Biomedical subjects

X Yang

Publications and source records attributed to X Yang.

At least 109 records · Page 6Linked to original sources

PubMed2001

Human homologue of Drosophila lats, LATS1, negatively regulate growth by inducing G(2)/M arrest or apoptosis.

The lats gene encodes a family of proteins conserved from insects to humans. Drosophila carrying lats mutant cells or mice deficient for Lats1 develop tumors in various tissues. The mammalian LATS1 protein was previously shown to bind to CDC2, suggesting that LATS1 may modulate G(2)/M cell cycle progression by affecting CDC2 activity. In this study, we introduced human LATS1 into LATS(-/-) MEF cells by adenovirus-mediated gene transfer. Overexpression of LATS1 causes G(2)/M arrest through inhibition of CDC2 kinase activity. Furthermore, overexpression of LATS1 significantly suppressed the human tumor cell growth in vitro and tumorigenicity in vivo by inducing either cell cycle arrest in G(2)/M or apoptosis. These observations suggest that LATS1 is a potent growth suppressor and, like other tumor suppressors, it suppresses growth by inducing cell cycle arrest or apoptosis.

Adenoviridae↗

PubMed2001

Magnetic resonance imaging permits in vivo monitoring of catheter-based vascular gene delivery.

BACKGROUND: Gene therapy is an exciting frontier in modern medicine. To date, most investigations about the imaging of gene therapy have primarily focused on noncardiovascular systems, and no in vivo imaging modalities are currently available for monitoring vascular gene therapy. The purpose of this study was to develop an in vivo imaging tool to monitor a catheter-based vascular gene delivery procedure. METHODS AND RESULTS: We produced gadolinium/blue dye and gadolinium/gene-vector media by mixing Magnevist with a trypan-blue or a lentiviral vector carrying a green fluorescent protein (GFP) gene. The gadolinium was used as an imaging marker for magnetic resonance (MR) imaging to visualize vessel wall enhancement, and the blue dye/GFP was used as a tissue stain marker for histology/immunohistochemistry to confirm the success of the transfer. Using Remedy gene delivery catheters, we transferred the gadolinium/blue dye (n=8) or gadolinium/GFP lentivirus (n=4) into the arteries of 12 pigs, that were monitored under high-resolution MR imaging. The results showed, in all 12 pigs, the gadolinium enhancement of the target vessel walls on MR imaging and the blue/GFP staining of the target vessel tissues with histology/immunohistochemistry. This study shows the potential of using MR imaging to dynamically visualize (1) where the gadolinium/genes are delivered; (2) how the target portion is marked; and (3) whether the gene transfer procedure causes complications. CONCLUSIONS: We present a technical development that uses high-resolution MR imaging as an in vivo imaging tool to monitor catheter-based vascular gene delivery.

Animals↗

PubMed2001

Synergistic activation of functional estrogen receptor (ER)-alpha by DNA methyltransferase and histone deacetylase inhibition in human ER-alpha-negative breast cancer cells.

Formation of transcriptional repression complexes such as DNA methyltransferase (DNMT) 1/histone deacetylase (HDAC) or methyl-CpG binding protein/HDAC is emerging as an important mechanism in silencing a variety of methylated tissue-specific and imprinted genes. Our previous studies showed that treatment of estrogen receptor (ER)-alpha-negative human breast cancer cells with the DNMT inhibitor 5-aza-2'-deoxycytidine (5-aza-dC) led to ER mRNA and protein re-expression. Also, the HDAC inhibitor trichostatin A (TSA) could induce ER transcript about 5-fold. Here we show that 5-aza-dC alone induced ER transcript about 30-40-fold, and the addition of TSA elevated ER mRNA expression about 10-fold more in the human ER-negative breast cancer cell lines MDA-MB-231 and MDA-MB-435. Overall, the combination of 5-aza-dC and TSA induced a 300-400-fold increase in ER transcript. Restoration of estrogen responsiveness was demonstrated by the ability of the induced ER protein to elicit estrogen response element-regulated reporter activity from an exogenous plasmid as well as induce expression of the ER target gene, progesterone receptor. The synergistic activation of ER occurs concomitantly with markedly reduced soluble DNMT1 expression and activity, partial demethylation of the ER CpG island, and increased acetylation of histones H(3) and H(4). These data suggest that the activities of both DNMT1 and HDAC are key regulators of methylation-mediated ER gene silencing.

Acetylation↗

PubMed2001

Functional isolation of the Candida albicans FCR3 gene encoding a bZip transcription factor homologous to Saccharomyces cerevisiae Yap3p.

We have isolated a C. albicans gene, named FCR3 (for fluconazole resistance 3), based upon its ability to suppress the FCZ hypersusceptibility of a Saccharomyces cerevisiae mutant strain (JY312) lacking the transcription factors Pdr1p and Pdr3p. The FCR3 ORF (1200 bp) encodes a 399 amino acid protein containing a basic leucine zipper (bZip) domain. Fcr3p displays the highest level of sequence homology with the S. cerevisiae Yap3p protein (34% identity, 45% similarity). We had previously shown that deletion of the PDR5 gene encoding a multidrug transporter completely abolished the ability of FCR3 to suppress the FCZ hypersusceptibility of JY312, suggesting that FCR3 confers FCZ resistance by activating PDR5 expression. We show here that the beta-galactosidase activity of a PDR5 promoter-lacZ construct in JY312 is increased two-fold upon FCR3 overexpression, demonstrating that FCR3 regulates PDR5 at the transcriptional level. We also show that FCR3 overexpression not only suppresses the hypersusceptibility of JY312 to 4-nitroquinoline-N-oxide (4-NQO) but also confers higher levels of resistance to this compound as compared to the wild-type KY320 strain. Since PDR5 is not involved in 4-NQO resistance, this result indicates that FCR3 can also activate the transcription of other genes that can confer 4-NQO resistance. Finally, Northern blot analysis indicates that FCR3 encodes a single 2.4 kb RNA transcript in C. albicans, suggesting that the FCR3 mRNA contains long 5' and/or 3' untranslated regions. The nucleotide sequence of the FCR3 gene has been deposited at GenBank under Accession No. AF342983.

ATP-Binding Cassette Transporters↗

PubMed2001

APP processing and synaptic plasticity in presenilin-1 conditional knockout mice.

We have developed a presenilin-1 (PS1) conditional knockout mouse (cKO), in which PS1 inactivation is restricted to the postnatal forebrain. The PS1 cKO mouse is viable and exhibits no gross abnormalities. The carboxy-terminal fragments of the amyloid precursor protein differentially accumulate in the cerebral cortex of cKO mice, while generation of beta-amyloid peptides is reduced. Expression of Notch downstream effector genes, Hes1, Hes5, and Dll1, is unaffected in the cKO cortex. Although basal synaptic transmission, long-term potentiation, and long-term depression at hippocampal area CA1 synapses are normal, the PS1 cKO mice exhibit subtle but significant deficits in long-term spatial memory. These results demonstrate that inactivation of PS1 function in the adult cerebral cortex leads to reduced Abeta generation and subtle cognitive deficits without affecting expression of Notch downstream genes.

Alzheimer Disease↗

PubMed2001

Is hydrogen peroxide produced during iron(II) oxidation in mammalian apoferritins?

The ferritins are a class of iron storage and detoxification proteins that play a central role in the biological management of iron. These proteins have a catalytic site, "the ferroxidase site", located on the H-type subunit that facilitates the oxidation of Fe(II) to Fe(III) by O(2). Measurements during the past 10 years on a number of vertebrate ferritins have provided evidence that H(2)O(2) is produced at this diiron ferroxidase site. Recently reported experiments using three different analytical methods with horse spleen ferritin (HoSF) have failed to detect H(2)O(2) production in this protein [Lindsay, S., Brosnahan, D., and Watt, G. D. (2001) Biochemistry 40, 3340-3347]. These findings contrast with earlier results reporting H(2)O(2) production in HoSF [Xu, B., and Chasteen, N. D. (1991) J. Biol. Chem. 266, 19965-19970]. Here a sensitive fluorescence assay and an assay based on O(2) evolution in the presence of catalase were used to demonstrate that H(2)O(2) is produced in HoSF as previously reported. However, because of the relatively few H-chain ferroxidase sites in HoSF and the reaction of H(2)O(2) with the protein, H(2)O(2) is more difficult to detect in this ferritin than in recombinant human H-chain ferritin (HuHF). The proper sequence of addition of reagents is important for measurement of the total amount of H(2)O(2) produced during the ferroxidation reaction.

Animals↗

PubMed2001

A first-tier rapid assay for the serodiagnosis of Borrelia burgdorferi infection.

BACKGROUND: The present recommendation for the serologic diagnosis of Lyme disease is a 2-tier process in which a serum sample with a positive or equivocal result by an enzyme-linked immunosorbent assay (ELISA) or immunofluorescent assay is then followed by supplemental testing by Western blot. Our laboratory has developed recombinant chimeric proteins composed of key Borrelia epitopes. These novel antigens are consistent and are easily standardized. METHODS: We adapted these recombinant proteins into a new immunochromatographic format that can be used as a highly sensitive and specific first-tier assay that can be used to replace the ELISA or immunofluorescent assay. RESULTS: This rapid test was equally sensitive (P>.05) and more specific (P<.05) than a frequently used commercial whole cell ELISA. The overall clinical accuracy achieved on agreement studies among 3 Lyme research laboratories on clinically defined serum panels was shown to be statistically equivalent to the commercial ELISA. The assay can detect anti-Borrelia burgdorferi antibodies in either serum or whole blood. CONCLUSION: This sensitive and specific rapid assay, which is suited for the physician's office, streamlines the 2-tier system by allowing the physician to determine if a Western blot is necessary at the time of the initial office visit.

Antibodies, Bacterial↗

PubMed2001

Invasiveness of hepatocellular carcinoma cell lines: contribution of hepatocyte growth factor, c-met, and transcription factor Ets-1.

To understand the mechanism of invasion and metastasis of hepatocellular carcinoma (HCC), the expression of c-met and Ets-1, and the effect of HGF on these cell's motility and invasion ability were examined in four hepatoma cell lines. The analysis revealed that the overexpression of c-met and Ets-1 is closely connected with the motility and invasion ability of the HCC cell lines. Invasion activity of HepG2 and HLE cells were enhanced by the addition of HGF to medium. HGF regulated c-met transcription in HepG2 and Bel-7402 cells, HGF also induced Ets-1 transcription in Bel-7402 cell. Bel-7402 cells stably transduced with the human Ets-1 gene showed significantly increased invasion potentials compared to parental and mock-transfected cells. The expression level of c-met, MMP1, MMP9, and u-PA in Bel-7402 cells transfected with Ets-1 were markedly increased, and as a consequence of c-met expression increase. Bel-7402 cells transfected with Ets-1 were more responsive to exogenous HGF stimulation in invasiveness and motility ability. In addition, conditioned by antisense Ets-1 oligonucleotide-treat-Bel-7402 cells transfected with Ets-1 gene and HLE hepatoma cells showed markedly reduced invasion activity, and down-regulated the transcription of Ets-1, c-met, u-PA, MMP-1, and MMP-9. These results strongly suggest that Ets-1 has a crucial role in the invasive property in hepatoma cell lines, and there may exist a loop to enhance the invasive ability of hepatoma cell lines.

Blotting, Northern↗

PubMed2001

Synthesis and biological activity of D- and L-chiro-inositol 2,3,4,5-tetrakisphosphate: design of a novel and potent inhibitor of Ins(3,4,5,6)P4 1-kinase/Ins(1,3,4)P3 5/6-kinase.

The synthesis of a novel and potent Ins(3,4,5,6)P4 1-kinase/Ins(1,3,4)P3 5/6 kinase inhibitor and its enantiomer is described. D-chiro-Inositol 2,3,4,5-tetrakisphosphate [D-chiro-Ins(2,3,4,5)P4, 3, Figure 1] and L-chiro-inositol 2,3,4,5-tetrakisphosphate [L-chiro-Ins(2,3,4,5)P4, ent-3] were synthesized from D-1,6-di-O-benzyl-chiro-inositol and L-1,6-di-O-benzyl-chiro-inositol, respectively. We examined inhibition of the multifunctional Ins(3,4,5,6)P4 1-kinase/Ins(1,3,4)P3 5/6-kinase from bovine aorta by 3 and ent-3. Compound 3 was a potent inhibitor with an IC(50) of 1.5 microM, and ent-3 was more than 20-fold less active. The results are compared to those for other inhibitory inositol polyphosphates with structure-activity relationship discussion. Compound 3 is a useful lead for development of further inhibitors of this important enzyme, and ent-3 should find applications in the newly emerging Ins(1,4,5,6)P4 signaling pathway.

Animals↗

PubMed2001

Model-independent source imaging using two-pion correlations in (2 to 8)a GeV Au+Au collisions.

We report a particle source imaging analysis based on two-pion correlations in high multiplicity Au+Au collisions at beam energies between 2A and 8A GeV. We apply the imaging technique introduced by Brown and Danielewicz, which allows a model-independent extraction of source functions with useful accuracy out to relative pion separations of about 20 fm. The extracted source functions have Gaussian shapes. Values of source functions at zero separation are almost constant across the energy range under study. Imaging results are found to be consistent with conventional source parameters obtained from a multidimensional Hanburg-Brown-Twiss analysis.

Journal Article↗

PubMed2001

Altered growth responses of pulmonary artery smooth muscle cells from patients with primary pulmonary hypertension to transforming growth factor-beta(1) and bone morphogenetic proteins.

BACKGROUND: Mutations in the type II receptor for bone morphogenetic protein (BMPR-II), a receptor member of the transforming growth factor-beta (TGF-beta) superfamily, underlie many cases of familial and sporadic primary pulmonary hypertension (PPH). We postulated that pulmonary artery smooth muscle cells (PASMCs) from patients with PPH might demonstrate abnormal growth responses to TGF-beta superfamily members. METHODS AND RESULTS: For studies of (3)H-thymidine incorporation or cell proliferation, PASMCs (passages 4 to 8) were derived from main pulmonary arteries. In control cells, 24-hour incubation with TGF-beta(1) (10 ng/mL) or bone morphogenetic protein (BMP)-2, -4, and -7 (100 ng/mL) inhibited basal and serum-stimulated (3)H-thymidine incorporation, and TGF-beta(1) and BMPs inhibited the proliferation of serum-stimulated PASMCs. In contrast, TGF-beta(1) stimulated (3)H-thymidine incorporation (200%; P<0.001) and cell proliferation in PASMCs from PPH but not from patients with secondary pulmonary hypertension. In addition, BMPs failed to suppress DNA synthesis and proliferation in PASMCs from PPH patients. Reverse transcription-polymerase chain reaction of PASMC mRNA detected transcripts for type I (TGF-betaRI, Alk-1, ActRI, and BMPRIB) and type II (TGF-betaRII, BMPR-II, ActRII, ActRIIB) receptors. Receptor binding and cross-linking studies with (125)I-TGF-beta(1) confirmed that the abnormal responses in PPH cells were not due to differences in TGF-beta receptor binding. Mutation analysis of PASMC DNA failed to detect mutations in TGF-betaRII and Alk-1 but confirmed the presence of a mutation in BMPR-II in 1 of 5 PPH isolates. CONCLUSIONS: We conclude that PASMCs from patients with PPH exhibit abnormal growth responses to TGF-beta(1) and BMPs and that altered integration of TGF-beta superfamily growth signals may contribute to the pathogenesis of PPH.

Activin Receptors↗

PubMed2001

Fatal propionic acidemia in mice lacking propionyl-CoA carboxylase and its rescue by postnatal, liver-specific supplementation via a transgene.

Propionic acidemia (PA) is an inborn error of metabolism caused by the genetic deficiency of propionyl-CoA carboxylase (PCC). By disrupting the alpha-subunit gene of PCC, we created a mouse model of PA (PCCA(-/-)), which died in 24-36 h after birth due to accelerated ketoacidosis. A postnatal, liver-specific PCC expression via a transgene in a far lower level than that in wild-type liver, allowed PCCA(-/-) mice to survive the newborn and early infant periods, preventing a lethal fit of ketoacidosis (SAP(+)PCCA(-/-) mice). Interestingly, SAP(+)PCCA(-/-) mice, in which the transgene expression increased after the late infant period, continued to grow normally while mice harboring a persistent low level of PCC died in the late infant period due to severe ketoacidosis, clearly suggesting the requirement of increased PCC supplementation in proportion to the animal growth. Based on these results, we propose a two-step strategy to achieve an efficient PA prevention in human patients: a partial PCC supplementation in the liver during the newborn and early infant periods, followed by a larger amount of supplementation in the late infant period.

Animals↗

PubMed2001

Stimulation of osteoprotegerin (OPG) gene expression by transforming growth factor-beta (TGF-beta). Mapping of the OPG promoter region that mediates TGF-beta effects.

Transforming growth factor-beta (TGF-beta) regulates osteoclastogenesis and osteoclast survival, in part through the induction of osteoprotegerin (OPG), a protein known to inhibit osteoclast formation and function. To explore the molecular basis of TGF-beta regulation of OPG expression, we evaluated the effects of TGF-beta on osteoclast formation, OPG protein secretion, mRNA expression, and gene transcription. The marked inhibitory effect of TGF-beta on osteoclast differentiation was confirmed in a co-culture model utilizing murine stromal/osteoblastic BALC cells and bone marrow hematopoietic precursors. This inhibition in osteoclast differentiation was preceded by a decrease in RANKL mRNA expression (5-fold) and a reciprocal increase in OPG mRNA (6.1-fold) and protein (7.1-fold) expression in BALC cells. At the promoter/transcriptional level, TGF-beta treatment resulted in a 3-10-fold increase in reporter gene activity directed by a 5.9-kilobase fragment of the human OPG promoter in transfection assays performed in UMR106 cells. The effect of TGF-beta was mimicked by TGF-beta2 and -beta3 but not by BMP-4, suggesting a TGF-beta signal-specific effect. Deletion analysis revealed that a 183-base pair region (-372 to -190) in the promoter was required for TGF-beta responsiveness, and this region was sufficient to confer TGF-beta inducibility to a heterologous (osteocalcin) minimal promoter. Substitution mutations that disrupted the Cbfa1- and/or Smad-binding elements present in the 183-base pair region resulted in a decrease in base-line expression and in the responsiveness to TGF-beta and Cbfa1. Collectively, these studies indicate the involvement and possible interaction of Cbfa1 and Smad proteins in mediating the effects of TGF-beta on OPG transcription.

Animals↗

PubMed2001

Familial chordoma, a tumor of notochordal remnants, is linked to chromosome 7q33.

Chordoma is a rare tumor originating from notochordal remnants that is usually diagnosed during midlife. We performed a genomewide analysis for linkage in a family with 10 individuals affected by chordoma. The maximum two-point LOD score based on only the affected individuals was 2.21, at recombination fraction 0, at marker D7S2195 on chromosome 7q. Combined analysis of additional members of this family (11 affected individuals) and of two unrelated families (one with 2 affected individuals and the other with 3 affected individuals), with 20 markers on 7q, showed a maximum two-point LOD score of 4.05 at marker D7S500. Multipoint analysis based on only the affected individuals gave a maximum LOD score of 4.78, with an approximate 2-LOD support interval from marker D7S512 to marker D7S684. Haplotype analysis of the three families showed a minimal disease-gene region from D7S512 to D7S684, a distance of 11.1 cM and approximately 7.1 Mb. No loss of heterozygosity was found at markers D7S1804, D7S1824, and D7S2195 in four tumor samples from affected family members. These results map a locus for familial chordoma to 7q33. Further analysis of this region, to identify this gene, is ongoing.

Chordoma↗

PubMed2001

An unexpected outcome during testing of commercially available demineralized bone graft materials: how safe are the nonallograft components?

STUDY DESIGN: Radiographic and histologic analyses of commercially available bone graft materials were performed. OBJECTIVE: To compare the osteoinductive efficacy of commercially available demineralized bone matrix material. SUMMARY OF BACKGROUND DATA: The relative in vivo bone formation and toxicology of the nonallograft components the make up various commercially available demineralized bone matrix products are not known. METHODS: An in vivo bone formation model was used in 30 athymic rats. Six different bone grafting materials were tested in subcutaneous and intermuscular locations. After 4 weeks, radiographic and histologic testing of bone formation was performed. RESULTS: Eight of nine rats implanted with Grafton demineralized bone matrix products died 1 to 4 days after implantation of the bone graft material. None of the remaining 10 animals implanted with the four other grafting materials died. The experiment was modified and completed with a lower dose of bone graft material. Pathologic analysis indicated that the cause of death was hemorrhagic necrosis of the kidneys, most likely caused by a toxic effect on the glomeruli and tubules. A possible causative factor may have been the glycerol in the graft material. CONCLUSIONS: Although the volume of Grafton product per kilogram of body weight used in this study was approximately eight times the maximum volume used in humans, the authors believe that this data must be reported because this product is used substantially in clinical settings. In addition, the osteoinductive performance and relative safety of the nonallograft components in all commercially available demineralized bone grafts are not known.

Animals↗

PubMed2001

Overexpression of KAI1 suppresses in vitro invasiveness and in vivo metastasis in breast cancer cells.

KAI1 is a metastasis suppressor gene for human prostate cancer and is also involved in the progression of a variety of other human cancers. Previously, we have demonstrated that KAI1 expression was down-regulated in metastatic breast cancer cell lines as well as in highly aggressive breast cancer specimens. To determine whether KAI1 expression is responsible for the metastasis suppression in breast cancer, we transfected the human KAI1 cDNA into two highly malignant breast cancer cell lines, LCC6 and MDA-MB-231, which both have low levels of endogenous KAI1 expression. Parental, vector-only transfectants and KAI1 transfectant clones were injected into the mammary fat pads and tail veins, respectively, of athymic nude mice and assessed for both spontaneous and experimental lung metastasis. High KAI1 expression significantly suppressed the metastatic potential of KAI1-transfected LCC6 cells. Metastasis suppression correlated with the reduced rate of tumor growth and a decreased clonogenicity in soft agar. Furthermore, KAI1 expression significantly suppressed the in vitro cell invasion in KAI1-transfected MDA-MB-231 cells. Our results suggested that KAI1 may function as a negative regulator of breast cancer metastasis.

Animals↗

PubMed2001

Bis(O,O'-di-p-tolyldithiophosphato-S,S')(1,10-phenanthroline-N,N')nickel(II).

The title coordination complex, [Ni(C14H14O2PS2)2(C12H8N2)] or [Ni(pMePh-dtp)2(phen)] (phen is 1,10-phenanthroline; dtp is diaryldithiophosphate), has a non-crystallographic twofold axis of symmetry through the Ni atom and the phen moiety. Two O,O-di-p-tolyldithiophosphate (dtp) ions act as bidentate ligands. The central metal atom is coordinated by four S atoms from two dtp groups and two N atoms from the phen ligand. The title compound displays distorted octahedral geometry around the central Ni atom.

Antioxidants↗

PubMed2001

(2-Methylquinolin-8-olato)iron(III) and -copper(II) complexes.

The crystal structures of tris(2-methylquinolin-8-olato-N,O)iron(III), [Fe(C10H8NO)3], (I), and aquabis(2-methylquinolin-8-olato-N,O)copper(II), [Cu(C10H8NO)2(H2O)], (II), have been determined. Compound (I) has a distorted octahedral configuration, in which the central Fe atom is coordinated by three N atoms and three O atoms from three 2-methylquinolin-8-olate ligands. The three Fe-O bond distances are in the range 1.934 (2)-1.947 (2) A, while the three Fe-N bond distances range from 2.204 (2) to 2.405 (2) A. In compound (II), the central Cu(II) atom and H2O group lie on the crystallographic twofold axis and the coordination geometry of the Cu(II) atom is close to trigonal bipyramidal, with the three O atoms in the basal plane and the two N atoms in apical positions. The Cu-N bond length is 2.018 (5) A. The Cu-O bond length in the basal positions is 1.991 (4) A, while the Cu-O bond length in the apical position is 2.273 (6) A. There is an intermolecular OW-H...O hydrogen bond which links the molecules into a linear chain along the b axis.

Journal Article↗