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Biomedical subjects

S Y Chang

Publications and source records attributed to S Y Chang.

At least 91 records · Page 5Linked to original sources
PubMed2000

Effects of induction anesthetic agents on outcome of assisted reproductive technology: a comparison of propofol and thiopental sodium.

BACKGROUND: The use of propofol, as compared to barbiturates (e.g. thiopental), for short surgical procedures has been associated with more rapid recovery from the procedure. Propofol, an intravenous anesthetic drug, is frequently used as an adjunct to transvaginal oocyte retrieval but little is known about its effects upon fertilization, embryo development, and pregnancy rate when used drug the for induction of general anesthesia. This study was conducted to compare the outcome of assisted reproductive technology (ART) with the use of propofol versus thiopental sodium for the induction of general anesthesia during oocyte retrieval. METHODS: In this retrospective study, 92 cases of infertile patients who underwent oocyte retrieval under the induction of general anesthesia with, respectively, either propofol (Group I, 72 cases) or thiopental sodium (Group II, 20 cases) were compared for fertilization rate, cleavage rate, and pregnancy rate. RESULTS: The fertilization rate was 68.9% for Group I and 66.7% for group II (p = 0.614). The cleavage rate was 96.5% for Group I and 94.8% for Group II (p = 0.294). The rate of good embryo grading and poor embryo grading was, respectively, 85.1% and 14.9% for Group I, versus 85.7% and 14.3% for Group II (p = 0.887). The pregnancy rate was 30.5% for Group I and 20.0% for Group II (p = 0.354). The implantation rate and abortion rate was, respectively, 9.1% and 18.2% for Group I versus 7.2% and 25.0% for Group II (implantation rate, p = 0.590; abortion rate, p = 0.600). CONCLUSION: There were no significant differences between these two groups for fertilization rate, cleavage rate, pregnancy rate, implantation rate and abortion rate. We suggest cautious use of propofol for the procedure of oocyte retrieval despite its associated more rapid post-operative recovery including less nausea/vomiting.

Anesthetics, Intravenous↗
PubMed2000

Thermal physiological consideration of precooling procedures in manned space craft.

OBJECTIVE: To explore a space craft precooling temperature at which excessive thermal stress on the crew member could be prevented or reduced in an overheated launch or reentry module. METHOD: Five young male volunteers wearing a space suit participated in 25 tests at sea level. The space suit was either ventilated in a volume air flow rate of 100 L/min (STPD) with ambient air at temperatures (Ta) of 15 degrees C, 10 degrees C, and 5 degrees C, respectively, or not ventilated. Rectal (Tr), mean skin (Tsk) and mean body (Tb) temperatures were measured. RESULT: At Ta 15 degrees C, Tr decreased without significance (from 37.0 +/- 0.2C to 36.7 +/- 0.3 degrees C) in 120-min tests, whereas mean Tsk and mean Tb decreased significantly, and subjects had local cold strain whether the space suit was ventilated or not; while at Ta 10 degrees C, Tr decreased from 37.0 +/- 0.3 degrees C to 36.3 +/- 0.3 degrees C (P < 0.05), subjects had a whole body cold strain, and both mean Tsk and Tb dropped continuously and significantly. CONCLUSION: Ambient temperature 15 degrees C, at which the thermal comfort states of crew was not significantly degraded, was acceptable after precooling in a space craft.

Adolescent↗
PubMed1999

Sequence features downstream of the primer-binding site of HIV type 1 subtype E shared by subtype G and a subset of subtype A.

Two distinct sequence features downstream of the primer-binding site (PBS) were identified in a full-length HIV-1 subtype E clone amplified in this study. Both features are frequently found in HIV-1 subtypes A and G and in more than half of the full-length intersubtype recombinant clones. One of these is the absence of a trinucleotide sequence, which is located 14 nucleotides downstream of the PBS and found only in subtypes B, C, D, F, and H. The other is an insertion of 24 nucleotides immediately downstream of the PBS, which was previously reported as a sequence feature shared by subtypes A, E, and G. The analysis conducted here revealed that this 24-nucleotide insertion contained two sequence motifs duplicated in adjacent regions and was not found in all HIV-1 subtype A clones. Furthermore, our finding suggests that the PBS region of all known full-length subtype E clones, which are A/E intersubtype recombinants, is derived from the group of HIV-1 subtype A, which contains a similar insertion.

Base Sequence↗
PubMed1999

Differential stability of the mRNA secondary structures in the frameshift site of various HIV type 1 viruses.

For many retroviruses, one or more ribosomal frameshift events are required for translation of the Gag-Pol precursor protein, which is subsequently processed into the structural and enzymatic proteins found in mature virions. A specific nucleotide motif, the slippery sequence, as well as a downstream mRNA secondary structure are generally believed to have roles in the frameshift event. In HIV-1, a particular stem-loop mRNA secondary structure has been proposed for subtype B. On the basis of this model, HIV-1 subtypes A, E, and F were found in this study to share a similar stem-loop structure predicted to have a lower thermodynamic stability as compared with HIV-1 subtypes B, C, and D. The potential impact of this differential thermodynamic stability on HIV-1 replication remains to be determined.

Base Sequence↗
PubMed1999

Sequence analysis of a new open reading frame located in the pathogenicity locus of Clostridium difficile strain 8864.

Strain 8864 is a natural isolate of Clostridium difficile that is toxin B-positive and toxin A-negative. Recent work showed that there is a genetic rearrangement occurring at the pathogenicity locus (PaLoc) of the bacteria. Our investigation in the PaLoc region revealed an open reading frame (tcdF) of 543 bp DNA not reported before. This tcdF could encode a putative polypeptide of 22 kDa. Although no peptide homology was found with other known proteins, we postulate that it could be a novel protein because not only highly consensus ribosome-binding and promoter sequences were found upstream of tcdF, transcript was also identified at the region occupied by tcdF.

Amino Acid Sequence↗
PubMed1999

Kinetic analysis of oral tolerance: memory lymphocytes are refractory to oral tolerance.

Oral administration of soluble Ag before immunization induces peripheral tolerance and is effective in suppressing animal models of autoimmune diseases. Although tolerance induction in primed animals is more clinically relevant, it is not well studied. Therefore, this study was designed to examine the feeding effects on different phases of the immune response. We observed that feeding a single high dose (250 mg) of OVA to OVA-primed BALB/c mice could induce OVA-specific suppression in the Ab production and T cell proliferation only at the naive and the activation phases of the immune response, whereas multiple high doses (100 mg/feed for 10 days) were effective at the effector phase. OVA-specific IL-4 production in culture supernatant was also suppressed in the tolerized groups. However, when the mice had resting memory lymphocytes, even multiple feeding regimens were not effective in tolerance induction, although multiple low doses (1 mg/feed for 10 days) partially suppressed Ab production. This phenomenon was confirmed by adoptive transfer study. Nevertheless, the reactivated memory response was suppressed partially by multiple high doses. Our findings have an important implication for understanding the mechanism of oral tolerance and for the therapeutic applications of oral tolerance to autoimmune diseases.

Administration, Oral↗
PubMed1999

Lack of infection in HIV-exposed individuals is associated with a strong CD8(+) cell noncytotoxic anti-HIV response.

Individuals repeatedly exposed to HIV, but who remain uninfected, form a population enriched for persons likely to have either natural or acquired resistance to the virus. We have studied four such exposed uninfected cohorts, representing 60 individuals, for evidence of protective immunity. This population included participants exposed to HIV through anal or vaginal receptive intercourse on multiple occasions over many years. We observed CD8(+)-cell noncytotoxic inhibition of HIV replication in acutely infected CD4(+) cells in the vast majority of individuals most recently exposed to the virus (within 1 year). The levels of this CD8(+)-cell response were sufficient to inhibit the in vitro infection of the exposed subjects' peripheral blood mononuclear cells. We found no evidence of a significant role for CCR5 Delta32 mutation in this population, nor did CD4(+) cell susceptibility to infection or HIV-specific cytotoxic T-lymphocytes correlate with resistance to infection in the individuals tested. Therefore, the observed strong noncytotoxic CD8(+)-cell anti-HIV responses may be an antiviral immune activity contributing to the apparent protection from infection in these exposed uninfected individuals.

Adult↗
PubMed1999

Maternal serum screening for down syndrome in pregnancies conceived by intra-uterine insemination.

The purpose of our study was to assess the influence of intra-uterine insemination (IUI) on the results of maternal serum Down syndrome screening. 43 women with IUI pregnancies and 4507 healthy women who conceived were studied. Ovulation in IUI pregnancies was induced by clomiphene and/or human menopausal gonadotrophin (hMG). Maternal serum levels of free beta-human chorionic gonadotrophin (hCG) and alpha-fetoprotein (AFP) were measured for Down syndrome screening. It was considered screen-positive when the risk of Down syndrome was 1 in 270 or greater in the second trimester. The value of maternal serum AFP was significantly lower in the IUI group (median=0.760 MoM) than in the control group (median=1.050 MoM). However, the value of free beta-hCG was not significantly different between the two groups. The positive rate of maternal serum Down syndrome in IUI pregnancies was similar to that of the control group. Our results indicate that IUI pregnancy may be associated with a lower level of AFP, although the mechanism for this difference remains unknown.

Adult↗
PubMed1999

Sensitive triple-quadrupole mass spectrometric assay for the determination of BMS-181885, a 5-HT1 agonist, in human plasma following solid phase extraction.

A sensitive, selective, accurate, precise and reproducible triple-quadrupole liquid chromatographic-mass spectrometric assay was developed and validated for BMS-181885 (I), a 5HT1 agonist, in human plasma using BMS-181101 as the internal standard (IS). The method involved solid phase extraction of plasma containing I and the IS using Isoelute CN cartridges. The supernatant was then evaporated to dryness at 40 degrees C. The residue was dissolved in 100 microL of the injecting solvent. The HPLC column was ODS-3, 2 x 100 mm. The mobile phase comprised 10 mM ammonium formate (pH = 4) and acetonitrile, 55:45 v/v, used in an isocratic condition. The mass spectrometer was programmed to admit the protonated molecules at m/z 461 (I) and m/z 370 (IS) via the first quadrupole filter and to select reaction monitoring of ions at m/z 152 for I and IS for the quantification. Standard curves were fitted to a weighted quadratic function over the concentration range 0.2-200 ng/mL. The lowest standard concentration (0.2 ng/mL) was experimentally established as the lower limit of quantitation of the assay. The mean predicted quality control concentrations deviated within +/- 11% of the corresponding nominal values; the intra-assay and inter-assay precisions were within 7.0% relative standard deviation. I was stable in the injection solvent at 4 degrees C for at least 24 h and for at least three freeze-thaw cycles. Freezer stability of I in plasma was demonstrated for at least 3 months. The extraction recovery of I was established as 97%. The validated assay was applied to a pharmacokinetic study of I in humans.

Analysis of Variance↗
PubMed1999

Efficacy of methotrexate treatment in viable and nonviable cervical pregnancies.

OBJECTIVES: This retrospective study examined the overall efficacy of methotrexate chemotherapy in the treatment of cervical pregnancy and attempted to determine whether differences in the response to methotrexate therapy exist between patients with viable and nonviable cervical pregnancies. STUDY DESIGN: A MEDLINE database search and a bibliographic review of the relevant literature were conducted to find reported cases of cervical pregnancy treated with methotrexate administration during the period from 1983 to 1997. Clinical and demographic characteristics, methotrexate regimen, concomitant invasive procedures, complications, and outcomes in viable and nonviable pregnancy groups were analyzed and compared. RESULTS: A total of 62 reported cases of cervical pregnancy were assessed. There were no statistically significant differences in demographic data, transfusion rate, and human chorionic gonadotropin remission time between viable and nonviable cervical pregnancy groups. Among the 35 cases of viable pregnancy 63% of women received systemic injection alone or a combination of systemic and local (intra-amniotic or intracervical) injection with methotrexate or potassium chloride and 37% had local injection of methotrexate (with or without potassium chloride) alone. Among the 23 cases of nonviable cervical pregnancy 96% of women received systemic methotrexate injection only. The need for >/=1 concomitant surgical procedure (such as simple curettage, dilation and curettage, cervical blocking, or uterine artery embolization) in conjunction with methotrexate therapy was significantly higher (P =.021) in the viable pregnancy group (43%) than in the nonviable pregnancy group (13%). The 94% success rate of preservation of the uterus in the viable pregnancy group was not significantly different from the 91% preservation rate in the nonviable pregnancy group. All patients who had successful uterine preservation returned to normal menstrual patterns. CONCLUSION: This retrospective study found that conservative treatment with methotrexate chemotherapy of patients with either viable or nonviable cervical pregnancies at <12 weeks' gestation carries a 91% success rate for preservation of the uterus. The structure of the cervix was restored and menstruation returned for all patients in whom the uterus was preserved after treatment. There was no evidence to suggest that the reproductive performance of these patients was affected by the treatment.

Abortifacient Agents, Nonsteroidal↗
PubMed1999

Cocktail modulator mixtures for overcoming multidrug resistance in renal cell carcinoma.

OBJECTIVES: To determine the effect of various modulators on intracellular drug accumulation in renal cell carcinoma (RCC) tumor cells and the modulation of cytotoxicity of various chemotherapeutic drugs on the native RCC cell line and acquired intrinsic multidrug resistance (MDR) sublines because MDR is a major obstacle to effective chemotherapy of RCC. METHODS: The cytotoxicity of adriamycin to RCC 8701 and its MDR subline was analyzed. Fourteen MDR modulators, including calcium antagonists, protein kinase C inhibitor, glutathione transferase inhibitor, protein/peptide synthesis inhibitors, respiratory chain inhibitors, uncoupling reagent, adenosine triphosphate synthesis inhibitor, and ionophores, were examined for their MDR-reverse activity using the microplate tetrazolium test. RESULTS: The intracellular adriamycin concentration significantly increased and reached maximum 4 hours after simultaneous treatment with calcium antagonists, tamoxifen, and oligomycin. The result demonstrated that verapamil, quinidine, tamoxifen, and oligomycin had an additive effect on the cytotoxicity of adriamycin and vinblastine against RCC8701 and RCC8701/ADR800 tumor cells. RCC8701/ADR800 tumor cells were more sensitive to modulator enhancement than native cells. The enhancement was related to the dosage and treatment duration of the modulators. Further trials on simultaneous additions to cocktail mixtures of the above four modulators showed no additive or synergistic effect on cytotoxicity against RCC8701/ADR800 tumor cells. CONCLUSIONS: Calcium antagonists and tamoxifen and oligomycin can individually be an effective chemotherapy adjunct for overcoming the native drug resistance or acquired MDR in RCC. Combination regimens, however, need more study regarding timing of administration, dosage, and frequency of modulators.

Antineoplastic Agents↗
PubMed1999

Prenatal diagnosis of trisomy 20 mosaicism by maternal serum screening for Down syndrome.

We report two cases of prenatally diagnosed trisomy 20 mosaicism associated with positive Down syndrome screening at 16 weeks' gestation. Both infants exhibited normal growth and mental development. These cases suggest that the multiple-marker screening test may play an important role in prenatal detection and diagnosis of chromosomal anomalies in addition to Down syndrome.

Adult↗
PubMed1999

Laparoscopic treatment of isolated tubal torsion in a premenarchal girl.

Tubal torsion in a premenarchal girl was diagnosed by pelvic ultrasonography and laparoscopy. A laparoscopic approach was used to resect the twisted tube. To our knowledge, this is the first reported case of laparoscopically managed torsion of a fallopian tube occurring in the absence of torsion of the ovary in a patient of this age group. Video-assisted minimally invasive surgery appears to be suitable for treatment of tubal torsion in children; hospitalization is short, cosmetic results are excellent, and return to normal activity is rapid. (J Am Assoc Gynecol Laparosc 6(2):209-211, 1999)

Child↗
PubMed1999

Detection of azoospermic factor genes in Chinese men with azoospermia or severe oligozoospermia.

PURPOSE: We investigated the prevalence of deletions in the azoospermic factor (AZF) region of chromosome Yq11 in Chinese men with infertility due to idiopathic azoospermia or severe oligozoospermia. The DAZ gene cluster was also examined for mutations. METHODS: Sixty-eight men with azoospermia or severe oligozoospermia taking part in an intracytoplasmic sperm injection program were recruited. Four loci specific for AZFa, AZFb, and AZFc were amplified from genomic DNA via polymerase chain reaction to determine whether deletions were present in the AZF region. Direct DNA sequencing of amplified products was also performed to look for mutations or polymorphism from exon 2 to exon 6 of the DAZ gene cluster. RESULTS: Six (9%) of the 68 patients had AZF deletions. None had mutations in exons 2 to 6 of DAZ. CONCLUSIONS: The prevalence of AZF deletions in our study was similar to those in Western reports, as was the lack of DAZ mutations.

Asian People↗
PubMed1999

Relationship of the human cumulus-free oocyte maturational profile with in vitro outcome parameters after intracytoplasmic sperm injection.

PURPOSE: We investigated whether the human oocyte maturational profile at the removal of cumulus/corona cells affects the fertilization rate and subsequent embryo quality after intracytoplasmic sperm injection. METHODS: A total of 1011 oocytes from 150 cycles was included in this retrospective analysis. Cumulus-free oocytes that were in prophase or metaphase I of meiosis at the removal of cumulus/corona cells were incubated in vitro until they reached metaphase II (in vitro-matured oocytes) and were then immediately injected with a single spermatozoa. Oocytes that were in metaphase II at the removal of cumulus/corona cells (MII oocytes) received sperm injection after 3-4 hr of preinjection incubation. RESULTS: The fertilization rate of the MII oocytes was significantly higher than that of in vitro-matured oocytes (81 vs 62%; P < 0.001). The cleavage rates were similar in the two groups (MII oocytes, 94%; in vitro-matured oocytes, 91%). However, MII oocytes had significantly higher percentages of good-quality embryos (grade 1-3 embryos, 87 vs 58%, P < 0.001) and embryos with high cumulative embryo scores (score 10-32 embryos, 62 vs 33%, P < 0.001). The mean cumulative embryo score of MII oocytes after fertilization was also higher than that of in vitro-matured oocytes (12.1 +/- 3.8 vs 8.8 +/- 3.4; P = 0.014). CONCLUSIONS: MII oocytes that extruded the first polar body at the removal of cumulus/corona cells had better fertilization rates and embryo morphology than in vitro-matured oocytes that extruded the first polar body following the removal of cumulus/corona cells and in vitro culture.

Embryo, Mammalian↗
PubMed1999

Cloning of the genomic sequence encoding a processed adenylate kinase 2 pseudogene.

A chromosomal DNA sequence harboring a processed AK2B pseudogene was isolated from a human genomic library. It was a variant of the AK2B gene sequence including several point mutations, deletions, and insertions. The nucleotide sequence of the ORF of the AK2B pseudogene predicted a truncated form of the AK2B mutant suggesting that the processed pseudogene is nonfunctional. A repetitive sequence, AAAAGAGAG, found in the 5' and 3' flanking regions of the pseudogene and the poly(A) tract in the 3' end junction suggest that a mRNA of AK2B may have been converted to the processed pseudogene by retrotransposition events. Previously, it was suggested that an adenylate kinase (AK) 2 related gene on chromosome 2, confirmed by Southern analysis using somatic cell hybrid cell lines, may be a processed pseudogene. It is proposed that the processed pseudogene isolated in this study may be the AK2 related nonfunctional gene localized on human chromosomes 2.

Adenylate Kinase↗