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Biomedical subjects

H Tan

Publications and source records attributed to H Tan.

At least 19 recordsLinked to original sources

Lipids and coronary heart disease in Asia.

In Western countries, it has been shown that coronary heart disease (CHD) is related to high serum total cholesterol (TC) levels. In less developed continents such as Asia and Africa, serum lipid levels are low and CHD incidence is much lower as compared with Western countries. With growing urbanization and industrialization in Asia, it has been shown that there is a concomitant rise in the level of serum TC and with it a rise in CHD. In all the Asian countries, serum TC levels are also higher in the urban compared with the rural population. Singapore, the only Asian country which is 100% urbanized since 1980, showed a rise of serum TC similar to that seen in the US and UK from the 1950s to the 1980s followed thereafter by a fall. This is reflected in the trend (rise followed by a fall) of CHD morbidity and mortality as well. In spite of a declining trend in serum TC level, CHD morbidity and mortality are still high in Singapore and comparable to the Western countries. The rest of the Asian countries show a different pattern from Singapore. In general, there is still a rising trend in serum TC level and in CHD mortality in most Asian countries. However, Japan is considered an exception in having a decreasing CHD mortality in spite of an increasing trend in serum TC. This may be attributed to a better control of other CHD risk factors such as hypertension and smoking. The rising trend in serum TC level remains a cause for concern, as this will emerge as a major problem for CHD morbidity and mortality in the future.

Asia, Southeastern↗

sanC--a novel gene involved in nikkomycin biosynthesis in Streptomyces ansochromogenes.

AIMS: To investigate the genes involved in the nikkomycin biosynthesis and their molecular mechanism. METHODS AND RESULTS: A 0.9 kbp SmaI fragment was cloned and sequenced which contains a complete open reading frame designated sanC (GenBank accession no. AF228522). In search of database, the deduced product of sanC was not homologous with any known proteins. The disruption and complementation of sanC showed that sanC is essential for nikkomycin biosynthesis in Streptomyces ansochromogenes. CONCLUSIONS, SIGNIFICANCE AND IMPACT OF THE STUDY: sanC is a novel and essential gene involved in nikkomycin biosynthesis in S. ansochromogenes.

Amino Acid Sequence↗

Acute disseminated encephalomyelitis in children: outcome and prognosis.

BACKGROUND: Acute disseminated encephalomyelitis (ADEM) is the most common demyelinating disorder of childhood. Its clinical features, prognosis and treatment vary in different reports. OBJECTIVES: To examine a series of children with ADEM for clinical findings, course, recurrences, and possible variables affecting outcome. METHODS: Multicentric data collected from 7 tertiary referral centers were registered and evaluated in a central database in 1990 - 2001 for clinical, laboratory, and MRI features. Course and prognosis were assessed in patients with at least 12 months' follow-up. RESULTS: Forty-six patients were evaluated. Median age at onset was 8 years, M/F ratio, 1.7/1. Most common symptoms and signs pertained to the motor system and consciousness. Of 39 children with 12 months' follow-up, 71 % recovered completely. Thirteen (33 %) children had relapses. Patients who had more than one relapse (n = 4) presented with new symptoms at each attack. Treatment with high-dose methylprednisolone was associated with complete recovery, and tapering over more than 3 weeks, with a lower rate of relapses. MRI lesions could persist even in asymptomatic patients; in particular, periventricular lesions tended to disappear later than others. CONCLUSIONS: Complete clinical recovery is common and serious complications are rare in childhood ADEM, but the rate of relapses is considerable. Clinical picture at first relapse may help to identify patients likely to experience multiple relapses. The timing and duration of steroid treatment affects outcome.

Adolescent↗

Phase I clinical and pharmacologic study of chronic oral administration of the farnesyl protein transferase inhibitor R115777 in advanced cancer.

PURPOSE: To determine the maximum-tolerated dose, toxicities, and pharmacokinetics of R115777, a farnesyl transferase inhibitor, when administered continuously via the oral route. PATIENTS AND METHODS: Patients with advanced solid malignancies were treated with R115777 using an interpatient dose escalation scheme starting at 50 mg bid. Pharmacokinetics were assessed on days 1, 28, and 56. RESULTS: Twenty-eight patients were entered onto the study and the median duration of treatment was 55 days. The dose-limiting toxicities were myelosuppression and neurotoxicity. At a dose of 400 mg bid, grade 4 leukocytopenia and neutropenia were seen in two of four patients. Neurotoxicity grade 3 developed in one of five patients at 500 mg bid and in one of 13 at 300 mg bid after 8 weeks of treatment. Common nonhematologic toxicities were nausea, vomiting, and fatigue. The recommended dose for phase II/III testing in this scheme is 300 mg bid. The pharmacokinetic studies indicated dose proportionality. Little accumulation occurred and steady-state levels were reached within 2 to 3 days. Analyses of historic tumor material showed that five of 15 of patients had a K-ras mutation in codon 12. Three patients with pancreatic, colon, and cervix carcinomas had stable disease and one patient with a colon carcinoma had a minor response accompanied by a more than 50% decrease in carcinoembryonic antigen tumor marker. A fifth patient, with platinum-refractory non-small-cell lung cancer, showed a partial response that lasted for 5 months. CONCLUSION: Continuous dosing of R115777 is feasible with an acceptable toxicity profile at a dose of 300 mg bid.

Administration, Oral↗

Complexities in ETS-domain transcription factor function and regulation: lessons from the TCF (ternary complex factor) subfamily. The Colworth Medal Lecture.

The ETS-domain transcription factor family can be divided into a series of subfamilies. Elk-1 represents the founding member of the ternary complex factor (TCF) subfamily. By focusing on the TCF subfamily, we can demonstrate the complexities that exist in the function and regulation of ETS-domain transcription factors. This article focuses on Elk-1 in detail and summarizes the functions of other TCFs. The key themes covered include the domain structure of the TCFs, the mechanisms of complex formation with serum response factor, regulation of TCFs by mitogen-activated protein kinase cascades, and transcriptional regulatory properties of the TCFs. Finally, the emerging role of the TCFs in vivo is discussed. A picture is developing indicating that, while these proteins exhibit significant sequence and functional conservation, key differences in their structure and regulation are being identified which may relate to unique functions of these proteins in vivo.

Amino Acid Sequence↗

Treatment of murine breast cancer cells with antisense RNA to the type I insulin-like growth factor receptor decreases the level of plasminogen activator transcripts, inhibits cell growth in vitro, and reduces tumorigenesis in vivo.

AIMS: To establish that cells from the murine mammary carcinoma cell line, EMT6, express type I insulin-like growth factor receptor (IGF-IR), tissue-type plasminogen activator (tPA), and urokinase-type plasminogen activator (uPA). To investigate the role of IGF-IR in growth, transformation, and tumorigenesis in addition to its relation to tPA and uPA in EMT6 cells. To assess the suitability of the EMT6/syngeneic mouse model for studying the role of IGF-IR in tumorigenesis. METHODS: The presence of transcripts for IGF-IR, tPA, and uPA was determined by northern blot analysis using poly (A(+)) RNA derived from EMT6 cells transfected with an antisense IGF-IR construct or a construct lacking the antisense IGF-IR insert. Flow cytometry was used to measure IGF-IR protein. Assays were performed to determine cell proliferation, transformation, and the tumorigenicity of antisense IGF-IR transfected EMT6 cells and control transfected EMT6 cells. RESULTS: There was strong expression of IGF-IR, tPA, and uPA in EMT6 cells. EMT6 cells from clones carrying antisense IGF-IR displayed a significant decrease in cell proliferation and lost the ability to form colonies in soft agar. A decrease in tumour size occurred when cells carrying the antisense IGF-IR were injected into syngeneic mice. Reduced expression of tPA and uPA was seen in EMT6 cells carrying the antisense IGF-IR construct. CONCLUSIONS: The IGF-IR plays a role in the progression, transformation, and tumorigenesis of EMT6 murine mammary carcinoma cells. The suppression of IGF-IR mRNA in EMT6 cells decreases tPA and uPA expression. EMT6 cells and the syngeneic mouse provide a suitable model for studying the role of IGF-IR in breast tumour progression.

Animals↗

Detection of widespread fluids in the Tibetan crust by magnetotelluric studies.

Magnetotelluric exploration has shown that the middle and lower crust is anomalously conductive across most of the north-to-south width of the Tibetan plateau. The integrated conductivity (conductance) of the Tibetan crust ranges from 3000 to greater than 20,000 siemens. In contrast, stable continental regions typically exhibit conductances from 20 to 1000 siemens, averaging 100 siemens. Such pervasively high conductance suggests that partial melt and/or aqueous fluids are widespread within the Tibetan crust. In southern Tibet, the high-conductivity layer is at a depth of 15 to 20 kilometers and is probably due to partial melt and aqueous fluids in the crust. In northern Tibet, the conductive layer is at 30 to 40 kilometers and is due to partial melting. Zones of fluid may represent weaker areas that could accommodate deformation and lower crustal flow.

Journal Article↗

Rubral tremor after thalamic infarction in childhood.

The occurrence of tremor after thalamic lesions is well known. Delayed rubral tremor secondary to bilateral thalamic infarction is a rare finding and has not been reported previously in childhood. We present two children with a combined resting-postural-kinetic tremor caused by bithalamic infarction. The first child was a male 14 months of age, and the second was a male 9 years of age. These children come from unrelated families. On hospital admission of the first patient, generalized seizures and routine electroencephalogram (EEG) findings with diffuse spike-wave discharges predominantly over the left frontal area were clinically observed, leading to the initial diagnosis of epilepsia partialis continua. However, clinical observation and video-EEG monitoring of the movements revealed nonepileptiform accompaniments, favoring the diagnosis of rubral tremor. In the second patient, EEG revealed no paroxysmal activity and was within normal limits for age. In both patients, cranial magnetic resonance imaging revealed ischemic lesions in thalami bilaterally but failed to reveal any mesencephalic lesion. These patients demonstrate that thalamic infarction can cause rubral tremor in childhood.

Ataxia↗

Endoscopic dacryocystorhinostomy in children.

BACKGROUND: Persistent nasolacrimal duct obstruction (NLDO) often requires treatment by probing, intubation, or balloon dacryoplasty. Refractory cases have been managed by external dacryocystorhinostomy (DCR), which leaves a scar; however, this procedure is generally avoided in young children. Endoscopic DCR has been successfully performed in adults and described in children. We report the success of this procedure in a series of pediatric patients. METHODS: A retrospective review of all endoscopic lacrimal procedures performed in a 3-year period was undertaken. Seventeen children (22 ducts) with persistent NLDO after at least one failed probing, with or without silicone tube placement, underwent endoscopic DCR. Follow-up ranged from 6 to 36 months, and success was defined as resolution of tearing and discharge by follow-up clinical evaluation and by parental history. RESULTS: All but 2 patients (88%) with NLDO showed complete resolution of tearing and discharge. These 2 patients had recurrent symptoms after the Crawford tubes were removed and required revision endoscopic DCR. No complications from this procedure were noted. CONCLUSIONS: Endoscopic DCR is a safe and effective means of treating persistent NLDO in infants and young children when simple probing, intubation, or balloon procedures have failed. The team ophthalmology-otolaryngology endoscopic approach provides a highly successful alternative for patients with a persistent distal obstruction that might otherwise require an external procedure.

Adolescent↗

Postoperative morbidity, mortality, costs, and long-term survival in severely obese patients undergoing orthotopic liver transplantation.

OBJECTIVE: Severely obese patients who undergo orthotopic liver transplantation are likely to have higher morbidity, mortality, costs, and a lower long-term survival. METHODS: This case-control study was done at a university hospital. One hundred twenty-one consecutive patients who underwent liver transplantation between 1994 and 1996 were studied. Severe obesity was defined as body mass index (BMI) more than 95th percentile (>32.3 for women and >31.1 for men), and moderate obesity was defined as BMI between 27.3 and 32.3 for women and 27.8 and 31.1 for men. The outcome measures were intraoperative complications, postoperative complications (wound infections, bile leak, vascular complications), length of hospital stay, costs of transplantation, and long-term survival RESULTS: The baseline characteristics, UNOS status, and cause of liver disease at the time of transplantation were similar in severely obese (n = 21, BMI = 37.4+/-4.8 kg/m2), obese (n = 36, BMI 28.7+/-0.9 kg/m2), and nonobese patients (n = 64, BMI 23.8+/-2.5 kg/m2). The intraoperative complications and transfusion requirements were similar in all three groups. The postoperative complications such as respiratory failure (p = 0.009) and systemic vascular complications (p = 0.04) were significantly higher in severely obese patients. The overall perioperative complication rate was 0.61 (39 of 64 patients) in nonobese patients, 0.77 (28 of 36 patients) in obese patients, and 1.43 (30 of 21 patients) in severely obese patients (p = 0.01). Infections were the leading cause of death in all groups accounting for 57-66% of deaths. The length of hospital stay was significantly higher in obese patients. The hospital costs of transplantation were higher ($30,000-$40,000) in severely obese patients than in nonobese patients. The long-term patient survival was similar between the groups (Kaplan-Meier analysis). CONCLUSIONS: Despite higher postoperative complications, severely obese patients have an acceptable long-term survival, which is comparable to nonobese patients. The cost of transplantation is higher among severely obese patients. There was no increased incidence of cardiovascular mortality among severely obese patients during the follow-up period.

Adult↗

Cloning and expressionanalysis of two cotton (Gossypium hirsutum L.) genes encodingcell wall proline-rich proteins.

Two cotton (Gossypium hirsutum L.) genes, ghprp1 and ghprp2, encoding cell wall proline-rich proteins (PRPs) have been cloned and characterized. The ghprpl gene has an open reading frame (ORF) that encodes a PRP of 299 amino acids (aa), whereas the ghprp2 gene contains an ORF that codes for a 310-aa PRP. The GhPRP1 has an 80% identity in aa sequence with that of GhPRP2. Like other plant cell wall PRPs, both cotton PRPs have a hydrophobic signal peptide at their N-termini, followed by repeating peptide units. Northern blot analyses showed that the ghprpl gene is predominantly expressed in the fiber during the elongation stage of fiber development. Reverse transcription (RT)-PCR analysis showed that ghprpl is expressed in both fiber and root tissues, whereas ghprp2 is in roots only. The ghprpl gene was shown to be present in the A1, A2, D1 and D5 genomes of Gossypium by PCR amplification, whereas the ghprp2 gene is only present in the A1 and A2 genomes. The ghprpl gene was over-expressed in the yeast Pichia pastoris, and the expressed GhPRP1 protein was used as an antigen to raise polyclonal antibodies (anti-GhPRP1). Western analysis using the anti-GhPRP1 probe detected a major protein band (50 kDa) in 5-31-day postanthesis (DPA) fibers. However, the 50 kDa protein was absent in other cotton tissues.

Amino Acid Sequence↗

Outcome prediction in severe traumatic brain injury with transcranial Doppler ultrasonography.

OBJECTIVE: To investigate the value of transcranial Doppler (TCD) ultrasonography in evaluating the outcome of severe traumatic brain injury and to correlate the TCD values with intracranial pressure (ICP) and cerebral perfusion pressure (CPP) monitoring. METHODS: A prospective study was conducted to evaluate the contribution of TCD ultrasonography to neurological outcome in a series of 96 severe traumatic brain injury patients. The quantitative variables of TCD ultrasonography included the mean blood flow velocity of the middle cerebral artery (MCA) and pulsatility index within the first 24 hours of admission. The ICP and CPP values were a lso recorded. Outcome in 6 months postinjury was evaluated using the Glasgow Outcome Scale (GOS 4-5 was considered as "good" and GOS 1-3 as "poor"). RESULTS: The mean blood flow velocity of the MCA was larger than 40 cm/s in 30 (51%) patients with good outcome whereas it was less than 40 cm/s in 27 (73%) patients with poor outcome (P<0.025). The mean PI in cases of good outcome (34 patients, 57%) was lower than 1.5 whereas in poor outcome (30 patients, 83%) was higher than 1.5 (P<0.001). The correlations of ICP and CPP to pulsatility index were statistically significant (P<0.01). CONCLUSIONS: TCD ultrasonography is valid in predicting the patient's outcome of 6 months and correlates significantly with ICP and CPP values when it is performed in the first 24 hours of severe traumatic brain injury.

Adolescent↗

[Effects of different disinfectants on levels of endotoxin in canals of chronic periapical periodontitis].

OBJECTIVE: The objective of this study is to compare effects of formocresol, camphorated phenol and Ya Kan (metronedazole) on endotoxin levels in canals of chronic periapical periodontitis. METHODS: A total of 30 patients with chronic periapical periodontitis were selected from outpatients, and 10 cases each were randomly picked out to treat by sealing with formocresol, camphorated phenol and Ya Kan respectively. All patients were both sampled before and after sealing of these disinfectants, and chromogenic substrate method of limulus amebocyte lysate (LAL) test was used to measure levels of endotoxin. RESULTS: The effects of Ya Kan, formocresol and camphorated phenol on levels of endotoxin did not showed significant difference. CONCLUSION: Some anti-anaerobic bacterial drugs can be used to treat chronic periapical periodontitis.

Anti-Infective Agents, Local↗

[Structure and function of sanL--a gene involved in nikkomycin biosynthesis of Streptomyces ansochromogenes].

The chromosome walking strategy has been used in this experiment and a 10 kb DNA fragment was cloned from the cosmid library of Streptomyces ansochromogenes using a partial DNA fragment involved in the nikkomycin biosynthesis as a probe. The nucleotide sequence showed that the DNA fragment contains two complete open reading frames (ORFs), they are designated as sanK and sanL respectively. The sanL is located on the upstream of sanK, it has 1281 nucleotides with ATG at 345 position as start codon and TGA at 623 position as stop codon. The deduced product is L-lysine 2-aminotransferase using Blastx program. The experiment of gene disruption indicated that this gene is closely related to nikkomycin biosynthesis of Streptomyces ansochromogenes.

Amino Acid Sequence↗

[Relationship among lymphatic metastasis, pericancerous lymphocytic reaction and dendritic cell infiltration in laryngeal carcinoma cells].

OBJECTIVE: To study the role and the clinical significance of dendritic cell infiltration against tumor cells in patients with laryngeal squamous cell carcinoma. METHODS: Immunohistochemical method using S-100 protein antibody was employed to detect dendritic cells (DC) on paraffin-embedded tissue sections from 23 patients with laryngeal squamous cell carcinomas. The relationships among the density of dendritic cell infiltration in laryngeal carcinomas and cervical lymphatic metastasis, pericancerous lymphocytic reaction and other clinicopathologic parameters were observed. RESULTS: The numbers of dendritic cells infiltrating among laryngeal carcinoma cells in patients with no cervical lymph metastasis was significantly larger than those with cervical lymphatic metastasis (t = 4.889, P < 0.01). Significant increase DC infiltration among laryngeal carcinoma cells was found in the group with intensively positive reaction of pericancerous lymphocyte than in the medium and weakly positive groups. The number of infiltrating dendritic cells in patients who had survived more than 5 years was significantly larger than those survived less than 5 years (t = 4.423, P < 0.01). The numbers of the infiltrating dendritic cells in patients with well-differentiated squamous cell carcinoma and poorly differentiated squamous cells carcinoma were 2.2 +/- 1.07 and 14.6 +/- 7.14 respectively, which were significantly different (q = 4.532, P < 0.05). CONCLUSION: The study showed that DC infiltration among laryngeal squamous carcinoma cells played an important role in the host immune reaction against tumor. It indicated that when the density of infiltrating DC is higher, the patients had less chance of cervical lymph metastasis and may have a longer survival time. There was a coordinative effect between DC infiltration in tumor cells and pericancerous lymphocyte reaction. Thus, the DC infiltration among laryngeal squamous cells could be used as an index of prognosis.

Aged↗

[Study of Raman-PL spectra for GaAs layer on Si substrate in hot wall epitaxy].

The quality of GaAs layer on the Si substrate under different growth conditions with HWE technology was studied by Raman and PL spectra. The results show that the ratio of peak value to area for the TO peak at 265 cm-1 increased gradually with the improvement of the GaAs crystallinity quality for the GaAs layer at 300 K. The FWHM of Raman spectra of TO peak at 265 cm-1 is narrow, and the Raman shift is 2 cm-1. In the PL spectra, the FWHM at 900 nm is narrow. Then the results show GaAs layer is highly structural quality. But if we can not measure the PL peak at 900 nm, or the FWHM of Raman spectra of TO peak at 265 cm-1 is not narrow, the GaAs layer is not crystallinity. Therefore, we can estimate the layer quality by Raman and PL spectra.

Arsenicals↗

Relaxation Spectra and Viscoelastic Behavior of a Model Hydrophobically Modified Alkali-Soluble Emulsion (HASE) Polymer in Salt/SDS Solutions.

The viscoelastic behavior of a semidilute hydrophobically modified alkali-soluble emulsion (HASE)-C20 polymer in NaCl and NaCl/SDS (sodium dodecyl sulfate) solutions was determined using a Rheometric fluids rheometer and the data were converted to relaxation spectra. The dynamic moduli can be fitted with a multiple modes Maxwell model. In the presence of increasing amounts of NaCl, the moduli decrease, where G', decreases more rapidly than G". However, in the presence of SDS and 0.4 M NaCl, the dynamic moduli increase to a maximum at a critical concentration and decrease thereafter. The relaxation spectra suggest that the structure of the polymer network is complex and it contains two to six relaxation times, depending on the NaCl or SDS/0.4 M NaCl concentrations. With increasing NaCl concentrations, the fastest peak shifts to longer times while the slowest peak decreases. This corresponds to the destruction of the network as the polymer backbone collapses to form clusters with a larger aggregation number. For HASE in SDS/0.4 M NaCl solutions, the lifetime of both the hydrophobic junction (fastest peak) and network relaxation (slowest peak) shift to longer times, which suggests the strengthening of active junctions by bound SDS molecules. However, beyond a critical SDS concentration, the relaxation time of the polymer and hydrophobic junction decreases to an asymptotic value. Copyright 2000 Academic Press.

Journal Article↗

Atmospheric mercury deposition in Guizhou, China

The atmospheric deposition of mercury including total gas phase mercury (TGM), gas phase divalent mercury (Hg2+), and gas phase monomethyl mercury (MMHg) was investigated. Samples were collected from central cities and nature reserve areas across the province. Techniques and equipment including moss bags, KCl-coated denuder and GARDIS-1A portable mercury vapor analyzer were employed for sample collection and analysis. The reliability of techniques and analytical methods used for the project was evaluated. The deposition of atmospheric mercury was reported in species in this important mercury polluted province for the first time. The spatial and temporal variability of mercury emissions were investigated and reported. Contribution of coal mercury emissions to the atmosphere mercury deposition of the province was also investigated.

Journal Article↗