Biomedical subjects
Publications and source records attributed to Li Li.
In the crystal structure of the title compound, (NH(4))[AsO(2)(OH)(C(6)H(4)NO(2))], the 4-nitrophenylarsonate anions and ammonium cations are linked through hydrogen bonds to form infinite chains along the b axis. The hydroxyl O atom of the 4-nitrophenylarsonate anion acts as both an acceptor and a donor of hydrogen bonds. All atoms are located in general positions.
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OBJECTIVE: The goal of this study was to determine whether the cardiostimulant effects of the endogenous beta(1)-adrenergic receptor (AR) agonist, (-)-norepinephrine are modified by polymorphic (Serine49Glycine [Ser49Gly], Glycine389Arginine [Gly389Arg]) variants of beta(1)-ARs in the nonfailing adult human heart. BACKGROUND: Human heart beta(1)-ARs perform a crucial role in mediating the cardiostimulant effects of (-)-norepinephrine. An understanding of the significance of Ser49Gly and Gly389Arg polymorphisms in the human heart is beginning to emerge, but not as yet in adult patients who have coronary artery disease (CAD). METHODS: The potency and maximal effects of (-)-norepinephrine at beta(1)-ARs (in the presence of beta(2)-AR blockade with 50 nM ICI 118,551 [erythro-DL-1(7-methylindan-4-yloxy)-3-isopropylamino-butan-2-ol]) for changes in contractile force and shortening of contractile cycle duration were determined in human right atrium in vitro from 87 patients undergoing coronary artery bypass grafting who were taking beta-blockers before surgery. A smaller sample of patients (n = 20) not taking beta-blockers was also investigated. Genotyping for two beta(1)-AR polymorphisms (Ser49Gly and Gly389Arg) was determined from a sample of blood taken at the time of surgery. RESULTS: (-)-Norepinephrine caused concentration-dependent increases in contractile force and reductions in time to reach peak force and time to reach 50% relaxation. There were no differences in the potency or maximal effects of (-)-norepinephrine in the right atrium from patients with different Ser49Gly and Gly389Arg polymorphisms. CONCLUSIONS: The cardiostimulant effects of (-)-norepinephrine at beta(1)-ARs were conserved across Ser49Gly and Gly389Arg polymorphisms in the right atrium of nonfailing hearts from patients with CAD managed with or without beta-blockers.
The inter-burst intervals (IBIs) of the stochastic bursting caused by the effect of coherence resonance (CR) in Hindmarsh-Rose model exhibited multiple mode and were approximately integer multiples of a basic IBI. A similar bursting pattern was found in the experiment on an experimental neural pacemaker perfused with solution whose extracellular calcium concentration ([Ca(2+) ](o) ) was lower than the normal level in which the firing pattern was period 1 spiking. The results verified the existence of the stochastic bursting and implied its CR mechanism. In addition, the distinction between the integer multiple bursting and the integer multiple spiking, another classical firing pattern caused by CR, was identified. The integer multiple bursting was generated in the parameter region where [Ca(2+) ](o) was lower than normal.
Innate immunity has recently gained renewed interest in its ability to regulate adaptive immunity. Among the innate immune signals, CpG DNA has revealed its potential as a vaccine adjuvant. However, the cellular mechanism for the effect of CpG DNA on the humoral immune response is not well understood. Here, we investigated the effects of CpG DNA on human B cell differentiation using highly purified B cell subsets: naive, germinal center (GC), and memory B cells. In the in vitro culture system that mimics the primary or secondary immune response in vivo, CpG DNA markedly augmented the proliferation and generation of plasma cells from naive and memory B cells. CpG DNA dramatically increased plasma cell generation from GC B cells. However, CpG DNA did not have effect on memory B cell generation from GC B cells. These results suggest that CpG DNA potentiates the B cell adaptive immune response by enhancing terminal differentiation, but does not affect the generation of memory B cells.
By using tryptophan scanning mutagenesis, we observed the kinetics and structure of the polymerization of tau into paired helical filaments (PHFs) independently of exogenous reporter dyes. The fluorescence exhibits pronounced blue shifts due to burial of the residue inside PHFs, depending on Trp position. The effect is greatest near the center of the repeat domain, showing that the packing is tightest near the beta-structure inducing hexapeptide motifs. The tryptophan response allows measurement of PHF stability made by different tau isoforms and mutants. Unexpectedly, the stability of PHFs is quite low (denaturation half-points approximately 1.0 m GdnHCl), implying that incipient aggregation should be reversible and that the observed high stability of Alzheimer PHFs is due to other factors. The stability increases with the number of repeats and with tau mutants promoting beta-structure, arguing for a gain of toxic function in frontotemporal dementias. Fluorescence resonance energy transfer (FRET) was used to analyze the distances of Tyr(310) to tryptophans in different positions. The degree of FRET in the soluble protein was position-dependent, with highest signals within the second and third repeats but low or no signals further away. In PHFs most mutants showed FRET, indicating that tight packing results from assembly of tau into PHFs.
Autosomal dominant polycystic kidney disease (ADPKD) occurs by germline mutation in PKD1 or PKD2. Evidence of homozygous inactivation of either gene in human cyst lining cells as well as in mouse knockout models strongly supports a two-hit mechanism for cyst formation. Discovery of trans-heterozygous mutations in PKD1 and PKD2 in a minority of human renal cysts has led to the proposal that such mutations also can play a role in cyst formation. In the current study, we investigated the role of trans-heterozygous mutations in mouse models of polycystic kidney disease. In Pkd1(+/-), Pkd2 (+/-) and Pkd1(+/-) : Pkd2 (+/-) mice, the renal cystic lesion was mild and variable with no adverse effect on survival at 1 year. In keeping with the two-hit mechanism of cyst formation, approximately 70% of kidney cysts in Pkd2 (+/-) mice exhibited uniform loss of polycystin-2 expression. Cystic disease in trans-heterozygous Pkd1(+/-) : Pkd2 (+/-) mice, however, was notable for severity in excess of that predicted by a simple additive effect based on cyst formation in singly heterozygous mice. The data suggest a modifier role for the 'trans' polycystin gene in cystic kidney disease, and support a contribution from threshold effects to cyst formation and growth.
Members of the EGF family of growth factors play critical roles during normal and neoplastic breast development. EGF family member HRGalpha is the only HRG1 isoform expressed in the mouse mammary gland and our previous experiments suggest that HRG1 has a unique role in mammary development. To determine the function of HRGalpha activity during mouse mammary gland development, we generated a HRGalpha-deficient mouse strain. Unlike mice with HRG1 or isoform specific HRGbeta gene deletions, HRGalpha-null mice survive to adulthood. HRGalpha-deficient mice display pronounced defects in mammary gland lobuloalveolar development at 17 days of pregnancy and 3 days post-partum. Terminal and lateral ductal alveoli were condensed and alveolar outgrowth during pregnancy was severely impaired. A dramatic reduction in beta-casein expression accompanied defective alveolar development in the HRGalpha-null mice, as determined by in situ hybridization and Northern blot analysis of HRGalpha-deficient mammary glands at 3 days post-partum. Expression of the milk-protein genes WAP and alpha-lactalbumin was not adversely affected. In situ incorporation of BrdU demonstrated that epithelial proliferation was significantly curtailed in mammary glands of HRGalpha-deficient mice at 17 days post-coitus and 3 days post-partum. These results demonstrate that HRGalpha is an important mammary gland mitogen regulating alveolar development and lactogenesis.
The goal of this study was to investigate in non-impaired humans the interaction between explicit and implicit learning in a catching task. The situation presented probabilistic contingencies between visual signals and various final pathways of the target. Subjects were asked to practice the interception task for 320 trials. Explicit instructions describing the probabilistic rules were given prior to (11 subjects), or in the middle of (11 subjects), physical practice. Eleven subjects not provided with verbal instructions served as control subjects. We measured the combination between explicit verbal instructions and implicit learning via kinematics of the end-effector and an outcome measure (i.e. spatial error). The time when explicit instructions were given resulted in systematic changes in the spatio-temporal ordering of the action. These data suggested that analyzing the way the task is executed with scrutiny allows a new understanding of how the aforementioned learning systems interact.
The pathway of oxidative folding of alpha-lactalbumin (alpha LA) (four disulfide bonds) has been characterized by structural and kinetic analysis of the acid-trapped folding intermediates. In the absence of calcium, oxidative folding of alpha LA proceeds through highly heterogeneous species of one-, two-, three-, and four-disulfide (scrambled) intermediates to reach the native structure. In the presence of calcium, the folding intermediates of alpha LA comprise two predominant isomers (alpha LA-IIA and alpha LA-IIIA) adopting exclusively native disulfide bonds, including the two disulfide bonds (Cys(61)-Cys(77) and Cys(73)-Cys(91)) located within the beta-sheet calcium binding domain. alpha LA-IIA is a two-disulfide species consisting of Cys(61)-Cys(77) and Cys(73)-Cys(91) disulfide bonds. alpha LA-IIIA contains Cys(61)-Cys(77), Cys(73)-Cys(91), and Cys(28)-Cys(111) disulfide bonds. The underlying mechanism of the contrasting folding pathways of calcium-bound and calcium-depleted alpha LA is congruent with the cause of diversity of disulfide folding pathways observed among many well-characterized three-disulfide proteins, including bovine pancreatic trypsin inhibitor and hirudin. Our study also reveals novel aspects of the folding mechanism of alpha LA that have not been described previously.
A drug that specifically inhibits erythropoiesis would be clinically useful. The erythropoietin (Epo) mutant Epo (R103A) could potentially be used for this purpose. Epo (R103A) has a single amino acid substitution of alanine for arginine at position 103. Because of this mutation, Epo (R103A) is only able to bind to one of the 2 subunits of the erythropoietin receptor (EpoR) homodimer and is thus a competitive inhibitor of Epo activity. To produce large quantities of Epo (R103A) to test in animal models of thalassemia and sickle cell disease, we expressed and purified recombinant Epo (R103A) from the yeast Pichia pastoris. Using this method milligram quantities of highly purified Epo (R103A) are obtained. The yeast-expressed Epo (R103A) is properly processed and glycosylated and specifically inhibits Epo-dependent cell growth and (125)I-Epo binding. Epo (R103A) does not, however, directly induce apoptosis in 32D cells expressing EpoR. Epo (R103A) inhibits erythropoiesis of human CD34(+) hematopoietic cells and completely blocks erythroid burst-forming unit formation in normal human bone marrow colony assays. Yeast-expressed Epo (R103A) is a specific inhibitor of primary erythropoiesis suitable for testing in animal models.
The insulin receptor substrate (IRS) family of signaling molecules is expressed in lymphocytes, although their functions in these cells is largely unknown. To investigate the role of IRS in the protection of T cells from activation-induced cell death (AICD), we transfected the T cell hybridoma A1.1, which is IL-4 responsive but lacks expression of IRS family members with cDNA encoding IRS1 or IRS2. Stimulation of these clones with immobilized anti-CD3-induced expression of CD69 to the same level as the parental A1.1 cells. However, the A1.1 IRS1-expressing cells were markedly resistant to AICD, while the A1.1 IRS2-expressing cells were not. Inhibition of phosphatidylinositol 3'-kinase in the A1.1 IRS1-expressing cells did not abrogate their resistance to AICD. Fas mRNA was induced similarly by anti-CD3 in A1.1, A1.1 IRS1-expressing, and A1.1 IRS2-expressing cells. However, induction of Fas ligand (FasL) mRNA and functional FasL protein was delayed and decreased in IRS1-expressing cells, but not in IRS2-expressing cells. The induction of transcription from a 500-bp FasL promoter and a minimal 16-mer early growth response element linked to luciferase was also impaired in the IRS1-expressing cells. These results suggest that overexpression of IRS1, but not IRS2, protects A1.1 cells from AICD by diminishing FasL transcription through a pathway that is independent of the tyrosine phosphorylation of IRS1 and phosphatidylinositol 3'-kinase activity.
OBJECTIVE: To study the role of the core protein of hepatitis C virus (HCV) in HCV pathogenesis and investigate the molecular mechanism of this protein in tumorigenesis. METHODS: By using the yeast two hybrid system 3, the bait plasmids of the gene of the core protein of HCV was constructed and transfected into AH109 yeast strain. Then this transfected AH109 yeast was mated with Y187 yeast containing liver cDNA library plasmids and cultured on quadropledropout (QDO) medium covered with x-alpha-gal and assayed for alpha-gal activity. The blue colonies growing on QOD were collected to extract the plasmids to transform Escherichia coli. Plasmids were extracted from the bacterium and sequenced. After bioinformatic analysis translin, a recombination hotspot binding protein interacting with HCV core protein was found. To further prove the interaction between translin protein and HCV core protein translation was performed by using reticulocyte lysate and immunoprecipitation in vitro. RESULTS: Among the 30 positive colonies, a colony was translin. The interaction between HCV core protein and translin protein could be proved not only in yeast, but also in vitro. CONCLUSION: The core protein of HCV can interact with translin protein, this can explain partly the tumorigenesis of HCV.
Chromatin acetylation and deacetylation catalyzed by histone acetyltransferases (HATs) and histone deacetylases (HDACs) are closely related to eukaryotic gene transcription. Although the binding of serum response factor (SRF) to the CArG boxes in the promoter region is necessary for SM22 expression, it has never been examined whether the local chromatin modification is involved in SM22 gene regulation. In this study, we used the SM22 gene as a model to address whether transcriptional activation of the gene can be manipulated through adjusting histone acetylation of the chromatin template and whether SRF- and HAT-containing coactivators can be recruited onto the SM22 promoter region during gene activation. Here, we showed that the stimulation of the SM22 promoter by the coactivator CREB-binding protein (CBP) was dependent on HAT activity. Overexpression of HDACs decreased SM22 promoter activity, whereas trichostatin A, an HDAC inhibitor, stimulated SM22 promoter activity in a CArG box-dependent manner and induced endogenous SM22 gene expression. Chromatin immunoprecipitation assays showed that trichostatin A treatment in 10T1/2 cells induces chromatin hyperacetylation in the SM22 gene. Although histone hyperacetylation of the SM22 gene occurred during SM22 gene expression and SRF and CBP immunocomplexes possess HAT activities in smooth muscle cells, both SRF and CBP were recruited to the CArG box-containing region of the promoter. This study provides evidence that chromatin acetylation is involved in smooth muscle cell-specific gene regulation.
Despite recent advances in the genetics of West Nile (WN) virus, relatively little is known about the molecular basis of virulence of this virus. In particular, although the genotype of the WN virus strain that was recently introduced into North America has been determined, there have been few experimental studies on the virulence phenotype of the virus. We compared genetic and neurovirulence properties of 19 strains of WN virus, including 2 from North America, and observed significant differences in their neuroinvasive phenotype in mice and hamsters that correlated with virus genotype. Virus isolated in North America was found to be highly neuroinvasive with a lack of age-related resistance to infection in mice normally associated with mosquito-borne flaviviruses.
OBJECTIVE: To investigate the clinical, histopathologic and CT features of localized Castleman disease complicated with paraneoplastic pemphigus (PNP) and pulmonary involvement. METHODS: The clinical, laboratory, histopathologic records and data of computed tomographic (CT) images of 4 patients of Castleman disease with PNP were reviewed. RESULTS: All of the four patients presented with PNP which was confirmed by pathological and immunological studies and also developed lung abnormalities, including bronchiolitis obliterans (n = 3), lung abscess (n = 1) and multiple lung infarction (n = 1), 2 to 5 months after the onset of PNP. Castleman's tumor, which was found incidentally during routine examination, manifested as a solitary and huge mass (5 to 14 cm in size) which markedly enhanced homogeneously on CT in the retroperitoneum (n = 3) and mediastinum (n = 1). Histologically, three cases were of hyaline-vascular type and the other one was of mixed type. Complete remission of PNP occurred 2 weeks to 8 months after surgical resection of the tumor. The condition of two patients with bronchiolitis obliterans failed to be improved. They had been presenting dyspnea and irritable cough 3 to 15 months after surgery. CONCLUSION: PNP and lung abnormalities are rare and severe complications of localized Castleman's disease. Early diagnosis and surgery are very important for prognosis.
We have produced a draft sequence of the rice genome for the most widely cultivated subspecies in China, Oryza sativa L. ssp. indica, by whole-genome shotgun sequencing. The genome was 466 megabases in size, with an estimated 46,022 to 55,615 genes. Functional coverage in the assembled sequences was 92.0%. About 42.2% of the genome was in exact 20-nucleotide oligomer repeats, and most of the transposons were in the intergenic regions between genes. Although 80.6% of predicted Arabidopsis thaliana genes had a homolog in rice, only 49.4% of predicted rice genes had a homolog in A. thaliana. The large proportion of rice genes with no recognizable homologs is due to a gradient in the GC content of rice coding sequences.
Polyphenol oxidases (PPOs; EC 1.10.3.2 or EC 1.14.18.1) catalyzing the oxygen-dependent oxidation of phenols to quinones are ubiquitous among angiosperms and assumed to be involved in plant defense against pests and pathogens. In order to investigate the role of PPO in plant disease resistance, we made transgenic tomato ( Lycopersicon esculentum Mill. cv. Money Maker) plants that overexpressed a potato ( Solanum tuberosum L.) PPO cDNA under control of the cauliflower mosaic virus 35S promoter. The transgenic plants expressed up to 30-fold increases in PPO transcripts and 5- to 10-fold increases in PPO activity and immunodetectable PPO. As expected, these PPO-overexpressing transgenic plants oxidized the endogenous phenolic substrate pool at a higher rate than control plants. Three independent transgenic lines were selected to assess their interaction with the bacterial pathogen Pseudomonas syringae pv. tomato. The PPO-overexpressing tomato plants exhibited a great increase in resistance to P. syringae. Compared with control plants, these transgenic lines showed less severity of disease symptoms, with over 15-fold fewer lesions, and strong inhibition of bacterial growth, with over 100-fold reduction of bacterial population in the infected leaves. These results demonstrate the importance of PPO-mediated phenolic oxidation in restricting plant disease development.