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Biomedical subjects

C H Liu

Publications and source records attributed to C H Liu.

At least 55 records · Page 3Linked to original sources
PubMed2000

Negative regulation of expression of the Bacillus megaterium bmlP1 gene by the bmlP1 3' flanking region.

We report that the expression of the Bacillus megaterium bmlP1 gene is subject to negative regulation by the bmlP1 3' flanking region. This repression occurred both in B. megaterium and in Escherichia coli. When the bmlP1 promoter was replaced with a heterologous promoter or when the orientation of the bmlP1 3' flanking region was reversed, the inhibitory effect was still observed. However, the bmlP1 3' flanking region was unable to exert repression on a heterologous gene when fused downstream in either orientation, and it was incapable of acting in trans. Dot blot and Northern blot analyses revealed that the repression occurred at the RNA level. Deletion analysis showed that the regulatory site responsible for the repression is located within a 116-bp region immediately following the bmlP1 gene. Possible mechanisms for this repression are discussed.

Bacillus megaterium↗
PubMed2000

Edg-1, the G protein-coupled receptor for sphingosine-1-phosphate, is essential for vascular maturation.

Sphingolipid signaling pathways have been implicated in many critical cellular events. Sphingosine-1-phosphate (SPP), a sphingolipid metabolite found in high concentrations in platelets and blood, stimulates members of the endothelial differentiation gene (Edg) family of G protein-coupled receptors and triggers diverse effects, including cell growth, survival, migration, and morphogenesis. To determine the in vivo functions of the SPP/Edg signaling pathway, we disrupted the Edg1 gene in mice. Edg1(-/-) mice exhibited embryonic hemorrhage leading to intrauterine death between E12.5 and E14.5. Vasculogenesis and angiogenesis appeared normal in the mutant embryos. However, vascular maturation was incomplete due to a deficiency of vascular smooth muscle cells/pericytes. We also show that Edg-1 mediates an SPP-induced migration response that is defective in mutant cells due to an inability to activate the small GTPase, Rac. Our data reveal Edg-1 to be the first G protein-coupled receptor required for blood vessel formation and show that sphingolipid signaling is essential during mammalian development.

Animals↗
PubMed2000

Immediate repair of intestinal injury during laparoscopically assisted vaginal hysterectomy.

With the increasing popularity of laparoscopic surgery in gynecologic diseases, complications with this procedure are noted more frequently. The majority of complications occur during operation, and most of the cases are immediately identified. The recovery and outcome are relatively good due to urgent repair and management. Herein, we report a complication--a trocar, inducing small intestinal damage, which was detected during laparoscopically assisted vaginal hysterectomy. The damage was repaired promptly extraperitoneally with an uneventful recovery. Through a review of the literature and our experience, possible preventive methods of this complication are discussed. In addition, by this case review, we hoped that such a complication could be avoided in the future.

Female↗
PubMed2000

Impact of assisted reproductive technology on modern medicine.

A surge in knowledge and interest in reproductive biology has occurred since the advent of assisted reproductive technology (ART) in the 1960s. These innovative medical advances soon challenged societies and invited criticism. Nevertheless, ART has superseded older therapies and serves as a back-up when all else fails. There are currently 61 ART clinics in Taiwan. Thanks to a group of young physicians and scientists who have devoted great effort in catching up with the modern advances in assisted reproduction, most of the important advances in ART have been introduced to Taiwan promptly and resulted in good success rates. The complications of multifetal pregnancies as well as controversies regarding gestational surrogacy and new technologies such as intracytoplasmic sperm injection, preimplantation genetic diagnosis, and cloning have challenged conventional wisdom, ethics, laws, and religions. Society now faces a dilemma in striking a balance among science, ethics, and human rights. It is, thus, advisable that we stand back once in a while and carefully consider where we should go next.

Ethics, Medical↗
PubMed2000

[Ribozyme which specifically cleave 12-lipoxygenase mRNA: in vitro activity and its dynamics].

The ribozyme gene which specifically cleaved 12-lipoxygenase mRNA was designed, synthesized and cloned according to hammer-head ribozyme model. A 25-bp-long segment of 12-lipoxygenase mRNA was chemically synthesized as substrate, which was incubated with transcribed ribozyme RNA to detect its cleavage activity in vitro. The results showed that the ribozyme had a relatively high cleavage activity against 12-lipoxygenase mRNA segment at 37 degrees C. It's kcat value and Km value was 0.083/min and 1300 nmol/L respectively. The ribozyme had a very high activity at 50 degrees C and its kcat value was 0.31/min.

Arachidonate 12-Lipoxygenase↗
PubMed2000

Unexpected recurrent seizures following repeated spinal injections of tetracaine--a case report.

A 36-year-old male patient was scheduled to undergo ureteroscopic lithotomy because of left ureteral stone under spinal anesthesia. After receiving a renewed spinal anesthesia with 8 mg tetracaine to compensate for the first attempt (with 10 mg tetracaine), which proved to be a failure, he was soon seized with episodic seizure attacks. Central nervous system toxicity of the local anesthetic might be the cause of the seizure. We brought forward this case for discussion for warning that the possibility of systemic toxicity of local anesthetic might exist despite a seemingly undisputable spinal anesthesia.

Adult↗
PubMed2000

[cDNA cloning, fusion expression in Escherichia coli and activity assay of hIL-11].

Human Interleukin-11 (hIL-11) is a multifunctional cytokine which plays an important role in regulating the proliferation and differentiation of cells in the hematopoeitic, lymphoid system etc. To obtain the IL-11 cDNA, a primary culture of Chinese fetal lung fibroblast was prepared from fresh tissue. Then the human IL-11 cDNA without the N-terminal signal peptide sequence was cloned by RT-PCR from the cells induced by PMA. The sequence indicated that there are three bases different from those previously reported, but with no change of the amino acids. The cDNA was inserted into the 3' end of trxA gene in thioredoxin gene fusion expression system pTRXFUS to construct the trxA and hIL-11 fusion expression vector, and expressed in E. coli. The fusion hIL-11 accounts for more than 20% of the total bacteria proteins. The expression product is present in soluble forms and has the full biological and immunological activities.

Cells, Cultured↗
PubMed2000

Effects of salvianolic acid-A on rat hepatic stellate cell proliferation and collagen production in culture.

AIM: To investigate the effects of salvionolic acid-A (SA-A), one of main effective components of Salvia miltiorrhiza for its antifibrotic action, on the cell proliferation and collagen production in cultured hepatic stellate cells (HSC). METHODS: HSC were isolated through in situ perfusion of liver with pronase E and collagenase, and gradient centrifugation with Nycodenz. The cultured HSC were incubated with SA-A 0.1-100 mumol/L for 24 h. MTT spectrometric assay and intercellular incorporation of methyl-[3H]thymidine ([3H]TdR) was used to assess the cell proliferation. The amount of collagen was semi-quantified by ponceau staining and image analysis, the amount of type I collagen secretion was measured with ELISA and normalized by the total protein of cell layer. The total RNA was prepared from the control cells and the drug treated cells respectively, and the expression of pro-collagen alpha 2 (I) mRNA was semi-quantitatively analyzed with RT-PCR. RESULTS: SA-A 100 mumol/L showed a little cytotoxity, SA-A 0.1-10 mumol/L did not influence cell morphology, and SA-A 1-100 mumol/L decreased the cell proliferation significantly in a concentration-dependent manner (P < 0.05). SA-A 1, 10, 100 mumol/L decreased the cell collagen deposition by 78.6%, 71.8%, and 61.3% of the control respectively (P < 0.05), and decreased type I collagen secretion to 53.1%, 52.6%, and 49.5% (P < 0.01 or P < 0.05). Both SA-A 1 and 10 mumol/L downregulated procollagen alpha 2 (I) mRNA expression remarkably (P < 0.05). CONCLUSION: SA-A inhibited HSC proliferation and collagen expression. The inhibitory effect on HSC activation is the main mechanism of SA-A action against liver fibrosis.

Animals↗
PubMed2000

[Studies on quality standards for Pollen Typhae(puhuang)].

OBJECTIVE: To work out quality standards for Pollen Typhae(Puhuang). METHOD: Isorhamnetin-3-O-neohesperidoside, typhaneoside, isorhamnetin and beta-sitosterol in Pollen Typhae marketed in ten cities of China were identified by TLC. The contents of isorhamnetin-3-O-neohesperidoside and typhaneoside were determined by HPLC. RESULT: The method is sensitive and specific for identifying isorhamnetin-3-O-neohesperidoside, typhaneoside, isorhamnetin and beta-sitosterol. The linear ranges of isorhamnetin-3-O-neohesperidoside and typhaneoside were 0.188-0.940 microgram with and average recovery of 97.77%; and 0.164-0.820 microgram with an average recovery of 98.42% respectively. CONCLUSION: The method can be used both qualitatively and quantitatively as standards for the quality control of Pollen Typhae.

Drugs, Chinese Herbal↗
PubMed1999

Vascular endothelial cell adherens junction assembly and morphogenesis induced by sphingosine-1-phosphate.

Vascular endothelial cells undergo morphogenesis into capillary networks in response to angiogenic factors. We show here that sphingosine-1-phosphate (SPP), a platelet-derived bioactive lipid, activates the EDG-1 and -3 subtypes of G protein-coupled receptors on endothelial cells to regulate angiogenesis. SPP induces the Gi/mitogen-activated protein kinase/cell survival pathway and the small GTPase Rho- and Raccoupled adherens junction assembly. Both EDG-1-and EDG-3-regulated signaling pathways are required for endothelial cell morphogenesis into capillary-like networks. Indeed, SPP synergized with polypeptide angiogenic growth factors in the formation of mature neovessels in vivo. These data define SPP as a novel regulator of angiogenesis.

Animals↗
PubMed1999

Sphingosine-1-phosphate: extracellular mediator or intracellular second messenger?

Sphingosine-1-phosphate (SPP), a polar sphingolipid metabolite, has received much attention recently as an extracellular mediator and an intracellular second messenger. It regulates a wide range of biological responses such as cell growth, death, differentiation, and migration. Recent identification of plasma membrane receptors and the cloning of SPP metabolizing enzymes have increased our understanding of the biology of SPP synthesis and action. However, controversy exists regarding the mode of action of this molecule. EDG-1 and related G-protein-coupled receptors were identified recently as plasma membrane receptors for SPP. In light of this recent discovery, many of the functions of SPP previously thought to be due to intracellular second messenger action should be reevaluated. In addition, signaling properties and functions of the three known receptors for SPP need to be fully delineated. The structures and the evolutionary conservation of SPP metabolizing enzymes from yeast to mammals support the hypothesis that SPP also plays a role as an intracellular second messenger. However, definitive assignment of the intracellular role of SPP awaits purification/molecular cloning of elusive intracellular receptors. Better knowledge of the molecular basis of SPP action is needed to assess the physiological and pathophysiological significance of this bioactive lipid mediator.

Animals↗
PubMed1999

Efficiency of supercritical fluid extraction for determining 4-nonylphenol in municipal sewage sludge.

When the sewage sludge containing the persistent, lipophilic, metabolite 4-nonylphenol (4-NP) has been disposed of in the environment it's toxic nature can lead to serious health risks to human beings and can also affect plants and aquatic organisms. Supercritical fluid extraction (SFE) is a new and powerful technique for extracting the organic contaminants from the solid phase. The present study was conducted to investigate optimal conditions for the quantitative extraction of 4-NP by SFE and to determine the concentration of 4-NP in municipal sewage sludge. The effect of several parameters such as temperature, pressure, static extraction time, dynamic extraction time, CO2 flow-rate, sample mass and modifier on the extraction were investigated. The optimal conditions for the extraction of the spiked sample were fluid pressure 97 bar, temperature 40 degrees C, flow-rate 3.0 ml/min, static extraction time 2 min, dynamic extraction time 5 min and modifier methanol (0.5 ml). Extracts were analyzed by gas chromatography-mass spectrometry. Concentration of 4-NP in the anaerobically degraded sludge of the De-Haw Sewage Treatment Plant in Taiwan was found to be 243.9 mg/kg. The extraction efficiency of the SFE method was compared with the conventional Soxhlet extraction method. The overall recovery of the SFE method was found to be greater and the results indicate that SFE is an efficient method for extracting 4-NP from sewage sludge.

Carbon Dioxide↗
PubMed1999

High-performance liquid chromatographic method for determination of tramadol in human plasma.

A modified high-performance chromatographic method using UV detection was developed for determination of tramadol concentration in human plasma. Plasma samples were extracted with ethyl acetate in a one-step liquid-liquid extraction (recovery 88.5+/-2.1%). Analysis of the extract was performed on a reversed-phase LiChrospher 60 RP-select B column with a particle size of 5 microm. The mobile phase consisted of 0.05 M KH2PO4 aqueous solution (pH 3.5) and acetonitrile in a ratio of 90:10 (v/v). Metoprolol was used as the internal standard and UV detection at 225 nm was employed. Accuracy of the assay in the concentration range examined was from 1.3 to 11.9% for the intra-day run and from 1.4 to 8.1% for the inter-day run. The precision of this method varied from 1.2 to 8.7%. The reproducibility of the method was determined to be from 0.8 to 7.2% over the six-day period. A limit of detection was 9 ng/ml at a signal-to-noise ratio of 3. This validated method was then applied to the determination of tramadol concentrations in healthy volunteers after oral administration of 100 mg of tramadol in capsules of Painlax and Tramal.

Adult↗
PubMed1999

Studies on the determination of diacetyl guanfubase A concentration in rabbit plasma and pharmacokinetics.

A gas chromatographic method for monitoring diacetyl guanfubase A in plasma is described. The procedure involved a single solvent extraction of drug from rabbit plasma into ethyl acetate with guanfubase A as an internal standard. The extract was analyzed subsequently on a gas chromatograph equipped with a hydrogen flame ionization detector. The recovery was 86.43% +/- 6.90% (+/- SD); the RSD of within-day and between-day was 2.81%-5.26% and 5.22%-8.24%, respectively; the regression line was linear over the concentration range of 25-200 micrograms/mL, the limit of detection was 10 micrograms/mL. No endogeneous interference was found in chromatograms of the biological samples. This method was applied to the pharmacokinetic study of diacetyl guanfubase A in rabbits.

Alkaloids↗
PubMed1999

Molecular characterization of germline mutations in the BRCA1 and BRCA2 genes from breast cancer families in Taiwan.

A total of 18 families with multiple cases of breast cancer were identified from southern Taiwan, and 5 of these families were found to carry cancer-associated germline mutations in the BRCA1 and BRCA2 genes. One novel cryptic splicing mutation of the BRCA1 gene, found in two unrelated families, was shown to be a deletion of 10 bp near the branch site in intron 7. This mutation causes an insertion of 59 nucleotides derived from intron 7 and results in a frameshift, leading to premature translational termination of BRCA1 mRNA in exon 8. Deletions of 2670delC, 3073delT and 6696-7delTC in the BRCA2 gene were found in three other breast cancer families. All three deletions are predicted to generate frameshifts and to result in the premature termination of BRCA2 protein translation. Several genetic polymorphisms in both BRCA1 and BRCA2 genes were also detected in this investigation.

Adult↗
PubMed1999

Development of spatial and temporal vision during childhood.

Using the method of limits, we measured the development of spatial and temporal vision beginning at 4 years of age. Participants were adults, and children aged 4, 5, 6, and 7 years (n = 24 per age). Spatial vision was assessed with vertical sine-wave gratings, and temporal vision was assessed with an unpatterned luminance field sinusoidally modulated over time. Under these testing conditions, spatial contrast sensitivity at every frequency increased by at least 0.5 log units between 4 and 7 years of age, at which point it was adult-like. Grating acuity reached adult values at 6 years of age. Temporal vision was more mature: at 4 years of age temporal contrast sensitivity at higher temporal frequencies (20 and 30 Hz) and critical flicker fusion frequency were already adult-like. Sensitivity at lower temporal frequencies (5 and 10 Hz) increased by 0.25 log units after the age of 4 to reach adult levels at age 7. The results suggest that temporal vision matures more rapidly than spatial vision during childhood. Thus, spatial and temporal vision are likely mediated by different underlying neural mechanisms that mature at different rates.

Adolescent↗
PubMed1999

Lighting direction affects recognition of untextured faces in photographic positive and negative.

Face recognition in photographic positive and negative was examined in a same/different matching task in five lighting direction conditions using untextured 3-D laser-scanned faces. The lighting directions were +60, +30, 0, -30 and -60 degrees, where negative values represent bottom lighting and positive values represent top lighting. Recognition performance was better for faces in positive than in negative when lighting directions were at +60 degrees. In one experiment, the same effect was also found at +30 degrees. However, faces in negative were recognized better than positive when the direction was -60 degrees. There was no difference in recognition performance when the lighting direction was 0 and -30 degrees. These results confirm that the effect of lighting direction can be a determinant of the photographic negative effect. Positive faces, which normally appear to be top-lit, may be difficult to recognize in negative partly because of the accompanying change in apparent lighting direction to bottom-lit.

Adult↗