Search PubMed⌕ Search

Biomedical subjects

Y T Liu

Publications and source records attributed to Y T Liu.

At least 37 records · Page 2Linked to original sources
PubMed1998

Identification of the binding partners for flightless I, A novel protein bridging the leucine-rich repeat and the gelsolin superfamilies.

Flightless-I (fliI) is a novel member of the gelsolin family that is important for actin organization during Drosophila embryogenesis and myogenesis. Drosophila fliI and the human homolog FLI both contain the classic gelsolin 6-fold segmental repeats and an amino-terminal extension of 16 tandem leucine-rich repeats (LRR). LRR repeats form amphipathic beta-alpha structural units that mediate protein-protein interactions. Although there are close to 100 known LRR domain-containing proteins, only a few binding pairs have been identified. In this paper, we used biochemical and genetic approaches to identify proteins that interact with human FLI. In vitro synthesized FLI bound to actin-Sepharose and binding was reduced by competition with excess soluble actin. Actin binding was mediated through the gelsolin-like domain and not the LRR domain. Although the FLI LRR module is most closely related to the LRR domains of Ras-interactive proteins, FLI does not associate with Ras, selected Ras effectors, or other Ras-related small GTPases. Two-hybrid screens using FLI LRR as bait identified a novel LRR binding partner. The 0.65-kilobase pair (kb) clone from the screen survived additional rounds of stringent two-hybrid pairwise assays, establishing a specific interaction. Binding to FLI LRR was corroborated by co-immunoprecipitation with FLI LRR. The translated sequence of the FLI LRR associated protein (FLAP) encodes a novel protein not represented in the data base. Northern blot analyses revealed four FLAP messages of approximately 2.7, 2.9, 3.3, and 5.1 kb, which are differentially expressed in the tissues tested. Skeletal and cardiac muscles are particularly rich in the 3.3-kb FLAP message, and the FLI message as well. Full-length FLAP clones were isolated from a mouse skeletal muscle cDNA library. They have an open reading frame which encodes for a protein containing 626 amino acids. Sequence analyses predict that the FLAP protein is rich in alpha-helices and contains stretches of dimeric coiled coil in its middle region and COOH terminus. The identification of actin and FLAP as the binding ligands for the gelsolin-like domain and the LRR domain, respectively, suggests that FLI may link the actin cytoskeleton to other modules implicated in intermolecular recognition and structural organization.

Amino Acid Sequence↗
PubMed1998

Therapeutic effect and pharmacokinetics of ketotifen transdermal delivery system.

Ketotifen transdermal delivery systems were prepared using polyisobutylene, liquid paraffin, and fatty acid. In vitro skin penetration studies were conducted in Franz diffusion cells using excised porcine skin to determine the skin permeation rates of ketotifen patches. A trend of increased skin penetration of ketotifen was observed as the amount of liquid paraffin in the patch was increased. In addition, we found that lauric acid was a suitable enhancer for percutaneous absorption of ketotifen. Challenge tests were performed in guinea pigs to determine the therapeutic effect of the delivery systems for the inhibition of anaphylactic shock using varied concentrations of chicken ovum albumin as sensitizer. Our results showed that compared with the treatment of intramuscular administration, the skin patch was more effective and produced higher survival rates. The pharmacokinetics of the ketotifen patch were determined by applying the skin patch to the dorsal skin of rabbits. The plasma levels were maintained constant (42.5-36.4 ng/ml) from 9 to 30 hr. From our study, the prepared ketotifen patch may further be developed for the treatment or prevention of allergic asthma.

Adhesives↗
PubMed1998

Molecular characterization of Gluconobacter oxydans recA gene and its inhibitory effect on the function of the host wild-type recA gene.

A DNA fragment containing the recA gene of Gluconobacter oxydans was isolated and further characterized for its nucleotide sequence and ability to functionally complement various recA mutations. When expressed in an Escherichia coli recA host, the G. oxydans recA protein could efficiently function in homologous recombination and DNA damage repair. The recA gene's nucleotide sequence analysis revealed a protein of 344 amino acids with a molecular mass of 38 kDa. We observed an E. coli-like LexA repressor-binding site in the G. oxydans recA gene promoter region, suggesting that a LexA-like mediated response system may exist in G. oxydans. The expression of G. oxydans recA in E. coli RR1, a recA+ strain, surprisingly caused a remarkable reduction of the host wild-type recA gene function, whereas the expression of both Serratia marcescens recA and Pseudomonas aeruginosa recA gene caused only a slight inhibitory effect on function of the host wild-type recA gene product. Compared with the E. coli RecA protein, the identity of the amino acid sequence of G. oxydans RecA protein is much lower than those RecA proteins of both S. marcescens and Pseudomonas aeruginosa. This result suggests that the expression of another wild-type RecA could interfere with host wild-type recA gene's function, and the extent of such an interference is possibly correlated to the identity of the amino acid sequence between the two classes of RecA protein.

Amino Acid Sequence↗
PubMed1998

Risk factors of non-arteritic anterior ischemic optic neuropathy (NAION): ocular or systemic.

We retrospectively analyzed 22 patients with non-arteritic anterior ischemic optic neuropathy (NAION) seen at Chung-Ho memorial hospital between 1994 and 1996 to investigate the risk factors of NAION. The risk factors were divided into two groups: ocular and systemic. The ocular factors include refractive state, intraocular pressure, and cup-disk ratio of fellow eye. The systemic factors include diabetes, hypertension and cardiovascular diseases. The analysis revealed: (1) only 22.6% of patients with NAION have systemic risk factors; (2) intraocular pressure is not specific to NAION; (3) most of fellow eyes (72.6%) have cup-disk ratio not more than 0.1; and (4) most patients (90.9%) are hyperopic or emmetropic, only 9% of patients are myopic in either affected or fellow eyes. The statistical comparison between ocular (including cup-disk ratio and refractive state) and systemic factors is significant. The correlation with systemic factors in our study was not so high as previous study had reported. On the contrary, crowding effect of small cup-disk ratio, which induces a vicious circle of generally circulatory compromised disk, may play an important role in NAION. Besides, hyperopic or at least emmetropic eyes are more prone to NAION than myopic eyes. This may be due to lack of flattening of the temporal excavation, therefore adding a predisposing factor to a generally circulatory compromised disk. The risk factors associated with NAION seem more strongly correlated with ocular factors than with systemic factors.

Adult↗
PubMed1997

Combined-modality therapy for squamous carcinoma of the buccal mucosa: treatment results and prognostic factors.

BACKGROUND: Reports on locoregional control and survival of squamous cell carcinoma of buccal mucosa are scarce in literature. In this study, a single institutions's experience of combined surgery and postoperative radiotherapy (RT) for buccal mucosal malignancy with favorable results was analyzed and presented. The prognostic factors on locoregional control were also discussed. METHODS: From January 1988 to July 1994, 57 patients with squamous cell carcinoma of buccal mucosa treated by surgery and RT were reviewed. The distributions according to American Joint Committee on Cancer (AJCC) staging were: stage II, 6; stage III, 21; and stage IV, 30 patients. Total dose of RT at the buccal area ranged from 45 Gy to 68.4 Gy, median 61.2 Gy. Tumor-related factors (AJCC stage, T stage, histologic grading, pathologic tumor invasion to skin of cheek, adjacent bony structures, and regional lymph nodes) and treatment-related factors (surgical margin, radiation dose, and the time interval between operation and RT) were analyzed to determine their influence on locoregional control. RESULTS: Three-year actuarial locoregional control rate, overall survival rate, and disease-specific survival rates were 64%, 55%, and 62%, respectively. Ten of these 22 patients (45%) with recurrent tumors were reoperated, but only 2 patients were successfully salvaged. Positive surgical margin and tumor invasion to skin of cheek were significantly poor prognostic factors on locoregional control by univariate analysis. In multivariate analysis, tumor invasion to skin of cheek was the only prognostic factor (p = .0014). CONCLUSIONS: Locoregional failure was the major cause of death for squamous buccal mucosa cancers managed with surgery and RT. Few recurrences could be detected early and successfully salvaged. Skin of cheek involvement is an important prognostic factor for buccal mucosa cancers.

Actuarial Analysis↗
PubMed1997

Free tissue transfer for leg reconstruction in children.

Twenty-five free tissue transfers for reconstruction after lower limb trauma or release of scar contractures were performed in 23 children over an 8-year period. The ages ranged from 2 to 14 years (mean 7.1 years). Fourteen (61%) patients had major associated injuries. The reconstruction sites were all in the distal leg. The overall vascular success rate was 96%. Three patients underwent re-explorations because of vascular insufficiency. One flap failed and two were salvaged. The causes of vascular complications were considered to be inadequate debridement of an avulsed vessel, venous kinking and inadequate protection of the vascular pedicle. The three cases with vascular insufficiency were children with associated injuries on the ipsilateral leg proximally. Postoperative complications were not uncommon (28%). Six of the seven complications occurred in patients with major associated injuries. The mean follow-up was 57 months. Long-term problems such as a limping gait, frequent flap ulcers, toe contracture or a bulky flap were common. Our results suggest that free tissue transfer is reliable and safe for the reconstruction of major leg injuries in children. Associated injuries proximal to the reconstructed defects on the ipsilateral leg predispose to more vascular complications. Since postoperative complications and long-term morbidity are common in children, special precautions should be taken with the preoperative assessment, planning, execution of surgery and postoperative care to achieve better results.

Accidents, Traffic↗
PubMed1997

Global distribution of the CCR5 gene 32-basepair deletion.

A mutant allele of the beta-chemokine receptor gene CCR5 bearing a 32-basepair (bp) deletion (denoted delta ccr5) which prevents cell invasion by the primary transmitting strain of HIV-1 has recently been characterized. Homozygotes for the mutation are resistant to infection, even after repeated high-risk exposures, but this resistance appears not to be total, as isolated cases of HIV-positive deletion homozygotes are now emerging. The consequence of the heterozygous state is not clear, but it may delay the progression to AIDS in infected individuals. A gene frequency of approximately 10% was found for delta ccr5 in populations of European descent, but no mutant alleles were reported in indigenous non-European populations. As the total number of non-European samples surveyed was small in comparison with the Europeans the global distribution of this mutation is far from clear. We have devised a rapid PCR assay for delta ccr5 and used it to screen 3,342 individuals from a globally-distributed range of populations. We find that delta ccr5 is not confined to people of European descent but is found at frequencies of 2-5% throughout Europe, the Middle East and the Indian subcontinent (Fig. 1). Isolated occurrences are seen elsewhere throughout the world, but these most likely represent recent European gene flow into the indigenous populations. The inter-population differences in delta ccr5 frequency may influence the pattern of HIV transmission and so will need to be incorporated into future predictions of HIV levels.

Africa↗
PubMed1997

A rapid non-invasive method for the detection of the haemochromatosis C282Y mutation.

We describe the rapid single-step detection, by mutagenically separated polymerase chain reaction (MS-PCR), of the HLE C282Y mutation, for which > 90% of haemochromatosis patients in the U.K. are homozygous. In addition to using purified DNA as a template, whole blood and lysed buccal cell extracts from mouthwash samples can be used. Therefore sample collection may be non-invasive and purification steps kept to a minimum.

Genetic Techniques↗
PubMed1997

The Sequential Structure of Movement Outcome in Learning a Discrete Timing Task.

The sequential structure of discrete movement outcomes in an elbow-flexion movement task was examined with a crossed design of 2 movement-time (125 and 500 ms) and 2 range-of-motion (5° and 20°) conditions over sets of 200 trials of practice. Traditional analyses of error score techniques, time-series analyses of the quantitative raw and differenced data, and a symbolic dynamic analysis of qualitative events arising from the data were conducted. The differenced data revealed a consistent order over 3-trial strings that was more apparent with larger steps in the data scores, but quantitative time-series and symbolic dynamic analyses of the raw movement-time data showed weaker relations. There were a few patterns of structure evident in the raw data time-series that were a function of the movement condition and the skill level of the subject. The analyses of the movement-time scores revealed that, in learning the discrete timing task, there is more order apparent in the intrinsic frame of reference of the difference scores than in the extrinsic frame of reference.

learning↗
PubMed1997

Susceptibility of Pseudomonas aeruginosa of various pyocin types to the newly synthesized ampicillin derivative, N-(6,7-difluoroquinolonyl)ampicillin.

Six hundred and thirty-two isolates of Pseudomonas aeruginosa of 17 pyocin types were collected in 1993 in Taiwan. Types 1, 10, 3, 35 and 12 were the most common pyocin types identified in Taiwan with isolation frequencies of 47.3%, 24.4%, 7.6%, 3.6% and 2.2%, respectively. Several pyocin subtypes were determined. All pyocin types (one isolate of each tested) were resistant to ampicillin and nalidixic acid, but sensitive to fluoroquinolone antibiotics, such as norfloxacin and enoxacin, indicating that cross-resistance to quinolone antibiotics of nalidixic acid and fluoroquinolone derivatives has not developed. A new ampicillin derivative of 6,7-difluoroquinolonic acid, N-(6,7-difluoroquinolonyl)-ampicillin (AU-1), was synthesized by coupling ampicillin with 6,7-difluoroquinolonic acid (FP-3). Compound AU-1 was much more active than either ampicillin or FP-3 alone against all pyocin types of P. aeruginosa and induced filamentation in most growing cells.

Ampicillin↗
PubMed1997

Factor V Leiden and thermolabile methylenetetrahydrofolate reductase in extreme old age.

Both factor V Leiden and the C677T methylenetetrahydrofolate reductase (MTHFR) gene mutation are associated with premature vascular disease, and yet are found at surprisingly high allele frequencies in European populations, 2.7% and 35% respectively. We have investigated the prevalence of these mutations in 87 UK residents over the age of ninety, to look for any evidence of their association with premature death. Five factor V Leiden heterozygotes were found, giving an allele frequency of 2.9%, similar to that in the general UK population. The frequency of the thermolabile C677T MTHFR mutation was 36% with 11% homozygotes, again similar to that in the UK population; these genotypes are in Hardy-Weinberg equilibrium, suggesting that there is not strong selection against the homozygous state. One person was both heterozygous for factor V Leiden and homozygous for the C677T mutation. This study suggests that neither factor V Leiden nor thermolabile MTHFR are risk factors for premature death.

Aged↗
PubMed1996

A retrospective lung cancer mortality study of people exposed to insoluble arsenic and radon.

The incidence of lung cancer for workers who had been exposed to insoluble arsenic in four mines was found to be 290/10(5). A dose-dependent decrease in the incidence was associated with a reduction in the concentration of insoluble arsenic in the air. The content of arsenic (expressed as the geometric mean) in the lung of subjects exposed to insoluble arsenic was 51.4 micrograms/g per dry lung tissue which was 17 times higher than the value of 3.0 micrograms/g per day lung tissue found in control groups. Moreover, the content of arsenic was found to correlate with the number of years working in the mine and with the incidence of lung cancer. Metabolic studies of arsenopyrite showed that it is converted to products such as arsenous acid, arsenic acid, methyl arsenate and dimethyl arsenate, which are identical to those generated from As2O3. Although these metabolic products are formed at a lower rate, they nonetheless show that arsenopyrite should be considered a carcinogen. Potential carcinogens such as As, Cr, Ni, Be, and Cd were evaluated in lung specimens of miners with lung cancer and compared with values obtained in controls using logistic regression analysis. Only As was found to be significantly associated with lung cancer. The concentration of As in lung tissues correlated well with the amount found in the air of the mining environment. A retrospective/prospective interference epidemiological investigation performed over a 40-year period showed that the risk of radon had been overestimated. After regulatory measures were implemented in the mines to control for exposure to Rn, the risk of exposure to Rn was found to be RR/WLM (relative risk per working level month) = 0.17%, which was 9 times lower than the values previously estimated.

Arsenic↗
PubMed1996

Intrastriatal and intraventricular infusion of brain-derived neurotrophic factor in the cynomologous monkey: distribution, retrograde transport and co-localization with substantia nigra dopamine-containing neurons.

The distribution and retrograde transport of brain-derived neurotrophic factor was examined using magnetic resonance imaging guided stereotaxic intracerebroventricular and intrastriatal infusion in the cynomologous monkey. Two intracerebroventricular animals were infused with brain-derived neurotrophic factor at a dose of 3 micrograms/h for 21 and 28 days. A third intracerebroventricular animal received sequential infusions of 15, 30 and 60 micrograms/h brain-derived neurotrophic factor each for seven days using an Alzet 2002 minipump. For the multiple intrastriatal animals (n = 5) a dose of 3 micrograms/h was infused into each site. One intrastriatal monkey was infused with vehicle solution of 10 mM phosphate-buffered saline pH 7.4 for 14 days resulting in no brain-derived neurotrophic factor immunoreactivity. Following the lower dose intracerebroventricular infusion, brain-derived neurotrophic factor immunoreactivity was confined to the ventricular ependymal layer. In the sequential higher dose intracerebroventricular case, the cannula was located mainly within the lateral ventricle, although there was damage to the ependymal wall and adjacent caudate nucleus. Brain-derived neurotrophic factor immunoreactivity revealed spread of injectate within the ipsilateral and to a lesser extent the contralateral caudate nucleus, septum, orbital cortex and ventricular ependymal wall. In this case, retrogradely labelled brain-derived neurotrophic factor neurons were found within the parafascicular thalamus and substantia nigra, pars compacta, as well as within cortex, vertical limb of the diagonal band and nucleus basalis. Brain-derived neurotrophic factor intrastriatal infusion retrogradely labelled perikarya within sensory motor cortex, parafascicular thelamus and substantia nigra, pars compacta. Sections from these cases dual-immunoreacted for brain-derived neurotrophic factor and tyrosine hydroxylase, the synthesizing enzyme for dopamine, revealed a subpopulation of pars compacta dopaminergic neurons which contained retrogradely transported brain-derived neurotrophic factor. These findings indicate that a select subgroup of nigral dopamine neurons retrogradely transport brain-derived neurotrophic factor in the primate. Furthermore it remains to be determined whether select nigral cells are responsive to the trophic influences of brain-derived neurotrophic factor in the normal and neuropathologic condition.

Animals↗
PubMed1996

Comparison of three typing methods for Pseudomonas aeruginosa.

Fifty-seven independent isolates of Pseudomonas aeruginosa from blood specimens were typed with 3 different methods: ribotyping, random amplified polymorphic DNA (RAPD) typing, and pyocin typing. Ribotyping was performed by probing the rRNA genes of genomic DNA that was digested separately with 4 different restriction enzymes. Digestion of DNA from 57 P. aeruginosa isolates with BamHI, ClaI, EcoRI, and PstI produced 4, 4, 6, and 7 patterns, respectively. As a result, ribotyping classified the 57 isolates into 22 types. Six new ribotypes that had not been described previously were found. One BamHI, 1 ClaI, 2 EcoRI, and 2 PstI patterns were novel. RAPD typing was performed with two different polymerase chain reaction (PCR) primers (RAPD1 and RAPD2). Both primers classified the 57 isolates into 15 RAPD types and produced identical patterns. The pyocin typing method classified the 57 isolates into 10 types. According to the results obtained in this study, the ribotyping has a discriminatory index of 0.865, RAPD, 0.785, and pyocin typing, 0.676, respectively. The ribotyping method was the most effective among the 3 methods compared for typing P. aeruginosa isolates.

Bacterial Typing Techniques↗
PubMed1995

[HPLC-DAD analysis of thirteen soporific sedative drugs in human blood].

An HPLC-DAD qualitative and quantitative method for the analysis of thirteen soporific sedative drugs in human blood established. These drugs were separated by HPLC with acetonitrile-water (35 : 65) (for barbital drugs), methanol-water (60 : 40) and methanol-10% triethylamine acetic acid solution (pH 7.5) (for benzodiazepam and phenothiazine drugs) as eluting phase systems and were detected with photodiode array detector (DAD). These drugs were identified by their spectral characteristics and retention times and quantitatively determined by their peak areas. In the concentration range 0.5-10 micrograms . ml-1, the concentration of all 13 drugs were in proportion to their peak areas. The correlation coefficients were all up to 0.99. The recovery rates from blood were all above 85% without interference from impurities. This method has been used to detect three poisoning samples from the clinic. Good results have been obtained.

Chromatography, High Pressure Liquid↗