Biomedical subjects

Y Liu

Publications and source records attributed to Y Liu.

At least 235 records · Page 13Linked to original sources

PubMed2003

Detecting the subregion proceeding to infarction in hypoperfused cerebral tissue: a study with diffusion and perfusion weighted MRI.

Diffusion and perfusion weighted MRI have been widely used in ischaemic stroke. We studied 17 patients in whom ischaemic areas showed an ischaemic core, an area of infarct growth and hypoperfused but ultimately surviving tissue. Apparent diffusion coefficients (ADC) were measured on days 1, 2, and 8 in the three subregions and in contralateral control areas. Cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT) were measured in these regions on day 1 perfusion maps. On day 1, the ischaemic core had very low ADC and CBF and increased MTT. The ADC in the ischaemic core gradually increased during the week. The area of infarct growth on day 1 had slightly but significantly decreased ADC (96% of control, P=0.028), moderately decreased CBF and increased MTT. On day 1 the hypoperfused but surviving tissue had slightly but significantly increased ADC (103% of control, P=0.001), mildly decreased CBF and increased CBV and MTT. The ADC of the area of infarct growth decreased to the same level as in the ischaemic core on days 2 and 8. That of surviving tissue was still above normal on day 2 (103% of control), but had returned to the normal level by day 8. Measurement of ADC combined with perfusion MRI may help distinguish different subregions in acutely hypoperfused brain.

Aged↗

PubMed2003

Quantum phase transition in quasi-one-dimensional BaRu6O12.

We report the first systematic study of the electrical transport and magnetic properties of BaRu6O12, which has a quasi-one-dimensional (quasi-1D) hollandite structure. We show that BaRu6O12 is quasi-1D electronically as well. Its physical properties were found to be extremely sensitive to disorder. Furthermore, a transition from being metallic with a resistance drop around 2 K to being weakly insulating as the applied magnetic field was increased was also found. We propose that these two features are related to the possible presence of a quantum phase transition in this material system.

Journal Article↗

PubMed2003

Sharing of the same embryogenic pathway in anorectal malformations and anterior sacral myelomeningocele formation.

The objective of this study was to determine whether anorectal malformations (ARMs) and anterior sacral myelomeningocele share the same embryogenic pathway in a mouse model. Etretinate (Ro 10-9359) was administrated to C57BL/6 mice on gestation day 9 (E9). Sections of embryos and fetuses from E9.5 to E18 were observed by HE staining. Immunohistochemical staining with anti-NeuN and anti-GFAP was also done to determine cell origins of a presacral mass. In etretinate-treated embryos, neuroepithelial cells proliferated in the presacral region on E9.5. On E12, a canal appeared between the ectopic proliferated neuroepithelium and hindgut. On E13, anorectum abnormally kept a canal with the ventral urogenital tract through a fistula. On E13.5, a huge mass formed in the presacral region. On E18, 76.9% (30/39) of fetuses had ARMs, 100% (39/39) had a presacral mass (71.8% were huge) and 100% (39/39) had a sacral defect. The types of ARMs were mainly rectourethral or rectocloacal fistula. The presacral mass was anterior sacral myelomeningocele. We thus established the first mouse model of the Currarino triad, congenital caudal anomalies, including ARM, sacral abnormality and presacral mass. These disorders share the same embryogenic pathway. The teratogenic target of etretinate is the tail bud. Abnormal differentiation of the tail bud mesenchyme leads to defects of the tailgut and caudal neural tube. The abnormal mass blocks normal descent of the dorsal cloaca through the most posterior part of the cloacal plate.

Anal Canal↗

PubMed2003

Limit on the electron neutrino magnetic moment from the kuo-sheng reactor neutrino experiment.

A search of neutrino magnetic moment was carried out at the Kuo-Sheng Nuclear Power Station at a distance of 28 m from the 2.9 GW reactor core. With a high purity germanium detector of mass 1.06 kg surrounded by scintillating NaI(Tl) and CsI(Tl) crystals as anti-Compton detectors, a detection threshold of 5 keV and a background level of 1 kg(-1) keV(-1) day(-1) at 12-60 keV were achieved. Based on 4712 and 1250 h of reactor ON and OFF data, respectively, the limit on the neutrino magnetic moment of mu(nu;(e))<1.3x10(-10)mu(B) at 90% confidence level was derived. An indirect bound of the nu;(e) radiative lifetime of m(3)(nu)tau(nu)>2.8x10(18) eV(3) s can be inferred.

Journal Article↗

PubMed2003

Elemental compositions and characteristics of aerobic granules cultivated at different substrate N/C ratios.

The effects of the substrate N/C ratios on the formation, elemental compositions and characteristics of aerobic granules were investigated in four sequencing batch reactors. Results showed that aerobic granules could form at substrate N/C ratios ranging from 5/100 to 30/100 and the substrate N/C ratio had a direct and profound effect on the elemental compositions and characteristics of the aerobic granules. Nitrifying populations in aerobic granules were enriched significantly with the increase in the substrate N/C ratio, while the respective ratio of cell oxygen, nitrogen and calcium to cell carbon were also determined by the substrate N/C ratio. It was found that cell hydrophobicity of aerobic granules was inversely related to the ratio of cell oxygen normalized to cell carbon. Since the cell calcium content in aerobic granules developed at different substrate N/C ratios was even lower than that in the seed sludge, it is reasonable to conclude that the cell calcium would not contribute to aerobic granulation. This study probably for the first time demonstrates that the elemental composition, microbial distribution and characteristics of aerobic granules are related to the substrate N/C ratio applied.

Bacteria↗

PubMed2003

Vitamin D target proteins: function and regulation.

Recent findings have indicated that calbindin-D(28k), the first known target of vitamin D action, is present in osteoblasts and protects against TNF and glucocorticoid induced apoptosis of osteoblastic cells. Cytokine mediated destruction of pancreatic beta cells, a cause of insulin dependent diabetes, is also inhibited by calbindin-D(28k). In calbindin-D(28k) transfected pancreatic beta cells free radical formation by cytokines is inhibited by calbindin. Thus, besides its role as a facilitator of calcium diffusion, calbindin has a major role in protecting against cellular degeneration in different cell types. Besides calbindin, the other known pronounced effect of 1,25(OH)(2)D(3) in intestine and kidney is increased synthesis of 25(OH)D(3) 24-hydroxylase (24(OH)ase) which is involved in the catabolism of 1,25(OH)(2)D(3). We have noted that CCAAT enhancer binding protein beta (C/EBPbeta) is induced by 1,25(OH)(2)D(3) in kidney and osteoblastic cells and can enhance the transcriptional response of 24(OH)ase to 1,25(OH)(2)D(3). These studies establish C/EBPbeta as a novel 1,25(OH)(2)D(3) target gene and indicate a role for C/EBPbeta in 24(OH)ase transcription. These studies extend our previous studies related to factors that affect vitamin D receptor (VDR) mediated 24(OH)ase transcription (YY1, TFIIB, CBP) and the effect of signaling pathways on 24(OH)ase transcription and cofactor recruitment.

Animals↗

PubMed2003

Photoreception in Neurospora: a tale of two White Collar proteins.

Neurospora crassa is the best-understood fungal organism in terms of the mechanism of light responses. All known Neurospora photoresponses are mediated by blue light. Two Per-Arnt-Simdomain containing transcription factors, WHITE COLLAR-1 (WC-1) and WC-2, are essential components for almost all light responses. Recently, WC-1was shown to be a blue-light photoreceptor. How light affects the DNA binding of the WC proteins to the promoter of the circadian clock gene frequency was also demonstrated. These studies established a mechanism that explains the light responses mediated by activation of transcription. The purpose of this review is to summarize the findings of recent studies on the molecular mechanism of photoreception in Neurospora.

DNA-Binding Proteins↗

PubMed2003

Models describing nonlinear interactions in graded neuron synapses.

An intracellular recording made from the retinal luminosity horizontal cell (LHC) demonstrated that repetitive red flashes enhanced the cell's responsiveness to red stimulus and depressed its responsiveness to green stimulus and that repetitive green flashes suppressed the cell's red response but produced little change in its green response. Based on the idea that the spectral plasticity of LHCs may reflect some synaptic efficacy changes between the LHC and various cones, a self-organizing system is proposed to investigate the possible manner of information processing and storage within the synapses. The results of model analysis suggest that the stimulus-pattern-related spectral plasticity is attributable to the excitatory interaction within the same kinds of synapses and the inhibitory interaction between different kinds of synapses. This system is able to encode and store the history of signal transmission in a graded and cumulative fashion.

Animals↗

PubMed2003

Changes in glial cell white matter AMPA receptor expression after spinal cord injury and relationship to apoptotic cell death.

Increasing evidence suggests that AMPA receptors (AMPARs) play a key role in mediating excitotoxic cell damage after acute spinal cord injury (SCI). However, the role of glial AMPARs in posttraumatic white matter injury requires further clarification. In the present study we examined the changes in AMPAR expression after SCI, the cellular distribution of these changes, and their association with apoptosis. Western blots revealed expression of GluR1, 3, and 4, but not GluR2, in spinal cord white matter. Immunohistochemistry was used to examine the distribution of AMPARs in spinal cord white matter. Quantification of AMPAR-expressing cells in spinal cord white matter indicated predominantly GluR3 expression in oligodendrocytes and predominantly GluR4 expression in astrocytes. A clip compression model of SCI was used to examine the changes in AMPAR expression in dorsal column white matter after injury. Quantitative analysis of GluR3 levels of expression indicated a significant decrease at 3 days postinjury compared to uninjured animals, followed by a recovery of expression by 2 weeks. GluR4 subunits followed a similar expression pattern. Gene message expression of GluR3 and GluR4 flip/flop mRNA splice variants exhibited a pattern of expression that correlated with protein expression. GluR3-expressing glia appeared to be more susceptible to apoptosis than GluR4-expressing cells. A large decline in GluR3-expressing oligodendrocytes suggests that this subunit may be associated with the induction of apoptosis in white matter glia, thus contributing to secondary injury mechanisms.

Alternative Splicing↗

PubMed2003

Modeling the bifurcating flow in an asymmetric human lung airway.

In a former paper, the inspiratory flow characteristics in a three-generation symmetric bifurcation airway have been numerically investigated using a control volume method to solve the fully three-dimensional laminar Navier-Stokes equations. The present paper extends the work to deal with asymmetric airway extracted from the 5th-11th branches of the model of Weibel (Morphometry of the Human Lung. New York Academic Press, Verlag, 1963) in order to more appropriately model human air passage. Computations are carried out in the Reynolds number range 200-1600, corresponding to mouth-air breathing rates ranging from 0.27 to 2.16l/s, representative for an averaged height man breathing from quiet to vigorous state. Particular attentions are paid to establishing relations between the Reynolds number and the overall flow characteristics, including flow patterns and pressure drop. The study shows that the ratios of airflow rate through the medial branches to that of their mother branches are the same, and this is also true for the ratios of airflow rate through the lateral branches. This partially explains why regular human breathing is not affected by airways of different sizes.

Bronchi↗

PubMed2003

Proteins incorporated into biomimetically prepared calcium phosphate coatings modulate their mechanical strength and dissolution rate.

In a previous investigation, we demonstrated that when bovine serum albumin (BSA) is biomimetically co-precipitated with Ca(2+) and PO(4)(3-) ions upon titanium-alloy implants, it becomes incorporated into the crystal lattice and is not merely deposited on its surface. Moreover, the protein elicited a change in crystal structure from an octacalcium phosphate type to a carbonated apatite one, which bears a closer resemblance to natural bone mineral. In the present study, we investigated the dissolution rate and mechanical strength of such BSA-containing coatings as a function of protein concentration within the bathing medium (10 ng/ml to 1.0 mg/ml). BSA-containing coatings released Ca(2+) ions more slowly (5 ppm/min) than did non-BSA-containing ones (10 ppm/min), but this rate did not change as a function of protein concentration within the bathing medium. In contrast, the strength of coatings increased almost linearly as a function of protein concentration within the bathing medium, indicating that BSA incorporated into the crystal lattice enhances its mechanical strength in a concentration-dependent manner.

Alloys↗

PubMed2003

Nucleus accumbens oxytocin and dopamine interact to regulate pair bond formation in female prairie voles.

Although oxytocin (OT) and dopamine (DA) have been implicated in pair bond formation in monogamous prairie voles (Microtus ochrogaster), the nature of potential interactions between these two neurochemical systems and the brain circuits important for such interactions in the regulation of pair bonding have not been explored. Here, we demonstrated that access to both OT and DA D2-type receptors is necessary for pair bond formation, as blockade of either type of receptor prevented partner preferences induced by OT or a D2-type agonist. We also demonstrated that the nucleus accumbens (NAcc) is a brain area important for such OT-DA interactions. In NAcc, blockade of OT receptors prevented partner preferences induced by a D2-type agonist whereas blockade of D2-type, but not D1-type, DA receptors blocked OT-induced partner preferences. Together, our data suggest that concurrent activation of OT and DA D2-type receptors in NAcc is essential for pair bond formation in female prairie voles.

Animals↗

PubMed2003

Pulsed electromagnetic fields affect phenotype and connexin 43 protein expression in MLO-Y4 osteocyte-like cells and ROS 17/2.8 osteoblast-like cells.

Osteocytes, the predominant cells in bone, are postulated to be responsible for sensing mechanical and electrical stimuli, transducing signals via gap junctions. Osteocytes respond to induced shear by increasing connexin 43 (Cx43) levels, suggesting that they might be sensitive to physical stimuli like low-frequency electromagnetic fields (EMF). Immature osteoblasts exhibit decreased intercellular communication in response to EMF but no change in Cx43. Here, we examined long term effects of pulsed EMF (PEMF) on MLO-Y4 osteocyte-like cells and ROS 17/2.8 osteoblast-like cells. In MLO-Y4 cell cultures, PEMF for 8 h/day for one, two or four days increased alkaline phosphatase activity but had no effect on cell number or osteocalcin. Transforming growth factor beta-1 (TGF-beta 1) and prostaglandin E(2) were increased, and NO(2-) was altered. PEMFs effect on TGF-beta1 was via a prostaglandin-dependent mechanism involving Cox-1 but not Cox-2. In ROS 17/2.8 cells, PEMF for 24, 48 or 72 h did not affect cell number, osteocalcin mRNA or osteocalcin protein. PEMF reduced Cx43 protein in both cells. Longer exposures decreased Cx43 mRNA. This indicates that cells in the osteoblast lineage, including well-differentiated osteoblast-like ROS 17/2.8 cells and terminally differentiated osteocyte-like MLO-Y4 cells, respond to PEMF with changes in local factor production and reduced Cx43, suggesting decreased gap junctional signaling.

Alkaline Phosphatase↗

PubMed2003

Dynamic cerebral autoregulation assessment using an ARX model: comparative study using step response and phase shift analysis.

Middle cerebral arterial blood velocity (MCAv) response to spontaneous and manipulated changes of arterial blood pressure (ABP) was studied in eight subjects using a linear autoregressive with exogenous input (ARX) model. ABP and MCAv were measured non-invasively by photoplethysmograph and transcranial Doppler ultrasound, respectively. Data were recorded at rest (spontaneous changes in ABP) and during thigh cuff (step-wise changes) and lower body negative pressure (sinusoidal changes of 1/12 Hz) tests in both normocapnia and hypercapnia (5% CO2). Since autoregulation is modulated by CO2, respiratory CO2 was simultaneously monitored to allow comparison of cerebral autoregulation status with different CO2 levels. ABP and MCAv were fitted by ARX models and dynamic cerebral autoregulation was estimated by analysing both the step responses and phase shift at the 1/12 Hz of the corresponding ARX models. The ARX model consistently modelled the phase lead of MCAv to ABP and it showed that the phase shift at 1/12 Hz of ARX model is consistent with the real phase shift of the data (p=0.59). Strong linear relationships between pCO2 and gradient of the step response (r=-0.58, p<0.0001) and between pCO2 and phase shift (r=-0.76, p<0.0001) were observed, which suggests that cerebral autoregulation can be assessed by step response or phase shift analysis of the ARX model fitted to ABP and MCAv data with spontaneous changes.

Adaptation, Physiological↗

PubMed2003

HLA-DRB1, DQB1 and DPB1 polymorphism in the Naxi ethnic group of South-western China.

Polymorphism of HLA-DRB1, DQB1 and DPB1 was revealed with a sequencing-based typing (SBT) method in unrelated healthy volunteers from the Naxi ethnic group. Among the 43 DRB1 alleles detected, the most common allele was DRB1*12021 with a frequency of 17%, followed by DRB1*08032, DRB1*09012 and DRB1*1404 with frequencies of 8.5%, 7.4% and 7.4%, respectively. Among 23 DQB1 alleles detected, the most frequent DQB1 allele was DQB1*03011/0309 (21.9%), followed by DQB1*0502 (16.4%) and DQB1*05031 (9.6%). For the DPB1 locus, the most common alleles were DPB1*0501 (25.5%), DPB1*0402 (14.6%) and DPB1*02012 (12.0%). The most common DRB1-DQB1-DPB1 haplotype was DRB1*1404-DQB1*05031-DPB1*0402 with a frequency of 5.26%, followed by the DRB1*08032-DQB1*06011-DPB1*1301 (3.51%). The distribution characteristics of the HLA class II alleles revealed that the Naxi ethnic group belonged to the Southern group of Chinese.

Alleles↗

PubMed2003

230-kDa and 190-kDa proteins in addition to desmoglein 1 as immunological targets in a subset of pemphigus foliaceus with a combined cell-surface and basement membrane zone immune staining pattern.

Pemphigus erythematosus, initially described as a combination of pemphigus with lupus erythematosus, and pemphigus foliaceus are now frequently considered localized and generalized variants of superficial pemphigus. Yet diagnostic criteria for pemphigus erythematosus remain controversial. Distinct from pemphigus foliaceus, pemphigus erythematosus displays immune depositions at the dermal-epidermal junction, which suggests additional immunopathological mechanisms. We present three patients with clinical and histopathologic signs of superficial pemphigus, who all exhibited an immunomorphology characteristic of pemphigus erythematosus. Complement depositions in a granular-linear fashion were consistently found at the dermal-epidermal junction besides in vivo bound and circulating antikeratinocyte cell-surface autoantibodies. Histopathology showed subcorneal acantholysis, and all sera contained antidesmoglein 1 but not antidesmoglein 3 autoantibodies detected by enzyme-linked immunosorbent assays (ELISA). Additional autoantibodies against a 230-kDa protein and against a 190-kDa protein comigrating with bullous pemphigoid antigen 1 (BP230) and periplakin, respectively, were present in all the patients' sera. As two sera specifically reacted with BP230 by ELISA, the presence of BP230-specific autoantibodies could be associated with dermal-epidermal immune staining in these patients. In pemphigus erythematosus, dermal-epidermal immune staining is generally attributed to the deposition of immune complexes, while the presence of BP230-specific autoantibodies has not been reported in this disease previously. Perhaps, the unique autoantibody profile of the patients in the study permits discrimination between patients with superficial pemphigus that display additional dermal-epidermal immune staining from those with conventional pemphigus foliaceus on a molecular basis. Further studies will be required to substantiate the frequency of this occurrence and to unravel its pathogenic significance.

Adult↗

PubMed2003

Pharmacokinetics and QT interval pharmacodynamics of oral haloperidol in poor and extensive metabolizers of CYP2D6.

We studied the pharmacokinetics and QT interval pharmacodynamics of a single 10 mg dose of oral haloperidol in a randomized, double-blind, placebo-controlled, crossover trial of healthy poor (PMs) and extensive (EMs) metabolizers of CYP2D6. There was a statistically significant greater mean QT(c) on haloperidol (421.6+/-20.1 ms) than on placebo (408.4+/-18.5 ms, P=0.0053) occurring 10 h post haloperidol/placebo administration. Men and women had similar ranges of QT(c) changes from placebo. Despite a statistically significant greater mean elimination half-life (19.1+/-3.6 vs 12.9+/-4.0 h, P=0.04) and lower mean apparent oral clearance (12.8+/-4.1 vs 27.0+/-11.3 ml/min/kg, P=0.02) of haloperidol in CYP2D6 PMs than in EMs, this exposure change did not translate into marked QT(c) changes from baseline that could be considered clinically important. Although the magnitude of the mean QT(c) prolongation on haloperidol relative to placebo is relatively small, it may assume significance in the presence of other risk factors for QT prolongation.

Adult↗

PubMed2003

HIV-1 infection is facilitated in T cells by decreasing p56lck protein tyrosine kinase activity.

Several studies have suggested an important role for the protein tyrosine kinase p56lck (Lck) in HIV infection; however, the exact nature of this role remains unclear. Using a series of well characterized Jurkat-derived cell lines having a wide range of Lck kinase activity, our results showed that, while the entry of HIV-1 into these cell lines was similar, the kinetics of virus production by these cells were very different. Cells expressing a kinase-inactive Lck showed accelerated viral replication, whereas, cells expressing Lck with normal or elevated enzymatic activity showed a delay in virus replication that was proportional to the initial level of endogenous Lck activity. The cell line having the highest initial Lck kinase activity showed the slowest rate of productive HIV-1 infection. Analysis of 2-LTR circles revealed that this inhibitory effect of Lck was not due to inhibition of reverse transcription of HIV-1 genome or migration of the proviral DNA into the nuclei. This affect of Lck was confirmed in additional studies that used either the S1T cell line lacking completely Lck or where the Lck activity was altered in Jurkat cells prior to infection. S1T cells showed a 3- to 12-fold increase in the level of infection compared to Jurkat cells despite similar CD4 and chemokine coreceptor expression and cell doubling times. Pretreatment of Jurkat with an antisense lck oligodeoxynucleotide inhibited the synthesis of functional Lck and facilitated the viral replication by the cells as did expressing a dominant-negative mutant Lck which increased the productive infection>3-fold. Conversely, whereas IL-16 had no affect on productive infection in S1T cells that lack Lck, IL-16 pretreatment of Jurkat cells resulted in an immediate (within 5 min) and sustained and gradual (over 5 h) increase in Lck activity that resulted in a reduction of HIV-1 replication that paralleled the increasing Lck kinase activity. These results show that the enzymatic activity of Lck kinase can affect viral replication, that a lack of, or decreased Lck activity facilitates viral replication. Conversely, Lck can mediate a delay in HIV-1 infection that is proportional to the initial endogenous Lck enzyme activity.

CD4 Antigens↗