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Biomedical subjects

Zhi Zheng

Publications and source records attributed to Zhi Zheng.

At least 19 recordsLinked to original sources
PubMed2026

Toxoplasma gondii infection disrupts secondary bile acid transformation in feline gut microbiota.

UNLABELLED: Bile acid (BA) transformation relies on gut microbiota and is vulnerable to Toxoplasma gondii infection, yet feline microbial BA-transforming capacity upon toxoplasmosis remains unclear. Here, we constructed a catalog of 2,474 nonredundant feline gut microbial genomes and integrated serum metabolomic data to verify BA transformation alterations. The results revealed that the feline gut microbiome harbored widespread genetic potential for BA transformation but lacked a complete 7α-dehydroxylation pathway due to the absence of the key gene baiE. The BA transformation-related genomes (2,045 in total) were predominantly from the phyla Bacillota_A and Actinomycetota, among which only 37 encoded baiB, all belonging to Bacillota_A. The distribution of BA transformation-related genes varied across intestinal regions: genes encoding 7α-HSDH were primarily enriched in the small intestine, whereas genes encoding 3α-HSDH, baiCD, and baiH were more abundant in the large intestine. Additionally, the abundance of genes encoding BSH and 3α-HSDH increased significantly in the small intestine on day 3 post-infection, accompanied by increases in the phylum Bacillota_C and genera such as Blautia_A, Enterococcus_E, and Ligilactobacillus. Serum metabolomics revealed a significant increase in cholesterol levels post-infection, supporting the impact of T. gondii infection on intestinal BA transformation. These findings illustrated that the feline gut microbiota played an important role in BA transformation and that T. gondii infection disrupted the microbial potential for secondary BA transformation. This study provided new insights into gut microbiota-associated metabolic perturbations during feline toxoplasmosis. IMPORTANCE: Bile acid (BA) transformation plays a critical role in host metabolism and immune regulation. Although studies on BA transformation are increasing, the capacity for BA transformation within the feline gut microbiota and the impact of Toxoplasma gondii infection on this capacity remain unclear. To bridge this gap, we constructed a catalog of 2,474 nonredundant feline gut microbial genomes and integrated serum metabolomic data to verify BA transformation alterations. Our findings revealed that the feline gut microbiome lacked a complete 7α-dehydroxylation pathway, and the specific functions involved in BA transformation may differ between the small and large intestines. Furthermore, integrated metagenomic and serum metabolomic analyses suggested that T. gondii infection disrupted BA transformation capacity in the small intestine. This study provided new insights into gut microbiota-associated metabolic perturbations during feline toxoplasmosis.

Toxoplasma gondii↗
PubMed2007

Unusual kinematics-driven chemistry: cleaving C-H but not COO-H bonds with hyperthermal protons to synthesize tailor-made molecular films.

Unconventional reaction-design strategies have been developed to exploit the intriguing kinematics that occur when adsorbed organic molecules are bombarded by a beam of hyperthermal protons: kinematic energy transfer is only effective in H-->H collisions and thus only C-H bonds are cleaved. This process yields a cross-linked molecular film with its chemistry governed by the selection of appropriate precursor molecules. Unlike the conventional wet-chemistry synthesis of cross-linked polymeric films, this new route uses no chemical initiators, additives, nor catalysts, and only requires a proton beam with a kinetic energy of a few electron volts in a dry-process mode compatible with molecular-device fabrication. The reaction designs are expressed unconventionally: reaction energy is tuned by the kinetic energy of the proton beam and reactant supply is controlled precisely by the proton fluence. However, conventional considerations such as bond-strength effects on kinematic outcomes and branching-ratio statistics are also important and they can extend the reaction applicability of the kinematics concept. For example, taking advantage of the fact that COO-H bonds are stronger than C-H bonds, we show, with practical reaction conditions, synthesis results, and surface analysis using X-ray photoelectron spectroscopy and atomic force microscopy, that we can break C-H bonds without breaking COO-H and other bonds, in the production of cross-linked molecular layers with any desirable COOH concentration and with no ester nor other chemical contaminations. The new reaction-design strategies are also applicable to the synthesis of molecular layers with other functionalities such as OH, and to the synthesis of a mixture of functionalities, such as OH/COOH, with a controllable concentration ratio.

Biomechanical Phenomena↗
PubMed2006

Core-shell microspherical Ti(1-x)Zr(x)O2 solid solution photocatalysts directly from ultrasonic spray pyrolysis.

A series of Ti(1-x)Zr(x)O(2) solid solutions photocatalysts (x = 0.000, 0.045, 0.090, 0.135, and 0.180) was directly obtained by an ultrasonic spray pyrolysis method. Compared with previous methods for solid solutions, our preparation was very fast. The resulting samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, nitrogen adsorption, and UV-vis diffuse reflectance spectroscopy. The characterizations revealed core-shell spherical structures of the resulting solid solutions. We evaluated photocatalytic activities of the solid solutions on degradation of rhodamine B in aqueous solution under simulated solar light. It was found that Ti(0.91)Zr(0.09)O(2) solid solution exhibited the highest photocatalytic activity among all the as-prepared samples. Its activity was much higher than that of P25. The formation mechanism of core-shell spherical structures was proposed. Moreover, we successfully extended this method to prepare microspheres of ceria and ceria-zirconia solid solutions. We think this general method may be easily scaled up for industrial production of microspherical solid solutions photocatalysts and catalysts.

Adsorption↗
PubMed2006

A new cross-linking route via the unusual collision kinematics of hyperthermal protons in unsaturated hydrocarbons: the case of poly(trans-isoprene).

The bombardment of a approximately 18 nm film of poly(trans-isoprene) molecules (approximately 300,000 carbon atoms per molecule) with a mass-separated proton beam at 10 eV has been shown to induce highly efficient cross-linking of several macromolecules per incident proton. In this new method using physical means to conduct synthetic chemistry, the hyperthermal protons preferentially cleave C-H bonds because of their unusual kinematics in hydrocarbons, and the carbon radicals thus created initiate a polymerization chain reaction of the isoprene C[double bond, length as m-dash]C bonds. The method produces ultrathin polymeric films via cross-linking with a dry process having high chemical selectivity and reactivity but requiring no thermal cost and no chemical additives, conditions that are commonly required in the fabrication of microelectronics and photonics.

Journal Article↗
PubMed2006

Sensitive and quantitative measurement of gene expression directly from a small amount of whole blood.

BACKGROUND: Accurate and precise quantification of mRNA in whole blood is made difficult by gene expression changes during blood processing, and by variations and biases introduced by sample preparations. We sought to develop a quantitative whole-blood mRNA assay that eliminates blood purification, RNA isolation, reverse transcription, and target amplification while providing high-quality data in an easy assay format. METHODS: We performed single- and multiplex gene expression analysis with multiple hybridization probes to capture mRNA directly from blood lysate and used branched DNA to amplify the signal. The 96-well plate singleplex assay uses chemiluminescence detection, and the multiplex assay combines Luminex-encoded beads with fluorescent detection. RESULTS: The single- and multiplex assays could quantitatively measure as few as 6000 and 24,000 mRNA target molecules (0.01 and 0.04 amoles), respectively, in up to 25 microL of whole blood. Both formats had CVs < 10% and dynamic ranges of 3-4 logs. Assay sensitivities allowed quantitative measurement of gene expression in the minority of cells in whole blood. The signals from whole-blood lysate correlated well with signals from purified RNA of the same sample, and absolute mRNA quantification results from the assay were similar to those obtained by quantitative reverse transcription-PCR. Both single- and multiplex assay formats were compatible with common anticoagulants and PAXgene-treated samples; however, PAXgene preparations induced expression of known antiapoptotic genes in whole blood. CONCLUSIONS: Both the singleplex and the multiplex branched DNA assays can quantitatively measure mRNA expression directly from small volumes of whole blood. The assay offers an alternative to current technologies that depend on RNA isolation and is amenable to high-throughput gene expression analysis of whole blood.

Fluorescence↗
PubMed2006

A multiplex branched DNA assay for parallel quantitative gene expression profiling.

We describe a novel method to quantitatively measure messenger RNA (mRNA) expression of multiple genes directly from crude cell lysates and tissue homogenates without the need for RNA purification or target amplification. The multiplex branched DNA (bDNA) assay adapts the bDNA technology to the Luminex fluorescent bead-based platform through the use of cooperative hybridization, which ensures an exceptionally high degree of assay specificity. Using in vitro transcribed RNA as reference standards, we demonstrated that the assay is highly specific, with cross-reactivity less than 0.2%. We also determined that the assay detection sensitivity is 25,000 RNA transcripts with intra- and interplate coefficients of variance of less than 10% and less than 15%, respectively. Using three 10-gene panels designed to measure proinflammatory and apoptosis responses, we demonstrated sensitive and specific multiplex gene expression profiling directly from cell lysates. The gene expression change data demonstrate a high correlation coefficient (R(2)=0.94) compared with measurements obtained using the single-plex bDNA assay. Thus, the multiplex bDNA assay provides a powerful means to quantify the gene expression profile of a defined set of target genes in large sample populations.

Alternative Splicing↗
PubMed2006

High luminescence quantum yields and long luminescence lifetime from Eu(III) complex containing two crystal water based on a new beta-diketonate ligand.

New members of family of Eu(III) complex based on the thenoylacetophenone have been synthesized and characterized. The compounds were found for high metal luminescence quantum yields and long luminescence lifetime, especially for compound with two crystal water, corresponding with other compounds containing two crystal water. The result is attributed to high molar absorption coefficients of the Eu(III) complex according to UV-vis and emission spectra. The high molar absorption coefficients balance quenching effect from OH oscillators of water contained in compound.

Acetophenones↗
PubMed2006

Epm2a suppresses tumor growth in an immunocompromised host by inhibiting Wnt signaling.

The genetic mechanisms responsible for increased incidence of lymphoma in immunocompromised individuals have not been fully elucidated. We show that, in a line of TCR transgenic TG-B mice, an insertional mutation in one allele of the Epm2a locus and epigenetic silencing of another led to a high rate of lymphoma with early onset. Overexpressing Epm2a suppressed the growth of established tumor cells and the development of lymphoma in the TG-B mice, while specific silencing of the locus increased tumorigenesis in the immune-deficient host. Downregulation of Epm2a expression is widespread among mouse and human lymphoma cell lines. Epm2a-encoded laforin is a phosphatase for GSK-3beta and an important repressor in the Wnt signaling pathway. Inactivation of Epm2a resulted in increased Wnt signaling and tumorigenesis.

Animals↗
PubMed2006

[Screening of a low alcohol dehydrogenase activity mutant of rhizopus oryzae and the regulation of Zn2+ and Mg2+].

Ethanol is the main by-product in the fermentation broth of Rhizopus oryzae As3.3461 for the production of high-optical purity L-lactic acid. Alcohol Dehydrogenase (ADH) is the branch pathway enzyme that catalyzes the transformation of ethanol from pyruvate in Rhizopus oryzae, which decreases the conversion rate of glucose to L-lactic acid. Thus, screening the mutants with lower ADH activity may increase lactate production dramatically. In present study, Rhizopus oryzae As3.3461 was mutated with N-methyl-N'-nitro-N-nitrosoguanidine (NTG), and 21 mutants which showed lower ADH activity were isolated with selective medium of Yeast-Peptone-Dextrose (YPD) containing 0.6% allyl alcohol (V/V). Compared with other mutants, the 12th mutant strain (named as HBF-12) shows the highest conversion rate of L-lactic acid. By contrast with Rhizopus oryzae As3.3461, the parent strain, the ethanol production and the ADH activity of HBF-12 decrease 73.6% and 76%, respectively. Whereas, the L-lactic acid production and the LDH activity of HBF-12 increase 41.2% and 19.6% than those of the parent strain, respectively. The activities of ADH and LDH of HBF-12 were regulated by Zn2+ and Mg2+, but showed opposite effects. Added with Zn2+ to the concentration of 0.01% improves the ADH activity dramatically, but inhibits the activity of LDH. By contraries, added with Mg2+ improves the LDH activity markedly, but inhibits the ADH activity slightly. In fermentation experiment, the addition of Zn2+ and Mg2+ show different effects on the accumulation of ethanol, L-lactic acid and the biomass in mutant HBF-12. When improve the concentration of Zn2+, the accumulation of L-lactic acid and the biomass show the decreased trend, but the production of ethanol show positive effect. With the improvement of the concentration of Mg2+, the production of lactic acid and biomass increase markedly, but no effect on the production of ethanol. When ferment under the concentrations of Zn2+ 0.01% and Mg2+ 0.04% in fermentation medium, the lactate production of HBF-12 reached the highest level, 96.21 g/L.

Alcohol Dehydrogenase↗
PubMed2006

[Preparation and properties of medical calcium phosphate cement].

The preparation of tetracalcium phosphate (Ca4(PO4)2O, TTCP)was studied. Then calcium phosphate cement (CPC) was prepared. The setting time, pH value, compressive strength, X-ray diffraction (XRD) and scanning electron microscope (SEM) analysis of CPC were studied. The results show that TTCP containing small amount of CaO can be successfully attained heated at 1 500 degrees C for 6 h in vacuum condition. The initial setting time and final setting time of CPC is 4 min and 15 min, respectively. Its compressive strength is 20 MPa after 1-day immersion and 35 MPa after 7-day immersion. The pH value of the solution changes between 6.4 and 8.9. These properties can satisfy the clinical requirements of CPC. The final product of CPC is flake-like or needle-like hydroxyapatite (Ca5(P04)3OH, HA). The continuous network structure of HA appears in the microstructure, this leads to increase the strength of the material. This CPC can be used as bone substitute material.

Bone Cements↗
PubMed2005

Synthesis and characterization of core-shell selenium/carbon colloids and hollow carbon capsules.

A novel Se/C nanocomposite with core-shell structures has been prepared through a facile one-pot microwave-induced hydrothermal process. The new material consists of a trigonal-Se (t-Se) core and an amorphous-C (a-C) shell. The Se/C composite can be converted to hollow carbon capsules by thermal treatment. These products were characterized by transmission electron microscopy (TEM), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), selected area electron diffraction (SAED), energy-dispersive X-ray (EDX) spectroscopy, and X-ray photoelectron spectroscopy (XPS).

Journal Article↗
PubMed2005

Small interfering RNA and gene expression analysis using a multiplex branched DNA assay without RNA purification.

The authors have developed a novel multiplex detection system that quantitatively measures the expression level of 11 messenger RNAs (mRNAs) directly from cell lysates or tissue homogenates without RNA purification. The system incorporates branched DNA (bDNA) technology from Bayer and a multiplex bead array platform from Luminex. In this study, a 21-nt synthetic small interfering RNA (siRNA; specifically designed to knockdown interleukin-8 [IL-8] expression) was delivered into HeLa cells. Using the multiplex bDNA assay, gene expression levels were measured simultaneously from cell lysates for 11 genes. After treating the HeLa cells for 20 h with phorbol myristate acetate (PMA), IL-8 mRNA levels were induced by almost 50-fold; transfection with 30 nM IL-8-specific siRNA reduced the PMA-induced IL-8 mRNA by 80%. In addition, PMA induced mRNA expression in IL-1alpha (3-fold) and IL-6 (4-fold); however, the IL-8 siRNA did not affect the expression of either of these 2 cytokine genes, indicating that the siRNA was selective for IL-8 mRNA expression. Three housekeeping genes' expression levels were measured under all conditions tested. The multiplex bDNA assay provides a powerful tool for quantitative multiplex gene expression analysis directly from cell lysates, which could be extremely valuable for conservation of rare or difficult-to-obtain samples.

Cytokines↗
PubMed2005

Characterization of spectroscopic of Pr(DBM)3(TPPO)2 containing poly(methyl methacrylate).

The absorption and fluorescence spectra of Pr(DBM)3(TPPO)2 (DBM: dibenzoylmethane, TPPO: triphenylphosphine oxide) containing poly(methyl methacrylate) (PMMA) were measured. The energy levels are assigned and analyzed in terms of the free-ion Hamiltonian model. From the data available in the absorption spectrum, various spectroscopic parameters such as the spherically symmetric part of the free-ion Hamiltonian (E(AVG)), Slater-Condon (F2, F4, F6), spin-orbit interaction (zeta), Judd-Ofelt (omega2, omega4, omega6) parameters and the reduced matrix elements are derived. The radiative properties of Pr(DBM)3(TPPO)2 containing PMMA were also predicted according to the Judd-Ofelt theory. The values of the fluorescence branching ratio and the emission cross section of 3P0 --> 3F2 fluorescence transition revealed that Pr(DBM)3(TPPO)2 containing PMMA is an efficient luminescent material.

Models, Chemical↗
PubMed2005

Electro-osmotic flow of a model electrolyte.

Electro-osmotic flow is studied by nonequilibrium molecular dynamics simulations in a model system chosen to elucidate various factors affecting the velocity profile and facilitate comparison with existing continuum theories. The model system consists of spherical ions and solvent, with stationary, uniformly charged walls that make a channel with a height of 20 particle diameters. We find that hydrodynamic theory adequately describes simple pressure-driven (Poiseuille) flow in this model. However, Poisson-Boltzmann theory fails to describe the ion distribution in important situations, and therefore continuum fluid dynamics based on the Poisson-Boltzmann ion distribution disagrees with simulation results in those situations. The failure of Poisson-Boltzmann theory is traced to the exclusion of ions near the channel walls resulting from reduced solvation of the ions in that region. When a corrected ion distribution is used as input for hydrodynamic theory, agreement with numerical simulations is restored. An analytic theory is presented that demonstrates that repulsion of the ions from the channel walls increases the flow rate, and attraction to the walls has the opposite effect. A recent numerical study of electro-osmotic flow is reanalyzed in the light of our findings, and the results conform well to our conclusions for the model system.

Journal Article↗
PubMed2004

Ultrathin polymer film formation by collision-induced cross-linking of adsorbed organic molecules with hyperthermal protons.

A new synthetic approach for the formation of ultrathin polymer films with customizable properties was developed. In this approach, the kinematic nature of proton collisions with simple organic molecules condensed on a substrate is exploited to break C-H bonds preferentially. The subsequent recombination of carbon radicals gives a cross-linked polymer thin film, and the selectivity of C-H cleavage preserves the chemical functionalities of the precursor molecules. The nature and validity of the method are exemplified with theoretical results from ab initio molecular dynamics calculations and experimental evidence from a variety of characterization techniques. Its applicability is demonstrated by the synthesis of ultrathin polymer films with precursor molecules such as dotriacontane, docosanoic acid, poly(acrylic acid) oligomer, and polyisoprene. The approach is fundamentally different from conventional chemical synthesis as it involves an unusual mix of physical and chemical processes including charge exchange, projectile penetration, kinematics, collision-induced dissociation, inelastic energy transfer, chain transfer, and chain cross-linking.

Journal Article↗
PubMed2004

Molecular cloning of nonsecreted endothelial cell-derived lipase isoforms.

To expand our knowledge of factors involved in lipid metabolism in the blood vessel wall, we have cloned unique molecular isoforms of endothelial cell-derived lipase (EDL) (HGMW-approved symbol/LIPG). One isoform encoded a truncated protein (EDL2a) lacking the first 80 amino acid residues of the previously characterized EDL1a isoform, including the signal peptide. A similar second clone (EDL2b) was identified that lacked not only the first 80 amino acids, but also a 74-amino-acid region that encodes a portion of the lid domain. RT-PCR analysis confirmed expression of EDL2a/2b isoforms in several human tissues and cultured cells, including endothelial cells. Western blot and immunofluorescence studies using stable transfectants revealed that EDL2a and EDL2b were localized in the cytosol, while, EDL1a was secreted into the culture medium. Cell extracts of EDL2a/2b transfectants did not have triglyceride or phospholipase activity. Thus endothelial cells express three EDL isoforms, two of which remain intracellular and do not function as lipases.

Amino Acid Sequence↗