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Biomedical subjects

T Huang

Publications and source records attributed to T Huang.

At least 91 records · Page 5Linked to original sources
PubMed1998

Optimization of post-column photolysis and electrochemical detection for the liquid chromatographic determination of 3-nitro-L-tyrosine.

A new post-column photolysis technology has been developed based on the use of a low pressure, low temperature UV lamp and TiO2 coated knitted reaction coil. As a test case the developed technique was used for the determination of 3-nitro-L-tyrosine by liquid chromatography with electrochemical detection. Different photolysis lamps and reactor tubing lengths were evaluated in terms of their effect on the separation efficiency and/or photolysis efficiency. A detection limit of 0.5 nM (10 fmol) for 3-nitro-L-tyrosine was achieved under optimized conditions, with a linear correlation coefficient of R2 = 0.9898 over a concentration range of 2-100 microM. Pre-injection photolysis of 3-nitro-L-tyrosine indicated that dihydroxyphenylalanine is the main photolysis product. In general, use of the photoreactor prior to liquid chromatography is an excellent method for exploring photodegradation products of an analyte in conjunction with the full range of available liquid chromatography detectors.

Animals↗
PubMed1998

Comparison of detection methods for liquid chromatographic determination of 3-nitro-L-tyrosine.

A liquid chromatographic method has been developed for the determination of 3-nitro-L-tyrosine. Different detection methods, including UV, oxidative and redox electrochemistry, and postcolumn photolysis followed by electrochemical detection, have been optimized and compared in terms of analysis time, detection limit and dynamic range. It was demonstrated that liquid chromatography with postcolumn photolysis followed by electrochemical detection is the most effective method, with an analysis time of 5 min, detection limit of 0.01 pmol, and a linear dynamic range from 2 nM to 100 microM.

Animals↗
PubMed1998

Defective retrovirus insertion activates c-Ha-ras protooncogene in an MNU-induced rat mammary carcinoma.

Endogenous retrovirus sequences are present in the genome of a wide variety of animal species. The activation of the proto-oncogenes of the ras family, particularly c-Ha-ras, by either point mutation or overexpression, has been shown to be associated with a vast number, of different cancers. here we report that the insertion of a defective retrovirus in the -1 intron of rat c-Ha-ras is responsible for the activation of the gene by over 10-fold overexpression in an MNU-induced rat mammary cancer. A portion of the 3' end of the retroviral sequence is expressed as a part of the c-Ha-ras transcript in the carcinoma tissue, indicating the direct involvement of this element in the transcription of the c-Ha-ras gene. The c-Ha-ras structural gene transcribed by the promoter of the defective retroviral element can neoplastically transform the NIH 3T3 cell line upon transfection.

3T3 Cells↗
PubMed1998

[Interference of human processed pseudogene and corresponding counter-measures in reverse transcriptase-polymerase chain reaction].

OBJECTIVE: This study aimed to set up an effective method to find the interference of processed pseudogene and overcome it in RT-PCR. METHODS: Using RT-PCR methods, the authors amplified the cytokeratin 19 cDNA or DNA sequence in human lung squamous cell carcinoma samples. RESULTS: They could find the influence of pseudogene through performing genomic DNA and nonreversed transcribed RNA controls. By digesting the extracted RNA sample with RNase-free DNase or regulating the annealing temperature based on mismatched primers, they could effectively eliminate the interference. CONCLUSION: The presence of processed pseudogene usually interferes in the experimental protocol in RT-PCR. This problem can be resolved with the method aforementioned.

Carcinoma, Squamous Cell↗
PubMed1998

Determination of L-phenylalanine based on an NADH-detecting biosensor.

An enzyme carbon paste electrode containing three different enzymes was developed for the determination of L-phenylalanine. This sensor is based on the enzymatic/electrochemical recycling of tyrosinase in combination with salicylate hydroxylase and L-phenylalanine dehydrogenase (PADH). The enzymes salicylate hydroxylase and tyrosinase were coimmobilized first in a carbon paste electrode for the sensitive detection of NADH. The principle of the bienzyme scheme is as follows: the first enzyme, salicylate hydroxylase, converts salicylate to catechol in the presence of oxygen and NADH. The second enzyme, tyrosinase, then oxidizes the catechol to o-quinone, which is electrochemically detected and reduced back to catechol at the electrode at an Eappl = -50 mV vs Ag/AgCl. This results in an amplified signal due to the recycling of the catechol and o-quinone between tyrosinase and the surface of the electrode. Prior to adding PADH, the salicylate hydroxylase-tyrosinase carbon paste electrode was characterized in terms of its sensitivity to NADH, pH dependence, buffer composition, interferences, and stability. Interference from ascorbic acid and uric acid was found to be minimal. Human serum was used to investigate whether this bienzyme system was suitable for the detection of NADH in serum and blood samples. The sensitivity for NADH was increased by a factor of 33 times using the bienzyme amplification scheme (electroreduction of o-quinone at Eappl = -50 mV) as opposed to the salicylate hydroxylase single-enzyme system (at which catechol would have been oxidized at Eappl = +150 mV vs Ag/AgCl). The detection limit for NADH achieved by the bienzyme carbon paste electrode was 1 vs 100 microM for the single-enzyme carbon paste electrode. The salicylate hydroxylase-tyrosinase system was then coupled with phenylalanine dehydrogenase for L-phenylalanine determination. This multienzyme sensor was able to achieve a linear range of 20-150 microM and a detection limit of 5 microM for L-phenylalanine. The sensitivity is sufficient since the reference clinical range for L-phenylalanine is 78-206 microM.

Amino Acid Oxidoreductases↗
PubMed1998

Long-term results of percutaneous balloon mitral valvuloplasty for mitral stenosis: a follow-up study to 11 years in 202 patients.

We studied the first 202 patients with rheumatic mitral stenosis (MS) who underwent percutaneous balloon mitral valvuloplasty (PBMV) with the Inoue balloon catheter for a follow-up (FU) period of 5-11 years. Pre- and post-PBMV and at FU, the mean left atrial pressure was 21.3+/-7.4, 10.2+/-5.6, and 11.2+/-4.1 mm Hg; mean diastolic mitral gradient was 18.4+/-7.3, 2.9+/-3.2, and 5.1+/-4.3 mm Hg; and mitral valve area was 1.0+/-0.3, 2.1+/-0.6, and 1.7+/-0.5 cm2. Functional status improved from New York Heart Association (NYHA) class IV in 3, class III in 119, and class II in 80 pre-PBMV to class I in 163, class II in 37, and class III in 2 post-PBMV, and was class I in 146, class II in 39, and class III in 17 patients at FU. In the 17 patients with NYHA class III at FU, mitral restenosis was the culprit; 4 underwent repeat PBMV, 12 had mitral valve replacement for severe mitral calcification and subvalvular fusion, and 1 refused further intervention. Thus PBMV using the Inoue balloon catheter is an effective method of relieving MS with excellent long-term results in patients without severe mitral calcification and subvalvular fusion.

Adolescent↗
PubMed1998

Improving the fixation method for preimplantation genetic diagnosis by fluorescent in situ hybridization.

PURPOSE: Our purpose was to modify a fixation method using Tween-20 and HCl (TH) and to compare it with a protocol using methanol and acetic acid (MA) for the improvement of preimplantation genetic diagnosis by fluorescence in situ hybridization (FISH). METHODS: Single blastomeres were allocated to either the TH or the MA procedure. The two methods were compared to evaluate efficiency of fixation and the intensities of FISH signals. RESULTS: With the TH method, 123 (93.9%) of 131 blastomeres were fixed, while only 95 (78.5%) of 121 were fixed with MA. Average scores for the intensity of FISH signals were significantly stronger for TH than for MA (P < 0.05). There was also a significant difference in signal intensity scores between the two methods for type-3 nuclei. CONCLUSIONS: Our results indicate that not only are fewer nuclei lost during fixation but also stronger FISH signals can be obtained with the TH method. Thus, modified TH can improve the overall efficiency of preimplantation genetic diagnosis.

Acetic Acid↗
PubMed1998

Effects of pre-exposure of mouse testis with low-dose (16)O8+ ions or 60Co gamma-rays on sperm shape abnormalities, lipid peroxidation and superoxide dismutase (SOD) activity induced by subsequent high-dose irradiation.

PURPOSE: To investigate the effects of pre-exposure of mouse testis with low-doses of (16)O8+ ions or 60Co gamma-rays on sperm shape abnormalities, lipid peroxidation and superoxide dismutase (SOD) activity induced by subsequent high-dose irradiation. MATERIALS AND METHODS: Testes of the B6C3F1 hybrid strain mice were pre-irradiated with 0.05 Gy of (16)O8+ ions or 60Co gamma-rays and then after 4 h given a test irradiation with 2 Gy of the same radiation type. SOD activity and thiobarbituric acid reactive substances (TBARS) in the testes were determined by spectrophotometric and TBA methods respectively at 4 h after irradiation. Testis weight, sperm count and sperm morphology were analysed at day 35 after irradiation. RESULTS: Compared with controls, there was a significant increase in SOD activity and a significant decrease in TBARS level of pretreated testes. Testis weight loss, sperm count reduction and sperm abnormalities were significantly lower in the pretreated testes. The bioeffects of a 2 Gy dose of (16)O8+ ions relative to 60Co gamma-rays were 1.84 +/- 0.28 for testis weight, 1.22 +/- 0.25 for sperm count and 1.29 +/- 0.10 for sperm abnormalities. CONCLUSIONS: These data suggest that pre-exposure of testes with a low dose of heavy ions or gamma-rays renders the organ more resistant to subsequent high-dose irradiation. The increase of SOD activity and the decrease of lipid peroxidation levels induced by low-dose ionizing irradiation may be involved in this resistance. The effects with heavy ion irradiation were greater than with gamma-rays.

Animals↗
PubMed1998

Reconstruction of a large abdominal wall defect using combined free tensor fasciae latae musculocutaneous flap and anterolateral thigh flap.

A large abdominal wall defect was reconstructed with the use of a flap combining the tensor fasciae latae musculocutaneous flap and the anterolateral thigh flap in four individuals who had undergone extensive abdominal wall resection because of cancer. The flap was harvested as a single combined composite flap and was transferred to the recipient site by means of microvascular surgery. Morbidity was minimal and the outcome was satisfactory in all instances.

Abdominal Muscles↗
PubMed1998

Impact of an educational program on bilateral heart catheterization practice patterns.

The value and necessity of performing right heart catheterizations for coronary artery disease have been increasingly questioned. Preliminary analyses of the procedure among Medicare and Medicaid patients in New York State revealed significant inter-hospital variations in the frequencies with which such catheterizations were performed. These data suggested that right heart catheterizations (RHC) were being performed routinely. Medicare and Medicaid claims data for bilateral catheterizations were analyzed before and after an educational intervention program involving the state's 53 catheterization laboratories. The educational intervention was multifaceted and consisted of disseminating suggested guidelines established with the assistance of the New York State Chapter of the American College of Cardiology, the Committee on Cardiovascular Disease of the Medical Society of the State of New York, and the Cardiac Advisory Council of the New York State Department of Health. Posteducational intervention assessments were made over a 4-year period. The baseline data for 1992 demonstrated that 10 (18.4%) laboratories had performed RHC routinely (70-100%) on Medicare and Medicaid patients undergoing catheterization. In contrast, 34 (64.2%) laboratories performed RHC in less than 20% of their Medicare cases, whereas 39 (73.5%) did so among Medicaid cases. Eighteen (34%) laboratories performed RHC in less than 10% of Medicare cases. These data indicated that there was significant inter-hospital variation in the frequency with which RHC was performed. Beginning in 1993, ongoing educational meetings and conferences were held with all laboratories, but especially with the 10 that were at the high end of the RHC performance level. As a result of this ongoing intervention, the rate of RHC among Medicare patients fell from 89/100,000 in 1992 to 65/100,000 beneficiaries in 1996. From another perspective, the percentage of catheterized Medicare patients undergoing RHC fell from 30.5% in 1992 to 17.4% in 1996. The decline among the 10 laboratories was even more dramatic; the percentage of catheterized Medicare patients undergoing RHC fell from 89.1% in 1992 to 31.6% in 1996. The parallel drop for Medicaid patients over the same time period was from 92.8 to 32.7%. The results of the study indicate that many previously performed RHC in patients with coronary artery disease were routine and not medically indicated. The dramatic decreases in RHC documented in this study over a 4-year period demonstrate the success of quality improvement efforts jointly undertaken by providers and a peer review organization.

Age Distribution↗
PubMed1998

[The relationship between herpes simplex virus II, human papillomavirus infection and infertility after artificial abortion].

In order to study the relationship between infection of sexually transmitted virus Herpes simplex virus II (HSV2), Human papillomavirus (HPV) and female infertility after artificial abortion, we collected 60 genital samples from infertile women who had accepted artificial abortions and 39 genital samples from normal women. Polymerase chain reaction (PCR) was used to detect HSV2 and HPV. The results were compared by x2. The positive rate of HSV2 in infertile and normal women were 80.0% and 25.6% respectively, there was a significant difference (P < 0.01); but that of HPV were 53.5% and 33.3%, which slowed no significant difference (P > 0.05). Mixed infection rates of HSV2 and HPV were 43.3% and 23.1% in infertile and normal women, a significant difference (P < 0.05) was statistically calculated. The results showed that there was a relationship between infertility after artificial abortion and genital infection of HSV2 and HPV or mited infection of HSV 2 and HPV. Taking total 99 genital samples into calculation, the mired infection rate of HSV 2 was 35.35%, a significant relatedness of HSV2 and HPV infection to infertility was proved by chi 2, chi 2 = 12.5, P < 0.01.

Abortion, Induced↗
PubMed1998

[An experimental study on limbal stem cells autograft transplantation with cryopreservation].

PURPOSE: The viability of limbal stem cells with cryopreservation and the treatment effect with cryopreserved limbal autograft transplantation for ocular surface disorders (OSDs) of stem cells deficiency in rabbits. METHODS: Limbal grafts included 2 mm of peripheral cornea and 2 mm of conjunctiva and OSDs models of corneal stem cells deficiency were created in right eyes of 12 rabbits. The grafts were cryopreserved in -196 degrees C liquid nitrogen by program-controlled Bio-Freezer. The limbal autograft transplantations for ocular surface reconstruction were performed after cryopreserved 60 days and 30 days. RESULTS: The stem cells deficiency result in corneal epithelium delay healing. Seven of 12 eyes were healed post-operative 22-26 days with a mean time of 24 +/- 1 days and four eyes with recurrent erosion. The swelling and neovascularization appearing with a mean time of 5 +/- 1 days were discovered. The cryopreserved limbal autograft transplantation can increase corneal epithelial healing with a mean time of 10 +/- 2 days. It was observed that corneal stromal swelling and neovascularization were markedly decreased, and neovascularization of two eyes were disappeared. CONCLUSIONS: Cryopreservation in liquid nitrogen can preserve the viability of limbal stem cells, and provide viable limbal grafts to treat OSDs in clinical patients.

Animals↗
PubMed1997

The effect of differences in the distribution of maternal age in England and Wales on the performance of prenatal screening for Down's syndrome.

We aimed to determine how differences in the age at which women had their pregnancies influenced the expected detection and false-positive rates of serum screening for Down's syndrome (i) between 1970 and 1993 in England and Wales, and (ii) between regions and districts of England and Wales in 1991. We applied published estimates of Down's syndrome screening to regional and district data on the age distribution of maternities and changes in the age distribution over time in England and Wales obtained from the Office of Population Censuses and Surveys. From 1970 to 1993 women, on average, became pregnant at an older age; the percentage of maternities among women aged 35 or more increased from 7 to 9.2 per cent. This was not a great enough change to have had a material effect on the performance of Down's syndrome screening. In 1991, the percentage of maternities among women aged 35 or more varied from 5 to 20 per cent among Health Districts, a difference that would influence the performance of screening; for example, using the triple test and a risk cut-off of 1 in 250, the detection rates would have varied from about 55 to 70 per cent and the false-positive rates from 4.4 to 8.8 per cent across different districts. The tendency for women to have their pregnancies at an older age would have had a negligible impact on the performance of serum screening for Down's syndrome, but differences in the age when women had their pregnancies in different parts of the country would lead to twice as many women being referred for amniocentesis in some districts than in others when offered the same method of serum screening and at the same risk cut-off level. The results will have important implications for the local purchasers of Down's syndrome screening services.

Adult↗
PubMed1997

Reliability of statistics on Down's syndrome notifications.

OBJECTIVES: To evaluate the completeness of notifications of Down's syndrome live births and terminations to the Office for National Statistics (ONS) using data from the National Down Syndrome Cytogenetic Register (NDSCR). To examine the agreement of observed birth prevalence of Down's syndrome with the expected birth prevalence derived from published maternal age specific rates. METHODS: The number of live births (adjusted to allow for the estimated underascertainment) and the number of terminations due to fetal Down's syndrome from NDSCR were compared with those figures reported to the ONS. Subsequently, using the NDSCR figures, the live birth prevalence of Down's syndrome that would have occurred in the absence of antenatal diagnosis and selective termination was calculated in England and Wales in the years 1990-1993. These figures were compared with those derived by applying published age specific prevalences to the maternal age distribution in England and Wales. RESULTS: It is estimated that only 48% and 46% respectively of Down's syndrome live births and terminations of pregnancy were notified to ONS between 1990 and 1993. The annual expected birth prevalences of Down's syndrome obtained by applying maternal age specific prevalences to the maternal age distribution were in close agreement with observed rates from NDSCR. CONCLUSIONS: There is considerable underreporting of Down's syndrome births and terminations to ONS. The NDSCR data are more complete and therefore the effects of screening should be monitored using data from this source, or using estimates derived from the age specific rates of Down's syndrome.

Abortion, Induced↗
PubMed1997

[Isolation of 28 new STSs at Xq27.3].

A plasmid sublibrary of the 475 kb insert of YAC209G4 was constructed by using pBS II KS vector. The library of 3,500 clones having 100-600 bp inserts was screened with the probe of the 475 kb insert blocked with competitor DNA. Sixty unique single copy clones were found and sequenced. Checking with GenBank, 28 new STSs were obtained. Genbank accession numbers are U26560-26587. Three STSs were tested by PCR with appropriate primers using human genomic DNA as template and showed specific amplification bands as expected.

Chromosome Fragility↗