Biomedical subjects
Publications and source records attributed to S Tan.
A quantitative method has been developed for the determination of piperylpiperidine in Wuwei Qingzhuo powder by reversed phase HPLC. The average recovery is 102.0% (RSD = 0.46%) and lowest detection concentration 0.03 microgram/ml. The linear range of piperylpiperidine is 1.875-30 micrograms/ml, r = 0.9999.
A reversed-phase HPLC method was described for the determination of psoralen and isopsoralen in tincture of Fructus Psoraleae. After adding the internal standard and diluting the sample to a definite volume, the sample was injected and analysed. The RSDs were within 2% and the minimum working concentrations below 1 microgram/ml; the average recoveries of psoralen and isopsoralen 102.8% and 99.5% respectively and the linear ranges of psoralen and isopsoralen 12-200 micrograms/ml and 13-210 micrograms/ml (r = 0.999) respectively.
High response rates are seen in patients undergoing dose-intensive chemotherapy and autologous marrow transplantation due to the ability of the therapy to overcome inherent or acquired drug resistance. However, relapse rates are also high because this drug resistance reversal is incomplete. Because both P-glycoprotein- and platinum-induced resistance appear to be clinically important and can be reversed in vitro with a short exposure of cyclosporin A (CSA) at 2000 and 5000 ng/ml, respectively, we undertook a trial of high-dose chemotherapy with carboplatin (1500mg/m2), mitoxantrone (75 mg/m2), and cyclophosphamide (120 mg/kg) over a 5-day period combined with escalating doses of CSA. Thirty-seven patients with primarily breast cancer (61% doxorubicin resistant) and ovarian cancer (85% platinum resistant) were treated with CSA given as a bolus 18 h prior to chemotherapy, followed by a 5-day infusion at doses of 5.0-28.2 mg/kg/day and the chemotherapy. The maximum tolerated dose of CSA was a bolus of 5.5 mg/kg and an infusion of 15. 9 mg/kg/day, which gave a mean serum CSA level of 1544 ng/ml. The dose-limiting toxicity was severe mucositis and enteritis, leading to infectious complications. Nephrotoxicity was seen in 42% and, while usually mild and reversible, was fatal in two patients with pretreatment creatinine clearances h80 ml/min. Grade III-IV isolated hyperbilirubinemia was seen in 39%, but appeared to be of no clinical significance. The overall response rate for the 26 patients with measurable/evaluable disease was 73% and 63% for those with doxorubicin- or platinum-resistant disease. The median overall survival and progression-free survival for the group were 18.1 and 8. 0 months. The overall survival for the nine patients with doxorubicin-resistant breast cancer was 19.3 months. Although we did not achieve CSA levels needed to reverse platinum resistance in vivo, levels approaching those needed to reverse P-glycoprotein resistance were reached at the maximum tolerated dose. The strategy of combining dose intensity with drug resistance reversal deserves further study, especially with the advent of potentially less toxic agents available to reverse P-glycoprotein-mediated resistance.
Mammalian transcription factor IIF (TFIIF) is a heterodimer composed of approximately 30-kDa (RAP30) and approximately 70-kDa (RAP74) subunits. TFIIF has been shown to bind RNA polymerase II and control the activity of the enzyme in both the initiation and elongation stages of transcription. Although previous studies have established a role for RAP30 in assembly of the preinitiation complex and in transcription initiation, information on the function of RAP74 in these processes has been lacking. Using a highly purified transcription system and assays that permit sensitive measurement of the contributions of both RAP30 and RAP74 to TFIIF function, we have investigated the roles of these TFIIF subunits in transcription initiation and elongation. Results of template competition experiments indicate that both RAP30 and RAP74 contribute to the formation of stable preinitiation intermediates containing RNA polymerase II. Investigation of the role of TFIIF in transcription initiation indicates that both RAP30 and RAP74 function in synthesis of the first few phosphodiester bonds of nascent transcripts and in formation of Sarkosyl-resistant pre-initiation intermediates. Finally, kinetic experiments indicate that both RAP30 and RAP74 function in TFIIF-mediated stimulation of the rate of RNA chain elongation by RNA polymerase II.
The C terminus of mammalian transcription factor RAP30 has been found to be a cryptic DNA-binding domain strikingly similar to the C-terminal DNA-binding domain present in conserved region 4 of members of the sigma 70 family of bacterial sigma factors. This RAP30 domain shares strongest sequence similarity with the DNA-binding domain present in region 4 of Bacillus subtilis sporulation-specific sigma K. Like the region 4 DNA-binding activity of Escherichia coli sigma 70, the RAP30 C-terminal DNA binding activity is masked in intact RAP30 but is readily detectable when the RAP30 C terminus is expressed as a fusion protein. Consistent with a role for RAP30 DNA-binding activity in transcription, mutations that abolish DNA binding also abolish transcription. Therefore, RAP30 may function at least in part through the action of an evolutionarily ancient DNA-binding domain that first appeared prior to the divergence of bacteria and eukaryotes.
A transcription factor designated SIII was recently purified from mammalian cells and shown to regulate the activity of the RNA polymerase II elongation complex. SIII is a heterotrimer composed of approximately 110-, 18-, and 15-kDa polypeptides and is capable of increasing the overall rate of RNA chain elongation by RNA polymerase II by suppressing transient pausing of polymerase at multiple sites on the DNA template. Here we describe the molecular cloning and characterization of a cDNA encoding the functional 15-kDa subunit (p15) of SIII. The p15 cDNA encodes a 112-amino-acid polypeptide with a calculated molecular mass of 12,473 Da and an electrophoretic mobility indistinguishable from that of the natural p15 subunit. When combined with the 110- and 18-kDa SIII subunits, bacterially expressed p15 efficiently replaces the natural p15 subunit in reconstitution of transcriptionally active SIII. A homology search revealed that the amino-terminal half of the SIII p15 subunit shares significant sequence similarity with a portion of the RNA-binding domain of Escherichia coli transcription termination protein rho and with the E. coli NusB protein, suggesting that SIII may be evolutionarily related to proteins involved in the control of transcription elongation in eubacteria.
CD14 is a membrane glycoprotein expressed specifically on monocytes and macrophages, and its expression is markedly increased during the process of monocyte differentiation. In order to study CD14 gene regulation, the human CD14 gene was cloned from a partial EcoRI digested chromosome 5 library. A 5.5-kilobase genomic clone contained the full-length CD14 coding sequence and 4.2 kilobases of 5'-upstream sequence. One major and one minor transcription start site were identified 101 and 130 base pairs (bp) upstream, respectively, from the protein translation start ATG. A DNA fragment containing 128 bp of upstream sequence had strong, monocyte-specific promoter activity in the CD14 positive monocytic cell line Mono Mac 6 as compared to the nonmonocytic cell lines HeLa and REX. Four regions in this DNA fragment interact with nuclear proteins isolated from monocytic cells. The Sp1 transcription factor bound to three different regions in the CD14 promoter. Mutation of the major Sp1 binding site (-110 bp) decreased tissue-specific promoter activity, and these results, together with transactivation experiments, demonstrate that Sp1 plays a critical role in the tissue-specific expression of CD14 in monocytic cells. CD14 Sp1 site oligonucleotides bound preferentially to a 105-kDa Sp1 species, which is present in higher relative levels in monocytic than non-monocytic cells, suggesting that modification of Sp1, such as phosphorylation, may explain how the Sp1 site mediates monocytic specific promoter activity.
We have assessed the effect of lengthening the expiratory limb of an Ayre's T-piece from 0.5 to 10 m for ventilation with a Nuffield series 200 ventilator and Newton valve, as this equipment is potentially suitable for infants and young children during anaesthesia for magnetic resonance imaging (MRI). We used lung models with compliances and resistances representative of the respiratory system with intubated trachea of a neonate, infant and child weighing 15-20 kg. The effects on ventilation were small, being greatest with the largest lung model where the longer T-piece resulted in a reduction in tidal volume from 261 to 236 ml and an increase in intrinsic and extrinsic positive end-expiratory pressure from 0.20 to 0.32 kPa and from 0.14 to 0.25 kPa, respectively. Such changes are unlikely to be clinically important and can be obviated by using the ventilator with the standard valve in children weighing 15-20 kg.
We have studied the complications associated with three techniques used to maintain extradural analgesia in labour: midwife top-up doses of 0.25% bupivacaine 10 ml, continuous infusion of 0.125% bupivacaine 10 ml h-1 and patient-controlled extradural analgesia (PCEA) with self-administered 3-ml bolus doses of 0.25% bupivacaine. A significantly higher intervention rate by an anaesthetist was required in the continuous infusion group. There was no difference in the mode of delivery between the three groups, although some women in the continuous infusion group had significantly denser motor block. There was a similar incidence of rectal pressure, unilateral block and missed segments in the three groups. Uneventful hypotension occurred in three women; two receiving PCEA and one receiving continuous infusion. Ten women experienced sensory blocks extending above T7 with no ill effects; seven receiving PCEA and three continuous infusion.
There are similarities between clear cell epithelial ovarian carcinoma and endodermal sinus tumours. Apart from the morphological and clinical characteristics there are immunohistochemical markers of value in differentiating these 2 tumours and the detection of a raised serum AFP is characteristic of endodermal sinus tumours. These 3 cases we describe show the fallibility of the classical differentiating criteria between these two tumours.
Using the property of universal approximation of multilayer perceptron neural network, a class of discrete nonlinear dynamical systems are modeled by a perceptron with two hidden layers. A backpropagation algorithm is then used to train the model to identify the nonlinear systems to a desired level of accuracy. Based on the identified model, a one-step-ahead predictive control scheme is proposed in which the future control inputs are obtained through some nonlinear optimization process. Making use of the online learning properties of neural networks, the predictive control scheme is further developed into an adaptive one which is robust to the incompleteness of identification. Simulation results show that this neural control scheme works well even for some very complicated nonlinear systems.
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Tonsillocoagulation was performed on 50 patients with chronic tonsillitis by virtue of YAG Laser. The patients' serum IgG, IgA, IgM, C3level and some acute phase reactant proteins (APRPs) including alpha 1-AGP, alpha 1-AT, Tf were measured pre- and postoperatively. In addition, tonsillar morphology was observed with light and electron microscope before and after tonsillocoagulation. Following up the patients for six to twelve months, we discovered that their immune function remained normal and that their symptoms of chronic tonsillitis had been controlled, it suggests that YAG Laser tonsillocoagulation can be a practical therapy for chronic tonsillitis.
The results of serum gamma-GT activities of 36 laryngeal cancer patients, were compared with that of 40 patients of benign group and 61 normal persons of control group, the difference between the first group and the other two groups is statistically significant (P < 0.01), whereas the difference between the later two groups shows no significance (P > 0.05), so measuring the serum gamma-GT activity is a simple and useful method for laryngeal cancer diagnosis. By following up 9 laryngeal cancer patients, the results indicated that measuring serum gamma-GT activity at regular intervals after treatment is a simple and useful method for observing the therapeutic effect, and for monitoring tumor recurrence or metastases.
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Cardiopulmonary and other organ dysfunction often occurs after operation on the descending thoracic aorta. Though there are multiple causes of organ dysfunction in this setting, free radical injury may play a prominent role. Xanthine oxidoreductase, an enzyme that generates oxidants after exposure to ischemia, could be released from ischemic liver and intestine during reperfusion. To test this hypothesis, we created aortic occlusion in eight rabbits for 40 minutes by inflation of a 4F Fogarty balloon catheter in the descending thoracic aorta. Eight sham-operated rabbits served as a control group. Two hours of reperfusion followed removal of the balloon catheter. Hemodynamic and acid-base status were maintained near baseline values during reperfusion. Plasma samples were obtained for determination of the activity of the hepatocellular enzymes xanthine oxidoreductase, aspartate aminotransferase, alanine transferase, and lactate dehydrogenase. Plasma xanthine oxidoreductase activity increased significantly (p < 0.001) during reperfusion (729 +/- 140 microU/ml, mean +/- standard error of the mean) compared with baseline (132 +/- 18 microM/mL). The other enzymes followed a similar pattern of release. We report the release of xanthine oxidoreductase in an animal model that simulates the situation of human thoracic aorta operations. The oxidants produced by the circulating xanthine oxidoreductase observed during reperfusion would likely be toxic to vascular endothelium, potentially contributing to multiple organ dysfunction.
Dimethyl sulfate, DNase I and micrococcal nuclease DNA cleavage were combined with the ligation-mediated polymerase chain reaction to obtain high resolution maps of the promoter regions for two cell-type-specific genes: the a-specific STE2 gene and the alpha-specific STE3 gene. We find that MCM1 binds in vivo in a-cells to a 16 bp P-box sequence located in the STE2 UAS. In alpha-cells, the footprint pattern is extended relative to a-cells, consistent with the additional binding of MAT alpha 2 to the sequences flanking each end of the P-box. A nucleosome was found adjacent to the P-box of the transcriptionally repressed a-specific STE2 UAS in alpha-cells, positioned so that the nucleosome overlaps the TATA-box. In contrast, such well-positioned nucleosomes were not found for the transcriptionally active STE2 UAS in a-cells, where instead the TATA box appears to be bound to the general transcription factor TFIID. These observations support the hypothesis that MAT alpha 2 repression of a-specific genes is mediated by nucleosomes, perhaps by exclusion of TFIID from the TATA-box.
A novel transcription factor that stimulates synthesis of accurately initiated transcripts by mammalian RNA polymerase II has been identified and purified to apparent homogeneity from rat liver extracts (Bradsher, J. N., Jackson, K. W., Conaway, R. C., Conaway, J. W. (1993) J. Biol. Chem. 268, 25587-25593). This factor, which we designate SIII, has a native molecular mass of approximately 140 kDa and is composed of three polypeptides of 110, 18, and 15 kDa. In this report, we demonstrate that SIII stimulates promoter-specific transcription by increasing the overall rate of RNA chain elongation by RNA polymerase II. Results of pulse-chase experiments indicate that SIII does not need to be present during preinitiation complex formation or transcription initiation in order to stimulate promoter-specific transcription. In addition, SIII is able to stimulate the rate of RNA chain elongation by RNA polymerase II during transcription of double stranded oligo(dC)-tailed templates. Taken together, these findings indicate that the factor exerts its activity directly on the elongation complex.