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Jianhua Guo

Publications and source records attributed to Jianhua Guo.

9 recordsLinked to original sources
PubMed2006

Global effect of indole-3-acetic acid biosynthesis on multiple virulence factors of Erwinia chrysanthemi 3937.

Production of the plant hormone indole-3-acetic acid (IAA) is widespread among plant-associated microorganisms. The non-gall-forming phytopathogen Erwinia chrysanthemi 3937 (strain Ech3937) possesses iaaM (ASAP16562) and iaaH (ASAP16563) gene homologues. In this work, the null knockout iaaM mutant strain Ech138 was constructed. The IAA production by Ech138 was reduced in M9 minimal medium supplemented with l-tryptophan. Compared with wild-type Ech3937, Ech138 exhibited reduced ability to produce local maceration, but its multiplication in Saintpaulia ionantha was unaffected. The pectate lyase production of Ech138 was diminished. Compared with wild-type Ech3937, the expression levels of an oligogalacturonate lyase gene, ogl, and three endopectate lyase genes, pelD, pelI, and pelL, were reduced in Ech138 as determined by a green fluorescent protein-based fluorescence-activated cell sorting promoter activity assay. In addition, the transcription of type III secretion system (T3SS) genes, dspE (a putative T3SS effector) and hrpN (T3SS harpin), was found to be diminished in the iaaM mutant Ech138. Compared with Ech3937, reduced expression of hrpL (a T3SS alternative sigma factor) and gacA but increased expression of rsmA in Ech138 was also observed, suggesting that the regulation of T3SS and pectate lyase genes by IAA biosynthesis might be partially due to the posttranscriptional regulation of the Gac-Rsm regulatory pathway.

Bacterial Proteins↗
PubMed2006

A test of homogeneity of Hardy-Weinberg disequilibrium across strata.

For genotype data being sampled from several strata with different allele frequencies, it is necessary to verify the assumption of homogeneity of Hardy-Weinberg disequilibrium across strata before testing Hardy-Weinberg law across strata. In practice, disequilibrium can be measured via fixation coefficients (ie, ratios of genotypic frequencies) or disequilibrium coefficients (ie, differences of genotypic frequencies). Test for homogeneity of Hardy-Weinberg disequilibrium using data from several populations has been derived according to fixation coefficients. In this article, using the likelihood score theory extended to nuisance parameters, we derive a homogeneity score test for comparing disequilibrium coefficients across several independent strata. Simulation results demonstrate that the homogeneity score test performs satisfactorily in the sense that its empirical size seldom exceeds the pre-chosen nominal level by more than 10% even for small sample sizes. Corresponding power and sample size formulae are provided as well. We illustrate our test with a real glyoxalase genotype data set.

Gene Frequency↗
PubMed2006

Comparative proteomic analysis of two Entamoeba histolytica strains with different virulence phenotypes identifies peroxiredoxin as an important component of amoebic virulence.

Entamoeba histolytica is a protozoan intestinal parasite that causes amoebic colitis and amoebic liver abscess. To identify virulence factors of E. histolytica, we first defined the phenotypes of two E. histolytica strains, HM-1:IMSS, the prototype virulent strain, and E. histolytica Rahman, a strain that was reportedly less virulent than HM-1:IMSS. We found that compared with HM-1:IMSS, Rahman has a defect in erythrophagocytosis and the ability to cause amoebic colitis in human colonic xenografts. We used differential in-gel 2D electrophoresis to compare the proteome of Rahman and HM-1:IMSS, and identified six proteins that were differentially expressed above a fivefold level between the two organisms. These included two proteins with antioxidative properties (peroxiredoxin and superoxide dismutase), and three proteins of unknown function, grainin 1, grainin 2 and a protein containing a LIM-domain. Overexpression of peroxiredoxin in Rahman rendered the transgenic trophozoites more resistant to killing by H2O2 in vitro, and infection with Rahman trophozoites expressing higher levels of peroxiredoxin was associated with higher levels of intestinal inflammation in human colonic xenografts, and more severe disease based on histology. In contrast, higher levels of grainin appear to be associated with a reduced virulence phenotype, and E. histolytica HM-1:IMSS trophozoites infecting human intestinal xenografts show marked decreases in grainin expression. Our data indicate that there are definable molecular differences between Rahman and HM-1:IMSS that may explain the phenotypic differences, and identify peroxiredoxin as an important component of virulence in amoebic colitis.

Animals↗
PubMed2005

On the formula for admixture linkage disequilibrium.

Admixture linkage disequilibrium (ALD), a phenomenon created by gene flow between genetically distinct populations, has for some time been used as a tool in gene mapping. It is therefore important to analyze the pattern of ALD over generations. In this study we explore two models of admixture: the gradual admixture (GA) model, in which admixture occurs at a variable rate in every generation; and the immediate admixture (IA) model, a special case of the GA model, in which admixture occurs in a single generation. In the case of ALD, the well-known formula of linkage disequilibrium (Delta(t)=(1-r)t Delta(0)) is not applicable under these two models. We note the effect of a random mating population (RMP) to the gametic frequencies from the parental population to the offspring population, and provide the correct formula for ALD.

Chromosome Mapping↗
PubMed2005

GaAs-based multiple-quantum-well spatial light modulators fabricated by a wafer-scale process.

The design, fabrication, and characterization of large, two-dimensional multiple-quantum-well modulator arrays are presented. Such arrays present a speed advantage compared with competing technologies such as liquid crystals and micromirrors, which are intrinsically limited to the kilohertz range. We discuss the design compromises to reach high-contrast, low-voltage swing optical structures compatible with complementary metal-oxide semiconductor-based integrated circuits and present experimental results. Contrast ratio of 5:1 (limited by the fill factor), variations in uniformity below 1nm, and frame rates in excess of 10kHz are demonstrated. Technology maturity for volume production is also discussed.

Journal Article↗
PubMed2002

On the use of historical control information for trend test in carcinogenesis.

In this article a new non-model-based significance test for detecting dose-response relationship with the incorporation of historical control data is proposed. This non-model-based test is considered simpler from a regulatory perspective because it does not require validating any modeling assumptions. Moreover, our test is especially appropriate to those studies in which the intravenous doses for the investigational chemical are labeled as, e.g., low, medium and high or the dose labels do not suggest any obvious choices of dose scores. This test can be easily adopted for detecting general dose-response shape, such as an umbrella pattern. Simple adjustments will be proposed for better control of the actual Type I error. Data sets from two carcinogenesis studies will be used to illustrate our method. We also evaluate the performance of the proposed test and the famous model-based Tarone's trend test with respect to size and power.

Animals↗
PubMed1999

Metal Complexes of Pyridylphenylisocyanides and Pyridylethynylphenylisocyanides as Building Blocks for Coordination Polymers and Supramolecular Assemblies.

The isocyanides 3-(4-pyridylethynyl)phenylisocyanide, 3, 4-(4-pyridylethynyl)phenylisocyanide, 6, 2,6-diisopropyl-4-(4-pyridylethynyl)phenylisocyanide, 9, and 2,6-diisopropyl-4-(4-pyridyl)phenylisocyanide, 11, were prepared. With PdI(2) and PtI(2), these isocyanides form the complexes trans-[MI(2)(CNR)(2)], 12-19 (M = Pd, Pt; CNR = 3, 6, 9, 11). The previously prepared complex trans-[PdI(2)(CNC(5)H(4)N-3)(2)] and trans-[PdI(2)(CNC(6)H(2)-(i-Pr)(2)-2,6-(CC-C(5)H(4)N-4)-4)(2)], 16, combine with copper bis(trifluoroacetylacetonate) in the ratio of 1:2 to form the adducts trans-[PdI(2)(CNC(5)H(4)N-3)(2)].2[Cu(tfacac)(2)].2CH(2)Cl(2), 20, and trans-[PdI(2)(CNC(6)H(2)-(i-Pr)(2)-2,6-(CC-C(5)H(4)N-4)-4)(2)].2[Cu(tfacac)(2)], 21, respectively. The complexes trans-[MI(2)(CNC(6)H(2)-(i-Pr)(2)-2,6-(C(5)H(4)N-4)-4)(2)], 19 (M = Pd) and 20 (M = Pt), react with [Pd(SO(3)CF(3))(2)(dppp)] (dppp = bisdiphenylphosphinopropane) to form the molecular squares [Pd(dppp)(trans-[MI(2)(CNC(6)H(2)-(i-Pr)(2)-2,6-(C(5)H(4)N-4)-4)(2)](4)(SO(3)CF(3))(8), 22 (M = Pd) and 23 (M = Pt). The crystal structure of 20 has been determined by X-ray crystallography. 20: C(34)H(28)Cl(4)Cu(2)F(12)I(2)N(4)O(8)Pd, monoclinic space group, P2(1)/n (No. 14), a = 10.899(3) Å, b = 13.903(1) Å, c = 17.827(6) Å, beta = 105.50(2) degrees, Z = 2, 2618 unique reflections, R = 0.093, R(w) = 0.091.

Journal Article↗
PubMed1997

Heterobimetallic Complexes with Phenylcyclopentadienyl Ligand: Syntheses and Structures of Tricarbonylchromium-eta(6),eta(5)-Phenylcyclopentadienyl-Transition Metal Complexes(1).

A new synthetic method of heterobimetallic complexes bridging with a pi,pi-phenylcyclopentadienyl ligand, tricarbonylchromium-eta(6),eta(5)-phenylcyclopentadienyl-transition metal complexes, was developed through the reactions of (eta(6)-C(6)H(5)C(5)H(5))Cr(CO)(3) or its sodium salt with transition metal complexes. The method is suitable for most transition metal elements with the advantages of easy manipulation, mild reaction conditions, and moderate to high yields. As indicated by (1)H NMR spectra, the interactions between the two pi systems of phenyl and cyclopentadienyl rings were weak. X-ray crystal structures of seven complexes were studied. Compound 23, [eta(6)-C(6)H(5)Cr(CO)(3)](2)C(10)H(10), crystallizes in orthorhombic space group Pbca with cell constants a = 29.616(8) Å, b = 12.861(5) Å, c = 12.397(7) Å, V = 4721(6) Å(3), Z = 8, R = 0.045, and R(w) = 0.045. Compound 3, (eta(6)-C(6)H(5)C(9)H(7))Cr(CO)(3), crystallizes in monoclinic space group P2(1)/c with cell constants a = 7.901(3) Å, b = 14.799(2) Å, c = 12.917(2) Å, beta = 99.72(2) degrees, V = 1488.7(4) Å(3), Z = 4, R = 0.044, and R(w) = 0.051. Compound 7, Cr(CO)(3)(eta(6),eta(5)-C(6)H(5)C(5)H(4))Ti(CO)(2)(eta(5)-C(5)H(5)), crystallizes in monoclinic space group P2(1)/c with cell constants a = 12.361(4) Å, b = 12.487(6) Å, c = 12.531(7) Å, beta = 93.48(4) degrees, V = 1930 Å(3), Z = 4, R = 0.047, and R(w) = 0.048. Compound 13, Cr(CO)(3)(eta(6),eta(5)-C(6)H(5)C(5)H(4))Mo(CO)(3)Br, crystallizes in monoclinic space group P2(1)/c with cell constants a = 14.685(2) Å, b = 8.509(3) Å, c = 14.960(3) Å, beta = 104.46(1) degrees, V = 1810.0(7) Å(3), Z = 4, R = 0.037, and R(w) = 0.037. Compound 19, Cr(CO)(3)(eta(6),eta(5)-C(6)H(5)C(9)H(6))Mn(CO)(3), crystallizes in triclinic space group P(-)(1) with cell constants a = 11.660(4) Å, b = 12.578(5) Å, c = 6.987(2) Å, alpha = 100.03(3) degrees, beta = 104.19(2) degrees, gamma = 71.99(3) degrees, V = 939.3(6) Å(3), Z = 2, R = 0.048, and R(w) = 0.065. Compound 21, Cr(CO)(3)(eta(6),eta(5)-C(6)H(5)C(5)H(4))Ru(PPh(3))(2)Cl, crystallizes with one molecule of EtOH in triclinic space group P(-)(1) with cell constants a = 14.033(4) Å, b = 16.163(6) Å, c = 10.411(3) Å, alpha = 104.22(3) degrees, beta = 103.50(2) degrees, gamma = 90.81(3) degrees, V = 2219(1) Å(3), Z = 2, R = 0.081, and R(w) = 0.096. Compound 22, Cr(CO)(3)(eta(6),eta(5)-C(6)H(5)C(5)H(4))Co(CO)(2), crystallizes in orthorhombic space group P2(1)2(1)2(1) with cell constants a = 15.083(5) Å, b = 16.391(5) Å, c = 6.351(4) Å, V = 1570(1) Å(3), Z = 4, R = 0.036, and R(w) = 0.039. The trans configurations of the two metal atoms in these molecules were found as expected; the phenyl and cyclopentadienyl or indenyl rings in the molecules were found to be not coplanar.

Journal Article↗