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Biomedical subjects

T Tan

Publications and source records attributed to T Tan.

At least 37 records · Page 2Linked to original sources
PubMed2000

Epidemiology of cutaneous lupus erythematosus in a tertiary referral centre in Singapore.

The aim of this retrospective study was to investigate the epidemiology, yield of investigations and proportion of patients who develop systemic lupus erythematosus (SLE) among the subsets of cutaneous lupus erythematosus (LE) in the Singapore Asian population. One hundred and twenty-five patients were diagnosed with cutaneous LE on clinico-pathological correlation, of which 73 had discoid lupus erythematosus (DLE), eight had subacute cutaneous LE (SCLE), 22 had acute LE lesions and the remainder had other less common forms of cutaneous LE. Histology was consistent with LE in 94.4% and suggestive in 4.8%. Direct immunofluorescence was positive in 61% of DLE, 86% of SCLE and 80% of acute LE cases. Antinuclear antibody (ANA) was present in the majority of acute LE (85%) and SCLE (88%) but only in 25% of DLE. Eight patients (11%) presenting with DLE had definite SLE at first presentation and two (2.7%) subsequently several months later. Of these patients, six had only mucocutaneous and serological criteria but two had major organ involvement. Five SCLE patients (63%) fulfilled the criteria for SLE, including two with major organ involvement.

Academic Medical Centers↗
PubMed2000

Tetracycline and nicotinamide for the treatment of bullous pemphigoid: our experience in Singapore.

AIM OF STUDY: To study the efficacy of tetracycline (or doxycycline) and nicotinamide in the treatment of less extensive bullous pemphigoid. METHODS: An open trial of 11 patients with bullous pemphigoid. Treatment was initiated with tetracycline 1.5-2 g/day and nicotinamide 1.5-2 g/day and gradually tapered down. Doxycycline was substituted for tetracycline in patients who could not tolerate tetracycline due to gastrointestinal side effects or headache. RESULTS: 6 out of 11 patients achieved complete response (> 90% decrease in lesions) while another 2 had partial response (50-90% decrease in lesions). CONCLUSION: Tetracycline/doxycycline and nicotinamide is a useful alternative treatment for localized bullous pemphigoid, especially in those whose concurrent medical illnesses preclude the use of systemic corticosteroids.

Aged↗
PubMed2000

[The influence of physiologic factors on the expression of striatal dopamine D2 receptors].

The aim of this study was to know whether the strain, sex, and age-related body weight of rat have influence on the expression of striatal dopamine D2 receptor. The data on striatal dopamine D2 receptor binding 125I-IBZM in 34 rats were used in the comparison between pairs of groups matched on strain, sex, and body weight. The result showed that the strain and sex of rats had no influence on the striatal dopamine D2 receptor binding 125I-IBZM, but there was a body weight-related decrease in the striatal dopamine D2 receptor binding 125I-IBZM. The results suggest that age-dependent decline of striatal dopamine D2 receptors is possible; therefore, strict age-matching is necessary to clinical studies.

Age Factors↗
PubMed2000

[Preclinical pharmacological study of a novel myocardial perfusion agent: 99mTc-Q3].

In order to provide an experimental foundation for clinical study, we made a preclinical pharmacological investigation of 99mTc-Q3, a novel myocardial perfusion imaging agent, technetium-99m-N,N'-ethylenebis (acetylace-toneiminato) bis (tris (3-methoxy-1-proply) phosphine). After the preparation of this compound, the kinetics of blood clearance in rabbits, biodistribution in mice, measurement of plasma protein binding rate, and myocardial perfusion imaging in dog were carried out. The labelling efficiency and radiochemical purity measured were over 99%, and the stability (in vitro) was good and stable up to 6 hr of testing at room temperature. The pharmacokinetics met the two-compartment model with 0.23 +/- 0.09 ml/min of excellent blood clearance, an initial half-time of 1.5979 +/- 0.4182 min, and a late half-time of 203 +/- 25.83 min. The biodistribution as shown in myocardial accumulation was earlier, the radioactive value was higher, and once extracted, it remained relatively constant in the myocardium for at least 4 hr. The tracer was rapidly cleared from the blood, lung and the liver. The scintigraphy imaging in dog demonstrated that it was rapidly cleared from the lung, and the radioactive concentration approached that of background 1 hr after injection. At 15 min after injection, the myocardial imaging displayed clearly up to 3 hr. In vitro protein binding rate was low (7.13 +/- 0.42%). The tolerance of this drug in mice was 500 times as much as in humans. In conclusion, 99mTc-Q3 exhibits favorable stability, biological property and safety, so clinical study of this preparation as a myocardial perfusion imaging agent is worthwhile.

Animals↗
PubMed2000

[Biodistribution and metabolism of radio-iodinated IBZM in rats].

The aim of this study was to assess the bio-distribution and metabolic behavior of radio-iodinated IBZM in rats. Routine and improved technologies were used. The results showed that the radio-iodinated IBZM had favorable bio-distribution and metabolic behavior. The radio-distribution was high and the radio-iodinated IBZM remained long in striatum where no metabolic by-products manifested at 30 minutes after injection. These suggested that radio-iodinated IBZM is an excellent dopamine D2 receptor imaging agent for SPECT in humans, and it is stressed that thyroid must be blocked by iodine during the study of imaging.

Animals↗
PubMed2000

[Evaluation of side-effects after 131I-therapy for differentiated thyroid carcinoma].

The purpose of this study was to evaluate the side-effects of differentiated thyroid carcinoma after treatment with 3.7-7.4 GBq of 131I. A total of 342 patients were treated with 131I from May, 1989 to January, 1999. The acute side-effects, the short-term and long-term side-effects were analyzed. The follow-up lasted 1-10 years with an average of 5.4 years. The results showed that thyroiditis occurred predominantly in the patients with a rate of 131I uptake > 30%, whereas sialoadenitis occurred more prevalently in the patients with a rate of 131I uptake < 30% (P < 0.001). The rates of nausea, vomiting, diarrhea and gastralgia were 12.2%, 5.2%, 3.5% and 2.7% respectively. There were no significant changes in the hemogram after treatment, compared against that before treatment. The overall rates of transient platelet abnormalities and leukopenia were 10.4% and 4.0% respectively, but the rates of the abnormalities in the patients with cumulative doses of 131I > 18.5 GBq were significantly higher than those in patients with cumulative doses of 131 I < 18.5 GBq. The lower rate of acute and short-term side-effects and the absence of long-term side-effects in this study indicate that 131I can be safely used to treat differentiated thyroid carcinoma.

Adenocarcinoma, Papillary↗
PubMed2000

[Methodological study on preparation of a novel myocardial perfusion imaging agent: 99mTc-Q3].

This study was intended to explore the methods of preparing technetium-99m-N, N'-ethylenebis (acetylacetoneiminato) bis [tris (3-methoxy-1-propyl) phosphine] (99mTc-Q3) as a newer cationic myocardial perfusion imaging agent. The optimum scheme of technetium labeling on the basis of exploring the effects of differently labeled conditions on radiochemical purity was established by a multivariate orthogonal experimental design. A newer agent for myocardial perfusion imaging was developed based on the optimum scheme by a stannous chloride reduction method. Preparation, separation, purification and quality control were performed by a chromatography. Experiments for stability (in vitro), sterility, apyrogen, safeness, and for imaging in animals were carried out. "A2B2C2" was chosen as the optimum scheme of this labeled complex. There each of A, B and C factors has significant effect on the radiochemical purity, and there is no one-class cross effect on the radiochemical purity between them. The labeling efficiency and radiochemical purity were measured over 99% labeled 10 min later (at R. T.). The stability (in vitro) was good and kept up to 4 hr or testing (range: 92%-99.37%). The prepared product was sterile, apyrogenic and safe. The scintigraphic imaging in rabbits demonstrated that the tracer accumulated early in the heart and the myocardial imaging displayed clearly up to 3 hr. The results of this methodological study demonstrate that not only high quality 99mTc-Q3 can be obtained but also a standardized procedure for labeling all kinds of 99mTc-agents can be set up, and on this basis, the one-step kit of 99mTc-Q3 may be developed.

Animals↗
PubMed2000

[Dynamic study of hepatocellular pathological change and uptake rate of 125I-insulin during experimental hepatocarcinogenesis].

This study was designed to observe the hepatocellular pathological change and uptake rate of 125I-insulin during experimental hepatocarcinogenesis in rats and clarify the possible mechanism of increasing uptake of 125I-insulin. 80 SD rats were divided into 2 groups, control and experimental groups. All of the rats were given common feed, and the rats of experimental group were given extra diethylnitrosamine (DENA) 70 mg/kg each week. At 6th, 11th, 15th and 20th week after start of the experiment, 10 control and 10 experimental rats were killed 1 hour post administration of 125I-insulin by tail vein. Blood, liver, lung, spleen, kidney, muscle and bone were collected; the radioactivity was measured and calculated %ID/g. The data of 2 groups were compared and examined with t-test. All of livers were pathologically examined. The results showed all livers of control group were normal. At 6th week, the surfaces of experimental rats' livers were coarse. Hepatocellular hyperplasia was observed, 125I-insulin-uptake rate was 1.86 time as much as that of control group. At 11th week, the liver's colour became lighter than that of control group. Hyperplasia and hepatocirrhosis were observed, 125I-insulin-uptake rate was 1.50 time as much as that of control group. At 15th week, hyperplastic nodules were observed in all experimental rats' livers. Hepatomacellulae were observed in 6 rat livers. 125I-insulin-uptake rate was 1.56 time as much as that of control group. At 20th week, the livers became enlarged out of shape. There were a lot of big or small greyish white nodules in all livers. Necrosis, liquefaction and hemorrhage were observed. Hepatomacellulae were observed in all of experimental rats livers. 125I-insulin-uptake rate was 1.46 time as much as that of control group. The differences of 125I-insulin-uptake rate between experimental and control groups were significant. These results demonstrated that the liver ability of uptaking 125I-insulin increased which mainly took place during the period of hepatocellular hyperplasia, and the hepatomacellulae kept this characteristic.

Animals↗
PubMed2000

[Preparation of 131I-VIP and 131I-VIP receptor imaging].

This study was aimed at the preparation of 131I-vasoactive intestinal peptide (VIP) and its preliminary application in clinical imaging. VIP was labeled with Na 131I using chloramine-T method, then isolated by Sephadex G-10 column chromatography and examined by silica 60F254 thin layer chromatography. The bacteria and pyrogen were examined and the safety test was carried out. One control and two patients suffering from abdomen tumor were investigated. The results showed that the labeling rate of 131I was 80% and the specific activity of 131I-VIP was 36 TBq/mmol. The radiochemical purity of 131I-VIP was over 98%, and it decreased to 95% after six hours' storage at 4 degrees C. It was proved that the 131I-VIP eluate had no bacteria, no pyrogen and no poison. The injected 131I-VIP was distributed into the lungs immediately and was eliminated through kidneys. The primary tumor could be visualized about half an hour to 3 hours after injection. This study demonstrates that 131I-VIP is suitable for in vivo imaging and may be used as an effective tracer to identify the tumor site in patients with VIP receptor positive carcinoma.

Animals↗
PubMed1999

Prognostic factors in 677 patients in Singapore with nondisseminated nasopharyngeal carcinoma.

BACKGROUND: The objective of the current study was to describe the survival of nasopharyngeal carcinoma (NPC) patients in Singapore, verify the prognostic value of the revised 1997 TNM staging system, and develop a multivariate prognostic model for NPC. In addition, the authors also examined the prognostic value of characteristics of lymph node spread and parapharyngeal involvement. METHODS: A prospectively maintained database containing clinical and computed tomography scan data was used to reclassify 677 NPC patients treated between 1992 and 1994 according to the new staging system. Records were linked with the death registry to ascertain the patient's vital status and date of death. Overall and stage specific survival were analyzed using the Kaplan-Meier method and the log rank test. Univariate and multivariate Cox proportional hazards regression analysis were used to obtain prognostic models. RESULTS: Two hundred seventy-four deaths (40.5%) occurred. The 5-year survival rate was 56.6% (95% confidence interval [95% CI], 52.3%, 60.7%). The stage specific 5-year survival rates were: Stage I, 88%; Stage IIA, 75%; Stage IIB, 74%; Stage III, 60%; Stage IVA, 35%; and Stage IVB, 28%. TNM stage was found to be a statistically significant prognostic factor (P < 0.0001). Cranial nerve (hazard ratio [HR]: 2.77), orbit (HR: 5.71), and intracranial involvement (HR: 2.46) conferred a particularly bad prognosis in univariate analysis. Independently significant prognostic factors were age; lymph node status; and paraoropharyngeal, cranial nerve, orbit, and nasal involvement. Among lymph node positive patients, independently significant prognostic lymph node characteristics were Ho level and laterality. Although parapharyngeal involvement appeared to be prognostically unimportant, paraoropharyngeal involvement distinguished a subgroup with a poorer prognosis (HR: 1.84; 95% CI, 1.45, 2.34; P < 0.0001). Lateral spread to the medial infratemporal fossa and beyond also was found to confer a poorer prognosis. CONCLUSIONS: The results of the current study show that the revised 1997 TNM staging system is prognostically useful. Subdivision into paraoropharyngeal involvement and using the medial infratemporal fossa to delineate prognostically significant lateral spread should be considered in future revisions.

Adolescent↗
PubMed1999

Concurrent chemoradiotherapy followed by adjuvant chemotherapy in Asian patients with nasopharyngeal carcinoma: toxicities and preliminary results.

PURPOSE: Nasopharyngeal carcinoma (NPC) is endemic in Singapore. Nearly 60% of the patients diagnosed with NPC will present with locally advanced disease. The North American Intergroup study 0099 reported improved survival outcome in patients with locally advanced NPC who received combined chemoradiotherapy when compared to radiotherapy alone. Hence we explored the feasibility and efficacy of a similar protocol in our patients. METHODS AND MATERIALS: Between June 1996 and December 1997, 57 patients were treated with the following schedule as described. Radical radiotherapy (RT) of 66-70 Gy to the primary and neck with cisplatin (CDDP) 25 mg/m2 on days 1-4 given by infusion over 6-8 hours daily on weeks 1, 4, and 7 of the RT. This is followed by a further 3 cycles of adjuvant chemotherapy starting from week 11 from the first dose of radiation (CDDP 20 mg/m2/d and 5-fluorouracil [5-FU] 1 gm/m2/d on days 1-4 every 28 days). RESULTS: The majority of patients (68%) had Stage IV disease. About 54% of patients received all the intended treatment; 75% received all 3 cycles of CDDP during the RT phase and 63% received all three cycles of adjuvant chemotherapy. The received dose intensity of CDDP and 5-FU of greater than 0.8 was achieved in 58% and 60% of the patients respectively. Two treatment-related deaths due to reactivation of hepatitis B and neutropenic sepsis respectively, were encountered. At median follow-up of 16 months, 14 patients had relapsed, 12 systemically and 2 loco-regionally. CONCLUSION: Due to the acceptable tolerability of such a protocol in our cohort of patients, we have embarked on a Phase III study to confirm the results of the 0099 Intergroup study in the Asian context.

Adult↗
PubMed1999

Differential mRNA expression and subcellular locations of PI3-kinase isoforms in sympathetic and sensory neurons.

Phosphatidylinositol 3-kinase (PI3-kinase) enzymes are key signalling molecules in the PC12 and neuronal cell survival pathway and are also involved in the regulation of retrograde axonal transport of nerve growth factor (NGF), with sympathetic neurons more sensitive to the effects of wortmannin/LY294002 than sensory neurons (Bartlett et al. [1997]; Brain Res. 761:257-262; Reynolds et al. [1998] Brain Res. 798:67-74). In this article, we characterized the mRNA expression of PI3-kinase isoforms in mouse sympathetic superior cervical ganglia (SCG) and sensory trigeminal ganglia (TGG) and examined the subcellular locations of immunoreactivity of the PI3-kinase isoforms in mouse cultured SCG and dorsal root ganglion (DRG) neurons. Both the SCG and the TGG express mRNA for the p110alpha, beta, gamma, delta, and vps34p PI3-kinase isoforms, but the TGG and not the SCG express mRNA for the p170 PI3-kinase isoform. In cultured SCG and DRG neurons, p110alpha, beta, and gamma immunoreactivity is in the SCG and DRG growth cones, and predominantly in puncta throughout the growth cone varicosity. However, in the cell bodies immunoreactivity varied, p110alpha is localized predominantly at the plasma membrane, while p110beta and gamma is localized in the perinuclear region of the cells. In addition, unlike other cell types, wortmannin has little effect on actin filament polymerization in either mouse cultured SCG or DRG neurons.

Actins↗
PubMed1999

A simplified CT-based definition of the lymph node levels in the node negative neck.

INTRODUCTION AND PURPOSE: Using three dimensional (3D) conformal radiotherapy (CRT) techniques for elective neck irradiation (ENI) may allow for local disease control to be maintained while diminishing xerostomia by eliminating major salivary glands (or parts thereof) from the treatment portals. The standardization of CT based target volumes for the clinically negative (elective) neck is a prerequisite for 3DCRT. The aim of the present study was to substantially modify an existing ('original') CT-based protocol for the delineation of the neck target volume, into a more practical ('simplified') protocol. This will allow for rapid contouring and the implementation of conformal ENI in routine clinical procedures. MATERIAL AND METHODS: An earlier ('original') version of the CT-based definition for elective neck node regions 2-5 was re-evaluated, using 15 planning CT scans of previously treated patients. The contouring guidelines were simplified by (1) using a smaller number of easily identifiable soft tissue- and bony anatomical landmarks, which in turn had to be identified in only a limited number of CT slices, and (2) by subsequently interpolating the contoured lymph node regions. The adequacy of target coverage and the sparing using both 'original' and 'simplified' delineation protocols was evaluated by DVH analysis after contouring the primary tumor, the neck and the major salivary glands in a patient with supraglottic laryngeal (SGL) carcinoma who was treated using a 3DCRT technique. RESULTS: The BEV projections of the 'original' and the 'simplified' versions of the 3D elective neck target showed good agreement and were found to be reproducible. The DVH's of the target and parotid glands were not significantly different using both contouring protocols. CONCLUSIONS: The 'simplified' protocol for the delineation of the 3D elective neck target produced both comparable target coverage and sparing of the major salivary glands. When used together with an interpolation program, this 'simplified' protocol substantial reduced the contouring time and makes ENI with sparing of the major salivary glands a practical and achievable goal.

Head and Neck Neoplasms↗
PubMed1999

Phase II trial of a paclitaxel and carboplatin combination in Asian patients with metastatic nasopharyngeal carcinoma.

PURPOSE: An earlier phase II trial of paclitaxel in patients with metastatic nasopharyngeal carcinoma (NPC) demonstrated a response rate of 22%. Hence we proceeded to study the combination of paclitaxel and carboplatin in these patients. PATIENTS AND METHODS: The 21-day regimen was as follows: i.v. paclitaxel 175 mg/m2 over three hours preceded by standard premedications, followed by i.v. carboplatin dosed at AUC of six infused over one hour. Only chemotherapy-naive patients with histological diagnoses of undifferentiated carcinoma of the nasopharynx, systemic metastases and radiologically measurable lesions were eligible. RESULTS: Thirty-two patients were accrued to this study. Twenty patients (62%) had at least two sites of metastasis. The main grade 3-4 toxicity was neutropenia (31%). Nine patients (28%) developed neutropenic sepsis, which caused the demise of one of them. Twenty-four patients (75%) responded to treatment, with one (3%) attaining a complete response. The median time to progression of disease was seven months and the median survival was 12 months. At one year, 52% of the patients were alive. CONCLUSIONS: The combination of paclitaxel and carboplatin is an active regimen in NPC. Its convenience of administration and good tolerability make it an attractive alternative regimen to consider for patients with metastatic disease.

Adult↗
PubMed1999

Induction chemotherapy followed by concurrent chemoradiotherapy in stage III unresectable non-small cell lung cancer.

The favourable experience with the combination regimen of vinorelbine, ifosfamide and cisplatin (NIP) in patients with metastatic non-small cell lung cancer (NSCLC) has led to a protocol assessing this regimen as an induction treatment in patients with stage III unresectable NSCLC, followed by thoracic radiotherapy with concurrent daily cisplatin as a radiosensitizer. Two cycles of NIP were administered 21 days apart; each cycle comprised i.v. vinorelbine 25 mg/m2 on days 1 and 8, i.v. ifosfamide 3 g/m2 on day 1 with MESNA as uroprotection, and i.v. cisplatin 50 mg/m2 on day 1. Radical thoracic radiotherapy commenced on day 43 to a total dose of 64 Gy and i.v. cisplatin 6 mg/m2 was given concurrently prior to each fraction of radiation as a sensitiser. Two more cycles of NIP were given to patients who responded favourably to the induction treatment about 2 weeks after completion of radiation. Between July 1995 and July 1997, 44 patients were treated with this protocol. This treatment schedule was generally well tolerated. Grade 3-4 neutropenia occurred in 50% of the patients and neutropenic sepsis was seen in 8. Grade 3-4 oesophagitis was uncommon. Most of the patients were able to complete the induction and concurrent chemoradiotherapy phase. Major response occurred in 75% of the patients with 2 (4.5%) complete responses (CR). A total of 6 patients achieved CR after chemoradiotherapy. At a median follow-up of 35 months, the median overall survival for all patients was 15 months with a 3-year survival rate of 24%. The median overall survival for stage IIIA patients was 19 months with a 3-year survival rate of 39% in contrast to 13 months' median overall survival and only 15% 3-year survival rate for stage IIIB. The NIP regimen results in a high response rate in NSCLC and this treatment programme seems to benefit selected patients with stage III disease.

Adult↗
PubMed1999

Perinatal outcome after in-vitro fertilization-surrogacy.

The perinatal outcome of pregnancies (both single and multiple) established after in-vitro fertilization (IVF)-surrogacy was evaluated and compared to the outcome of pregnancies that resulted from standard IVF. Analysis of medical records and a telephone interview with physicians, IVF-surrogates, and commissioning mothers were conducted to assess prenatal follow up and delivery care in several hospitals. 95 IVF-surrogates delivered 128 liveborn (65 singletons, 27 sets of twins and two sets of triplets). The commissioning mothers and the IVF-surrogates average ages were 37.7 +/- 5.0 and 30.4 +/- 4.7 years old respectively. IVF-surrogates carrying twin and triplet gestations delivered substantially earlier than those who gestated singleton pregnancies (36.2 +/- 0.4 versus 35.5 versus 38.7 +/- 0.3 weeks gestation respectively; P < 0.001). Twin newborns were significantly lighter than singleton infants born through IVF-surrogacy (2.7 +/- 0.06 versus 3.5 +/- 0.07 kg; P < 0.001). The incidence of low birth weight infants rose from 3.3% in the single births to 29.6% (P < 0.01) in the twins and to 33.3% in the triplets born through IVF-surrogacy. The incidence of prematurity was significantly greater in both twins delivered by IVF-surrogates (20.4%) and infertile IVF patients (58%). The occurrence of pregnancy-induced hypertension and bleeding in the third trimester was four to five times lower in the IVF-surrogates, independently of whether they were carrying multiples. The incidence of Caesarean section was 21.3% for singleton gestations, while two times higher in the IVF-surrogates carrying multiples (56.3%). Postpartum complications occurred in 6.3% of patients and the incidence of malformation was similar to those reported for the general population. The results provide general reassurance regarding perinatal outcome to couples who wish to pursue IVF-surrogacy.

Adult↗
PubMed1999

Neonatal catecholaminergic ventricular tachycardia--a case report.

A case of neonatal catecholaminergic ventricular tachycardia is reported. Episodes of fetal tachycardia were detected in a female baby and just after birth, sustained monomorphic ventricular tachycardia of complete left bundle branch block pattern and inferior axis were recorded, suggesting a right ventricular outflow origin. Routine examination did not reveal overt heart disease. Ventricular tachycardia was induced by crying or sucking, elicited by isoproterenol infusion, and was suppressed by intravenous injection of ATP or propranolol. The baby's arrhythmia was controlled with oral propranolol. The ventricular tachycardia seemed to be caused by triggered activity.

Adenosine Triphosphate↗