Biomedical subjects

S Y Liu

Publications and source records attributed to S Y Liu.

At least 73 records · Page 4Linked to original sources

PubMed1996

Nucleus 22-channel cochlear mini-system implantations in Mandarin-speaking patients.

This article evaluates the benefits of the Mini System of the Nucleus 22-Channel Cochlear Implant on the speech perception and auditory functions of Mandarin-speaking patients. Tests adapted specifically for the assessment of a tonal language were administered in the best-aided condition preoperatively to four Mandarin-speakers. These scores were compared postoperatively with implant alone or with lipreading scores to quantify speech perception and auditory improvements resulting from the Nucleus 22 Mini-System cochlear implant. Four postlingually deafened adults underwent cochlear implant surgery using a Nucleus 22-Channel Mini-System Device via an inverted "U" postauricular incision and the posterior tympanotomy approach, without complications. After up to 2 years of rehabilitation, all four patients exhibited continuous improvement in both speech perception and auditory abilities over time. The improvements made by our Mandarin-speaking patients are comparable to studies on Western-language-speaking patients implanted with the same device, indicating that the Nucleus 22 Mini System enables profoundly and totally deaf patients to distinguish between the four separate tones present in Mandarin Chinese.

Adult↗

PubMed1995

Simultaneous in vivo comparison of two-versus three-wavelength mixed venous (Svo2) oximetry catheters.

OBJECTIVE: Venous oximetry catheters provide useful realtime information about mixed venous hemoglobin saturation (Svo2). Currently available systems utilize either two or three wavelengths of light to obtain these measurements. Previous animal and clinical studies have attempted to compare the accuracy of these two devices under similar circumstances. However, the relative accuracy of the two-wavelength versus three-wavelength systems has never been assessed under identical conditions. For this purpose, we designed an animal model for simultaneous measurement of Svo2, over a wide range of physiologic and pathologic states. METHODS: Seven anesthetized swine underwent simultaneous placement of two- and three-wavelength catheters. Paired data points consisted of values obtained from a reference oximeter and from each of the catheters. Observations were obtained every 15 min during the following manipulations: (1) eucarbic hypoxia induced by reducing FiO2 to 0.18, 0.15, and 0.12 for 15 min each; (2) stimulated surgical manipulation; and (3) hypovolemic shock produced by hemorrhage to a mean arterial pressure of 50 torr for 1 hr. Data were analyzed by calculation of mean error (bias) and precision for each system in comparison with the oximeter. RESULTS: The overall error of the two-wavelength system was +0.15%, with a precision of +/- 2.52%. The three-wavelength system had an overall error of +3.71%, with a precision of +/- 2.30%. Overall correlation between catheter Svo2 and oximeter values was the same for both devices (r = 0.99). CONCLUSIONS: Both currently available in vivo spectrophotometric systems are capable of producing satisfactory results over wide ranges of Svo2. In contradistinction to older reports, we found that the two-wavelength Svo2 system produced results equivalent to those obtained from the three-wavelength device. In this regard, there is no detectable advantage in accuracy to measuring in vivo Svo2 with three rather than with two wavelengths.

Animals↗

PubMed1995

Correlative study on the expression of p53 and DNA ploidy in acute nonlymphocytic leukemia.

We used the flow cytometric immunoassay to study the correlation between the rumor-suppressor gene product p53- and the DNA ploidy in 30 de novo cases of acute nonlymphocytic leukemia (ANLL). The results showed that 15 cases were positive expression for p53. As compared with p53 negative (p53) cases, the patients with positive p53 (p53+) had higher percentage of bone marrow blasts and lower peripheral leukocyte and platelet counts, which had no influence on the complete remission rate. Before treatment, DNA diploidy was seen in 18 cases including 12 p53- cases, and DNA aneuploidy in 12 cases including 9 p53+. After therapy, aneuploidy could be transformed into diploidy. Patients with P53+ or having aneuploidy in complete remission were at risk for early relapse. We believe that p53 may be involved in the process of leukemogenesis and progression of ANLL.

Aneuploidy↗

PubMed1995

The occurrence of silicon-containing particles in calcified lesions of DBA/2NCrj mice.

The crystalline structure in calcified deposits of DBA/2 mice was analysed, because understanding this is essential in assessing the significance of this species as an animal model for spontaneous soft-tissue mineralization. In order to remove the thin soft tissue which covers the lesion, the samples were bombarded with an argon beam. The uncoated samples were analysed with an electron-probe microanalyser. The deposits were composed of a calcium phosphate material. At a higher magnification, smaller particles surrounding these large deposits were found. There were three types of particles: rod-shaped (calcium phosphate), polygonal (silicate) and round (about 1 microns dia).

Animals↗

PubMed1995

Role of the liver-enriched transcription factor HNF-1 alpha in expression of the CYP2E1 gene.

The role of the trans-acting factor HNF-1 alpha in activating CYP2E1 gene expression was confirmed by transient co-transfection of an HNF-1 alpha expression plasmid and the CYP2E1 promoter fused to the chloramphenicol acetyl transferase (CAT) reporter gene. Only HNF-1 alpha, and not HNF-1 beta, HNF-4, C/EBP alpha, C/EBP beta, or DBP, was able to activate the CYP2E1 promoter. The extent of activation was proportional to the number of copies of the HNF-1 binding sequence upstream of the promoter. Removal or mutation of the HNF-1 binding sequence led to inactivation of the promoter in response to HNF-1 alpha. Gel-shift Western blot analysis using a synthetic HNF-1 binding sequence derived from CYP2E1 and rat liver nuclear extract revealed that the protein-DNA complex obtained with adult rat liver nuclear extract consisted of both HNF-1 alpha and HNF-1 beta proteins. The shifted bands produced by nuclear extracts from adult, where the endogenous CYP2E1 gene is active, and fetal rat liver, where the gene is inactive, were found to migrate differently, suggesting that the population of factors, possibly including different ratios of HNF-1 alpha and HNF-1 beta proteins, may change during development. However, the co-transfection study did not show cooperativity between the two factors. Elements upstream of the HNF-1 binding site were found to affect the activity of the promoter negatively in the transfection assay. DNase I hypersensitive site mapping revealed a hypersensitive site in this inhibiting element in the adult rat liver sample but not in liver from newborn animals.

Aging↗

PubMed1995

Studies on the agronomic characteristics, yield, and saikosaponin content of two Bupleurum species in Taiwan.

Two Bupleurum species (Bupleurums spp.), i.e., B. falcatum L. cv. Tainung No. 1 and B. kaoi Liu, Chao, et Chuang, were compared for their differences in seed germination, plant characteristics and root yield, and saikosaponin content. Experimental data showed that the most suitable temperature for seed germination of the two species was 16 degrees C. Two treatments, cold stratification at 4 degrees C for 8 weeks and presoaking by running water for 2 days, resulted in higher germination rates. Tainung No. 1 possessed a higher 1,000-seed weight than B. kaoi. However, field survival rate was higher for B. kaoi than for Tainung No.1. Results from field experiments also revealed that stem diameter, leaf width and fresh weight of various plant parts except the root were superior for Tainung No. 1 to B. kaoi. On the contrary, tiller number and root diameter and weight of B. kaoi were higher than those of Tainung No. 1. Harvest data and elevation had significant effects on the agronomic performance of the two Bupleurum spp. Measurements of most traits of the 6 month-old plants were superior to those of the 3 and 10 month-old plants. Cultivation at higher elevation (850 m) favored the development of leaf weight and root length, while cultivation at lower elevation (85 m) facilitated the development of plant height, root diameter, and root weight. Analysis of saikosaponin concentration in the root tissue revealed that average contents of 3.19 and 3.80 mg/g, respectively, for plants grown at the elevations of 850 m and 85 m. Comparison between the two species showed no significant difference in saikosaponin content, ranging from 3.45 to 3.55 mg/g.

Bupleurum↗

PubMed1995

Tone perception of Mandarin-speaking postlingually deaf implantees using the Nucleus 22-Channel Cochlear Mini System.

Because Mandarin Chinese is a tonal language, testing the patient's ability to distinguish among four tones is of paramount importance. This paper evaluates the efficacy of the Nucleus 22-Channel Mini System for Mandarin Chinese by comparing the postoperative tone perception test results with the results of the closed-set monosyllable, trochee, and spondee (MTS) test, and the open-set phonetically balanced (PB) word and sentence comprehension tests, which also incorporate tonal features, for eight Mandarin-speaking postlingually deaf patients implanted with this device. Except for one patient, the data clearly indicate that patients who had increased scores on tone perception after implantation also had improvements on other test batteries. Results also substantiate our previous observation that the Nucleus 22-channel cochlear implant enables profoundly and totally deaf patients to distinguish four separate tones in Mandarin Chinese. This would seem to support our earlier speculation that the acoustic cues of fundamental frequency of the four Mandarin tones are extracted by the Multipeak coding strategy of the 22-channel device and transferred to the cochlea, where they are perceived as rate pitch.

Adult↗

PubMed1994

Effects of repeated cocaine injections on cochlear function.

The effects of repeated cocaine administration on cochlear function were evaluated by measuring amplitude-intensity and latency-intensity functions of the whole-nerve action potential of the auditory nerve. Whole-nerve action potential input/output functions obtained using tone-pips of 0.5, 1, 2, 4 and 8 kHz in a group of cocaine-treated subjects were compared with those obtained in saline-treated animals. All measurements were made 24 h after the last treatment. Amplitudes of whole-nerve action potentials were enhanced in the cocaine-treated animals compared to the control group. No statistically significant differences in latency-intensity functions were seen after cocaine treatment. The effect of chronic cocaine exposure also was examined on catecholamine innervation in the cochlea using immunohistochemical techniques. The density of adrenergic innervation was reduced in the cocaine-treated animals.

Acoustic Stimulation↗

PubMed1994

Antiplatelet activity of tetramethylpyrazine.

Tetramethylpyrazine (TMPZ) is an active ingredient of a Chinese herbal medicine. We have previously shown that TMPZ possesses antithrombotic activity in rat thrombotic models. Inhibition of platelet aggregation and promotion of disaggregation contributed to the antithrombotic activity of TMPZ. In this study, we evaluated the antiplatelet actions of TMPZ using human platelets and found that antiplatelet activity of TMPZ included the inhibition of intracellular Ca++ mobilization (mainly the release from internal stores), the enhancement of intracellular cAMP by inhibition of phosphodiesterase activity, and the reduction of GP IIb/IIIa exposure on the surface of activated platelets.

Calcium↗

PubMed1994

Effects of selenium and alpha-tocopherol on liver damage induced by feeding grains from an endemic area of Keshan disease in rats.

Previous studies have shown the pathogenic effects of grains cultivated in the endemic areas of Keshan disease and selenium is effective in the prevention of this disease. In this study, liver damages induced by feeding grains from an endemic area (endemic diet), and the effects of selenium and alpha-tocopherol supplement were examined. After 3 months on the endemic diet, the amounts of serum enzymes were significantly increased when compared to controls (animals receiving diet from a non-endemic area). Liver enzymes (alkaline phosphatase and choline esterase) were also found to be altered in the serum, further suggesting liver damages in animals on an endemic diet. Supplement of the endemic diet with selenium or alpha-tocopherol reversed the changes in serum enzymes. Increase in lipid peroxidation in the liver of animals on the endemic diet was observed when compared to that in control animals. Selenium and alpha-tocopherol supplements prevented the increase in lipid peroxidation in the liver by the endemic diet. Semi-quantitative histochemical analysis of glutamate dehydrogenase and succinate dehydrogenase in liver tissue showed that the livers of animals on an endemic diet were more sensitive to ischemic damages in vitro. Supplementation of the endemic diet with either selenium or alpha-tocopherol reduced the sensitivity to ischemic damages. The results suggest that increased lipid peroxidation in the liver of rats on an endemic diet may be responsible for liver damages and elevation of serum enzymes.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1994

Treatment of locally recurrent soft tissue sarcomas of the retroperitoneum: report of 30 cases.

To assess the results in treating locally recurrent soft tissue sarcomas of the retroperitoneum, we reviewed the clinical, therapeutic, and pathologic characteristics of 30 patients who underwent surgical exploration. Complete resection was achieved in 18 patients (60%), 6 with en bloc resection of adjacent organs involved by the tumors. Following the first operation for recurrent lesions, the median survival was 33 months for those undergoing complete resection and 14 months for those undergoing partial resection or biopsy (P = 0.04). Patients with a disease-free interval (DFI) of > 24 months were associated with better prognosis than those with DFI of < or = 24 months (median survival: 40 months vs. 17 months, P = 0.03). Patients with tumor size of < or = 20 cm had longer survival than those with tumor size of > 20 cm (median survival: 39 months vs. 23 months, P = 0.04). Among 14 patients who received adjuvant radiation therapy, four patients whose tumors had been considered unresectable at first exploration for recurrence underwent complete resection after preoperative radiation therapy. An aggressive surgery aimed at complete resection in treating recurrent retroperitoneal sarcomas is strongly recommended. We suggest that in large tumors preoperative radiation therapy should be used to reduce the tumor volume and therefore a higher rate of complete resection may be achieved.

Adult↗

PubMed1994

Total pelvic exenteration for locally advanced rectal carcinoma.

Total pelvic exenteration was performed in 31 patients (30 males and 1 female) who had rectal cancers involving adjoining pelvic structures. Twenty-nine patients had primary tumors and two had recurrent diseases after previous abdominoperineal resection. Preoperative irradiation was used in nine patients with fixed tumors. When performing the surgical procedure, we also actively employed lateral node dissection to make the operation more radical. Three patients (one with primary tumor and two with recurrent) underwent the exenteration with partial sacrectomy because of the sacral involvement and they all died of local failure within 15 months. The overall 5-year survival rate was 52 percent for all patients and 56 percent for those who had primary tumors. The results suggest that total pelvic exenteration with lateral node dissection should be performed for locally advanced rectal cancer if the tumor is not completely fixed to the pelvic wall and preoperative irradiation should be used to convert a fixed tumor to a resectable one.

Adult↗

PubMed1994

Antiplatelet structure-activity relationship of tetramethylpyrazine.

Tetramethylpyrazine (TMPZ) is an active component of certain plants previously found to have inhibitory effects on platelet function using both in vivo and in vitro assays(1). In this study, we examined the antiplatelet activity of structural analogues of TMPZ in order to assess structural requirements for activity. Functional requirements included nitrogen substitutions on the aromatic ring; substitutions could be either heterocyclic or ring substituted in the meta position. Enhanced antiplatelet activity was associated with increasing the number of alkyl groups on the pyrazine ring as well as increasing the length of unbranched alkyl side chains. Increased inhibition of platelet aggregation correlated with increased lipophilicity of the compounds tested. In addition, several compounds were identified which deserve further pharmacological investigation.

Aminopyridines↗

PubMed1994

Antitumor agents--CLI. Bis(helenalinyl)glutarate and bis(isoalantodiol-B)glutarate, potent inhibitors of human DNA topoisomerase II.

Evaluation of a number of cytotoxic antitumor sesquiterpene lactones and their derivatives has led to the discovery of bis(helenalinyl)glutarate (4) and bis(isoalantodiol-B)glutarate (10) as potent inhibitors of human-derived topoisomerase II. Unlike etoposide, which inhibits by preventing the DNA rejoining process, compounds 4 and 10 inhibit topoisomerase II without causing DNA breakage. The structure-activity relationships of 4, 10, and related compounds are discussed.

Cell Line↗

PubMed1994

Synthesis of novel water-soluble 7-(aminoacylhydrazono)-formyl camptothecins with potent inhibition of DNA topoisomerase I.

Eighteen new water-soluble 7-(aminoacylhydrazono)-formyl camptothecins were synthesized and evaluated for their ability to cause protein-linked DNA breaks and to inhibit topoisomerase I activity. Compared with camptothecin, five of the compounds were as potent or more potent in these tw assays but were less toxic in several cancer cell lines. The results suggest that the 7 position in the B ring is a suitable location for introducing a polar moiety into camptothecin producing analogues with enhanced topoisomerase I inhibiting activity.

Antineoplastic Agents↗

PubMed1994

Alteration of lysophosphatidylcholine content in low density lipoprotein after oxidative modification: relationship to endothelium dependent relaxation.

OBJECTIVE: The aim was to examine the formation of lipid peroxidation products and the alteration in phospholipid content in low density lipoprotein (LDL) after oxidative modification by CuSO4, and subsequently, to determine the ability of the modified LDL to impair endothelium dependent relaxation in rat aortic rings. METHODS: Blood samples were obtained from normal human volunteers. LDL was prepared by sequential ultracentrifugation and it was oxidatively modified in the presence of 5 microM CuSO4. Lipid peroxidation products (thiobarbituric acid reactive substances, TBARS), and alterations in electrophoretic mobility and phospholipid content were determined in normal (native) and oxidised LDL. Endothelium dependent relaxation was produced by acetylcholine (10(-8)-10(-5) M) in phenylephrine precontracted rat aortic rings. RESULTS: LDL incubated for 24 h with 5 microM CuSO4 at 20 degrees C and 37 degrees C with constant agitation displayed higher amounts of TBARS than the respective native LDL. While the amounts of TBARS in LDL modified at 20 degrees C and 37 degrees C were similar, the former condition resulted in statistically smaller changes of phospholipid contents. LDL with higher lysophosphatidylcholine content showed greater impairment of endothelium dependent relaxation in rat aortic rings than LDL with lower lysophosphatidylcholine content. CONCLUSIONS: The raised lysophosphatidylcholine level in oxidatively modified LDL was related to the ability of the LDL to impair endothelium dependent relaxation. However, lipid peroxidation products assessed by TBARS did not relate to the phospholipid changes in LDL and therefore cannot be used to predict the vascular effects of LDL after oxidative modification.

Acetylcholine↗

PubMed1994

Enhancement of endothelium dependent relaxation in the rat aortic ring by selenium supplement.

OBJECTIVE: The aim was to examine the effect of selenium supplement on endothelium dependent relaxation in rat aortic rings. METHODS: Rats were supplemented with selenium for 3 d (intraperitoneal injection of 4.33 mumol sodium selenite-kg1 body weight.d-1). Saline injections served as controls. Rat aortic ring was precontracted with phenylephrine and endothelium dependent relaxation was produced by the addition of acetylcholine. RESULTS: Acetylcholine-induced endothelium dependent relaxation was enhanced in aortic rings from rats after receiving selenium supplement as compared to control rats. For comparison, endothelium independent vasodilators (sodium nitroprusside and cromakalim) were investigated. Selenium supplement did not affect the relaxation produced by these vasodilators. N-nitro-L-arginine methyl ester (L-NAME) abolished acetylcholine induced relaxation in aortic rings from animals with selenium supplement while indomethacin had no effect on the relaxation. Direct addition of selenium or glutathione peroxidase and glutathione into the organ bath had no effect on acetylcholine induced endothelium dependent relaxation. CONCLUSIONS: The enhanced relaxation after selenium supplement was due to an increase in the release of nitric oxide since L-NAME was effective in blocking the relaxation. The lack of an effect by indomethacin indicated little role for cyclooxygenase products in this system. Our results suggest that the effect of selenium supplement on endothelium dependent relaxation is mediated by cellular changes that cannot be mimicked by the direct addition of selenium or the selenium dependent enzyme glutathione peroxidase.

Acetylcholine↗

PubMed1994

A novel cis-acting element controlling the rat CYP2D5 gene and requiring cooperativity between C/EBP beta and an Sp1 factor.

The rat CYP2D5 gene encodes a cytochrome P450 and is expressed in liver cells. Its expression commences a few days after birth, and maximal mRNA levels are achieved when animals reach puberty. Transfection and DNA binding studies were performed to investigate the mechanism controlling developmentally programmed, liver-specific expression of CYP2D5. Transfection studies using a series of CYP2D5 upstream DNA chloramphenicol acetyltransferase gene fusion constructs identified a segment of DNA between nucleotides -55 and -156 that conferred transcriptional activity in HepG2 cells. Activity was markedly increased by cotransfection with a vector expressing C/EBP beta but was unaffected by vectors producing other liver-enriched transcription factors (C/EBP alpha, HNF-1 alpha, and DBP). DNase I footprinting revealed a region protected by both HepG2 and liver cell nuclear extracts between nucleotides -83 and -112. This region displayed some sequence similarity to the Sp1 consensus sequence and was able to bind the Sp1 protein, as assessed by a gel mobility shift assay. The role of Sp1 in CYP2D5 transcription was confirmed by trans activation of the 2D5-CAT construct in Drosophila melanogaster cells by using an Sp1 expression vector. C/EBP beta alone was unable to directly bind the -83 to -112 region of the promoter but was able to produce a ternary complex when combined with HepG2 nuclear extracts or recombinant human Sp1. C/EBP alpha was unable to substitute for C/EBP beta in forming this ternary complex. A poor C/EBP binding site is present adjacent to the Sp1 site, and mutagenesis of this site abolished formation of the ternary complex with the CYP2D5 regulatory region. These result establish that two transcription factors can work in conjunction, possibly by protein-protein interaction, to activate the CYP2D5 gene.

Aging↗