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Biomedical subjects

T Tan

Publications and source records attributed to T Tan.

At least 19 recordsLinked to original sources
PubMed1996

Producing positive, negative, and no cooperativity by mutations at a single residue located at the subunit interface in the aspartate receptor of Salmonella typhimurium.

Site-directed mutagenesis of the aspartate receptor of Salmonella typhimurium (Tars) at serine 68, a residue located within the aspartate binding pocket and at the subunit interface, identified this residue as an allosteric switch in this receptor. Substitutions at this position can affect both the type and degree of binding cooperativity observed. Negative cooperativity is observed in the wild-type receptor (nH = 0.7 +/- 0.1) and is maintained by the mutations S68C (nH = 0.8 +/- 0.02), S68V (nH = 0.9 +/- 0.05), and S68D (half-of-the-sites). Binding at only half of the sites was detectable in the S68D mutant, an extreme form of negative cooperativity. No cooperativity (nH = 1.0 +/- 0.03) was observed in the mutant S68A. Positive cooperativity was generated by the substitutions S68T (nH = 1.2 +/- 0.09), S68L (nH = 1.2 +/- 0.1), S68N (nH = 1.3 +/- 0.2), and S68I (nH = 1.4 +/- 0.2). Binding measurements indicated that the substitutions S68Q, S68E, and S68F decrease affinity of the first ligand binding 500-fold, 7000-fold, and 1600-fold, respectively.

Allosteric Regulation↗
PubMed1995

[Effect of 153Sm-EDTMP on hematopoiesis and vital organs of 93 patients with bone tumor].

In the present study data on blood cell count, serum biochemistry, electrolyte, enzyme and vital organs of 93 patients with bone tumor or metastasis were investigated before and after treatment with 153Sm-EDTMP. The results showed that, 7 days and 30 days after the administration of 153Sm-EDTMP (< 29.6 MBq) (0.8 mCi/kg), the levels of hemoglobin, WBC lymphocyte count, and the liver and kidney function of all patients were not significantly different from the baseline data before treatment (P > 0.05). Although at 7 days, there was a declination of the granulocyte count, it returned to normal at 30 days (P > 0.05). The platelet count was significantly decreased (0.05 > P > 0.01). at 30 days after the administration of 153Sm-EDTMP. Thirteen patients received 74-185 MBq (2-5mCi/kg) and their myelo biopsies at 3 and 18 months showed no sign of acute or chronic toxicosis.

Adult↗
PubMed1995

[Effect of Cladonia alpestris on Trichomonas vaginalis in vitro].

In this paper, an experimental research is reported on the effect of water extract of Cladonia alpestris and S-(-) usnic acid on Trichomonas vaginalis in vitro. The results showed that both the water extract of Cladonia alpestris and S-(-)usnic acid exhibited a strong effect against Trichomonas vaginalis in vitro. As the time of action of the agents was prolonged, the mortality of Trichomonas vaginalis increased. For S-(-) usnic acid, 0.4 mg/ml was the lowest effective concentration against Trichomonas vaginalis in vitro. No remarkable differences were found in the effect of the S-(-)usnic acid and metronidazole at concentrations of 0.4 mg/ml and 0.6 mg/ml.

Animals↗
PubMed1995

[153Sm-EDTMP for moderate and severe bone cancer pain].

One hundred and thirty-six patients with bone cancer pain were treated with 153Sm-EDTMP (ethylenediamine-tetramethylene phosphonic acid). Pain free was noted in 49 cases (36%, 49/136) and pain relief in 77 cases (56.6%, 77/136), the total relief rate being 92.6% (126/136). The data from 76 patients with moderate and severe pain showed there were no significant relationships between the patients' age, the dose of 153Sm-EDTMP and the analgesic effects (P > 0.05). The pain relief observed in the patients with chest pain (ribs metastases) was earlier than that in other groups (P < 0.05). We didn't find any clinical side-effects, so 153Sm-EDTMP is safe for use.

Adult↗
PubMed1995

Bullous systemic lupus erythematosus--a case report and review.

We report a case of a 20-year-old Chinese woman who presented with an 8-month history of a widespread pruritic blistering eruption. Histology, direct immunofluorescence and indirect immunofluorescence studies were consistent with bullous systemic lupus erythematosus (SLE). The lesions responded dramatically to dapsone 100 mg daily. Bullous SLE is a rare blistering condition with a distinctive combination of clinical, histologic and immunopathologic features that together constitute a unique bullous disease phenotype. The differential diagnoses and in particular the association between bullous SLE and epidermolysis bullosa acquisita are emphasized.

Adult↗
PubMed1994

[125I-alpha-sec-butyl-p-hydroxybenzyl alcohol receptor competitive binding assays in animal body].

Based on the receptor competitive binding assays in the mice and rat body, it has been proved that both diazepam and alpha-sec-butyl-p-hydroxybenzyl alcohol (G-018) can inhibit 125I-G-018 binding with brain benzodiazepine receptor. Inhibiting effects were obvious in the cortex, cerebellum, hippocampus and midbrain. But in the medullao blongata and hypothalamus no inhibiting effect was observed. Experimental results have demonstrated that the inhibiting effect is consistent with distribution of benzodiazepine receptor in the brain. Also, experimental results have shown no difference between in vitro and in vivo. The G-018 binding with benzodiazepine receptor has been clarified under physiologic conditions.

Animals↗
PubMed1994

[Biodistribution and metabolism of 3H-gastrodigenin and 3H-gastrodin in mice].

The biodistribution and metabolism of 3H-gastrodigenin and 3H-gastrodin after intravenous injection were studied by the detection of their radioactivity in mice tissue; the radioactive elements of mice tissue extracts after intravenous injection of 3H-gastrodin were analyzed with thin-layer chromatography (TLC). The results demonstrated that gastrodin could penetrate through the blood-brain barrier into the brain, and it was rapidly decomposed into the gastrodigenin in brain, liver and blood. Then gastrodigenin preserved in brain and mediated its pharmacological inhibitive effects on the central nervous system. Most of the gastrodigenin and gastrodin were excreted by the kidney. The findings also suggested that gastrodin might exist in the enterohepatic circulation.

Animals↗
PubMed1994

[Characterization of receptor-mediated binding of 99mTc-NGA in vitro].

This paper reports results of an assay of the binding of 99mTc-galactosylneoglycoalbumin (NGA) and plasma membranes of the rat liver in vitro. The data showed that 99mTc-NGA could be bound to the membrane receptor with high affinity. Specificity and saturability, and that the amount of membrane-bound 99mTc-NGA varied linearly with the amount of membrane within each reaction tube. The biphasic curve of scatchard plot revealed that 99mTc-NGA was bound to two sites of the receptor with different affinity and concentration (K1 8.4089 x 10(9) L/mol, R1 1.7350 x 10(-12) mol/mg); K2 2.0827 x 10(8) L/mol, R2 6.9530 x 10(-12) mol/mg). Therefore, the authors consider that 99mTc-NGA is a promising hepatic receptor agent for imaging.

Albumins↗
PubMed1993

Efficacy and safety of multidrug therapy in paucibacillary leprosy in Singapore.

A total of 49 patients with paucibacillary leprosy (PB) who completed multidrug therapy (MDT) between 1985 and 1990 were analysed retrospectively for efficacy and complications; 20 (40.8%) patients had borderline-tuberculoid (BT), 13 (26.5%) had tuberculoid (TT), 1 (2.1%) had indeterminate (I) and 15 (30.0%) had pure neural (N) leprosy; 26 patients (76.5% of 34 non-neural leprosy) were skin biopsied for histological cure before MDT was stopped. Of these 26 patients, 19 had histological clearance at 6 months while the remaining 7 cleared beyond 1 year (18-36 months). The remaining 8 non-neural patients who refused rebiopsy had MDT for 6-8 months and the MDT was stopped when there was clinical clearance. Of the 15 neural (N) leprosy patients, 11 were given MDT for 6 months while the rest had 12-18 months of treatment; 1 patient with neural leprosy, who was treated for 6 months, relapsed with BT leprosy 18 months post-treatment. There were few complications among the 49 patients-4 (8.2%) patients developed reaction to dapsone, 1 (2.0%) had the dapsone syndrome, 2 (4.1%) had haemolytic anaemia and 1 (2.0%) had dapsone hepatitis; 7 (14.3%) patients had type I reaction.

Adult↗
PubMed1993

[The preparation of 99mTc-NGA instant lyophilized kit for hepatic imaging].

The preparation of one-step kit for the 99mTc labelled galactosyl-neo-glycoalbumin (NGA) using SnCl2 reduced method was reported in this paper. We developed a method of quality control and established the optimum scheme of technetium labelling on the basis of exploring the effects of varied labelled conditions on radiochemical purity. Our data indicates : (a) the kit is sterile, pyrogen-free and no toxic effects; (b) the operation is simple and fast; (c) its period of validity lasts no less than 3 months; (d) the radiochemical purity > 95%; (e) the stability of 99mTc-NGA in vitro > 4 hours; (f) the results of animal imaging and clinical probation are satisfactory.

Albumins↗
PubMed1993

[Pharmacokinetic studies on 99mTc-NGA in human].

Two normal subjects and three patients with hepatic disease were intravenously injected each with a single dose of 99mTc-NGA (galactosyl-neoglycoalbumin), a liver receptor imaging agent. The results showed that pharmacokinetics of 99mTc-NGA accorded with the two compartment open model. In the normal subjects, T1/2 alpha and T1/2 beta averaged 1.65 and 19.39 min respectively, indicating a rapid distribution process and a slow elimination process. There were significant differences in pharmacokinetics of 99mTc-NGA between the normal subjects and the patients with hepatic disease, and therefore the relevant parameters are of importance for the evaluation of hepatic function.

Adolescent↗
PubMed1992

[Hepatic carcinoma treated by hepatic arterial embolization using 131I and chemotherapeutic agent gelatin microspheres: report of 9 cases].

Nine patients with inoperable hepatoma were treated by using hepatic arterial embolization 131I and chemotherapeutic agent gelatin microsphere (131I-CA-GM). The emission CT after operation detected that the microspheres were concentrated on tumor area. The ratio between the radioactivity in tumor and that in liver was 4.1:1. A case died of ictopic embolization; the others survived 3, 4, 5, 19, 24, 7, 8, and 12 months respectively. Three of them were still alive. 131I-CA-GM has triple anticarcinogenic actions, including the arterial occlusion, targeting chemotherapy and internal radiation. The microspheres can selectively accumulate in the tumor artery and can be easily traced by gamma-camera or emission CT. 131I-CA-GM is a hopeful embolic agent for the treatment of liver cancer, but some problems about ectopic arterial embolization should be further studied.

Carcinoma, Hepatocellular↗
PubMed1991

Characterization of the performance of shoe insert materials.

It has been widely reported that shoe inserts are an effective interventional modality either for the relief of discomfort to the feet associated with a variety of orthopedic disorders or conditions or simply for comfort. Results from many types of experimental tests have been used to obtain the shock absorption capacity of shoe insert materials. The authors contend in this study that, while shock absorption is a highly desirable property, it is by no means the only that should be used to characterize these materials. Thus, a new index of performance of these materials is proposed. This index is computed from data, obtained in a simple experimental test, on both the shock absorption and energy return performances of the insert material.

Data Collection↗
PubMed1991

[Study of the mechanism of gastrodin and derivatives of gastrodigenin].

The tritiated alpha-isobutylhydroxybenzyl alcohol (3H-G018) was found to be able to bind benzodiazepine (BZ) receptor on the rat brain membrane. The 125I labeled G-018 also had the similar binding activity with this receptor. In the present investigation, we observed that gastrodigenin and its derivatives inhibited the 125I-G018 binding of BZ receptor competitively, but no inhibition was observed with gastrodin. The results suggested that Gastrodigenin was bound to BZ receptor, and otherwise, gastrodin would have no direct interaction with BZ receptor. Probably, it might metabolize into gastrodigenin in vivo, and then got through the blood brain barrier and bound to BZ receptor, which mediated its pharmacological effects on the central nervous system.

Animals↗
PubMed1991

[An experimental study on hepatic arterial embolization with 131I-MMC-GM].

We designed a new gelatin microsphere (GM, 65 micron in diameter), which could combine with mitomycin C and 131I. The test in vitro showed that the GM had excellent drug release effect. Hepatic arterial embolization was carried out in 6 dogs with 131I-MMC-GM. The dogs survived from 4 to 28 days before being killed. Scintigraphy indicated that high radioactivity was concentrated in the liver, but was very low in the blood and thyroid. Pathologic study found that the GM was trapped in hepatic arterioles. The GM was eliminated by foreign body giant cells and the lumen of arterioles was occupied by granulations 14-28 days after operation. 131I-MMC-GM is a multiple anticancer agent which can exert triple action of targeting chemotherapy, internal radiotherapy and arterial embolization.

Animals↗