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Y Liu

Publications and source records attributed to Y Liu.

At least 829 records · Page 46Linked to original sources
PubMed2000

Qualitative assessment of isocyanate skin exposure in auto body shops: a pilot study.

BACKGROUND: Little is known about the extent of human isocyanate skin exposure in auto body shops and the effectiveness of personal protective equipment. Animal studies have suggested that skin exposure to isocyanates may be an important risk factor for respiratory sensitization leading to asthma. This study provides initial data on hexamethylene diisocyanate skin exposure in three auto body shops. METHODS: Three auto body shops of different size which use different paint systems were examined for the presence of aliphatic isocyanates on environmental surfaces and workers' skin and for breakthrough of personal protective equipment. Qualitative detection of contamination by isocyanates was conducted using a wipe-sampling technique. Assessment focused on the painters and their tasks, although other auto body repairers were also evaluated. RESULTS: Environmental surfaces such as painters' workbenches, spray equipment, and cleaning tools were found contaminated with isocyanates. Painters had frequent contact with contaminated surfaces, often without wearing gloves. Moderate to heavy contamination of some skin surfaces was found with painters from two of the three auto body shops. Latex gloves used for skin protection showed significant penetrations by isocyanates even after a single painting session. CONCLUSIONS: Contaminated environmental surfaces and skin exposure to isocyanates were documented in several auto body shops. Latex gloves were not adequate protection for workers using isocyanate paints. Further research which would better quantify skin exposure, and its potential relationship to respiratory sensitization and asthma is warranted.

Asthma↗
PubMed2000

Acute respiratory symptoms in workers exposed to vanadium-rich fuel-oil ash.

BACKGROUND: Occupational exposure to fuel-oil ash, with its high vanadium content, may cause respiratory illness. It is unclear, however, what early acute health effects may occur on the pathway from normal to compromised respiratory function. METHODS: Using a repeated measures design, we studied prospectively 18 boilermakers overhauling an oil-fired boiler and 11 utility worker controls. Subjects completed a respiratory symptom diary five times per day by using a 0-3 scale where 0=symptom not present, 1=mild symptom, 2=moderate symptom, and 3=severe symptom. Daily symptom severity was calculated by using the highest reported score each day for upper and lower respiratory symptoms. Daily symptom frequency was calculated by summing all upper or lower airway symptom reports, then dividing by number of reporting times. Respiratory symptom frequency and severity were analyzed for dose-response relationships with estimated vanadium and PM(10) doses to the lung and upper airway by using robust regression. RESULTS: During the overhaul, 72% of boilermakers reported lower airway symptoms, and 67% reported upper airway symptoms. These percentages were 27 and 36 for controls. Boilermakers had more frequent and more severe upper and lower respiratory symptoms compared to utility workers, and this difference was greatest during interior boiler work. A statistically significant dose-response pattern for frequency and severity of both upper and lower respiratory symptoms was seen with vanadium and PM(10) in the three lower exposure quartiles. However, there was a reversal in the dose-response trend in the highest exposure quartile, reflecting a possible healthy worker effect. CONCLUSIONS: Boilermakers experience more frequent and more severe respiratory symptoms than utility workers. This is most statistically significant during boiler work and is associated with increasing dose estimates of lung and nasal vanadium and PM(10).

Adult↗
PubMed2000

In vivo fMRI demonstration of hypothalamic function following intraperitoneal glucose administration in a rat model.

The hypothalamic functional MRI (fMRI) response in an animal model was studied following energy intake. Six fasted (12 h) Sprague-Dawley (SD) rats were administered an intraperitoneal injection of glucose (0.72 grams/kg body weight), while a mid-sagittal slice through the hypothalamus was continuously imaged for 60 min using a conventional T2*-weighted gradient-echo sequence. All rats demonstrated a significant acute transient decrease in the fMRI signal intensity (mean: 3.4%) in the hypothalamic region within 12-16 min after intraperitoneal glucose injection. The SD rat may be a suitable model for future fMRI studies of the hypothalamus involving the administration of exogenous nutrients and medications.

Animals↗
PubMed2000

Comparison of the temporal response in perfusion and BOLD-based event-related functional MRI.

Event-related functional MRI (ER-fMRI) based on both blood oxygen level-dependent (BOLD) contrast and perfusion contrast has been recently developed to study human brain activation due to brief stimulation. In this report, both BOLD- and perfusion-based ER-fMRI were directly compared using repeated single-trial, short visual stimulation (1 sec) in six human volunteers. The results show that the cerebral blood flow change reached a maximum approximately 1 sec earlier than the BOLD signal change (4.2 +/- 0.2 sec vs. 5.1 +/- 0.2 sec after the stimulation, P < 0.05). The full width at half maximum of the hemodynamic response measured by perfusion was not significantly different from that measured with BOLD (5.1 +/- 0.6 sec vs. 5.9 +/- 0.6 sec). A positive linear correlation was found between the maximum perfusion and maximum BOLD signal changes (r = 0. 77, P = 0.07).

Cerebrovascular Circulation↗
PubMed2000

The single neurofilament subunit of the lamprey forms filaments and regulates axonal caliber and neuronal size in vivo.

Neurofilaments (NFs) are composed of a heteropolymer of three related subunits in mammalian neurons, where they are a major component of the cytoskeleton in large neurons and are thought to regulate axonal diameter. NFs in the lamprey, while ultrastructurally and functionally indistinguishable from mammalian NFs, are polymers of a single subunit protein, NF180. In this study, we use the simplicity of lamprey NFs and the accessibility of the lamprey central nervous system (CNS) to examine the effects of overproducing NFs in an identified giant neuron in vivo, and thus to elucidate the role of NFs in regulating neuronal size and axonal caliber in the vertebrate CNS. We show that overexpression of NF180 tagged with a variant of Green Fluorescent Protein (EYFP) in identified lamprey neurons (ABCs) and in human neuroblastoma (NB2a) cells results in the assembly of exogenous NF180 into ultrastructurally normal NFs that are tightly packed and unphosphorylated. These accumulate in the somata of NB2a cells and produce somatic swelling by 3 days post-transfection. NF180 overexpression in lamprey ABCs in vivo causes exogenous NFs to accumulate in ABC axons, somata, and dendrites, and induces a significant increase in axonal diameter without increasing axonal NF packing density. Overexpression of EYFP alone has none of these effects. We conclude that NF180 normally plays a critical role in determining axonal caliber in ABCs and may influence neuronal size in situations where NFs accumulate in the soma, such as after axonal injury.

Animals↗
PubMed2000

The human red nucleus and lateral cerebellum in supporting roles for sensory information processing.

A functional MRI study compared activation in the red nucleus to that in the lateral cerebellar dentate nucleus during passive and active tactile discrimination tasks. The study pursued recent neuroimaging results suggesting that the cerebellum may be more associated with sensory processing than with the control of movement for its own sake. Because the red nucleus interacts closely with the cerebellum, the possibility was examined that activity in red nucleus might also be driven by the requirement for tactile sensory processing with the fingers rather than by finger movement alone. The red and dentate nuclei were about 300% more active (a combination of activation areas and intensities) during passive (non-motor) tactile stimulation when discrimination was required than when it was not. Thus, the red nucleus was activated by purely sensory stimuli even in the absence of the opportunity to coordinate finger movements or to use the sensory cues to guide movement. The red and dentate nuclei were about 70% more active during active tactile tasks when discrimination was required than when it was not (i.e., for simple finger movements alone). Thus, the red nucleus was most active when the fingers were being used for tactile sensory discrimination. In both the passive and active tactile tasks, the observed activation had a contralateralized pattern, with stronger activation in the left red nucleus and right dentate nucleus. Significant covariation was observed between activity in the red nucleus and the contralateral dentate during the discrimination tasks and no significant correlation between the red nucleus and the contralateral dentate activity was detected during the two non-discrimination tasks. The observed interregional covariance and contralateralized activation patterns suggest strong functional connectivity during tactile discrimination tasks. Overall, the pattern of findings suggests that the activity in the red nucleus, as in the lateral cerebellum, is more driven by the requirements for sensory processing than by motor coordination per se.

Adult↗
PubMed2000

Chromatography of human prothrombin from Nitschmann fraction III on DEAE Sepharose Fast Flow using axial and radial flow column.

An axial column (3 x 2.6 cm) and a radial flow column (3.5 x 5 cm) packed with DEAE Sepharose Fast Flow media was evaluated for the separation of human prothrombin from Nitschmann fraction III. Under radial flow conditions, a sample flow rate up to 14 mL/min (approximately 18 bed vols/h) was achieved. Breakthrough capacity was determined and both columns had almost the same breakthrough capacity per mL media, indicating that the sample loading was independent of radial column geometry.

Chromatography, Ion Exchange↗
PubMed2000

Crocidolite induces cell transformation and p53 gene mutation in BALB/c-3T3 cells.

Cell transformation is one of the most common assays used to study morphological changes in the multistep process of carcinogenesis. The present study was initiated to investigate the ability of crocidolite to induce cell transformation in BALB/c-3T3 cells and to analyze the relationship between p53 mutations and crocidolite-induced cell transformation, if any. Cell transformation was carried out according to standard procedures. Exponentially growing cells were exposed to different concentrations (0.2-20 microg/cm(2)) of crocidolite fibers for 72 h. Foci obtained from cell transformation were analyzed for their ability to grow in soft agar (anchorage-independence) and p53 alterations. The results of this study demonstrate that there was an increase in transformation frequency (TF) with an increase in concentration of crocidolite. Also, focal cells were able to grow on soft agar, indicating anchorage-independence. cDNA was prepared from RNA isolated from Type 3 foci and subjected to mutational analysis. Eleven exons of the p53 gene from eight transformed cell lines were analyzed for alterations using polymerase chain reaction single-strand conformation polymorphism (PCR-SSCP). Alterations were found in seven of eight cell lines, two of them were in exons 4-6, and five in exons 9-11. The alterations were randomly scattered among the crocidolite dose groups. These results suggest that crocidolite induces mutations predominantly in exons 9-11 of the p53 gene in a nondose-dependent manner.

3T3 Cells↗
PubMed2000

Anti-tumor and anti-carcinogenic activities of triterpenoid, beta-boswellic acid.

Boswellin (BE), a methanol extract of the gum resin exudate of Boswellia serrata, contains naturally occurring triterpenoids, beta-boswellic acid and its structural related derivatives, has been used as a traditional medicine for the treatment of inflammatory and arthritic diseases. Topical application of BE to the backs of mice markedly inhibited 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced increases in skin inflammation, epidermal proliferation, the number of epidermal cell layers, and tumor promotion in 7,12-dimethylbenz[a]anthracene (DMBA)-initiated mice. Feeding 0.2% of BE in the diet to CF-1 mice for 10-24 weeks reduced the accumulation of parametrial fat pad weight under the abdomen, and inhibited azoxymethane (AOM)-induced formation of aberrant crypt foci (ACF) by 46%. Addition of pure beta-boswellic acid, 3-O-acetyl-beta-boswellic acid, 11-keto-beta-boswellic acid or 3-O-acetyl-11-keto-beta-boswellic acid to human leukemia HL-60 cell culture inhibited DNA synthesis in HL-60 cells in a dose-dependent manner with IC50 values ranging from 0.6 to 7.1 microM. These results indicate that beta-boswellic acid and its derivatives (the major constituents of Boswellin) have anti-carcinogenic, anti-tumor, and anti-hyperlipidemic activities.

Animals↗
PubMed2000

Pulsed electromagnetic field stimulation of MG63 osteoblast-like cells affects differentiation and local factor production.

Pulsed electromagnetic field stimulation has been used to promote the healing of chronic nonunions and fractures with delayed healing, but relatively little is known about its effects on osteogenic cells or the mechanisms involved. The purpose of this study was to examine the response of osteoblast-like cells to a pulsed electromagnetic field signal used clinically and to determine if the signal modulates the production of autocrine factors associated with differentiation. Confluent cultures of MG63 human osteoblast-like cells were placed between Helmholtz coils and exposed to a pulsed electromagnetic signal consisting of a burst of 20 pulses repeating at 15 Hz for 8 hours per day for 1, 2, or 4 days. Controls were cultured under identical conditions, but no signal was applied. Treated and control cultures were alternated between two comparable incubators and, therefore, between active coils; measurement of the temperature of the incubators and the culture medium indicated that application of the signal did not generate heat above the level found in the control incubator or culture medium. The pulsed electromagnetic signal caused a reduction in cell proliferation on the basis of cell number and [3H]thymidine incorporation. Cellular alkaline phosphatase-specific activity increased in the cultures exposed to the signal, with maximum effects at day 1. In contrast, enzyme activity in the cell-layer lysates, which included alkaline phosphatase-enriched extracellular matrix vesicles, continued to increase with the time of exposure to the signal. After 1 and 2 days of exposure, collagen synthesis and osteocalcin production were greater than in the control cultures. Prostaglandin E2 in the treated cultures was significantly reduced at 1 and 2 days, whereas transforming growth factor-beta1 was increased; at 4 days of treatment, however, the levels of both local factors were similar to those in the controls. The results indicate enhanced differentiation as the net effect of pulsed electromagnetic fields on osteoblasts, as evidenced by decreased proliferation and increased alkaline phosphatase-specific activity, osteocalcin synthesis, and collagen production. Pulsed electromagnetic field stimulation appears to promote the production of matrix vesicles on the basis of higher levels of alkaline phosphatase at 4 days in the cell layers than in the isolated cells, commensurate with osteogenic differentiation in response to transforming growth factor-beta1. The results indicate that osteoblasts are sensitive to pulsed electromagnetic field stimulation, which alters cell activity through changes in local factor production.

Alkaline Phosphatase↗
PubMed2000

Changes in gene expression with iron loading and chelation in cardiac myocytes and non-myocytic fibroblasts.

Iron overload is associated with long-term cardiac iron accumulation and tissue changes such as fibrosis. To determine short-term iron-dependent changes in expression of genes associated with iron homeostasis and fibrosis we measured mRNA on Northern blots prepared from cultured rat neonatal cardiomyocytes and non-myocytes (fibroblasts) as a function of iron loading and chelation. Transferrin receptor mRNA was reduced in myocytes exposed to various concentrations of iron for 3 days and this decline was associated with a 63% decline in iron-response element (IRE) binding of iron regulatory protein-1, indicating that myocytes utilize IRE-dependent mechanisms to modulate gene expression. In myocytes iron caused a dose-dependent decline in mRNAs coding for transforming growth factor- beta(1)(TGF- beta(1)), biglycan, and collagen type I while plasminogen activator inhibitor-1 mRNA was unaffected by iron loading and decorin mRNA doubled. Total TGF- beta bioactivity was also decreased by iron loading. Thus, the effects of iron loading on genes related to cardiac fibrosis are gene-specific. Addition of deferoxamine for 1 day did not have any significant effect on any of these genes. Parallel changes in gene expression were exhibited by non-myocytes (fibroblasts), where chelation also decreased TGF- beta(1)mRNA and activity, and mRNA for collagen type I and biglycan, and collagen synthesis. In addition to these changes in transcripts associated with matrix formation the mRNA of the metabolic enzyme glyceraldehyde-3-phosphate dehydrogenase was unaffected by iron loading but doubled in both cell types upon treatment with deferoxamine. These findings suggest that in both cardiac myocytes and non-myocyte fibroblasts gene expression is coupled to intracellular iron pools by gene-specific and IRE-dependent and idependent mechanisms. This linkage may influence matrix deposition, a significant component of cardiac injury.

Animals↗
PubMed2000

Sensitivity enhancement of HCACO by using an HMQC magnetization transfer scheme.

Previous theoretical calculations have demonstrated that the multiquantum relaxation rate of (1)H(alpha)-(13)C(alpha)(R(MQ)) is, on average, 1.3 +/- 0.4 or 1.7 +/- 0.6 times slower than the single-quantum relaxation rate of (13)C(alpha)(R(C)) for a sample with or without, respectively, amide protons. By taking advantage of this fact and by using the PEP sensitivity enhancement scheme, an HMQC version of the HCACO experiment has been developed. We demonstrate that this new experiment is 23 and 55% more sensitive than the original HSQC version of the HCACO experiment, at constant times of 7 and 27 ms, respectively, for a sample of the BC domain of the ciliary neurotrophic factor receptor protein dissolved in D(2)O at 20 degrees C.

Algorithms↗
PubMed2000

Three-dimensional electrophoretic NMR correlation spectroscopy.

A novel method of three-dimensional electrophoretic NMR correlation spectroscopy (3D EP-COSY) has been proposed, developed, and implemented. It has a demonstrated potential of facilitating simultaneous structural assignments of multiple proteins in mixtures. The principle is to add a pulsed DC electric field that introduces a new dimension of electrophoretic flow, in which resonances of different molecules can be separated by their electrophoretic migration rates without physical separation. As a result, two COSY spectra were simultaneously obtained in a single 3D EP-COSY experiment from a mixture of 150 mM l-aspartic acid and 148 mM 4, 9-dioxa-1,12-dodecanediamine with concurrent resolution of their chemical shifts and J-coupling constants. This approach creates a new horizon of multidimensional electrophoretic NMR. The technical advance opens doors for structure characterization of complex protein systems and protein interactions, which are at the basis of biochemical mechanisms and the phenomena of living systems.

Alkanes↗
PubMed2000

The 2(3)Delta(g) State of (7)Li(2).

Using pulsed perturbation-facilitated optical-optical double resonance (PFOODR) spectroscopy, the 2(3)Delta(g) state of (7)Li(2) (electronic configuration (varsigma(g)2s) (4ddelta(g)), effective principal quantum number n* = 4.101) has been observed and assigned. Molecular constants and a RKR potential energy curve were obtained. The major molecular constants are Copyright 2000 Academic Press.

Journal Article↗
PubMed2000

Several log increase in therapeutic transgene delivery by distinct adeno-associated viral serotype vectors.

We previously demonstrated that rAAV vectors carrying human and canine factor IX (FIX) cDNA can infect, stably persist, and secrete functional human and canine FIX following direct intramuscular injection. In an attempt to improve FIX protein secretion for eventual therapeutic use, we set out to determine if alteration of the AAV capsid would affect skeletal muscle transduction and factor IX secretion. Two reasons to pursue this question were (1) the persistence of high-titer neutralizing antibody (NAB) to AAV2 and (2) our previous study that supported a restricted tropism of muscle fiber types to AAV2 transduction. Using an identical CMV/canine factor IX (cFIX) expression cassette, we cross-packaged this genome into virions generated from each of the five AAV serotypes. In a dose-response assay, equivalent amounts of rAAV/cFIX serotypes were tested in vitro and in vivo. In tissue culture cells, FIX antigen levels secreted into the supernatant varied depending on the AAV serotype used; type 2 transduced maximally, with serotypes 3, 1, 5, and 4, respectively, expressing lower levels. However, when the same viruses were tested in vivo using immunodeficient NOD/SCID animals, we obtained surprisingly different results. While the time to onset of detectable serum levels appeared the same for all serotypes, types 1, 3, and 5 produced 100- to 1000-fold more cFIX than type 2. In fact, 12 weeks after transduction, type 1 continued to express levels of cFIX on average at 80 microg/ml followed by type 5 (6.52 microg/ml), type 3 (3.27 microg/ml), type 4 (258 ng/ml), and finally type 2 (90 ng/ml). Coagulant activity of cFIX as measured by aPTT supported the circulating levels measured by ELISA demonstrating the secreted protein was functional, and RT-PCR of injected tissue correlated with the serotype-specific transduction data. In summary, we found significant differences in cFIX expression upon introducing various rAAV serotypes into mouse muscle. These data have direct bearing on the design of AAV gene therapy clinical trials for hemophilia and should also extend to most therapeutic transgenes.

Animals↗