Biomedical subjects

M Tan

Publications and source records attributed to M Tan.

At least 55 records · Page 3Linked to original sources

PubMed2001

Effects of testosterone and clomiphene on spectral EEG and visual evoked response in a young man with posttraumatic epilepsy.

The effects of testosterone and clomiphene on epilepsy was studied in a young man with posttraumatic seizures. In the control period, digital EEG and visual evoked potentials (VEPs) were recorded under carbamazapine therapy. After testosterone (T), seizures lessened and almost disappeared; the theta, delta, alpha, and beta powers decreased; VEPs increased. After clomiphene, VEPs considerably increased in size; clinical picture slightly improved; EEG power spectrum remained unchanged. It was suggested that T may be beneficial for epilepsy treatment by suppressing the EEG synchronization (slow wave activity) and attenuating the entropy state of the epileptic brain.

Adolescent↗

PubMed2001

[Application of laparoscopic technique in splenectomy].

OBJECTIVE: To investigate the application and effect of laparoscopic splenectomy (LS) in the treatment of spleen diseases. METHODS: Under CO2 pneumoperitoneum, laparoscopic splenectomy was performed on 43 patients. General conditions before and after operation, platelet counting, complications and recovery of patients were studied. RESULTS: Laparoscopic splenectomy was performed without complications in all the patients. In the patients with ITP, the effective rate of LS was 89.3%. The difficulty of operation was identified when the diameter of the spleen was over 15 cm assessed by ultrasonic examination, and the operative time was usually prolonged. CONCLUSIONS: LS is one of the best choices when proper indications exist and good techniques under laparoscopy are provided.

Adolescent↗

PubMed2000

Route of decomposition of thiomersal (thimerosal).

The route of formation and identification of the principal degradation products of thimerosal (thiomersal) has been undertaken. The initial oxidation to dithiosalicylic acid is followed by cleavage of the disulphide bond of the dithiosalicylic acid by the ethylmercuric ion to reform 1.5 mol of thimerosal with concurrent oxidation to form 0.5 mol of 2-sulfinobenzoic acid for each mole of dithiosalicylic acid. In the presence of copper ions 2-sulfobenzoic acid was also formed. A mechanism has been proposed which accounts for the stoichiometry of the cleavage reaction observed and the significance of the reaction is discussed.

Anti-Infective Agents, Local↗

PubMed2000

PTGF-beta, a type beta transforming growth factor (TGF-beta) superfamily member, is a p53 target gene that inhibits tumor cell growth via TGF-beta signaling pathway.

Identification and characterization of p53 target genes would lead to a better understanding of p53 functions and p53-mediated signaling pathways. Two putative p53 binding sites were identified in the promoter of a gene encoding PTGF-beta, a type beta transforming growth factor (TGF-beta) superfamily member. Gel shift assay showed that p53 bound to both sites. Luciferase-coupled transactivation assay revealed that the gene promoter was activated in a p53 dose- as well as p53 binding site-dependent manner by wild-type p53 but not by several p53 mutants. The p53 binding and transactivation of the PTGF-beta promoter was enhanced by etoposide, a p53 activator, and was largely blocked by a dominant negative p53 mutant. Furthermore, expression of endogenous PTGF-beta was remarkably induced by etoposide in p53-positive, but not in p53-negative, cell lines. Finally, the conditioned medium collected from PTGF-beta-overexpressing cells, but not from the control cells, suppressed tumor cell growth. Growth suppression was not, however, seen in cells that lack functional TGF-beta receptors or Smad4, suggesting that PTGF-beta acts through the TGF-beta signaling pathway. Thus, PTGF-beta, a secretory protein, is a p53 target that could mediate p53-induced growth suppression in autocrinal as well as paracrinal fashions. The finding made a vertical connection between p53 and TGF-beta signaling pathways in controlling cell growth and implied a potential important role of p53 in inflammation regulation via PTGF-beta.

Binding Sites↗

PubMed2000

Micronized purified flavonidic fraction compared favorably with rubber band ligation and fiber alone in the management of bleeding hemorrhoids: randomized controlled trial.

PURPOSE: The aim of this study was to assess the role of micronized purified flavonidic fraction in the management of bleeding nonprolapsed hemorrhoids. METHODS: Patients were randomly assigned to receive ispaghula husk alone, rubber band ligation plus ispaghula husk, or micronized purified flavonidic fraction plus ispaghula husk. Other colorectal diseases were excluded by colonoscopy. Blinded observers noted the time for bleeding to stop completely, recurrences, and treatment complications. RESULTS: A total of 162 patients were randomly assigned with no significant differences in the age and gender distributions among the groups. Hemorrhoidal bleeding was relieved most expediently in the micronized purified flavonidic fraction plus ispaghula husk group (ispaghula husk alone n = 66, mean (standard error of the mean) 10.6 (2.3) days; rubber band ligation plus ispaghula husk n = 57, 5.6 (1.1) days; micronized purified flavonidic fraction plus ispaghula husk n = 39, 3.9 (1.2) days; P = 0.03). However, there were no significant differences in the recurrences at six months of follow-up (ispaghula husk alone n = 8 (12 percent); rubber band ligation plus ispaghula husk n = 12 (21 percent); micronized purified flavonidic fraction plus ispaghula husk n = 2 (5.1 percent); P = 0.075). No complications or side-effects were noted. CONCLUSIONS: micronized purified flavonidic fraction used with fiber supplements rapidly and safely relieved bleeding from nonprolapsed hemorrhoids.

Adult↗

PubMed2000

Ambulatory manometry in patients with colonic J-pouch and straight coloanal anastomoses: randomized, controlled trial.

PURPOSE: Bowel function after ultralow anterior resection may be improved by a colonic J-pouch. The aim of this study was to compare the bowel function and ambulatory manometry in patients randomly assigned to straight coloanal anastomosis or colonic J-pouch. METHODS: Forty-seven consecutive patients underwent ultralow anterior resection for adenocarcinoma. The colonic J-pouch was constructed with 6-cm limbs. A bowel function questionnaire was administered at one year after surgery. Ambulatory manometry was performed before and at one year after surgery. RESULTS: Values are expressed below as mean and (standard error of the mean). Patients with colonic J-pouch were found to have less frequent stools (4.6 (0.3) vs. 7.1 (0.9) stools/day; P < 0.05) and stool clustering (35 vs. 63.2 percent; P < 0.05) and were less unlikely to soil when passing flatus (85 vs. 35.3 percent; P < 0.05). The ambulatory anorectal pressure gradient was better preserved in the colonic J-pouch group (30.3 (3.7) vs. 18 (2.6) mmHg; P < 0.05). Stool frequency was predicted by the mean rectal pressures (t = 3.368; P = 0.003). However, higher mean rectal pressures were tolerated by the colonic J-pouch for each daily bowel movement (6.7 (0.6) vs. 4.4 (0.5) mmHg/stool; P = 0.008). Anal sampling episodes and slow wave activity were impaired postoperatively in both groups. The minimal anal pressures were lower in patients unable pass flatus without soiling (12.4 (5.3) vs. 26 (2.3) mmHg; P = 0.004). Large contraction waves were not seen, and this may be related to the absence of severe defecation problems with 6-cm colonic J-pouches. CONCLUSIONS: A colonic J-pouch resulted in better bowel function and more favorable ambulatory manometric findings at one year of follow-up.

Adenocarcinoma↗

PubMed2000

Dentin sialoprotein (DSP) has limited effects on in vitro apatite formation and growth.

Sialoproteins such as bone sialoprotein (BSP) and dentin sialoprotein (DSP) accumulate at the mineralization fronts in bone and dentin, respectively, suggesting they have some function in the mineralization process. BSP, a highly phosphorylated protein rich in polyglutamate repeats, is an effective nucleator of hydroxyapatite (HA) formation in vitro. The present study examines the effect of DSP, a low phosphorylated but related sialoprotein, on the formation and growth of HA. In vitro, in a gelatin gel diffusion system, DSP at low concentrations (<25 microg/ml) slightly increased the yield of HA formed at 3.5 and 5 days, while at higher concentrations (50-100 microg/ml) it slightly inhibited accumulation. Fewer mineral crystals were formed in the presence of high concentrations of DSP but they tended to aggregate (making them appear larger by electron microscopic analysis) than those formed in DSP-free gels. X-ray diffraction line broadening analysis failed to show significant changes in c-axis crystal dimensions with increasing DSP concentration. When HA-seed crystals were coated with DSP before inclusion in the gelatin gel there was a reduction in mineral accumulation relative to HA-seeds which had not been coated with DSP, but the extent of inhibition was significantly less than that seen in this system with other mineralized tissue matrix sialoproteins, such as osteopontin or BSP. The low affinity of DSP for well-characterized seed crystals and the limited effect of this protein on HA formation and growth suggest that the role of DSP in dentin is not primarily that of a mineralization regulator.

Animals↗

PubMed2000

Low molecular weight analysis of tears using matrix assisted laser desorption ionization-time of flight mass spectrometry.

Many low molecular weight substances in human tears, including protein and lipid species, have yet to be characterized. Some of these uncharacterized substances may well be important in the pathogenesis of ocular surface disease or in ocular discomfort. The aim of this study was to build a biochemical profile of low molecular weight species in tears, and to determine its repeatability. A total of 80 tear samples were collected from 11 subjects. Tear samples were dialysed to remove salts, added to a matrix of alpha-cyano-4-hydroxycinnamic acid, and analysed using matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry. Species were separated based on their mass to charge ratio (m:z). The repeatability of the appearance of the different species was analysed using logistic regression and diurnal and day-to-day repeatability were ascertained. Peptides were identified in the range of 848 3897 Da. Of these, 39 peptides were found to be present in more than 10/80 samples. There was no diurnal variation in the peptides. All species were found to occur repeatably, with the exception of peptide 1653 Da.This study has demonstrated that the majority of low molecular weight species in tears are repeatably present and do not exhibit diurnal variation. Further study aims to characterize these species and to identify changes in tear profiles between subject groups.

Adult↗

PubMed2000

[Para-limbic relaxing incisions for reduction of astigmatism within the scope of catarct surgery].

PURPOSE: Limbal relaxing incision (LRI) is an easy and safe procedure to reduce astigmatism. It should be clarified, whether the effect is discussed controversely, because the varying corneal diameter and consequently the varying LRI position was not considered. PATIENTS AND METHODS: 56 patients aged 76 +/- 9 years with preoperative astigmatism of 1.6 D (0.6 to 7.0 D) underwent an almost astigmatically neutral cataract procedure (3.2 mm temporal clear corneal phacoemulsification with foldable lens implantation) and received independently from the given corneal diameter limbus related relaxing incisions of 80 degrees length and 0.6 mm depth. We performed the paired LRI in 4.5 mm, 5 mm and 5.5 mm distance from the corneal center on the steeper meridian. RESULTS: 4.3 months postoperatively we observed an astigmatic reduction of -1.0 D (-0.1 to -3.2 D) following LRI with a 9 mm optical zone, LRI with 10 mm diameter led to an astigmatic reduction of -0.4 D (-0.1 to -2.9 D) and LRI with 11 mm diameter were followed by an astigmatic reduction of -0.3 D (+0.5 to -1.1 D). Undercorrections were more frequently observed in younger patients, overcorrections more in elderly people. CONCLUSION: The application of three different kinds of limbus related relaxing incisions, with 4.5, 5 and 5.5 mm distance from the corneal center or 9, 10 and 11 mm optical zone respectively, corresponds to the variable anatomic situation of the limbus, therefore leading to nearly predictable data and explaining the divergent results of previous reports. The nearer the LRI is applied to the corneal center, the stronger is the relaxing effect.

Aged↗

PubMed2000

Marginal models for longitudinal continuous proportional data.

Continuous proportional data arise when the response of interest is a percentage between zero and one, e.g., the percentage of decrease in renal function at different follow-up times from the baseline. In this paper, we propose methods to directly model the marginal means of the longitudinal proportional responses using the simplex distribution of Barndorff-Nielsen and Jørgensen that takes into account the fact that such responses are percentages restricted between zero and one and may as well have large dispersion. Parameters in such a marginal model are estimated using an extended version of the generalized estimating equations where the score vector is a nonlinear function of the observed response. The method is illustrated with an ophthalmology study on the use of intraocular gas in retinal repair surgeries.

Algorithms↗

PubMed2000

Testing secondary hypotheses following sequential clinical trials.

Sequential monitoring in a clinical trial poses difficulty in hypotheses testing on secondary endpoints after the trial is terminated. The conventional likelihood-based testing procedure that ignores the sequential monitoring inflates Type I error and undermines power. In this article, we show that the power of the conventional testing procedure can be substantially improved while the Type I error is controlled. The method is illustrated with a real clinical trial.

Biometry↗

PubMed2000

A positive cis-acting DNA element is required for high-level transcription in Chlamydia.

The spacer A/T region is a positive cis-acting DNA element that was identified in the Chlamydia trachomatis rRNA promoter region. We have now demonstrated that similar sequences in other chlamydial promoters are important for transcription. Substitution of candidate spacer A/T regions in four chlamydial promoters decreased transcription by partially purified C. trachomatis RNA polymerase in an in vitro transcription assay. Addition of a spacer A/T region to the dnaK promoter, which does not contain an identifiable spacer A/T region, increased transcription 16-fold. Transcription of Escherichia coli promoters by C. trachomatis RNA polymerase also appeared to be dependent on the spacer A/T region. However, the effect of the spacer A/T region on transcription by E. coli RNA polymerase was small. In summary, the spacer A/T region is a novel DNA element that is required for high-level transcription of many promoters by chlamydial RNA polymerase.

Base Sequence↗

PubMed2000

Sertoli cell tumor in a prepubertal boy mimicking testicular torsion.

A 9-year-old boy presented with left, intermittent testicular pain that was present for 3 days. On physical examination, left testis was grossly enlarged and firm but mildly tender. Serum alpha-fetoprotein and beta-human chorionic gonadotropin levels were within normal range. Color doppler ultrasonography which was performed to rule out testicular torsion revealed an intratesticular mass located at the upper pole of left testis and left radical orchiectomy was performed. The histopathological diagnosis was Sertoli cell tumor.

Biopsy, Needle↗

PubMed2000

Antitumor activity of temozolomide combined with irinotecan is partly independent of O6-methylguanine-DNA methyltransferase and mismatch repair phenotypes in xenograft models.

The activity of temozolomide combined with irinotecan (CPT-11) was evaluated against eight independent xenografts (four neuroblastomas, three rhabdomyosarcomas, and one glioblastoma). In all studies, temozolomide was administered p.o. daily for 5 consecutive days/cycle, found in preliminary studies to be the optimal schedule for administration. Irinotecan was administered i.v. for 5 days for 2 consecutive weeks/cycle. Treatment cycles were repeated every 21 days for a total of three cycles over 8 weeks. In combination, temozolomide and CPT-11 induced complete responses in four neuroblastomas, two rhabdomyosarcomas, and the glioblastoma line. The activity of the combination was significantly greater than the activity of either agent administered alone in four tumor lines. Of interest, the interaction appeared independent of tumor MGMT or mismatch repair phenotype, suggesting that the mechanism of synergy may be independent of O6-methylation by temozolomide. Pharmacokinetic studies indicated no detectable interaction between these two agents. Further, coadministration of CPT-11 appeared to reduce the toxicity of temozolomide in tumor-bearing mice.

Administration, Oral↗

PubMed1999

Incidences of asymmetries for the palmar grasp reflex in neonates and hand preference in adults.

It was hypothesized that adult handedness might be predicted from the neonatal grasp reflex. Grasp reflex was measured from right and left hand (10 trials for each hand) in neonates. According to significance for the difference between the mean grasp reflex strength from the right and left hands, the subjects were designated as right-, left-, and mixed-handers. Adult hand preference was assessed by Edinburgh Handedness Inventory. The percentage of left-handedness (8.3%) in neonates coincided with adult left-handedness (6.3-9.2%). The percentage of consistent right-hand preference in adults coincided with percentage of right-handedness in neonates (25.7%). The high percentage of neonatal mixed-handedness was similar to that to be expected from the right shift model of hand preference. It was concluded that left-handedness and consistent right-handedness may be determined prenatally, under genetic and/or hormonal control, and that a large majority of neonatal handedness, mixed-handers, might change their hand preference in favor of right-handed-ness under socio-cultural and developmental influences of speech centres.

Adult↗

PubMed1999

A Bayesian hierarchical model for multi-level repeated ordinal data: analysis of oral practice examinations in a large anaesthesiology training programme.

Oral practice examinations (OPEs) are used in many anaesthesiology programmes to familiarize anaesthesiology residents with the format of the oral examination administered by the American Board of Anesthesiology. The OPE outcome (final grade) consists of 'Definite Not Pass', 'Probable Not Pass', 'Probable Pass' and 'Definite Pass'. In our study to assess the validity of the OPE, residents took an average of two (ranging from one to six) OPEs, each of which was evaluated by two board certified anaesthesiologists randomly selected from a pool of 12. A key question of interest was to identify factors, for example, the length of training, didactic experience and other characteristics, that most influence OPE outcome. In addition, we were interested in assessing the reliability of the final grade, that is, the covariance parameters are of interest as well. However, estimating variance components in multi-level data with an unequal number of repeated ordinal outcomes presents several statistical challenges, such as how to estimate high dimensional random effects parameters, especially for ordinal outcomes. We propose a Bayesian hierarchical proportional odds model for data with such complexity. The flexibility of such a model allows us to make inference on the association of OPE outcomes with other factors and to estimate the variance components as well.

Anesthesiology↗

PubMed1999

The micronuclear gene encoding a putative aminoacyl-tRNA synthetase cofactor of the ciliate Euplotes octocarinatus is interrupted by two sequences that are removed during macronuclear development.

The micronuclear gene of the ciliated protozoan Euplotes octocarinatus (Eo) syngen 1 encoding the putative aminoacyl-tRNA synthetase cofactor (ARCE), as well as its macronuclear version and the corresponding cDNA, were amplified and sequenced. Analyses of the sequences revealed that the micronuclear gene contains two sequences (430 and 625bp long) that are missing in the macronuclear version of this gene. These sequences are called 'internal eliminated sequences' (IESs) and appear to occur in all ciliates. The two IESs are located in the coding region of the micronuclear gene. One IES is flanked by a pair of dinucleotide 5'-TA-3' direct repeats and the other one by a pair of hepta-nucleotide 5'-TTACTGA-3' direct repeats. Inside the two IESs, several other sequence repeats were found. The macronuclear DNA molecule carrying this gene is 1517bp long and shows characteristics typical of macronuclear chromosomes of hypotrichous ciliates. Copy number determination revealed that the molecule is amplified to only about 750 copies per macronucleus. The deduced protein is a 441-amino-acid (aa) polypeptide with a molecular mass of 50kDa. It shares a conserved endothelial monocyte-activating polypeptide II (EMAP II)-like carboxyl-terminal domain and a hydrophilic central domain containing a KEKE-motif with a group of proteins associated with aminoacyl-tRNA synthetases and tRNAs.

Amino Acid Sequence↗

PubMed1999

Transcriptional activation of the human glutathione peroxidase promoter by p53.

Glutathione peroxidase (GPX) is a primary antioxidant enzyme that scavenges hydrogen peroxide or organic hydroperoxides. We have recently found that GPX is induced by etoposide, a topoisomerase II inhibitor and a p53 activator. In a search for a cis-element that confers potential p53 regulation of GPX, we identified a p53 binding site in the promoter of the GPX gene. This site bound to purified p53 as well as p53 in nuclear extract activated by etoposide. A luciferase reporter driven by a 262-base pair GPX promoter fragment was transcriptionally activated by wild type p53 in a p53 binding site-dependent manner. The same reporter was also activated in a p53 binding site-independent manner by several p53 mutants. The p53 binding and transactivation of the GPX promoter were enhanced by etoposide in p53-positive U2-OS cells. Etoposide-induced transactivation was blocked by a dominant negative p53 mutant, indicating that endogenous wild type p53, upon activation by etoposide, transactivated the GPX promoter. Furthermore, expression of endogenous GPX was induced significantly at both mRNA and enzyme activity levels by etoposide in U2-OS cells but not in p53-negative Saos-2 cells. This is the first report demonstrating that GPX is a novel p53 target gene. The finding links the p53 tumor suppressor to an antioxidant enzyme and will facilitate study of the p53 signaling pathway and antioxidant enzyme regulation.

Base Sequence↗