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Biomedical subjects

Y J Liu

Publications and source records attributed to Y J Liu.

At least 19 recordsLinked to original sources
PubMed2006

Thermal characteristics of microwave ablation in the vicinity of an arterial bifurcation.

PURPOSE: The objective of this research was to reveal the thermal characteristics of microwave ablations in the vicinity of an arterial bifurcation. METHODS: The temperature distribution after microwave heating of a liver-like material in the close proximity of an arterial bifurcation was simulated using the finite element method. Coupled fluid flow and solid heat transfer were taken into consideration and a three-dimensional analysis was performed. An experimentally determined SAR (specific absorption rate) generated by the absorption of microwaves in liver-like material was used in the analysis instead of utilizing electromagnetic calculations. Several different tests of time-controlled ablations with varying distances between the microwave antenna and the bifurcation were performed and detailed temperature distributions near the bifurcation were obtained. RESULTS: The interaction between the recirculation flow in the bifurcation and the heat transfer in the surrounding tissue makes the temperature distribution near the bifurcation complicated. Most importantly, after a period of continuous heating with constant microwave output power, the maximum temperatures caused by the ablation did not always increase with the distance between the antenna and the bifurcation. CONCLUSION: It can be concluded that inadequate ablations can be the result not only from a close proximity between the antenna and the blood vessel, but also from a complicated blood flow in large vessels whose structure causes recirculation flow.

Arteries↗
PubMed2004

Toxicity and cerebrospinal fluid levels of carboplatin chronically infused into the brainstem of a primate.

PURPOSE: Carboplatin was infused into the brainstem of cynomolgus monkeys to investigate neurotoxicity and systemic exposures following chronic local delivery. METHODS: Infusions at 0.42 microl/h were intended to deliver 0.025 (n = 2), 0.075 (n = 3), 0.25 (n = 5), and 0.75 (n = 3) mg/kg by day 30. Laboratory tests, radiographic measurements, and clinical observations were used to monitor toxicity. Blood and cerebrospinal fluid (CSF) were sampled for platinum. RESULTS: Lethargy and ataxia were observed after week 4 in the monkeys given 0.075 mg/kg, and week 2 in the monkeys given 0.25 mg/kg when the infused doses were approximately 250 and 400 microg, respectively. Rapidly progressive neurotoxicity with the 0.75 mg/kg dose required termination of the infusions at days 4-10. Hematology and chemistry values were unremarkable in all groups. Blood levels of platinum remained undetectable in 0.025 and 0.075 mg/kg dose groups. Levels in the 0.25 mg/kg group were 3.1 +/- 0.6 microg/l at 2 weeks and 5.2 +/- 0.8 microg/l at 1 month. The CSF platinum levels varied. Animals in the 0.25 mg/kg group had higher CSF levels at 2 weeks (avg. 65 microg/l, range 36-89) compared to their 1 month value (avg. 60 microg/l, range 7-170), despite the constant infusion. CONCLUSION: Carboplatin can be chronically infused into monkey brainstems. Neurotoxicity is the predominant side effect and is dose-dependent. Pharmacokinetics of local and systemic delivery are different for carboplatin. Further studies are needed to monitor toxicity at higher flow rates and to investigate drug binding to abnormal central nervous system (CNS) tissues.

Animals↗
PubMed2004

Role of Ichthyophthirius multifiliis in the Infection of Aeromonas hydrophila.

Aeromonas hydrophila and Ichthyophthirius multifiliis are important fish pathogens. To clarify their relationship, two host models, goldfish with trauma and those infected with I. multifiliis, were used to study infection kinetics of A. hydrophila 4332 tagged with plasmid pGFPuv (Ah4332(GFP)). The results showed that in fish suffering from ichthyophthiriosis, the bacterial infection process was accelerated and more persistent than in the other groups. It is suggested that I. multifiliis plays an important role in the infection of A. hydrophila. Mechanical trauma caused by I. multifiliis might act as a portal of entry for A. hydrophila present in the water, thereby facilitating the invasion of bacteria. The ectoparasite might also serve as a vector and reservoir of pathogenic bacteria.

Aeromonas hydrophila↗
PubMed2003

Association of estrogen receptor alpha and vitamin D receptor gene polymorphisms with bone mineral density in Chinese males.

Osteoporosis is a common health problem not only in females but also in males, however, studies of osteoporosis in males are relatively rare compared to those in females. This is especially true in genetics studies. We evaluated the effects of PvuII and XbaI polymorphisms in the estrogen receptor alpha (ER-alpha) gene and ApaI polymorphism in the vitamin D receptor (VDR) gene on BMD variation in a random sample of 352 unrelated males from 401 Chinese nuclear families. BMD was measured at the lumbar spine (L1-L4) and hip (femoral neck, trochanter, intertrochanteric region). Raw BMD values were adjusted by age, age(2), height, and weight as covariates. We found no significant results for the 3 individual markers on BMD variation, however, ER-alpha haplotype analyses yielded some interesting results. Carriers of haplotype pX had a 4.98% lower BMD at the trochanter (P = 0.02) and 3.55% lower BMD at the lumbar spine (P = 0.09) than non-carriers. PX subjects had a 3.42% higher BMD at the trochanter and 3.26% higher BMD at the lumbar spine than others (P = 0.07 and P = 0.10, respectively). Such results were highly comparable with the significant or nearly significant interactions between ER-PvuII and ER-XbaI on BMD values at the trochanter (P = 0.03) and spine (P = 0.11). No significant results were observed for the interactions between ER-PvuII and VDR-ApaI, between ER-XbaI and VDR-ApaI, and between any of ER-alpha haplotypes and VDR-ApaI locus. Our results suggest that the ER-alpha haplotypes, not individual markers, may be associated with BMD variation at some skeletal sites in our Chinese male samples.

Absorptiometry, Photon↗
PubMed2003

No evidence for linkage and/or association of human alpha2-HS glycoprotein gene with bone mineral density variation in Chinese nuclear families.

Osteoporosis is an important health problem in the world. Alpha2-HS glycoprotein (AHSG) is involved in bone formation and metabolism and has been considered as an important candidate gene for osteoporosis. In this study, we simultaneously tested linkage and/or association of the AHSG gene with the variation of bone mineral density (BMD), an important risk factor for osteoporosis. A sample of 1,260 subjects from 401 Chinese nuclear families (including both parents and their daughters) were studied. The daughters' ages ranged from 20 to 45 years. All the subjects were genotyped by PCR-RFLP (polymerase chain reaction-restriction fragment length polymorphism) at polymorphic Sac I site inside the exon 7 of the AHSG gene. This polymorphism involves a nucleotide substitution of C to G at the middle nucleotide of the codon at amino acid position 238, resulting in the replacement of threonine (ACC) with serine (AGC). BMD was measured at the lumbar spine and hip region by dual-energy X-ray absorptiometry (DXA). Using the QTDT (quantitative trait transmission disequilibrium test), we found no significant results for association or linkage between the AHSG gene and BMD variation at the spine or hip. Our data provided no evidence to support the AHSG gene as a quantitative trait locus (QTL) for the BMD variation in a Chinese population.

Absorptiometry, Photon↗
PubMed2003

Tests of linkage and association of the COL1A2 gene with bone phenotypes' variation in Chinese nuclear families.

In the present study, we simultaneously test linkage and/or association of the collagen type I alpha 2 (COL1A2) gene with bone mineral density (BMD) and bone area. A total of 1280 subjects from 407 Chinese nuclear families (including both parents and their daughters) were genotyped for an intragenic marker MspI in the COL1A2 gene. BMD and bone area at the lumbar spine and hip were measured by dual-energy X-ray absorptiometry. Applying the QTDT (quantitative transmission disequilibrium test) program, we performed tests for population stratification, within-family association (via transmission disequilibrium test), total association, linkage, and linkage while modeling association. Significant or marginal within-family associations were found with BMD at the lumbar spine (P = 0.013), trochanter (P = 0.004), and total hip (P = 0.053) and with bone area at the intertrochanteric region (P = 0.024) and total hip (P = 0.048). The positive associations were confirmed in permutations except for bone area at total hip (P > 0.10). A small proportion (<1%) of the population variance of bone phenotypes can be explained by the MspI polymorphism; however, it may be underestimated given the significant population stratification detected in our sample. Due to the limited number of sib pairs in this sample, we did not find evidence of linkage. In summary, the MspI polymorphism is likely to be in linkage disequilibrium with a nearby functional mutation affecting BMD and bone area.

Adult↗
PubMed2002

Retinopathy in a Chinese population with type 2 diabetes: factors affecting the presence of this complication at diagnosis of diabetes.

This study examined the prevalence of retinopathy in 2131 patients with type 2 diabetes attending a Beijing hospital for the first time. The median age of patients was 58 years (IQR 50-65). The overall prevalence of retinopathy was 27.3% (95% CI: 25.4-29.2) and for proliferative retinopathy 7.8% (95% CI: 6.7-8.9). When all patients were considered together, duration of diabetes (OR=1.8; P=0.001) and albumin excretion rate (OR=1.5; P=0.019) were independent risk factors for retinopathy. Blue-collar occupation (OR=1.5; P=0.047) and blood pressure (OR=1.2; P=0.021) were additional risk factors for non-proliferative and proliferative retinopathy respectively. Amongst the 773 newly diagnosed patients, 21% (95% CI: 17.8-23.6) already had retinopathy. The median age of those patients with retinopathy at diagnosis of diabetes was 3 years higher that those without retinopathy, and blue-collar workers (OR=2.2; P=0.012) as well as female gender were particularly at risk (OR=2.0; P=0.033). There was a strong correlation between duration of diabetes with the presence of retinopathy (r=0.95; P=0.01). By extrapolation, it could be estimated that some degree of hyperglycaemia might have been present for more than 20 years before diabetes was diagnosed. These findings emphasise the importance of earlier diagnosis of diabetes and its complications, especially in socially disadvantaged groups.

Age of Onset↗
PubMed2002

Oncospheres of Taenia solium develop into cysticerci in normal mice.

In vitro-hatched oncospheres of Taenia solium, prepared by the sodium hypochlorite method and adjusted to approximately 5 x 10(2)/2ml phosphate buffer saline, were injected intramuscularly or intravenously into normal Balb/c mice. When these mice were sacrificed 2 months later, all cysticerci were exclusively recovered in the lungs from the mice with intravenous inoculation, but not with intramuscular injection. A high infection rate of 76% was obtained and a total of 45 cysticerci were collected from 50 mice. Thirty-five cysticerci were mature and with normal appearance but the rest were either with abnormal appearance (4) or degenerated (6). These findings give strong evidence that T. solium oncospheres may migrate to the normal mouse lung through venous circulation and develop in this organ.

Animals↗
PubMed2001

Subsets of human dendritic cell precursors express different toll-like receptors and respond to different microbial antigens.

Toll-like receptors (TLRs) are ancient microbial pattern recognition receptors highly conserved from Drosophila to humans. To investigate if subsets of human dendritic cell precursors (pre-DC), including monocytes (pre-DC1), plasmacytoid DC precursors (pre-DC2), and CD11c(+) immature DCs (imDCs) are developed to recognize different microbes or microbial antigens, we studied their TLR expression and responses to microbial antigens. We demonstrate that whereas monocytes preferentially express TLR 1, 2, 4, 5, and 8, plasmacytoid pre-DC strongly express TLR 7 and 9. In accordance with these TLR expression profiles, monocytes respond to the known microbial ligands for TLR2 (peptidoglycan [PGN], lipoteichoic acid) and TLR4 (lipopolysaccharide), by producing tumor necrosis factor (TNF)-alpha and interleukin (IL)-6. In contrast, plasmacytoid pre-DCs only respond to the microbial TLR9-ligand, CpG-ODNs (oligodeoxynucleotides [ODNs] containing unmethylated CpG motifs), by producing IFN-alpha. CD11c(+) imDCs preferentially express TLR 1, 2, and 3 and respond to TLR 2-ligand PGN by producing large amounts of TNF-alpha, and to viral double-stranded RNA-like molecule poly I:C, by producing IFN-alpha and IL-12. The expression of distinct sets of TLRs and the corresponding difference in reactivity to microbial molecules among subsets of pre-DCs and imDCs support the concept that they have developed through distinct evolutionary pathways to recognize different microbial antigens.

Biomarkers↗
PubMed2001

Depletion of circulating natural type 1 interferon-producing cells in HIV-infected AIDS patients.

Natural interferon-alpha producing cells (IPCs) are a newly characterized blood cell type, which is the major source of type I interferons in antiviral innate immune responses. The relationship between the number of circulating IPCs, HIV disease progression, and the occurrence of HIV-related complications was investigated. The study of 25 healthy donors and 54 HIV-infected subjects demonstrated a direct correlation between blood IPC number, interferon-alpha production, and clinical state of HIV-infected subjects. Asymptomatic long-term survivors had increased IPC number and function relative to uninfected controls and infected individuals with progressive disease. IPC numbers were markedly reduced in AIDS patients developing opportunistic infections and cancer. A negative correlation was found between the IPC number in the blood and the HIV viral load, suggesting that IPCs are important in controlling HIV replication. This study provides the first evidence that IPCs are being affected during the course of HIV infection and suggests that these cells can play a vital role in the protection against opportunistic pathogens and cancer. (Blood. 2001;98:906-912)

AIDS-Related Opportunistic Infections↗
PubMed2001

Human thymic stromal lymphopoietin preferentially stimulates myeloid cells.

The sequence of a novel hemopoietic cytokine was discovered in a computational screen of genomic databases, and its homology to mouse thymic stromal lymphopoietin (TSLP) suggests that it is the human orthologue. Human TSLP is proposed to signal through a heterodimeric receptor complex that consists of a new member of the hemopoietin family termed human TSLP receptor and the IL-7R alpha-chain. Cells transfected with both receptor subunits proliferated in response to purified, recombinant human TSLP, with induced phosphorylation of Stat3 and Stat5. Human TSLPR and IL-7Ralpha are principally coexpressed on monocytes and dendritic cell populations and to a much lesser extent on various lymphoid cells. In accord, we find that human TSLP functions mainly on myeloid cells; it induces the release of T cell-attracting chemokines from monocytes and, in particular, enhances the maturation of CD11c(+) dendritic cells, as evidenced by the strong induction of the costimulatory molecules CD40 and CD80 and the enhanced capacity to elicit proliferation of naive T cells.

Amino Acid Sequence↗
PubMed2001

Distinct cytokine profiles of neonatal natural killer T cells after expansion with subsets of dendritic cells.

Natural killer T (NKT) cells are a highly conserved subset of T cells that have been shown to play a critical role in suppressing T helper cell type 1-mediated autoimmune diseases and graft versus host disease in an interleukin (IL)-4-dependent manner. Thus, it is important to understand how the development of IL-4- versus interferon (IFN)-gamma-producing NKT cells is regulated. Here, we show that NKT cells from adult blood and those from cord blood undergo massive expansion in cell numbers (500-70,000-fold) during a 4-wk culture with IL-2, IL-7, phytohemagglutinin, anti-CD3, and anti-CD28 mAbs. Unlike adult NKT cells that preferentially produce both IL-4 and IFN-gamma, neonatal NKT cells preferentially produce IL-4 after polyclonal activation. Addition of type 2 dendritic cells (DC2) enhances the development of neonatal NKT cells into IL-4(+)IFN-gamma(-) NKT2 cells, whereas addition of type 1 dendritic cells (DC1) induces polarization towards IL-4(-)IFN-gamma(+) NKT1 cells. Adult NKT cells display limited plasticity for polarization induced by DC1 or DC2. Thus, newly generated NKT cells may possess the potent ability to develop into IL-4(+)IFN-gamma(-) NKT2 cells in response to appropriate stimuli and may thereafter acquire the tendency to produce both IL-4 and IFN-gamma.

Adult↗
PubMed2001

Interferon-beta induces the development of type 2 dendritic cells.

Suppression of interleukin 12 (IL-12) production by dendritic cells (DCs) has been hypothesized to be a principal mechanism underlying the biological action of interferon (IFN)-beta used for treatment of multiple sclerosis (MS), a chronic inflammatory disease of the central nervous system with possible autoimmune origin. How IFN-beta interacts with DCs to inhibit IL-12 production remains unclear. In this study, we found that DCs derived from human blood monocytes, upon culture in the presence of IFN-beta with granulocyte-macrophage colony- stimulating factor (GM-CSF) and IL-4, differentiated into a population expressing CD14- CD1a- HLA-DR+. This population expressed CD123 (IL-3Ralpha). IFN-beta dose-dependently increased IL-3Ralpha+ DCs and decreased CD1a+ DCs. After 7 days' culture with IFN-beta at a concentration of 10 000 U/ml, more than 40% of DCs expressed IL-3Ralpha. IFN-beta, together with GM-CSF and IL-4, also induced maturation of IL-3Ralpha-expressing cells, as reflected by upregulation of HLA-DR and of the costimulatory molecules CD40, CD80 and CD86. In contrast to control DCs, IFN-beta-treated DCs produced predominantly IL-10 but only low levels of IL-12p40. Correspondingly, IFN-beta-treated DCs strongly suppressed IFN-gamma production but enhanced IL-10 production by allogeneic blood mononuclear cells. Our data suggest that IFN-beta in vitro can induce the development of DC2, which provide a permissive environment for Th2 differentiation. This finding represents a novel mechanism for action of IFN-beta in MS.

Antigens, CD1↗
PubMed2001

Distinct CpG DNA and polyinosinic-polycytidylic acid double-stranded RNA, respectively, stimulate CD11c- type 2 dendritic cell precursors and CD11c+ dendritic cells to produce type I IFN.

Two classes of nucleic acids, bacterial DNA containing unmethylated CpG motifs and dsRNA in viruses, induce the production of type I IFN that contributes to the immunostimulatory effects of these microbial molecules. Thus, it is important to determine which cells produce type I IFN in response to CpG DNA and dsRNA. CD4(+)CD11c(-) type 2 dendritic cell precursors (pre-DC2) were identified as the main producers of type I IFN in human blood in response to viruses. Here we asked whether pre-DC2 also produce type I IFN in response to CpG DNA and dsRNA. Oligodeoxynucleotides containing particular palindromic CpG motifs induced pre-DC2, but not CD11c(+) blood DC or monocytes, to produce IFN-alpha. In contrast, a synthetic dsRNA, polyinosinic polycytidylic-acid, induced CD11c(+) DC, but not pre-DC2 or monocytes, to produce IFN-alphabeta. These data indicate that CpG DNA and polyinosinic-polycytidylic acid stimulate different types of cells to produce type I IFN and that it is important to select oligodeoxynucleotides containing particular CpG motifs to induce pre-DC2 to produce type I IFN, which may play a key role in the strong adjuvant effects of CpG DNA.

Cell Differentiation↗
PubMed2001

Dendritic cell lineage, plasticity and cross-regulation.

Dendritic cells (DCs) are professional antigen-presenting cells that have an extraordinary capacity to stimulate naïve T cells and initiate primary immune responses. Here we review progress in understanding the additional functions of DCs in regulating the types of T cell-mediated immune responses and innate immunity to microbes. In addition, evidence for the existence of myeloid and lymphoid DC lineages and their different functions are summarized. We propose that the diverse functions of DCs in immune regulation are dictated by the instructions they received during innate immune responses to different pathogens and from their evolutionary lineage heritage.

Animals↗
PubMed2001

Survey of polycyclic aromatic hydrocarbons (PAHs) in arterial street air of Hangzhou.

The presence of particulate and vapor PAHs, SO2 and NOx and other interrelated conditions (temperature, traffic intensity and wind velocity) were investigated in the arterial street air of Hangzhou. The concentration of the nine PAHs in the air was mean to 11.7 micrograms/m3, and the content of benzo(a) pyrene was up to 0.108 microgram/m3. The contents of PAHs in the sampling sites were in good relation to the traffic intensity, and would be also affected by the terrain and meteorological conditions. The occurrences of PAHs in ambient air were mainly affected by their physical, chemical characters and temperature. The three- and four-ring PAHs (MW < or = 228) mainly existed in the vapor phase and the five-ring PAHs (MW > 228) existed predominately in the particulate phase. The fraction of vapor PAHs in the total nine PAHs was 84.2% in the air of the sampling sites. In the morning and evening, the concentrations of PAHs in the arterial street air were higher than that on the noon and the diurnal variation of PAHs was similar to that of the traffic gas NOx. A conclusion would be drawn that the major source of PAHs in the arterial street air was the traffic. And the results indicated that 75% of BaP would come from traffic source and remaining 25% of BaP would come from non-traffic source.

Air Pollutants↗
PubMed2001

[Determination of anions in liquid crystal samples by UV-photolysis-ion chromatography].

A new method for the determination of anions in liquid crystal samples by UV-photolysis-ion chromatography was developed. The sample pretreatment method, the photolytic conditions and the chromatographic parameters were optimized. The results indicate that there have five anions (F-, Cl-, NO2-, Br-, I-) in the liquid crystal sample. By the filtration with the Dionex OnGuard RP and P cartridges, most of the organic compounds in the photolyzed sample solution can be removed. In the process of photolysis, the efficiency can be remarkably enhanced by the adding of H2O2. Iodide in the liquid crystal sample can be accurately determined by adding of 0.1 mmol/L NaOH. In the five anions, fluoride, choloride, nitrite and bromide can get their maximal responses when the photolysis time is 2 h. With the strongest reducibility, iodide only needs 1.5 h to get the highest response. The separation of the five anions was accomplished with Dionex IonPac AS16 column and the determination can be completed in 25 min. The recoveries for the five anions were between 85.1% and 111.5%.

English Abstract↗