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Biomedical subjects

Y Liu

Publications and source records attributed to Y Liu.

At least 307 records · Page 17Linked to original sources
PubMed2001

The presence of 9-cis-beta-carotene in cytochrome b(6)f complex from spinach.

Cytochrome b(6)f complex with stoichiometrically bound beta-carotene molecule was purified from spinach chloroplasts. The configuration of this beta-carotene was studied by reversed-phase HPLC and resonance Raman spectroscopy. Both the absorption spectrum of this beta-carotene in dissociated state and the Raman spectrum in native state can be unambiguously assigned to a 9-cis configuration. This finding is in contrast to the predominantly all-trans isomers commonly found in membranes and protein-pigment complexes of chloroplasts, suggesting that the 9-cis-beta-carotene is an authentic component and may have a unique structural and functional role in cytochrome b(6)f complex.

Chromatography, High Pressure Liquid↗
PubMed2001

An antibody-immobilized capillary column as a bioseparator/bioreactor for detection of Escherichia coil O157:H7 with absorbance measurement.

A capillary-column-based bioseparator/bioreactor was developed for detection of Escherichia coli O157:H7 by chemically immobilizing anti-E. coli O157:H7 antibodies onto the inner wall of the column, forming the "sandwich" immunocomplexes (immobilized antibody-E. coli O157: H7-enzyme-labeled antibody) after the sample and the enzyme-labeled antibody passed through the column and detecting the absorbance of the product in the bioreactor with an optical detector. The effects of the blocking agent, flow rate of samples and substrates, buffer, MgCl2, and pH on the detection of E. coli O157:H7 were investigated. The parameters, 2% BSA in 1.0 x 10-2 M, pH 7.4, PBS as the blocking agent, 0.5 mL/h as the sample flow rate, 1.0 x 10(-2) M MgCl2, and 2.0 x 10(-4) M p-nitrophenyl phosphate in 1.0 M, pH 9.0 Tris buffer as the substrate for the enzymatic reaction, and 1.0 mL/h as the substrate flow rate, were used in the bioseparator/bioreactor system for detection of E. coli O157:H7. The selectivity of the system was checked, and other pathogens, including Salmonella typhimurium, Campylobacterjejuni, and Listeria monocytogenes, had no interference with the detection of E. coli O157:H7. Its working range was from 5.0 x 10(2) to 5.0 x 10(6) cfu/mL, and the total assay time was < 1.5 h without any enrichment. The relative standard deviation was approximately 2.0-7.3%.

Antibodies, Bacterial↗
PubMed2001

Pseudomonas aeruginosa corneal infection affects cholinergic enzymes in rat lacrimal gland.

Since the increased use of extended-wear contact lenses, Pseudomonas aeruginosa has emerged as a primary etiological agent of ulcerative keratitis. Clinical isolates have been classified into two types: cytotoxic and non-cytotoxic. This study revealed significant immune and neuro-enzymatic changes elicited by the two types of P. aeruginosa in the lacrimal gland of rats. The humoral immune response in the lacrimal gland to the non-cytotoxic strain was significantly lower than to the cytotoxic strain, possibly due to the immunogenicity of the extracellular toxin; however, the same effect was not seen in the serum. Choline acetyltransferase and acetylcholinesterase are known to be responsible for synthesis and degradation of acetylcholine, respectively, binding receptors on acini and plasma cells, modulating their activity, and constituting the principle regulator of tear secretion. Following infection, neuro-enzyme activities were significantly modified to reduce the concentration of acetylcholine and therefore potentially reduce secretion from the glands. The data lead to the hypothesis that P. aeruginosa may have the potential to reduce the protective barrier provided by the lacrimal gland to benefit pathogenicity. It was also observed that the neuro-enzyme response of the lacrimal glands of uninfected eyes of the test animals was the same as that of infected eyes, implying that the signal may be relayed by common lymphoidal tissue or the central nervous system and a measurable response returned to both eyes.

Animals↗
PubMed2001

Vaccinia virus E3L interferon resistance protein inhibits the interferon-induced adenosine deaminase A-to-I editing activity.

The RNA-specific adenosine deaminase (ADAR1) is an interferon-inducible editing enzyme that converts adenosine to inosine. ADAR1 contains three distinct domains: a N-terminal Z-DNA binding domain that includes two Z-DNA binding motifs; a central double-stranded RNA binding domain that includes three dsRNA binding motifs (dsRBM); and a C-terminal catalytic domain responsible for A-to-I enzymatic activity. The E3L protein of vaccinia virus mediates interferon resistance. E3L, similar to ADAR1, also contains Z-DNA binding and dsRNA binding motifs. To assess the possible role of E3L in modulating RNA editing by ADAR1, we examined the effect of E3L on ADAR1 deaminase activity. Wild-type E3L protein was a potent inhibitor of ADAR1 deaminase enzymatic activity. Analysis of mutant E3L proteins indicated that the carboxy-proximal dsRBM of E3L was essential for antagonism of ADAR1. Surprisingly, disruption of the Z-DNA binding domain of E3L by double substitutions of two highly conserved residues also abolished its antagonistic activity, whereas deletion of the entire Z domain had little effect on the inhibition. With natural neurotransmitter pre-mRNA substrates, E3L weakly inhibited the site-selective editing activity by ADAR1 at the R/G site of the glutamate receptor B subunit (GluR-B) pre-mRNA and the A site of serotonin 2C receptor (5-HT2CR) pre-mRNA; editing of the intronic hotspot (+)60 site of GluR-B was not affected by E3L. These results demonstrate that the A-to-I RNA editing activity of the IFN-inducible adenosine deaminase is impaired by the product of the vaccinia virus E3L interferon resistance gene.

Adenosine↗
PubMed2001

Crystallization and preliminary X-ray crystallographic analysis of native and selenomethionyl recombinant tabtoxin-resistance protein complexed with acetyl-coenzyme A.

Tabtoxin-resistance protein (TTR), an acetyltransferase from Pseudomonas syringae pv. tabaci, was overexpressed in Eschericha coli M15 and the TTR fusion protein complexed with acetyl-coenzyme A (AcCoA) was purified and crystallized. Diffraction data were collected to 3.0 A resolution in-house and the crystal was found to belong to space group P2(1), with unit-cell parameters a = 47.6, b = 66.6, c = 53.5 A, beta = 104.3 degrees. Furthermore, a selenomethionine (SeMet) TTR fusion protein derivative was overexpressed in the same expression system and its complex with AcCoA was purified in a reductive environment. The SeMet TTR derivative crystallized in two forms: the first was identical to that observed for native crystals and the second belonged to space group C2, with unit-cell parameters a = 101.7, b = 45.6, c = 84.2 A, beta = 105.8 degrees. Data from the P2(1) crystal form were collected in-house to 2.3 A resolution. Subsequently, three different wavelength data sets of the C2 crystal form to 1.55 A resolution were collected at the Advanced Photon Source at Argonne National Laboratory.

Acetyl Coenzyme A↗
PubMed2001

Nonrandom chromosomal imbalances in human ovarian surface epithelial cells immortalized by HPV16-E6E7 viral oncogenes.

We had previously immortalized human ovarian surface epithelial (HOSE) cells using HPV16E6E7 ORFs. In order to identify crucial genetic events involved during cell immortalization, the genomic profile of immortalization of five HOSE cell lines was analyzed by comparative genomic hybridization. Our results showed that chromosomal imbalance was common in HOSE cells after immortalization. The common chromosomal imbalances identified in immortal HOSE cells are: +19q13.1 (5/5 lines), -13q12 approximately qter (4/5 lines), +5q15 approximately q33 (3/5 lines), +20q11.2 approximately q13.2 (3/5 lines) and -22q11.2 approximately qter (3/5 lines). Other chromosomal imbalances, which were detected in two of the five immortal HOSE cell lines, included gains on chromosome 1 and 11q12 approximately q13, and losses on 2p, 4q, 8p, 10p and 11q14 approximately qter. The chromosomal imbalances observed in HOSE cells before immortalization include -8pter approximately p11.2, -11q23 approximately qter, -13q12 approximately qter and +19 which may represent early genetic events during cell immortalization. The genomic profile was examined in one HOSE cell line (HOSE 6-3) at various stages of immortalization. The genomic profiles of HOSE 6-3 cells after crisis were largely stable. A few additional chromosomal imbalances were detected in the immortalized HOSE cells after an extensive culture period including +11pter approximately q23, -15q23 approximately qter, and +17q12 approximately qter. Identification of nonrandom chromosomal imbalance in immortalized HOSE cells may facilitate the identification of specific chromosomes harboring genes involved in the immortalization of human ovarian surface epithelial cells.

Cell Line↗
PubMed2001

Neuroprotective effect of treatment with human albumin in permanent focal cerebral ischemia: histopathology and cortical perfusion studies.

In recent experimental studies, we demonstrated a highly beneficial neuroprotective effect of moderate- to high-dose human albumin treatment of transient focal cerebral ischemia, but we did not define the effect of albumin therapy in permanent focal cerebral ischemia. In this study, anesthetized Sprague-Dawley rats were subjected to permanent middle cerebral artery occlusion by retrograde insertion of an intraluminal nylon suture coated with poly-L-lysine. Albumin was administered i.v. at 2 h after onset of middle cerebral artery occlusion, in doses of either 1.25 (n=8) or 2.5 g/kg (n=6). In a separate group of animals, albumin (2.5 g/kg) was given 1 h after middle cerebral artery occlusion (n=6). Vehicle-treated rats (n=6) received 0.9% saline in equivalent volumes. Neurological status was evaluated during and 24 h after middle cerebral artery occlusion. One day after middle cerebral artery occlusion, infarct volumes and brain edema were determined. In a separate group of animals, cortical perfusion was assessed by Laser-Doppler perfusion imaging. Albumin (1.25 g/kg; n=3) or vehicle (sodium chloride 0.9%; n=3) was administered at 2 h after onset of middle cerebral artery occlusion. Higher-dose albumin therapy (2.5 g/kg) significantly improved the neurological score compared to vehicle rats at 24 h, when administered at either 1 or 2 h after middle cerebral artery occlusion. Total infarct volume was reduced by albumin (2.5 g/kg given at 2 h) by 32% compared with vehicle-treated rats. Both albumin doses (1.25 and 2.5 g/kg) significantly reduced cortical and striatal infarct areas at several coronal levels when administered at 2 h after middle cerebral artery occlusion. Brain swelling was not affected by albumin treatment. Cortical perfusion declined during middle cerebral artery occlusion in both groups. Treatment with albumin led to 48% increases in cortical perfusion (P<0.002), but saline caused no change. These results support a beneficial effect of albumin therapy in permanent focal cerebral ischemia.

Animals↗
PubMed2001

Palladium(II)-catalyzed synthesis of alpha-alkylidene-gamma-butyrolactams from N-allylic 2-alkynamides. Total synthesis of (+/-)-isocynodine and (+/-)-isocynometrine.

An efficient method for preparing alpha-alkylidene-gamma-butyrolactams via the Pd(II)-catalyzed cyclization of acyclic N-allylic 2-alkynamides via halopalladation, intramolecular olefin insertion, and beta-heteroatom elimination was developed. The reaction is less influenced by the leaving group and the concentration of the halide ions in comparison with the cyclization of acyclic alkynoates. The total syntheses of (+/-)-isocynodine and (+/-)-isocynometrine were realized using this method.

Alkaloids↗
PubMed2001

Genetic background but not metallothionein phenotype dictates sensitivity to cadmium-induced testicular injury in mice.

Sensitivity to cadmium (Cd)-induced testicular injury varies greatly among mouse strains. For instance, 129/SvJ (129) mice are highly sensitive while C57BL/6J (C57) mice are refractory to Cd-induced testicular injury. Metallothionein (MT), a Cd-binding protein, is thought to be responsible for the strain susceptibility to Cd toxicity. In this study, MT-I/II knockout (MT-null) and wild-type 129 mice were used to determine the role of MT in Cd-induced testicular injury. Two additional strains of mice (C57 and the C57 x 129 F1cross) were also used to help define the role of genetic background in Cd toxicity. Mice were given 5-20 micromol/kg ip CdCl(2) and testicular injury was examined 24 h later by histopathology and testicular hemoglobin concentration. Cd produced dose-dependent testicular injury in all strains of mice, except for C57 mice, in which testicular injury could not be produced. MT-null mice were more sensitive than C57 x 129 mice but were equally sensitive as 129 mice to Cd-induced testicular injury. Fourteen days after 15 micromol/kg ip Cd administration, testicular atrophy was evident in MT-null, 129, and C57 x 129 mice but was absent in C57 mice. The resistance of C57 mice to Cd-induced testicular injury could not be attributed solely to a decreased uptake of (109)Cd nor to a greater amount of testicular MT. Microarray analysis revealed a higher expression of glutathione peroxidase in the testes of C57 mice, as well as genes encoding antioxidant components and DNA damage/repair, but their significance to Cd-induced injury is not immediately clear. Thus, this study demonstrates that it is genetic strain, not MT genotype, that is mechanistically important in determining susceptibility to Cd-induced testicular injury.

Animals↗
PubMed2001

Activity-dependent nuclear translocation and intranuclear distribution of NFATc in adult skeletal muscle fibers.

TTranscription factor nuclear factor of activated T cells NFATc (NFATc1, NFAT2) may contribute to slow-twitch skeletal muscle fiber type-specific gene expression. Green fluorescence protein (GFP) or FLAG fusion proteins of either wild-type or constitutively active mutant NFATc [NFATc(S-->A)] were expressed in cultured adult mouse skeletal muscle fibers from flexor digitorum brevis (predominantly fast-twitch). Unstimulated fibers expressing NFATc(S-->A) exhibited a distinct intranuclear pattern of NFATc foci. In unstimulated fibers expressing NFATc-GFP, fluorescence was localized at the sarcomeric z-lines and absent from nuclei. Electrical stimulation using activity patterns typical of slow-twitch muscle, either continuously at 10 Hz or in 5-s trains at 10 Hz every 50 s, caused cyclosporin A-sensitive appearance of fluorescent foci of NFATc-GFP in all nuclei. Fluorescence of nuclear foci increased during the first hour of stimulation and then remained constant during a second hour of stimulation. Kinase inhibitors and ionomycin caused appearance of nuclear foci of NFATc-GFP without electrical stimulation. Nuclear translocation of NFATc-GFP did not occur with either continuous 1 Hz stimulation or with the fast-twitch fiber activity pattern of 0.1-s trains at 50 Hz every 50 s. The stimulation pattern-dependent nuclear translocation of NFATc demonstrated here could thus contribute to fast-twitch to slow-twitch fiber type transformation.

Active Transport, Cell Nucleus↗
PubMed2001

Overexpression of Cbfa1 in osteoblasts inhibits osteoblast maturation and causes osteopenia with multiple fractures.

Targeted disruption of core binding factor alpha1 (Cbfa1) showed that Cbfa1 is an essential transcription factor in osteoblast differentiation and bone formation. Furthermore, both in vitro and in vivo studies showed that Cbfa1 plays important roles in matrix production and mineralization. However, it remains to be clarified how Cbfa1 controls osteoblast differentiation, bone formation, and bone remodelling. To understand fully the physiological functions of Cbfa1, we generated transgenic mice that overexpressed Cbfa1 in osteoblasts using type I collagen promoter. Unexpectedly, Cbfa1 transgenic mice showed osteopenia with multiple fractures. Cortical bone, which was thin, porous, and enriched with osteopontin, was invaded by osteoclasts, despite the absence of acceleration of osteoclastogenesis. Although the number of neonatal osteoblasts was increased, their function was impaired in matrix production and mineralization. Furthermore, terminally differentiated osteoblasts, which strongly express osteocalcin, and osteocytes were diminished greatly, whereas less mature osteoblasts expressing osteopontin accumulated in adult bone. These data indicate that immature organization of cortical bone, which was caused by the maturational blockage of osteoblasts, led to osteopenia and fragility in transgenic mice, demonstrating that Cbfa1 inhibits osteoblast differentiation at a late stage.

Animals↗
PubMed2001

Local costimulation reinvigorates tumor-specific cytolytic T lymphocytes for experimental therapy in mice with large tumor burdens.

Cytotoxic T cells recognize tumor Ags and destroy cancer cells in vitro. Adoptive transfer studies with transgenic T cells specific for tumor Ags have demonstrated that CTL are effective only in mice with small tumor burdens and thus appear to have limited potential in cancer immunotherapy. Here we used transgenic mice that express the TCR specific for an unmutated tumor Ag P1A and multiple lineages of P1A-expressing tumors to address this critical issue. We found that local costimulation, either by expression of B7-1 on the tumor cells or by local administration of anti-CD28 mAb 37N, reinvigorated the function of CTL specific for the tumor Ag, as it substantially increased the efficacy of CTL therapy for mice with large tumor burdens. Our study suggests that CTL-based immunotherapy can be manipulated to deal with large tumors.

Abatacept↗
PubMed2001

Cost-effectiveness of automated external defibrillators on airlines.

CONTEXT: Installation of automated external defibrillators (AEDs) on passenger aircraft has been shown to improve survival of cardiac arrest in that setting, but the cost-effectiveness of such measures has not been proven. OBJECTIVE: To examine the costs and effectiveness of several different options for AED deployment in the US commercial air transportation system. DESIGN, SETTING, AND SUBJECTS: Decision and cost-effectiveness analysis of a strategy of full deployment on all aircraft as well as several strategies of partial deployment only on larger aircraft, compared with a baseline strategy of no AEDs on aircraft (but training flight attendants in basic life support) for a hypothetical cohort of persons experiencing cardiac arrest aboard US commercial aircraft. Estimates for costs and outcomes were obtained from the medical literature, the Federal Aviation Administration, the Air Transport Association of America, a population-based cohort of Medicare patients, AED manufacturers, and the Bureau of Labor Statistics. MAIN OUTCOME MEASURES: Quality-adjusted survival after cardiac arrest; costs of AED deployment on aircraft and of medical care for cardiac arrest survivors. RESULTS: Adding AEDs on passenger aircraft with more than 200 passengers would cost $35 300 per quality-adjusted life-year (QALY) gained. Additional AEDs on aircraft with capacities between 100 and 200 persons would cost an additional $40 800 per added QALY compared with deployment on large-capacity aircraft only, and full deployment on all passenger aircraft would cost an additional $94 700 per QALY gained compared with limited deployment on aircraft with capacity greater than 100. Sensitivity analyses indicated that the quality of life, annual mortality rate, and the effectiveness of AEDs in improving survival were the most influential factors in the model. In 85% of Monte Carlo simulations, AED placement on large-capacity aircraft produced cost-effectiveness ratios of less than $50 000 per QALY. CONCLUSION: The cost-effectiveness of placing AEDs on commercial aircraft compares favorably with the cost-effectiveness of widely accepted medical interventions and health policy regulations, but is critically dependent on the passenger capacity of the aircraft. Placing AEDs on most US commercial aircraft would meet conventional standards of cost-effectiveness.

Aircraft↗
PubMed2001

Redirect the assembly of hexagonal MCM-41 into cubic MCM-48 from sodium silicate without the use of an organic structure modifier.

In contrast to earlier methods requiring the presence of organic modifiers for the preparation of cubic MCM-48 mesostructures from low cost sodium silicate, we show that this three dimensional framework structure can be readily assembled in the absence of co-surfactants simply by using the overall SiO2/OH- ratio as means of controlling the surfactant packing parameter.

Journal Article↗
PubMed2001

Transplants of cells genetically modified to express neurotrophin-3 rescue axotomized Clarke's nucleus neurons after spinal cord hemisection in adult rats.

To test the idea that genetically engineered cells can rescue axotomized neurons, we transplanted fibroblasts and immortalized neural stem cells (NSCs) modified to express neurotrophic factors into the injured spinal cord. The neurotrophin-3 (NT-3) or nerve growth factor (NGF) transgene was introduced into these cells using recombinant retroviral vectors containing an internal ribosome entry site (IRES) sequence and the beta-galactosidase or alkaline phosphatase reporter gene. Bioassay confirmed biological activity of the secreted neurotrophic factors. Clarke's nucleus (CN) axons, which project to the rostral spinal cord and cerebellum, were cut unilaterally in adult rats by T8 hemisection. Rats received transplants of fibroblasts or NSCs genetically modified to express NT-3 or NGF and a reporter gene, only a reporter gene, or no transplant. Two months postoperatively, grafted cells survived at the hemisection site. Grafted fibroblasts and NSCs expressed a reporter gene and immunoreactivity for the NGF or NT-3 transgene. Rats receiving no transplant or a transplant expressing only a reporter gene showed a 30% loss of CN neurons in the L1 segment on the lesioned side. NGF-expressing transplants produced partial rescue compared with hemisection alone. There was no significant neuron loss in rats receiving grafts of either fibroblasts or NSCs engineered to express NT-3. We postulate that NT-3 mediates survival of CN neurons through interaction with trkC receptors, which are expressed on CN neurons. These results support the idea that NT-3 contributes to long-term survival of axotomized CN neurons and show that genetically modified cells rescue axotomized neurons as efficiently as fetal CNS transplants.

Animals↗
PubMed2001

Metallothionein-null and wild-type mice show similar cadmium absorption and tissue distribution following oral cadmium administration.

Cadmium (Cd) is an environmental pollutant and is toxic to many tissues. Food is the primary source of Cd exposure for the general population. Metallothionein (MT), a cysteine-rich, Cd-binding protein, plays an important role in Cd detoxication. However, the role of MT in Cd absorption and distribution is still controversial. For example, some reports assert that MT in the intestine decreases Cd absorption and increases its distribution to the kidney, relative to the liver. Therefore, to further clarify the role of MT in Cd absorption and tissue distribution, MT-I/II knockout (MT-null) mice and their parental background wild-type mice were given a single dose of (109)Cd (1-300 micromol/kg po or 0.1-30 micromol/kg iv). Cd content in 15 organs was determined 4 h after Cd administration by gamma scintillation spectrometry. Approximately 60% of the Cd administered iv was retained in liver, and about 5% was retained in kidney in both MT-null and wild-type mice. The distribution of iv administered Cd was independent of dose. In contrast, when administered po, approximately 0.15% of the lowest dose (1 micromol/kg) and 0.75% of the highest dose (300 micromol/kg) was detected in the liver of both MT-null and wild-type mice. Similarly in kidney, approximately 0.05% of the dose was detected after the lowest dose and about 0.15% after the higher doses in both MT-null and wild-type mice. In summary, this study demonstrates that the absorption and initial distribution of orally administered Cd is dose dependent but is not influenced by MT.

Administration, Oral↗