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Biomedical subjects

S Tan

Publications and source records attributed to S Tan.

At least 55 records · Page 3Linked to original sources
PubMed2001

[The psychological effect of clinical examination on women with tubal infertility].

OBJECTIVE: To comprehend the psychological effects in the course of diagnosis and treatment of infertility on the sexuality, emotional feeling and marriage of women with tubal infertility. METHODS: The study involved 180 hospitalized patients who were awaiting tube operation from May to September in the year 2000. A survey was made by using questionnaire about sexuality, emotional feeling and marriage after infertility examinations. RESULTS: The sexual intercourse frequency of 46.2% infertile women decreased and no influences on sexual living satisfaction were confirmed during basal body temperature (BBT) examination. 92.3% to 93.2% of the infertile women were sad after hysterosalpingography(HSG) and laparoscopy. 78.9% of them felt remorse when the result of semen examination was normal. 56.6% of them would choose in vitro fertilization and embryo transfer(IVF-ET); 38.9% of the infertile couples' wedlock would not be stable and 10.5% of them would be divorced in the case of continuing infertility 2 years after tube operation. CONCLUSION: Sexual intercourse in almost half of the infertile couples decreased during BBT examination. Most infertile women became sad when they were informed of the abnormal results of HSG and laparoscopy and the normal results of semen analysis.

Adult↗
PubMed2001

[Polycystic ovaraian syndrome and hyperinsulinemia].

OBJECTIVE: To identify the relationship between polycystic ovarian syndrome and hyperinsulinemia. METHODS: Age, body height, body weight, serum estradiol, progesterone, testosterone, follicle stimulating hormone (FSH), luteinizing hormone (LH), prolactin (PRL), triiodothyronine (T3), tetraiodothyronine (T4), insulin, oral glucose tolerance test (OGTT), and cortisol were measured in 28 patients with polycystic ovarian syndrome (PCOS). RESULTS: Sxiteen patients (57.1% of total) had hyperinsulinemia. Among them one patient was found diabetic. No difference was noted in age, height, body weight, body mass index, serum estradiol, progesterone, testosterone, FSH, LH, PRL, T3, T4, cortisol, and glucose of OGTT between hyperinsulinemia and non-hyperinsulinemia patients. However the LH/FSH ratio (2.4 +/- 1.5) in hyperinsulinemia patients was significantly higher than 1.2 +/- 0.6 in non-hyperinsulinemia patients (P = 0.0125). In addition, the results showed that the fasting serum insulin, insulin after OGTT, the insulin/glucose ratio at 30, 120 minutes, 180 minutes, the area under curve of and the insulin, insulin resistant index (IRI) were higher in hyperinsulinemia pateints than in non-hyperinsulinemia patients respectively. Furthermore, the fasting insulin level, insulin/glucose ratio were found to be negatively related to insulin sensitivity index and positively related with beta-cell functioning index. CONCLUSION: Hyperinsulinemia and insulin resistance accompany with some of the PCOS patients in China. Further investigations will be necessary to clarify the relevant mechanisms.

Adult↗
PubMed2000

Novel dimerization fold of RAP30/RAP74 in human TFIIF at 1.7 A resolution.

General transcription factor IIF (TFIIF) is required for transcription by RNA polymerase II; it consists minimally of a heterodimer of RNA polymerase-associated proteins RAP30 and RAP74. According to solution and mutagenesis studies, the multiple domains of RAP30 and RAP74 bind PolII, TFIIB, TAF250 and DNA in interactions that are essential for transcription initiation and elongation. The X-ray structure of the RAP30/RAP74 interaction domains at 1.7 A resolution reveals a novel "triple barrel" dimerization fold and suggests with mutant data that interactions with the transcription apparatus are mediated not only by this tripartite beta-barrel, but also via flexible loops and alpha and beta-structures extending from it.

Amino Acid Motifs↗
PubMed2000

Crystallization of the yeast MATalpha2/MCM1/DNA ternary complex: general methods and principles for protein/DNA cocrystallization.

We describe our efforts to crystallize binary MCM1/DNA and ternary MATalpha2/MCM1/DNA complexes, including the unsuccessful attempts to crystallize MCM1/DNA complexes and the successful design of DNA crystal packing that resulted in high-resolution crystals of the MATalpha2/MCM1/DNA complex. We detail general procedures useful for preparing protein/DNA cocrystals, including improved methods for producing and purifying DNA-binding proteins and DNA fragments, for purifying protein/DNA complexes, and for controlling pH conditions during crystallization. We also describe the rational design of DNA for protein/DNA cocrystallization attempts, based on our analysis of how straight and bent DNA with single base-pair overhangs can pack end-to-end in a crystal.

Base Pairing↗
PubMed2000

Patients' perception of sound levels in the surgical suite.

STUDY OBJECTIVES: To measure sound levels that our patients are exposed to in the surgical suite and their perception of these sound levels. DESIGN: Sound levels experienced by 100 patients undergoing general anesthesia for elective surgery during three phases: induction and maintenance of anesthesia in the operating room (OR), and recovery from anesthesia in the recovery room, were measured using a Type 4436 Noise Dose Meter. The equivalent continuous sound levels (Leq), maximum sound levels (Lmax), and the sources of sounds were noted. Patients were interviewed 24 hours after anesthesia about their perception of the sound levels they had experienced in the OR and recovery rooms. MEASUREMENTS AND MAIN RESULTS: The Leq during the induction, maintenance, and recovery phases were 70.3 +/- 16.8 dB(A), 66.2 +/- 4.1 dB(A) and 71.8 +/- 6.1 dB(A), respectively. These sound levels are much higher than international recommendations for hospital acute care areas and exceed the thresholds to produce noise-induced cardiovascular and endocrine effects. Sound levels were significantly higher during the induction and recovery phases compared to the maintenance phase. Thirty-two patients found the induction phase noisy and 33 patients found the recovery phase noisy. The sound levels distressed 16 patients and 52 patients would have preferred a quieter environment. There was no difference in the sound levels experienced by those who expressed dissatisfaction with the sound levels and those who did not. Much of the noise, particularly staff conversations, unnecessary alarms, and preparation of equipment, could have been prevented by simple measures. CONCLUSION: Noise prevention in the OR and recovery room needs more attention and should be a routine part of patient care.

Anesthesia↗
PubMed2000

Characterization of the Porphyridium cruentum Chl a-binding LHC by in vitro reconstitution: LHCaR1 binds 8 Chl a molecules and proportionately more carotenoids than CAB proteins.

The Porphyridium cruentum light harvesting complex (LHC) binds Chl a, zeaxanthin and beta-carotene and comprises at least 6 polypeptides of a multigene family. We describe the first in vitro reconstitution of a red algal light-harvesting protein (LHCaR1) with Chl a/carotenoid extracts from P. cruentum. The reconstituted pigment complex (rLHCaR1) is spectrally similar to the native LHC I, with an absorption maximum at 670 nm, a 77 K fluorescence emission peak at 677 nm (ex. 440 nm), and similar circular dichroism spectra. Molar ratios of 4.0 zeaxanthin, 0.3 beta-carotene and 8.2 Chl a per polypeptide for rLHCaR1 are similar to those of the native LHC I complex (3.1 zeaxanthin, 0.5 beta-carotene, 8.5 Chl a). The binding of 8 Chl a molecules per apoprotein is consistent with 8 putative Chl-binding sites in the predicted transmembrane helices of LHCaR1. Two of the putative Chl a binding sites (helix 2) in LHCaR1 were assigned to Chl b in Chl a/b-binding (CAB) LHC II [Kühlbrandt et al. (1994) Nature 367: 614-21]. This suggests either that discrimination for binding of Chl a or Chl b is not very specific at these sites or that specificity of binding sites evolved separately in CAB proteins. LHCaR1 can be reconstituted with varying ratios of carotenoids, consistent with our previous observation that the carotenoid to Chl ratio is substantially higher in P. cruentum grown under high irradiance. Also notable is that zeaxanthin does not act as an accessory light-harvesting pigment, even though it is highly likely that it occupies the position assigned to lutein in the CAB LHCs.

Journal Article↗
PubMed2000

The effect of polishing systems on microleakage of tooth coloured restoratives: Part 1. Conventional and resin-modified glass-ionomer cements.

The purpose of this in vitro study was to investigate the effect of polishing systems on the microleakage of conventional and resin-modified glass-ionomer cements. Class V cavities were prepared at the cemento-enamel junction of 80 freshly extracted posterior teeth. The prepared teeth were randomly divided into two groups and restored with conventional or resin-modified glass-ionomer cements. The restored teeth were stored in distilled water at 37 degrees C for 1 week after removal of excess restorative with diamond finishing burs. The restored teeth were then divided into four groups of 10 and finished and polished using the following systems: Two Striper MFS; Sof-Lex XT; Enhance Composite Finishing and Polishing System; Shofu Composite Finishing Kit. The finished restorations were subjected to dye penetration testing. Results showed that the microleakage at dentin margins of conventional glass-ionomer cements and enamel margins of resin-modified glass-ionomer cements are significantly affected by the different polishing systems.

Analysis of Variance↗
PubMed2000

Changes in prostaglandin and nitric oxide levels in the hyperdynamic circulation following liver resection.

BACKGROUND AND AIMS: Significant changes in hepatic haemodynamics occur after major hepatectomy, but the pathogenesis of this phenomenon is unclear. This study investigates the serum profile of prostaglandin and nitric oxide in the hepatic and systemic circulation before and after hepatectomy and the temporal relationship of these to changes in the hepatic blood flow. METHODS: Blood samples were collected from the internal jugular, portal and hepatic veins of six Yorkshire pigs (17-25 kg) before, immediately after and 48 h after partial hepatectomy. RESULTS: Serum levels of prostacyclin I2 (PGI2) and prostaglandin E2 (PGE2) from the systemic circulation, the portal circulation and from the hepatic veins were found to differ considerably even before hepatectomy. After the hepatectomy was performed, there was a significant rise in PGI2 levels in the systemic circulation (P=0.027). Hepatic blood flow and cardiac output were measured before hepatectomy, 24 and 48 h after hepatectomy in another six pigs. A significant increase in hepatic blood flow (P=0.029) occurred after the hepatectomy and this was accompanied by a concomitant increase in the cardiac output (P=0.042). The increase in PGI2 concentration in the systemic circulation after hepatectomy appears to accompany the development of hyperdynamic hepatic and systemic circulations. No significant change was found in circulating PGE2 levels in the systemic, portal and hepatic veins at the three collection intervals (i.e. pre, post and 48 h after hepatectomy). The PGE2 levels in the hepatic vein, however, were significantly higher from than in the portal vein (P=0.028). No significant changes were observed in the level of nitric oxide. CONCLUSION: This study demonstrates an increase in the total hepatic blood flow after hepatectomy together with a threefold increase in prostacyclin in the systemic circulation. The liver was identified as the main source of circulatory prostaglandin.

Animals↗
PubMed2000

Extremal-point densities of interface fluctuations in a quenched random medium

We give a number of exact, analytical results for the stochastic dynamics of the density of local extrema (minima and maxima) of linear Langevin equations and solid-on-solid lattice growth models driven by spatially quenched random noise. Such models can describe nonequilibrium surface fluctuations in a spatially quenched random medium, diffusion in a random catalytic environment, and polymers in a random medium. In spite of the nonuniversal character for the quantities studied, their behavior against the variation of the microscopic length scale can present generic features, characteristic of the macroscopic observables of the system.

Journal Article↗
PubMed2000

Analysis of fission yeast primase defines the checkpoint responses to aberrant S phase initiation.

To investigate the checkpoint response to aberrant initiation, we analyzed the cell cycle checkpoint response induced by mutations of Schizosaccharomyces pombe DNA primase. DNA primase has two subunits, Spp1 and Spp2 (S. pombe primases 1 and 2). Spp1 is the catalytic subunit that synthesizes the RNA primer, which is then extended by DNA polymerase alpha (Polalpha) to synthesize an initiation DNA structure, and this catalytic function of Polalpha is a prerequisite for generating the S-M phase checkpoint. Here we show that Spp2 is required for coupling the function of Spp1 to Polalpha. Thermosensitive mutations of spp2(+) destabilize the Polalpha-primase complex, resulting in an allele-specific S phase checkpoint defect. The mutant exhibiting a more severe checkpoint defect also has a higher extent of Polalpha-primase complex instability and deficiency in the hydroxyurea-induced Cds1-mediated intra-S phase checkpoint response. However, this mutant is able to activate the Cds1 response to S phase arrest induced by temperature. These findings suggest that the Cds1 response to the S-phase arrest signal(s) induced by a initiation mutant is different from that induced by hydroxyurea. Interestingly, a polalphats mutant with a defective S-M phase checkpoint and an spp2 mutant with an intact checkpoint have a similar Polalpha-primase complex stability, and the Cds1 response induced by hydroxyurea or by the mutant arrests at the restrictive temperature. Thus, the Cds1-mediated intra-S phase checkpoint response induced by hydroxyurea can also be distinguished from the S-M phase checkpoint response that requires the initiation DNA synthesis by Polalpha.

Alleles↗
PubMed2000

Syncollin is differentially expressed in rat proximal small intestine and regulated by feeding behavior.

Gradients of gene expression are maintained along the proximal-distal axis of the mammalian small intestine despite a continuously regenerating epithelium. To study the molecular mechanisms responsible for this phenomenon, we utilized a subtractive hybridization strategy to isolate genes differentially expressed in the duodenum but not ileum. We isolated and sequenced 15 clones. The clones were fragments of genes encoding lipases, proteases, and an esterase. A novel clone was characterized and subsequently shown to encode syncollin, a secretory granule protein that binds to syntaxin in a calcium-sensitive manner. RT-PCR and S1 nuclease protection assay were used to clarify the 5'-end of syncollin. Syncollin was expressed in the rat pancreas, spleen, duodenum, and colon. In situ hybridization localized syncollin expression in the pancreas to acinar cells and in the duodenum to villus epithelial cells.

Amino Acid Sequence↗
PubMed2000

Imprint switching for non-random X-chromosome inactivation during mouse oocyte growth.

In mammals, X-chromosome inactivation occurs in all female cells, leaving only a single active X chromosome. This serves to equalise the dosage of X-linked genes in male and female cells. In the mouse, the paternally derived X chromosome (X(P)) is imprinted and preferentially inactivated in the extraembryonic tissues whereas in the embryonic tissues inactivation is random. To investigate how X(P) is chosen as an inactivated X chromosome in the extraembryonic cells, we have produced experimental embryos by serial nuclear transplantation from non-growing (ng) oocytes and fully grown (fg) oocytes, in which the X chromosomes are marked with (1) an X-linked lacZ reporter gene to assay X-chromosome activity, or (2) the Rb(X.9)6H translocation as a cytogenetic marker for studying replication timing. In the extraembryonic tissues of these ng/fg embryos, the maternal X chromosome (X(M)) derived from the ng oocyte was preferentially inactivated whereas that from the fg oocyte remained active. However, in the embryonic tissues, X inactivation was random. This suggests that (1) a maternal imprint is set on the X(M) during oocyte growth, (2) the maternal imprint serves to render the X(M) resistant to inactivation in the extraembryonic tissues and (3) the X(M) derived from an ng oocyte resembles a normal X(P).

Amnion↗
PubMed2000

X-chromosome inactivation in XX androgenetic mouse embryos surviving implantation.

Using genetic and cytogenetic markers, we assessed early development and X-chromosome inactivation (X-inactivation) in XX mouse androgenones produced by pronuclear transfer. Contrary to the current view, XX androgenones are capable of surviving to embryonic day 7.5, achieving basically random X-inactivation in all tissues including those derived from the trophectoderm and primitive endoderm that are characterized by paternal X-activation in fertilized embryos. This finding supports the hypothesis that in fertilized female embryos, the maternal X chromosome remains active until the blastocyst stage because of a rigid imprint that prevents inactivation, whereas the paternal X chromosome is preferentially inactivated in extra-embryonic tissues owing to lack of such imprint. In spite of random X-inactivation in XX androgenones, FISH analyses revealed expression of stable Xist RNA from every X chromosome in XX and XY androgenonetic embryos from the four-cell to morula stage. Although the occurrence of inappropriate X-inactivation was further suggested by the finding that Xist continues ectopic expression in a proportion of cells from XX and XY androgenones at the blastocyst and the early egg cylinder stage, a replication banding study failed to provide positive evidence for inappropriate X-inactivation at E6. 5.

Animals↗
PubMed2000

Validation of the fluorescence polarization assay and comparison to other serological assays for the detection of serum antibodies to Brucella abortus in bison.

A number of serological tests were compared for the detection of antibodies to Brucella abortus in bison (Bison bison). The performance of the fluorescence polarization assay (FPA) in both the preliminary evaluation and a subsequent blind validation indicated that this test was the most suitable for serological diagnosis of brucellosis in bison. The sensitivity and specificity in the preliminary evaluation were 92.1% and 99.4%, respectively. The sensitivity and specificity in a subsequent blind study were 96.3% and 97.6%, respectively. In a double blind study conducted on bison vaccinated with B. abortus strain 19, the data suggests that the FPA can differentiate bison infected with B. abortus from bison vaccinated with B. abortus strain 19. Both the indirect immunoassay (IELISA) and the competitive immunoassay (CELISA) performed nearly as well as the FPA. The buffered antigen plate agglutination test (BPAT) and the complement fixation test (CFT) did not perform as well as the FPA, CELISA or the IELISA in both studies. The FPA is a homogeneous assay eliminating the washing steps and reducing incubation to minutes rather than hours saving on time, equipment, materials, reagents and cost. These attributes, together, with its excellent sensitivity and specificity make the FPA an attractive test for the detection of serum antibodies to Brucella abortus in bison.

Agglutination Tests↗
PubMed2000

Safety and immunogenicity of lyophilized, live attenuated hepatitis A vaccine in non-human primate model.

OBJECTIVE: To evaluate the safety and immunogenicity of lyophilized, live attenuated hepatitis A vaccine (H2 strain) in rhesus monkeys. METHODS: Nine adult rhesus monkeys were used as experimental animals. The rhesus monkeys without anti-HAV were divided randomly into the aqueous vaccination group (4 rhesus monkeys), the lyophilized vaccination group (3 rhesus monkeys), and the control group (2 rhesus monkeys). Monkeys were inoculated by intramuscular injection, with control monkeys being inoculated with Minimum Essential Medium Eagle (MEM). Following vaccination, the monkeys were observed for the development of diarrhoea and other adverse side-effects, such as changes in appetite, frequency of defaecation and stool consistency for seven days. At the weeks 2, 3, 4, 6, 8, 10 and 12 positnoculation, the peripheral blood was collected from all animals and assayed for anti-HAV and alanine aminotransferase (ALT) and aspartate aminotransferase (AST), at weeks 0, 4 and 8 postinocuation, needle-biopsy specimens were taken at weeks 0, 4, 8 and 12, all monkeys were sacrificed and tissue samples were taken from liver, lung, heart, kidney and brain for pathological examination at week 12. RESULTS: Animals were immunized with a dose of 7.0 logTCID50/ml which is stable after freeze-drying. During the 12-week observation, no animals showed abnormal elevations of liver enzymes (ALT and AST) and no change in appetite or activity. Two monkeys (one in the aqueous group and the other in lyophilized group) showed possible lesions at week 8. The lyophilized vaccine, in addition to eliciting an anti-HAV IgG response similar to aqueous vaccine (P > 0.05), also showed IgM anti-HAV response at week 2 which was not observed with aqueous vaccine. CONCLUSIONS: These results demonstrate that lyophilized, live hepatitis A vaccine is safe and highly immunogenic in primates, supporting its further evaluation in human clinical studies.

Animals↗
PubMed2000

[Studies on vaccination schedule of inactivated hepatitis A vaccine].

OBJECTIVE: To evaluate three vaccination schedules of inactivated hepatitis A vaccine in rhesus monkeys (Macaca Mulatta). METHODS: Seventeen rhesus monkeys were divided randomly into four groups. The first group of five monkeys was immunized with vaccination schedule 1 (one immunization at week 0); The second group of five monkeys was immunized with vaccination schedule 2 (first injection at week 0, and booster one at week 4); the third group of five monkeys was immunized with vaccination schedule 3 (first injection at week 0, and booster one at week 24); and the fourth group of two monkeys with MEM as control. Rhesus monkeys were inoculated by intramuscular injections to detect the ALT (alanine aminotransferase), liver pathology and anti-HAV at different time. RESULTS: During the 52-week observation, no abnormal elevation of ALT or liver pathology appeared. The IgG response for vaccination schedule 1 reached the highest level (13 219 mIU/ml), and decreased gradually to 2 056 mIU/ml at week 52. After booster immunization at week 4, the IgG response for vaccination schedule 2 was 13 863 mIU/ml at week 12, and decreased to 6 285 mIU/ml. The highest level of IgG (40 638 mIU/ml) for vaccination schedule 3 appeared at week 28 after booster injection at week 24. Further more, at week 52 the IgG level for vaccination schedule 3 was also the highest among the three vaccination schedules. CONCLUSIONS: The inactivated hepatitis A vaccine is safe and well immunogenic. The vaccination schedule 3 showed the best immune response among the three vaccination schedules.

Adult↗