Biomedical subjects

Ying Zhang

Publications and source records attributed to Ying Zhang.

At least 109 records · Page 6Linked to original sources

PubMed2006

Dynamic interactions of cortactin and membrane type 1 matrix metalloproteinase at invadopodia: defining the stages of invadopodia formation and function.

Metastatic tumor cells that actively migrate and invade surrounding tissues rely on invadopodia to degrade extracellular matrix (ECM) barriers. Invadopodia are membrane protrusions that localize enzymes required for ECM degradation. Little is known about the formation, function, and regulation of invadopodia. Here, we show that invadopodia have two distinct aspects: (a) structural for organizing the cellular actin cytoskeleton to form membrane protrusions and (b) functional for using proteolytic enzyme(s) for ECM degradation. Small interfering RNA (siRNA) inhibition established that organization of invadopodia structure requires cortactin, whereas protease inhibitor studies identified membrane type 1 matrix metalloproteinase (MT1-MMP) as the key invadopodial enzyme responsible for gelatin matrix degradation in the breast carcinoma cell line MDA-MB-231. The inhibition of invadopodial structure assembly by cortactin depletion resulted in a block of matrix degradation due to failure of invadopodia formation. Either protease inhibition or MT1-MMP siRNA depletion moderately decreased the formation of invadopodial structures that were identified as actin-cortactin accumulations at the ventral cell membrane adherent to matrix. The invadopodia that were able to form upon MT1-MMP inhibition or depletion retained actin-cortactin accumulations but were unable to degrade matrix. Examination of cells at different time points as well as live-cell imaging revealed four distinct invadopodial stages: membrane cortactin aggregation at membranes adherent to matrix, MT1-MMP accumulation at the region of cortactin accumulation, matrix degradation at the invadopodia region, and subsequent cortactin dissociation from the area of continued MT1-MMP accumulation associated with foci of degraded matrix. Based on these results, we propose a stepwise model of invadopodia formation and function.

Actins↗

PubMed2006

Differential adhesion of microspheres mediated by DNA hybridization I: experiment.

We have developed a novel method to study collective behavior of multiple hybridized DNA chains by measuring the adhesion of DNA-coated micron-scale beads under hydrodynamic flow. Beads coated with single-stranded DNA probes are linked to surfaces coated with single target strands through DNA hybridization, and hydrodynamic shear forces are used to discriminate between strongly and weakly bound beads. The adhesiveness of microspheres depends on the strength of interaction between DNA chains on the bead and substrate surfaces, which is a function of the degree of DNA chain overlap, the fidelity of the match between hybridizing pairs, and other factors that affect the hybridization energy, such as the salt concentration in the hybridization buffer. The force for bead detachment is linearly proportional to the degree of chain overlap. There is a detectable drop in adhesion strength when there is a single base mismatch in one of the hybridizing chains. The effect of single nucleotide mismatch was tested with two different strand chemistries, with mutations placed at several different locations. All mutations were detectable, but there was no comprehensive rule relating the drop in adhesive strength to the location of the defect. Since adhesiveness can be coupled to the strength of overlap, the method holds promise to be a novel methodology for oligonucleotide detection.

Adhesiveness↗

PubMed2006

The role of NBS1 in the modulation of PIKK family proteins ATM and ATR in the cellular response to DNA damage.

Ataxia telangiectasia mutated (ATM) and ataxia telangiectasia and Rad3-related (ATR) kinases have been considered the primary activators of the cellular response to DNA damage. They belong to the protein kinase family, phosphoinositide 3-kinase-related kinase (PIKKs). In human beings, deficiency of these kinases leads to hereditary diseases, namely ataxia telangiectasia (AT) with ATM deficiency and ATR-Seckel with ATR deficiency. NBS1, a component of MRE11/RAD50/NBS1 (MRN) complex, is another important player in DNA damage response (DDR). Mutations of NBS1 are responsible for Nijmegen breakage syndrome (NBS), a human hereditary disease with the characteristics that almost encompassed those of AT and ATR-Seckel. NBS1 has been conventionally thought to be a downstream substrate of ATM and ATR in DDR; however, recent studies suggest that NBS1/MRN functions upstream of both ATM and ATR by recruiting them to the proximity of DNA damage sites and activating their functions. In this mini-review, we would emphasize the requirement of NBS1 as an upstream mediator for the modulation of PIKK family proteins ATM and ATR.

Animals↗

PubMed2006

Morphine promotes Jurkat cell apoptosis through pro-apoptotic FADD/P53 and anti-apoptotic PI3K/Akt/NF-kappaB pathways.

Opiates have been shown to inhibit cell growth and trigger apoptosis, but the underlying molecular mechanisms remain unclear. We have previously shown that morphine induces Fas expression and promotes Fas-mediated apoptosis. Here, we investigated the mechanisms by which morphine modulates apoptosis in human Jurkat cells. Morphine-induced apoptosis was inhibited by transfection with a dominant negative Fas-associated death domain (FADD) plasmid, revealing that morphine-induced apoptosis is dependent on FADD. Furthermore, suppression of endogenous p53 expression by RNA interference technology considerably attenuated the morphine-induced apoptosis. In addition, morphine-induced apoptosis seems to be dependent on the activation of phosphatidylinositol 3-kinase (PI3K), as PI3K inhibition by the PI3K inhibitor LY294002 significantly enhanced morphine-induced apoptosis. Moreover, inhibition of Akt or nuclear factor-kappaB (NF-kappaB) expression by RNA interference technology also dramatically increased morphine-induced apoptosis. Our study thus demonstrates that morphine induces Jurkat cell apoptosis through FADD/p53, anti-apoptotic PI3K/Akt and NF-kappaB pathways.

Analysis of Variance↗

PubMed2006

V1 spinal neurons regulate the speed of vertebrate locomotor outputs.

The neuronal networks that generate vertebrate movements such as walking and swimming are embedded in the spinal cord. These networks, which are referred to as central pattern generators (CPGs), are ideal systems for determining how ensembles of neurons generate simple behavioural outputs. In spite of efforts to address the organization of the locomotor CPG in walking animals, little is known about the identity and function of the spinal interneuron cell types that contribute to these locomotor networks. Here we use four complementary genetic approaches to directly address the function of mouse V1 neurons, a class of local circuit inhibitory interneurons that selectively express the transcription factor Engrailed1. Our results show that V1 neurons shape motor outputs during locomotion and are required for generating 'fast' motor bursting. These findings outline an important role for inhibition in regulating the frequency of the locomotor CPG rhythm, and also suggest that V1 neurons may have an evolutionarily conserved role in controlling the speed of vertebrate locomotor movements.

Action Potentials↗

PubMed2006

NAD(P)H oxidase in paraventricular nucleus contributes to the effect of angiotensin II on cardiac sympathetic afferent reflex.

We previously reported that reactive oxygen species (ROS) in paraventricular nucleus (PVN) modulated cardiac sympathetic afferent reflex (CSAR) and mediated the effect of angiotensin II (Ang II) in the PVN on the CSAR. In the present study, we investigated whether the NAD(P)H oxidase in the PVN was a key source of ROS which modulated the CSAR and contributed to the effect of Ang II on the CSAR. In anesthetized rats with sinoaortic denervation and vagotomy, renal sympathetic nerve activity (RSNA) and arterial pressure were recorded. The CSAR was evaluated by the RSNA response to epicardial application of bradykinin (BK). The NAD(P)H oxidase activity in the PVN was measured with lucigenin-enhanced chemiluminescent method. Microinjection of the NAD(P)H oxidase inhibitor, either apocynin (1.0 nmol) or phenylarsine oxide (PAO, 1.0 nmol), into the PVN significantly inhibited the CSAR. Microinjection of Ang II (0.3 nmol) into the PVN significantly augmented the CSAR. The effects of Ang II were not only abolished by pretreatment with either apocynin or PAO in the PVN but also partially inhibited by xanthine oxidase inhibitor allopurinol. Either epicardial application of BK or microinjection of Ang II into the PVN significantly increased NAD(P)H oxidase activity in the PVN. The effect of Ang II on NAD(P)H oxidase activity was abolished by pretreatment with AT(1) receptor antagonist losartan in the PVN. These findings suggested that NAD(P)H oxidase in the PVN was a major source of the ROS in modulating the CSAR, and the NAD(P)H oxidase contributes to the effect of Ang II on the CSAR.

Afferent Pathways↗

PubMed2006

Amperometric immunosensor based on toluidine blue/nano-Au through electrostatic interaction for determination of carcinoembryonic antigen.

A new current amplified immunosensor for the determination of carcinoembryonic antigen (CEA) was demonstrated in this work. The electrode architecture was fabricated by positively charged toluidine blue (TB) coated on negatively charged poly-sulfanilic acid (PSAA) modified glassy carbon electrode (GCE) surface through electrostatic interactions to form a TB/PSAA film, which provided an interface containing amine groups to assemble gold nanoparticles (nano-Au) for immobilization of carcinoembryonic antibody (anti-CEA) and horseradish peroxidase (HRP) instead of bovine serum albumin (BSA) to block sites against non-specific binding. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were employed to characterize the electrochemical properties of the modified processes. The CVs reduction current of the immunosensor charged linearly in two concentration ranges of CEA from 0.5 to 5.0 and 5.0 to 120.0 ng/ml in presence of 0.3mM H2O2 in analyte solution, and the detection limit was 0.2 ng/ml at three times background noise. The proposed method is economical, efficient and potentially attractive for clinical immunoassays.

Biosensing Techniques↗

PubMed2006

[A novel plasmid-mediated aminoglycosides-modifying enzyme gene, aph (2'')-Ie, in a strain of high-level gentamicin resistant Enterococcus casseliflavus].

OBJECTIVE: To identify the aminoglycoside resistance gene in the high-level gentamicin resistant (HLGR) enterococcus and its transmission mechanism. METHODS: A HLGR strain, HZ95, of Enterococcus casseliflavus was screened by agar dilution method. The aminoglycoside activation enzyme genes were screened by PCR. The PCR products underwent purification, cloned, and sequenced. Plasmids were extracted and underwent Southern hybridization. Plasmid-mediated aminoglycoside modifying enzymes were cloned. The resistance of the HZ05 strain to different antimicrobial agents was determined by K-B method or agar dilution method. RESULTS: A new aminoglycosides-modifying enzyme, APH (2'')-Ie, leading to HLGR, was found in the plasmid of the HZ95 bacteria. The aph (2'')-Ie gene and partial sequence of a streptomycin adenylyltransferase gene (str) were contained in the 8.7-kb cloned fragment, and the transposase gene (tnpA) was on the upper stream. The aph (2'')-Ie gene was located on the 16-kb plasmid with the amino acid sequence 96.1% homologous with chromosome-mediated APH (2'')-Id aminoglycoside-modifying enzyme. CONCLUSION: HLGR can be caused by a new plasmid-mediated aminoglycosides-modifying enzyme, APH (2'')-Ie, which can be transmitted among plasmids or chromosome with other resistant genes through transposase.

Anti-Bacterial Agents↗

PubMed2006

Self-consistent fluid variational theory for the dissociation of dense nitrogen.

The self-consistent fluid variational theory is used to calculate the pressure dissociation of dense nitrogen at high temperatures. The accurate high-pressure and high-temperature effective pair potentials are adopted to describe the intermolecular interactions, which are made to consider molecular dissociation. This paper focuses on a mixture of nitrogen atoms and molecules and is devoted to the study of the phenomenon of pressure dissociation at finite temperature. The equation of state and dissociation degree are calculated from the free-energy functions in the range of temperature of 2000-15 000 K and density of 0.2-3.0 gcm(3), which can be compared with other approaches and experiments.

Journal Article↗

PubMed2006

Pharmacokinetics, pharmacodynamics and safety of once-daily versus twice-daily dosing with enfuvirtide in HIV-infected subjects.

OBJECTIVE: To investigate the pharmacokinetics, safety/tolerability and antiviral activity of enfuvirtide administered once-daily (QD) versus twice-daily (BID). DESIGN: An open-label, randomized, multiple dose, two-period crossover study comparing 180 mg enfuvirtide, two injections QD versus 90 mg enfuvirtide, two injections, BID. METHODS: Steady-state intensive pharmacokinetic samples were obtained on days 7 and 14. RESULTS: Thirty-seven subjects received at least one dose of enfuvirtide. Thirty-three subjects completed both dosing periods. The regimens were bioequivalent based on the ratio of geometric mean area under the curve (AUC)0-tau [112 +/- 6.2 microg x h/ml QD; 115 +/- 6.4 microg x h/ml 2 x BID; QD/BID 0.98; 90% confidence interval (CI) 0.89,1.07]. The maximum observed plasma concentration within a dosing interval (Cmax) was 49% higher for QD (9.5 +/- 2.7 microg/ml) versus BID (6.3 +/- 1.7 microg/ml) and the pre-dose plasma concentration (Ctrough) was 57% lower for QD (1.6 +/- 1.1 microg/ml) versus BID (3.8 +/- 1.3 microg/ml). The LSM decrease in viral load from baseline to day 7 was 1.0 +/- 0.14 log10 (n = 18) for QD and 1.4 +/- 0.2 log10 (n = 17) for BID (LSM difference 0.385; P = 0.07). Linear regression analysis suggested that decline in viral load up to day 7 was associated with Ctrough but not Cmax or AUC. There were no significant differences in adverse events between the two dosing regimens. CONCLUSIONS: Administration of enfuvirtide 180 mg QD results in bioequivalence compared with 90 mg BID based on AUC with a similar short-term safety profile, but a trend towards a weaker antiretroviral effect. Larger and longer-term studies are needed to determine if 180 mg once daily is an effective dosing alternative for enfuvirtide.

Adult↗

PubMed2006

Cryo-EM reconstruction of dengue virus in complex with the carbohydrate recognition domain of DC-SIGN.

Dengue virus (DENV) is a significant human pathogen that causes millions of infections and results in about 24,000 deaths each year. Dendritic cell-specific ICAM3 grabbing nonintegrin (DC-SIGN), abundant in immature dendritic cells, was previously reported as being an ancillary receptor interacting with the surface of DENV. The structure of DENV in complex with the carbohydrate recognition domain (CRD) of DC-SIGN was determined by cryo-electron microscopy at 25 A resolution. One CRD monomer was found to bind to two glycosylation sites at Asn67 of two neighboring glycoproteins in each icosahedral asymmetric unit, leaving the third Asn67 residue vacant. The vacancy at the third Asn67 site is a result of the nonequivalence of the glycoprotein environments, leaving space for the primary receptor binding to domain III of E. The use of carbohydrate moieties for receptor binding sites suggests a mechanism for avoiding immune surveillance.

Binding Sites↗

PubMed2006

Interruption of pacemaker signals by a diencephalic nucleus in the African electric fish, Gymnarchus niloticus.

The African electric fish Gymnarchus niloticus rhythmically emits electric organ discharges (EODs) for communication and navigation. The EODs are generated by the electric organ in the tail in response to the command signals from the medullary pacemaker complex, which consists of a pacemaker nucleus (PN), two lateral relay nuclei (LRN) and a medial relay nucleus (MRN). The premotor structure and its modulatory influences on the pacemaker complex have been investigated in this paper. A bilateral prepacemaker nucleus (PPn) was found in the area of the dorsal posterior nucleus (DP) of the thalamus by retrograde labeling from the PN. No retrogradely labeled neurons outside the pacemaker complex were found after tracer injection into the LRN or MRN. Accordingly, anterogradely labeled terminal fibers from PPn neurons were found only in the PN. Iontophoresis of L-glutamate into the region of the PPn induced EOD interruptions. Despite the exclusive projection of the PPn neurons to the PN, extracellular and intracellular recordings showed that PN neurons continue their firing while MRN neurons ceased their firing during EOD interruption. This mode of EOD interruption differs from those found in any other weakly electric fishes in which EOD cessation mechanisms have been known.

Action Potentials↗

PubMed2006

Prehypertension, diabetes, and cardiovascular disease risk in a population-based sample: the Strong Heart Study.

There are few data about the impact of the recently-defined category of prehypertension (systolic blood pressure 120 to 139 mm Hg or diastolic blood pressure 80 to 89 mm Hg) on cardiovascular disease incidence. It is also unknown whether this association differs between individuals with or without diabetes. A total of 2629 Strong Heart Study participants free from hypertension and cardiovascular disease at baseline examination were followed for 12 years to observe incident cardiovascular disease. Approximately 42% of the 2629 participants had diabetes. We assessed the prevalence of prehypertension and the hazard ratios of incident cardiovascular disease associated with prehypertension. Prehypertension was more prevalent in diabetic than nondiabetic participants (59.4% versus 48.2%, P<0.001 adjusted for age). Compared with nondiabetic participants with normal blood pressure, the hazard ratios of cardiovascular disease were 3.70 (95% confidence interval: 2.66, 5.15) for those with both prehypertension and diabetes, 1.80 (1.28, 2.54) for those with prehypertension alone and 2.90 (2.03, 4.16) for those with diabetes alone. Impaired glucose tolerance or impaired fasting glucose also greatly increased the cardiovascular disease risk in prehypertensive people. Clinical investigation of more aggressive interventions, such as drug treatment for blood pressure control for prehypertensive individuals with impaired fasting glucose, impaired glucose tolerance, or diabetes is warranted.

Aged↗

PubMed2006

Binding capacity of in vitro deglycosylated IgA1 to human mesangial cells.

IgA nephropathy (IgAN) is the most common glomerular disease and it is characterized by deposition of IgA1 molecules in mesangium. Recent studies had demonstrated that serum and mesangial IgA1 in IgAN were deglycosylated and IgA1 could bind to human mesangial cells (HMC) through a novel receptor. The aim of the current study is to investigate and compare the binding capacities of different in vitro deglycosylated IgA1 on human mesangial cells. Serum IgA1 was purified by jacalin affinity chromatography and then was desialylated (DesIgA1) and/or degalactosylated (Des/DeGalIgA1) with neuraminidase and/or beta-galactosidase. The efficacy of deglycosylations was assessed by Peanut agglutinin (PNA) and Vicia villosa (VV) lectin. The sizes of normal IgA1 and deglycosylated IgA1 were determined by Sephacryl S-300 chromatography and binding capacities to primary HMC were evaluated by radioligand binding assays. Normal IgA1 and deglycosylated IgA1 could bind to HMC in a dose-dependent, saturable manner. The maximal binding capacities and binding sites/cell of DesIgA1 and Des/DeGalIgA were significantly higher than that of normal IgA1. However, more aggregated IgA1 was found in DesIgA1 and Des/DeGalIgA1. Scatchard analysis revealed a similar Kd of normal IgA1 and deglycosylated IgA1. The current study suggested that the binding capacities of DesIgA1 and Des/DeGalIgA1 to HMC were significantly higher than that of normal IgA1, which at least in part was due to more macromolecular IgA1 in deglycoslated IgA1. However, there were no significant differences in the affinities of normal IgA1, DesIgA1 and Des/DeGalIgA1 with HMC. Deglycosylated IgA1 might play an important role in pathogenesis of IgAN.

Glomerulonephritis, IGA↗

PubMed2006

Inducible activation of CEBPB, a gene negatively regulated by BCR/ABL, inhibits proliferation and promotes differentiation of BCR/ABL-expressing cells.

Translational regulation by oncogenic proteins may be a rapid and efficient mechanism to modulate gene expression. We report here the identification of the CEBPB gene as a target of translational regulation in myeloid precursor cells transformed by the BCR/ABL oncogene. Expression of CEBPB was repressed in 32D-BCR/ABL cells and reinduced by imatinib (STI571) via a mechanism that appears to depend on expression of the CUG-repeat RNA-binding protein CUGBP1 and the integrity of the CUG-rich intercistronic region of c/ebpbeta mRNA. Constitutive expression or conditional activation of wild-type CEBPB induced differentiation and inhibited proliferation of 32D-BCR/ABL cells in vitro and in mice, but a DNA binding-deficient CEBPB mutant had no effect. The proliferation-inhibitory effect of CEBPB was, in part, mediated by the CEBPB-induced GADD45A gene. Because expression of CEBPB (and CEBPA) is low in the blast crisis (BC) stage of chronic myelogenous leukemia (CML) and is inversely correlated with BCR/ABL tyrosine kinase levels, these findings point to the therapeutic potential of restoring C/EBP activity in CML-BC and, perhaps, other types of acute leukemia.

Bone Marrow Cells↗

PubMed2006

Isolation and in vitro characterization of pancreatic progenitor cells from the islets of diabetic monkey models.

Recent studies on the identification of stem/progenitor cells within adult mouse and human pancreatic islets have raised the possibility that autologous transplantation might be used in treating type 1 diabetes. However, it is not yet known whether such stem/progenitor cells are impaired in type 1 diabetic patients or diabetic animal models. The latter would also allow us to test the efficacy of autologous transplantation in large animal models prior to clinical applications. The present study aims to determine the existence of stem/progenitor cells in the islets of diabetic monkey models and to assess the proliferation and differentiation potential of such cells in vitro. Our results indicate that there are pancreatic progenitor cells in the adult pancreatic islets in both normal and type 1 diabetic monkeys. The isolated pancreatic progenitor cells can be greatly expanded in culture. Upon the removal of growth medium, these cells spontaneously form islet-like cell clusters, which could be further induced to secrete insulin by inductive factors. Furthermore, the secretion of insulin and C-peptide from the islet-like cell clusters responds to glucose and other stimuli, indicating that the differentiated cells not only resemble beta-cells but also possess the unique biological function of beta-cells. This study provides a foundation for further characterization of adult pancreatic progenitor cells and autologous transplantation using pancreatic progenitor cells in treating diabetic monkeys.

Animals↗

PubMed2006

Characterization of truncated hantavirus nucleocapsid proteins and their application for serotyping.

Hemorrhagic fever with renal syndrome (HFRS) is a fulminant infectious disease characterized by fever, hemorrhage, renal impairment, and thrombocytopenia. Hantaviruses associated with this belong to different serotypes: Hantaan (HTN), Seoul (SEO), Dobrava/Belgrade (DOB), and Puumala (PUU). The first two, HTN and SEO, are endemic in China. To investigate the epidemiology of HFRS and virus transmission in China, we constructed prokaryotic plasmids encoding truncated recombinant HTN and SEO nucleocapsid proteins (NPs), which lacked 154 amino acid (aa), 99 aa, or 49 aa in the N-terminal region, respectively. After expression, the truncated rNPs were tested as serotyping antigens, particularly for use in the enzyme-linked immunosorbent assay (ELISA). In addition, 68 acute and 52 convalescent sera were collected from HFRS patients from Harbin, Lantian, and Kaifeng regions in China in 2004, which had hantavirus specific antibodies by IFA. A neutralization test was used to differentiate these, which showed that 73 were due to HTN infection, 33 to SEO infection, and 14 undetermined. By ELISA, the truncated rNPs, that lacked 99 (rNP100) or 49 (rNP50) N-terminal amino acids of the NPs of HTN and SEO, were able to differentiate HTNV and SEOV-specific immune sera, but the rNP155 could not. Particularly, the ELISAs based on the rNP50s had a result comparable to PRNT. Thus, the rNP50 is recommended as efficient serotyping antigen for hantavirus infection diagnosis by ELISA.

Animals↗

PubMed2006

Anti-fatigue activity of a triterpenoid-rich extract from Chinese bamboo shavings (Caulis bamfusae in taeniam).

The anti-fatigue activity of a pentacyclic triterpenoid extract from bamboo shavings (EBS) from the bark of bamboo (Bambusa tuldoides Munro), was evaluated in BALB/c mice. EBS, isolated by the supercritical CO(2) fluid extraction (SFE) technique, was given to mice at concentrations of 0.04 (low-dose group), 0.08 (middle-dose group) and 0.25 g/kg body weight (high-dose group). The anti-fatigue activity of EBS was estimated by the change in body weight, weight-loaded swimming test and climbing test, and corresponding parameters including serum urea nitrogen, hepatic glycogen and blood lactic acid were measured. The results showed that an appropriate level of EBS could prolong the weight-loaded swimming and climbing time, and had an active effect on the serum urea nitrogen, hepatic glycogen and blood lactic acid level in BALB/c mice, which significantly embodied the anti-fatigue activity of EBS. Overall, it is predicted that EBS, being a composition mainly containing a group of pentacyclic triterpenoids, and its main triterpenoid components have great potential for application in relevant fields for its anti-fatigue activity.

Animals↗