces ansochromogenes].

A 7.0 kb DNA fragment was cloned by reverse genetics, which was located in the gene cluster of nikkomycin biosynthesis of Streptomyces ansochromogenes. Besides sanF--a gene related to nikkomycin biosynthesis of S. ansochromogenes, the sequence of a 2.2 kb BglII DNA fragment upstream sanF was determined. This 2.2 kb DNA fragment cointains two complete open reading frames (ORF). ORF1 consists of 1233 base pairs, ORF2 consistis of 195 base pairs, and they encode proteins with 410 amino acids and 64 amino acids respectively, which were designated as sanH and sanI. In search of databases, the deduced products of sanH has 46% amino acid identities and 62% amino acid similarities in comparison with the cytochrome P450 of Streptomyces griseolus, and the deduced protein of sanI has 56% amino acid identities and 70% amino acid similarities with the ferredoxin of S. griseolus. The function of sanH gene was studied using strategy of gene disruption, and the result showed that the disruption of sanH didn't influence nikkomycin biological activity in S. ansochromogenes.

Amino Acid Sequence↗
PubMed2000

[Effect of 5,7-dihydroxytryptamine on the distribution pattern of calcitonin gene-related peptide in different motoneuron pools].

OBJECTIVE: The effect of 5,7-dihydroxytryptamine (5,7-DHT) on distribution pattern of calcitonin gene-related peptide (CGRP) in different motoneuron pools was studied in rats. METHODS: Cholera toxin B subunit coupled with colloidal gold (CB-Au) retrograde labeling combined with CGRP immunocytochemistry technique was mainly used. RESULTS: In control group, there was a different distribution pattern of CGRP-LI content in soleus motoneuron (SOL-Mn) and extensor digitorum longus motoneuron (EDL-Mn) pools. SOL-Mn pools had a higher ratio of neurons lacking CGRP-LI/weak CGRP-LI and a lower proportion of strongly CGRP-LI labeled ones. Comparing with control, there was a marked shift to increasing of CGRP-LI content in SOL-Mn pool and slight decrease in EDL-Mn pools 14 days after 5,7-DHT. All the SOL-Mns were CGRP-LI positive and the ratio of CGRP-LI strongly positive Mns significantly increased (P < 0.001) while 5,7-DHT did not increase the ratio of CGRP-LI strongly positive Mn in EDL-Mn pool. CONCLUSIONS: Except muscular motor activity, the different distribution pattern of CGRP-LI content in SOL-Mn and EDL-Mn pools is related to different 5-HT inputs. SOL-Mns may receive more 5-HT inputs.

5,7-Dihydroxytryptamine↗
PubMed2000

Effect of kanglemycin C on lymphokin a production and gene expression of mouse splenocyte and macrophage.

AIM: To study the effect of kanglemycin C (KC) on production and gene transcription of lymphokins. METHODS: Cell proliferation and lymphokin activities were quantified with MTT colorimetry and ELISA, and gene transcriptions of lymphokins semi-quantified with RT-PCR. RESULTS: Suppression of KC on proliferation of enriched T-and B-cell respectively mediated by Con A and LPS was declined by addition of exogenous IL-1, IL-2, and IL-6. KC 80 nmol/L markedly inhibited IL-2 and IL-6 production and mRNA transcription of incubated mouse splenocytes induced by Con A. Additionally, KC had some suppression on IL-1beta and IL-6 productions of peritoneal macrophage stimulated by LPS (5microg/mL), whereas cyclosporine (CS) had not. CONCLUSION: Immunosuppression of KC came true partially through the decrease of IL-1beta, -2 and -6 productions, especially of IL-2. However, CS's immunosuppression was mainly through the decrease of IL-2 production.

Animals↗
PubMed1999

Purification and cloning of amyloid precursor protein beta-secretase from human brain.

Proteolytic processing of the amyloid precursor protein (APP) generates amyloid beta (Abeta) peptide, which is thought to be causal for the pathology and subsequent cognitive decline in Alzheimer's disease. Cleavage by beta-secretase at the amino terminus of the Abeta peptide sequence, between residues 671 and 672 of APP, leads to the generation and extracellular release of beta-cleaved soluble APP, and a corresponding cell-associated carboxy-terminal fragment. Cleavage of the C-terminal fragment by gamma-secretase(s) leads to the formation of Abeta. The pathogenic mutation K670M671-->N670L671 at the beta-secretase cleavage site in APP, which was discovered in a Swedish family with familial Alzheimer's disease, leads to increased beta-secretase cleavage of the mutant substrate. Here we describe a membrane-bound enzyme activity that cleaves full-length APP at the beta-secretase cleavage site, and find it to be the predominant beta-cleavage activity in human brain. We have purified this enzyme activity to homogeneity from human brain using a new substrate analogue inhibitor of the enzyme activity, and show that the purified enzyme has all the properties predicted for beta-secretase. Cloning and expression of the enzyme reveals that human brain beta-secretase is a new membrane-bound aspartic proteinase.

Amino Acid Sequence↗
PubMed1999

Multiplexed automated DNA sequencing directly from single bacterial colonies.

Sample preparation has been one of the major bottlenecks for large-scale DNA sequencing projects in terms of time and cost. To improve sample throughput and to integrate the front-end tasks to capillary-array DNA sequencers, protocols for directly sequencing the plasmids from a single bacterial colony in fused-silica capillaries were developed. After the colony is picked, lysis is accomplished in situ in the plastic sample tube using either a thermocycler or a heating block. Upon heating, the plasmids are released while chromosomal DNA and membrane proteins are denatured and precipitate to the bottom of the tube. After adding enzyme and Sanger reagents, the resulting solution was aspirated into the reaction capillaries by a syringe pump, and cycle sequencing was initiated. No deleterious effect upon the reaction efficiency, the on-line purification system, or the capillary electrophoresis separation was observed, even though the crude lysate was used as the template. Multiplexed online DNA sequencing data from 8 parallel channels allowed base calling up to 620 bp with an accuracy of 98%. The entire system can be automatically regenerated for repeated operation. By the marriage of colony sequencing with the capillary array sequencer, both the front end and the back end of DNA sequencing are combined in a miniaturized format. This protocol will ultimately reduce the cost of sequencing to well below current levels.

DNA, Bacterial↗
PubMed1999

Automated and integrated system for high-throughput DNA genotyping directly from blood.

An automated and integrated system for DNA typing directly from blood samples has been developed. The multiplexed eight-array system is based on capillary microfluidics and capillary array electrophoresis. Three short-tandem-repeat loci, vWA, THO1, and TPOX, are coamplified simultaneously in a fused-silica capillary by a hot-air thermocycler. Blood is directly used as the sample for polymerase chain reaction (PCR) without any pretreatment. Modifications of standard protocols are necessary for direct PCR from blood. A programmable syringe pump plus a set of multiplexed liquid nitrogen freeze/thaw switching valves are employed for liquid handling in the fluid distribution network. The system fully integrates sample loading, PCR, addition of an absolute standard, on-line injection of sample and standards, separation and detection. The genotypes from blood samples can be clearly identified in eight parallel channels when the electropherograms are compared with that of the standard allelic ladder by itself. Regeneration and cleaning of the entire system prior to subsequent runs are also integrated into the instrument. The instrumentation is compatible with future expansion to hundreds of capillaries to achieve even higher throughput.

Automation↗
PubMed1999

Efficacy and safety of rectal thiopental: sedation for children undergoing computed tomography and magnetic resonance imaging.

PURPOSE: We evaluated the clinical safety, effectiveness, efficiency and potential side effects of rectally administered thiopental in 30 children undergoing computed tomography (CT) and magnetic resonance imaging (MRI). METHODS: The doses of thiopental used were 50 mg/kg for infants under 6 months of age, 35 mg/kg for infants between 6 and 12 months of age and 25 mg/kg for older children. After administration of the sedative, oxygen saturation was continuously monitored and vital signs were recorded every 20 min during the imaging procedure and then every 20 min until discharge. RESULTS: Successful sedation and adequate imaging were obtained in 29 of 30 (96.7%) patients. Respiratory depression was not observed in any patient. However, oxygen saturation dropped below 90% transiently (to 88%) in three patients (10.0%) and this was immediately corrected by repositioning the child's neck to open the upper airway. All successfully sedated patients were asleep within 15 min (mean +/- SD 7.3 +/- 2.7 min) and sedation was sufficient for at least 30 min. Prolonged sedation was observed in two patients. CONCLUSIONS: We believe that rectal thiopental is a safe, effective and efficient form of sedation for pediatric imaging.

Administration, Rectal↗
PubMed1999

Plasma and urine carnitine levels and carnitine supplementation in children with malnutrition.

The purpose of the present investigation was to determine serum and urinary carnitine levels in children suffering from protein-energy malnutrition (PEM) before and after dietary treatment and carnitine supplementation, and to compare them with those in healthy children. Plasma and urine carnitine levels were lower in patients with marasmus and kwashiorkor than in controls. There was no statistical difference between groups with and without carnitine supplementation on the first day. On the fifth day, in groups receiving carnitine supplementation, plasma and urine carnitine levels were significantly higher than in groups without supplementation (p < 0.01). On the 15th day there was no statistical significance between groups with PEM and controls.

Carnitine↗
PubMed1999

[Angiotensin 1-converting enzyme gene insertion/deletion polymorphism in patients with coronary artery disease and essential hypertension and its nucleotide sequence].

OBJECTIVE: To determine angiotensin 1-coverting enzyme(ACE) gene insertion/deletion(I/D) polymorphism distributions in patients with coronary artery disease(CAD) and essential hypertension(EH),and to detect its nucleotide sequence. METHODS: ACE genotypes of 137 patients with CDA, 42 patients with EH and 63 healthy people were detected by PCR methods. At the same time, nucleotide sequences of D and I allele were determined by fluorescein labeling automatic sequencing method. RESULTS: the frequency of DD genotype in CAD group was significantly higher than that in control group (0.45 and 0.21,P < 0.01), but there was no significant difference of ACE geneI/D polymorphism distribution between EH and control group. The lengths of D and I alleles are 191bp and 479bp separately and their nucleotide sequences are somewhat different with the results of foreign countries. CONCLUSION: ACE gene I/D polymorphism is an independent risk factor of CAD, but it has no relationship with EH. A 288bp insertion segment results in the I/D polymorphism of ACE gene.

Adult↗
PubMed1999

Patients' knowledge and attitude towards treatment and control of hypertension: a nation-wide telephone survey conducted in Malaysia.

The telephone survey of 2,526 hypertensive subjects showed 94% of the respondents were aware of the importance in controlling hypertension. Among these 504 were not on anti-hypertensive medication while the majority of 2,022 were currently on anti-hypertensive medication. Of those who were not on medication, 80% (n = 403) were found non-hypertensive on follow-up. The remaining 20% (n = 101) were confirmed hypertensive and were offered medication. However, 38 subjects refused to take medication and 63 subjects complied with medication but subsequently gave up. The main reasons for giving up medication included lack of motivation (38%), doctors' advice (20%), side effects (19%) and concern of side effects (10%). Of 2,022 hypertensive respondents who were currently on medication, almost half (44%, n = 890) required a change of medication due to side effects (40%, n = 356) or the blood pressure not controlled with the previous medication (33%, n = 294). Despite the change in medication, 42% (n = 150) still continued to suffer from some form of side effects. The information obtained from this survey suggested it is important to recommend some strategies to improve patient compliance. These strategies comprise of motivating the patient, improving medication with less side effects, improving potency and efficiency of medication, and reduction of cost in medication. In addition, convenient blood pressure monitoring such as home blood pressure monitoring is also encouraged.

Adult↗
PubMed1999

[Study of levels of antibody against coxsackievirus B in different adults in Changsha area].

In order to verify the antibody levels against coxsackievirus B(CVB) in different adults, specific anti-CVB-IgM and anti-CVB-IgG have been detected in 46 viral myocarditis, 121 viral-hepatitis patients and 108 healthy donors by using immuno-enzyme histochemical method, and the antibody titres were also tested. The results showed that the positive rate of anti-CVB in viral myocarditis group, viral hepatitis group and donor group were 80.4% (37/46), 25.6% (31/121) and 40.7% (44/108), respectively. The GMT of anti-CVB-IgM and anti-CVB-IgG in viral myocarditis group, hepatitis group and donor group were 1:84.84, 1:9.07, 1:64.00 and 1:179.27, 1:9.59, 1:21.42, respectively. The positive rate and GMT of anti-CVB-IgM and anti-CVB-IgG in viral myocarditis group were significantly higher than those in the other two groups. The positive rate had no statistical difference between men and women. The results indicate that the majority of the healthy population in Changsha area is susceptible for CVB and most cases of the viral myocarditis many be related to CVB infection. It is considered that CVB can cause many diseases. Furthermore, there are no effective vaccine against CVB so far. One should think of the probability of CVB infection when encountering a patient.

Adolescent↗
PubMed1999

[Repair of huge skin defect on leg and foot with multiple pedicled blocking randomized fasciocutaneous flap].

OBJECTIVE: In order to increase the survival area of pedicled fasciocutaneous flap, a multiple pedicled blocking randomized fasciocutaneous flap was designed. METHODS: From January 1991 to September 1998, this technique was used to repair 33 cases, including 27 males and 6 females and the ages ranged from 6 to 58 years. All of the patients were suffered from traffic accidents. In these cases, 22 cases had skin defects of legs and feet with bone, nerve and tendon exposed, 5 cases had osteomyelitis as well as internal fixaters exposed and the other 6 had deformity from scar. The size of the flap was 25.0 cm x 13.0 cm x 2.4 cm at its maximum and 6.0 cm x 3.5 cm x 1.5 cm at its minimum. Based on the traditional blocking flap, according to the severity of the wound and conditions of the neighboring tissues, a flap having 2 to 4 orthogonal pedicles with a width of 1.5 to 3.0 cm was designed. The medical-graded stainless steel sheet was implanted below the deep fascia, and after blocking for 3 to 6 days, the side pedicles were divided. 6 to 14 days later, one of the two remaining pedicles was divided and was transferred to repair the defect. RESULTS: 31 cases were followed up for 6 months to 5 years without any trouble of the joints. The flap had a good external appearance and was high pressure-resistant. CONCLUSION: The multiple pedicled blocking randomized fasciocutaneous flap increased the size of the flap and the length to width ratio. It had the following advantages: manage at will, high resistance to infection and a large survival area of flap.

Accidents, Traffic↗
PubMed1999

[Construction of Streptococcus mutans surface protein antigen eukaryotic expression vector pcDNA3-PAc. II. Testified efficiency of repeated using glass fiber chromatographic column].

OBJECTIVE: To explore one method getting highly purified plasmid DNA and costing low. METHODS: According to principle of extraction and purification plasmid DNA of glass fiber chromatographic column, its operation sequence was improved so that disposable glass fiber chromatographic column could be used repeatedly. The concentration and purity of plasmid DNA obtained by 12 times repeated using glass fiber chromatographic column were determined by spectrophotometry. Moreover, Those plasmid DNA obtained were tested by restriction enzyme and agarose gel electrophoresis, Ligation in vitro and transformation test. RESULTS: 12 times repeated use of glass fiber chromatographic column made no significant difference to the concentration and purity of obtained plasmid DNA (P < 0.05), and plasmid DNA was completely digested by restriction enzyme. The digested fragments were well ligated together by the action of T4 DNA Ligase in ATP ligating buffer in vitro and ligated DNA was well transformed into E. coli. CONCLUSION: Repeated use glass fiber chromatographic column can obtain a lot of highly purified plasmid DNA and cost is low. Digestion, ligation and transformation of those plasmid DNA are not affected. The results may be significant in molecular cloning and study of gene vaccination.

Antigens, Surface↗
PubMed1999

[The curative effect of daphnlin spray on treating rhinitis].

OBJECTIVE: To observe the effect of Daphnlin spray on decongesting rhinocleisis and to search effective drugs for treating rhinitis. METHOD: 105 patients collected from chronic simple rhinitis, chronic hypertrophic rhinitis and perennial allergic rhinitis were treated with daphnlin spray (daphnlin group) or ephedrine spray (ephedrine group). RESULT: The total efficiency of daphnlin group in treating rhinitis above is 90.9% and that of ephedrine group (69.3%) in 1 minute and for ephedrine group is mostly (68.7%) between 1 to 3 minutes. The keeping curative effect time for daphnlin spray is mostly (70.4%) above 5 hours and for ephedrine spray is mostly (71.8%) in 3 hours. After a week, the nasal resistances are difference between daphnlin group and ephedrine group. CONCLUSION: Daphnlin spray is better than ephedrine spray in decongesting rhinocleisis, keeping curative effect and in safety, so daphnli is one kind of effective drugs in treating rhinitis.

Administration, Inhalation↗