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Biomedical subjects

Y Liu

Publications and source records attributed to Y Liu.

At least 469 records · Page 26Linked to original sources
PubMed2001

Asbestos fiber burdens in lung tissues of Hong Kong Chinese with and without lung cancer.

To investigate the asbestos exposure level in non-occupational population and its relation to lung cancer, pulmonary asbestos fiber counts were observed with a modified alkali digestion method, in lung tissues from 65 random surgically treated lung cancer patients (42 males and 23 females) and that obtained from 107 random autopsy cases who died of either accidental death or acute myocardial infarction (44 males and 63 females) during 1987-1988. The patients and cases were all Hong Kong Chinese with no definite history of occupational exposure to asbestos. The non-lung cancer cases (NLCC) were divided into three groups based on different age ranges: 10 approximately, 40 approximately and 70 approximately years. The results showed that the medians of uncoated fiber counts (0, 32 and 52 fibers per mg dry tissue [f/mgDT] in the different age groups, respectively) increased in an age-dependent manner (P<0.01). However, the medians of coated fiber (asbestos body) counts were all 0 f/mgDT, with no statistically significant difference among the groups, showing a very low level of asbestos body burden in NLCC. In each age group, no difference in those counts between males and females was observed (P>0.05). Moreover, those counts in male lung cancer cases (medians of 62.5 and 17.5 f/mgDT, respectively) were greater than that in the control (32.5 and 0 f/mgDT, respectively) (P<0.01, P<0.05, respectively), however, regarding the female groups there was no statistically significant difference from the control. The results suggest that there is an environmental exposure to asbestos in Hong Kong Chinese, the level of which is, however, generally not sufficient to induce asbestos body. Environmental asbestos exposure in Hong Kong males may be one of the carcinogenic factors leading to lung cancer.

Accidents↗
PubMed2001

The stability of cytokeratin 18 in human liver cells during colchicine-induced microtubule disruption.

The cytoskeleton plays important roles in cell function and is therefore implicated in the pathogenesis of many human liver diseases, including malignant tumors. The stability of cytokeratin proteins during tumor transformation in human hepatocellular carcinoma has been studied with a molecular approach previously. The results demonstrate that the cytokeratin is modulated in human hepatocellular carcinoma. Besides this, three low molecular weight cytokeratin molecules (named HCC CK) are found. This indicates that these HCC CKs have undergone modulation from the human hepatocyte cytokeratin 18. We also checked the cytokeratin profile of the human hepatoma cell line PLC/PRF/5 with the same methods to ensure the HCC CK molecules are produced by modulation but not protein degradation. The stability of cytokeratin molecules was studied by a different approach. The cytokeratin compositions of human liver cells (Chang cell line) were analysed under the effects of microtubule-disrupting drug (colchicine) by SDS-PAGE, Western blot, immunoprecipitation using a commercially available monoclonal anti-cytokeratin 18 antibody and immunofluorescent staining. Within 1 h of treatment, the microtubule began to collapse and the filamentous structure was shortening. The microtubule had almost collapsed and became fragmented to form a lattice-like network after 24 h of treatment. The cytokeratin was modulated after long-term (24 h) treatment of colchicine, and the molecular weight became 14 kD and the antigenicity was lost. The stability of cytokeratin molecules was related to the intact microtubule network, after disruption of the microtubule the cytokeratin would be modulated. The intact microtubule network was a stabilizing factor of cytokeratin 18 in human liver cells.

Blotting, Western↗
PubMed2001

Effect of polymer molecular weight and addition of calcium stearate on response of MG63 osteoblast-like cells to UHMWPE particles.

Periprosthetic osteolysis and implant loosening is associated with the presence of ultrahigh molecular weight polyethylene (UHMWPE) wear debris particles. Osteoblast phenotypic expression in vitro is affected by UHMWPE particles, suggesting that bone formation may also be affected by wear debris. Here we tested the hypothesis that the response of osteoblasts to UHMWPE can be modified by changes in UHMWPE particle chemistry. We used four different commercially available preparations of GUR UHMWPE particles to determine if chemical composition (+/- Ca-stearate) or polymer molecular weight (3.1-4.2 million or 5.4-6.5 million g/mol) modulates osteoblast response. Particles were characterized by size distribution, morphology, and number of particles added to the culture medium. They had an average equivalent circle diameter ranging from 0.46-1.26 microm. MG63 cell response was assessed by measuring cell number, cellular and cell layer alkaline phosphatase, and prostaglandin E2 (PGE2) production. There were dose-dependent effects of the particles on cell response. Cell number and PGE, production were increased, while alkaline phosphatase specific activity was decreased. In addition, there was a marked difference between cultures treated with particles containing Ca-stearate and as a function of polymer molecular weight. Particles of higher molecular weight caused a greater stimulation of proliferation and inhibition of alkaline phosphatase than particles of lower molecular weight. The presence of Castearate exerted a more pronounced depression of osteoblast phenotype as well as a significantly greater increase in PGE2 release by the cells. The present study shows that chemical composition and polymer molecular weight of UHMWPE are capable of modulating osteoblast response to particles. The results suggest that osteoblast differentiation is inhibited by UHMWPE particles, whereas cell proliferation and PGE2 production are stimulated. This may have direct effects on osteoblasts and bone formation, but also paracrine effects on cells of the monocytic lineage inducing bone resorption and promoting inflammation which may lead to aseptic loosening. The present results suggest that the cellular events in aseptic loosening may be modulated or even accelerated by changes in the composition of the UHMWPE used to fabricate implants.

Alkaline Phosphatase↗
PubMed2001

Expression of the Xvax2 gene demarcates presumptive ventral telencephalon and specific visual structures in Xenopus laevis.

vax2 is a recently isolated homeobox gene, that plays an important role in controlling the dorso-ventral patterning of the retina. In this paper we present a thorough description of the Xvax2 expression pattern all along Xenopus embryogenesis, and compare this pattern in detail to that shown by Xvax1b and Xpax2, two genes also involved in ventral eye development. At early neurula stages, while Xpax2 starts to be expressed within the eye field, both Xvax2 and Xvax1b are exclusively activated in the presumptive ventral telencephalon. Since midneurula stages, Xvax2 and Xvax1b are also transcribed in the medial aspect of the eye field. At tailbud and tadpole stages, Xvax2, Xvax1b and Xpax2 expression overlaps in the optic stalk and nerve and in the optic disk, while Xvax2 and Xvax1b also display specific activation domains in the ventral retina as well as in the ventral telencephalon and diencephalon. Finally, during metamorphosis a high level of both Xvax2 and Xvax1b transcription is maintained in the optic chiasm. In addition, Xvax1b is transcribed in the ventral hypothalamus and in the hypophysis, whereas a strong Xvax2 expression is retained in the ventral portion of the mature retina.

Animals↗
PubMed2001

Paper alert. Immunology.

A selection of interesting papers that were published in the two months before our press date in major journals most likely to report significant results in immunology.

Allergy and Immunology↗
PubMed2001

Dissecting glycoprotein quality control in the secretory pathway.

In the early secretory pathway, asparagine-linked glycosylation facilitates the conformational maturation of diverse polypeptides by promoting their physical engagement with the glycoprotein-folding machinery. Misfolded glycoproteins are selectively eliminated from the endoplasmic reticulum by a stringent process of conformation-based quality control. Recent studies indicate that a small ensemble of oligosaccharide-processing enzymes and lectins use the asparagine-linked appendage to orchestrate the selective disposal of numerous transport-defective glycoproteins from the early secretory pathway. The glycan-based disposal system functions as an evolutionarily conserved terminal checkpoint in eukaryote genome expression. That the mechanisms by which glycoprotein substrates are recruited for degradation diverge at the level of signal recognition reflects a previously unappreciated component of cellular differentiation in higher eukaryotes.

Animals↗
PubMed2001

A case-control study of maternal alcohol consumption and intrauterine growth retardation.

PURPOSE: Heavy maternal drinking during pregnancy causes fetal alcohol syndrome, but whether more moderate alcohol consumption is associated with such adverse pregnancy outcomes as intrauterine growth retardation (IUGR) remains controversial. METHODS: Using data from a case-control study, we examined the association between maternal alcohol consumption and risk for IUGR among 701 case and 336 control infants born during 1993-1995 in Monroe County, New York. RESULTS: Our results provide no evidence of an independent association between moderate maternal alcohol consumption (<14 drinks per week) and risk for IUGR. The risk for IUGR among heavy drinkers (> or =14 drinks per week) around the time of conception was OR = 1.4 (95% CI 0.7-2.6) for IUGR < or = 5th percentile and OR = 1.4 (95% CI 0.7-2.8) for IUGR 5th-10th percentile. For heavy drinkers during the first trimester, the OR was 1.3 (95% CI 0.4-4.5) for IUGR < or = 5th percentile and OR = 1.3 (95% CI 0.4-4.8) for IUGR 5th-10th percentile. CONCLUSIONS: Since IUGR is a heterogeneous outcome with a possible multifactorial origin, further studies are needed to examine the combined effects of alcohol and other environmental and genetic factors on IUGR risk for subgroups of IUGR.

Adult↗
PubMed2001

Optimization of shaded surface display for CT angiography.

RATIONALE AND OBJECTIVES: The authors performed this study to determine the optimum threshold for performing computed tomographic (CT) angiography with shaded surface display (SSD). MATERIALS AND METHODS: A dedicated phantom was developed with an 8-mm luminal diameter. Each of 19 vessels had stenoses ranging from 0% to 93.8%. Five blinded, experienced reviewers separately measured each vessel by using SSD with display thresholds of 50, 100, 150, and 200 HU. RESULTS: For vessel diameters of 2 mm and larger, the best threshold value was 100 HU. This yielded measurements within 2% of the actual diameter and produced no false occlusions. For vessels 1 mm in diameter, the best threshold remained 100 HU, but this threshold was significantly less accurate than the standard (P = .0001) and produced two false occlusions in 15 vessels. For vessels 0.5 mm in diameter, the best threshold was 50 HU, although this still produced measurements significantly less accurate than the gold standard (P = .036) and one false occlusion in 15 vessels. CONCLUSION: CT angiography with SSD and an optimized threshold value is a useful technique in vessels 1 mm and larger.

Angiography↗
PubMed2001

A novel method for the preparation of III-V semiconductors: sonochemical synthesis of InP nanocrystals.

A novel method for the preparation of III-V semiconductor has been provided in this paper. At room temperature, InP nanocrystals with diameter of approximately 9 nm were successfully obtained under high-intensity ultrasonic irradiation for 4 h from the reaction of InCl(3).4H2O, yellow phosphorus and KBH4 in the mixed solvents of ethanol and benzene. Changing some parameters can effectively control the size of the products and possible explanations were offered. The products were characterized by X-ray powder diffraction, transmission electron microscope and electron diffraction pattern. The ultrasonic irradiation and the solvents are both important in the formation of the product.

Journal Article↗
PubMed2001

Pulsatile flow simulation in arterial vascular segments with intravascular ultrasound images.

Previous studies have indicated a correlation between local variation in wall shear stress in arterial blood flow and atheroma development. The purpose of this study was to analyze the hemodynamics in vascular segments from morphologically realistic three-dimensional (3D) reconstruction, and to compare the computed wall shear stress in a compliant vascular segment model and the corresponding rigid walled model. Cross-sectional images of the segments of femoral and carotid arteries in five Yucatan miniswine were obtained using intravascular ultrasound (IVUS) imaging and the segment geometry was reconstructed at different times in the cardiac cycle. The actual measured wall motion from the reconstruction was employed to specify the moving boundaries for simulation of physiological distensibility. Velocity profiles and wall shear stress were computed using unsteady computational fluid dynamics analysis. The computed results revealed that the maximum wall shear stress in the compliant model was approximately 4-17 percent less than that in the rigid model if the wall motion is larger than 10 percent. Our analysis demonstrates that inaccuracies due to inflow velocity profile can be minimized by the extension of the model upstream. The phase angle between the diameter change and wall shear is affected by the local changes in geometry of the arteries. These simulations can be potentially used to analyze the effect of regional wall motion changes in the presence of atherosclerotic lesions on the local fluid dynamics and to correlate the same with subsequent growth of the lesions.

Animals↗
PubMed2001

On-line monitoring and controlling system for fermentation processes.

A personal computer-based on-line monitoring and controlling system was developed for the fermentation of microorganism. The on-line HPLC system for the analysis of glucose and ethanol in the fermentation broth was connected to the fermenter via an auto-sampling equipment, which could perform the pipetting, filtration and dilution of the sample and final injection onto the HPLC through automation based on a programmed procedure. The A/D and D/A interfaces were equipped in order to process the signals from electrodes and from the detector of HPLC, and to direct the feed pumps, the motor of stirrer and gas flow-rate controller. The software that supervised the control of the stirring speed, gas flow-rate, pH value, feed flow-rate of medium, and the on-line measurement of glucose and ethanol concentration was programmed by using Microsoft Visual Basic under Microsoft Windows. The signal for chromatographic peaks from on-line HPLC was well captured and processed using an RC filter and a smoothing algorithm. This monitoring and control system was demonstrated to be effective in the ethanol fermentation of Zymomonas mobilis operated in both batch and fed-batch modes. In addition to substrate and product concentrations determined by on-line HPLC, the biomass concentration in Z. mobilis fermentation could also be on-line estimated by using the pH control and an implemented software sensor. The substrate concentration profile in the fed-back fermentation followed well the set point profile due to the fed-back action of feed flow-rate control.

Journal Article↗
PubMed2001

The surface enhanced Raman scattering effects of composite nanocrystals of Ag-TiO2.

The composite particles of Ag-TiO2 both in a nanocrystal form was prepared by photoreduction of AgNO3 in the rutile colloidal solution. The surface plasmon absorption (SPA) band of the silver clusters supported on the TiO2 nanocrystal was red shift, and a strong surface enhanced Raman scattering (SERS) effect for the composite particles of Ag-nanocrystalline TiO2 was observed. The SERS effect is relating to the red shift phenomenon of SPA band, which could be explained by induced-resonance effect.

Colloids↗
PubMed2001

Diurnal variations in alpha power density and subjective sleepiness while performing repeated vigilance tasks.

OBJECTIVE: Diurnal variations in EEG activity and subjectively rated sleepiness while performing repeated vigilance tasks were examined. METHODS: Nine diurnally active healthy males underwent repeated vigilance tasks at 08:00, 11:00, 14:00, 17:00 and 20:00 h. An electroencephalogram (EEG) was taken while the subjects performed the tasks with their eyes open. The alpha power spectra (8.6-13.3 Hz) of EEG was integrated. Subjectively rated sleepiness, reaction time and oral temperature were also measured. RESULTS: Significant diurnal variations were found for alpha power, subjectively rated sleepiness and oral temperature. The alpha power was significantly smaller at 08:00 than at 11:00, 14:00, 17:00 and 20:00 h. The subjectively rated sleepiness was significantly larger at 08:00 than at 11:00, 17:00 and 20:00 h. The diurnal variation in alpha power did not correspond to that in subjectively rated sleepiness. On the other hand, repeated vigilance tasks increased the alpha power, subjectively rated sleepiness and reaction time at each time of day. The increase in alpha power was significantly greater at 14:00 than at 08:00 and 20:00 h. CONCLUSIONS: The diurnal variation was found in alpha power while performing vigilance tasks. Furthermore, the increase in alpha power with repetition of the task depended on the time of day.

Adult↗
PubMed2001

The human genome: an immuno-centric view of evolutionary strategies.

A hallmark of modern biology is the realization of the fundamental unity of biological processes in all life forms. Consequently, the complete genome sequencing of various bacteria, yeast (Saccharomyces cerevisiae), fly (Drosophila melanogaster) and worm (Caenorhabditis elegans) over the past five years has already had an impact on all of biology. "Model organisms" have contributed a great deal to immunology; for example, the Toll receptors of the fly provided the impetus for the investigation of Toll-like receptors, which proved to be fundamental elements in the mammalian innate immune system. The recent release of a draft sequence of the human genome provides the first panoramic view of the 30000-35000 human genes in the human genetic blueprint and provides a plethora of new details, the significance of which will take some time to appreciate. The over-riding concepts that emerge from these studies relate primarily to general evolutionary processes that are equally as relevant to immunology as they are to other disciplines of biology.

Amino Acid Sequence↗
PubMed2001

Interplay between AAUAAA and the trans-splice site in processing of a Caenorhabditis elegans operon pre-mRNA.

About half of Caenorhabditis elegans genes have a 1-2 bp mismatch to the canonical AAUAAA hexamer that signals 3' end formation. One rare variant, AGUAAA, is found at the 3' end of the mai-1 gene, the first gene in an operon also containing gpd-2 and gpd-3. When we expressed this operon under heat shock control, 3' end formation dependent on the AGUAAA was very inefficient, but could be rescued by a single bp change to create a perfect AAUAAA. When AGUAAA was present, most 3' ends formed at a different site, 100 bp farther downstream, right at the gpd-2 trans-splice site. Surprisingly, 3' end formation at this site did not require any observable match to the AAUAAA consensus. It is possible that 3' end formation at this site occurs by a novel mechanism--trans-splicing-dependent cleavage--as deletion of the trans-splice site prevented 3' end formation here. Changing the AGUAAA to AAUAAA also influenced the trans-splicing process: with AGUAAA, most of the gpd-2 product was trans-spliced to SL1, rather than SL2, which is normally used at downstream operon trans-splice sites. However, with AAUAAA, SL2 trans-splicing of gpd-2 was increased. Our results imply that (1) the AAUAAA consensus controls 3' end formation frequency in C. elegans; (2) the AAUAAA is important in determining SL2 trans-splicing events more than 100 bp downstream; and (3) in some circumstances, 3' end formation may occur by a trans-splicing-dependent mechanism.

Animals↗
PubMed2001

Citrus pectin: characterization and inhibitory effect on fibroblast growth factor-receptor interaction.

This study was undertaken to characterize the pectin from four citrus species and to determine their in vitro inhibitory activities on the binding of fibroblast growth factor (FGF) to the FGF receptor (FGFR). Pectin from various parts of lemon, grapefruit, tangerine, and orange were isolated and characterized. Tangerine had the highest pectin content among the four citrus species. Segment membrane contained as much as or more pectin than flavedo/albedo. Anhydrogalacturonic content was highest in pectin from segment membrane of tangerine and flavedo/albedo of grapefruit. Lemon pectin contained the highest methoxyl content (MC), and grapefruit contained the largest proportion of lower molecular weight (<10000 Da) pectin. Tangerine contained the highest neutral sugar in both flavedo/albedo and segment membrane. The interdependency of heparin on factor-receptor interaction provides a means for identifying new antagonists of growth factor activity and thus for treatment of various diseases. These results showed that pectin significantly inhibited the binding of FGF-1 to FGFR1 in the presence of 0.1 microg/mL heparin. The pectin from the segment membrane of lemon was the most potent inhibitor. The inhibition activity was significantly correlated with sugar content, MC, and size of pectin. Kinetic studies revealed a competitive nature of pectin inhibition with the heparin, a crucial component of the FGF signal transduction process. The observation that the heparin-dependent biological activity of FGF signal transduction is antagonized by citrus pectin should be further investigated for the use of these pectins as anti-growth factor agents for potential health benefits.

Citrus↗
PubMed2001

New cytotoxic sesterterpenes from the sponge Sarcotragus species.

Five new (1-3, 5, and 7) and two known (4, 6) furanosesterterpene tetronic acids were isolated from the marine sponge Sarcotragus sp. by bioactivity-guided fractionation. These compounds showed cytotoxicity against a panel of five human tumor cell lines. The gross structures were established on the basis of NMR and MS analyses. The compounds showed interesting variations of geometry and absolute configuration.

Animals↗