Biomedical subjects

L Wang

Publications and source records attributed to L Wang.

At least 325 records · Page 18Linked to original sources

PubMed2001

Monte Carlo evaluation of tissue inhomogeneity effects in the treatment of the head and neck.

PURPOSE: To use Monte Carlo dose calculation to assess the degree to which tissue inhomogeneities in the head and neck affect static field conformal, computed tomography (CT)-based 6-MV photon treatment plans. METHODS AND MATERIALS: We retrospectively studied the three-dimensional treatment plans that had been used for the treatment of 5 patients with tumors in the nasopharyngeal or paranasal sinus regions. Two patients had large surgical cavities. The plans were designed with a clinical treatment planning system that uses a measurement-based pencil-beam dose-calculation algorithm with an equivalent path-length inhomogeneity correction. Each plan employs conformally-shaped 6-MV photon beams. Patient anatomy and electron densities were obtained from the treatment planning CT images. For each plan, the dose distribution was recalculated with the Monte Carlo method, utilizing the same beam geometry and CT images. The Monte Carlo method accurately accounts for the perturbation effects of local tissue heterogeneities. The Monte Carlo calculated dose distributions were compared with those from the clinical treatment planning system. RESULTS: The degree to which tissue inhomogeneity affects the dose distributions of individual fields varies with the specific anatomic geometry, especially the size and location of air cavities in relation to the beam orientation and field size. Most of the beam apertures completely enclose the air cavities within or adjacent to the gross tumor volume (GTV). Equivalent squares (including blocking) ranged from approximately 5 to 9.5 cm. A common feature observed for individual fields is that the Monte Carlo calculated doses to tissue directly behind and within an air cavity are lower. However, after combining the fields employed in each treatment plan, the overall dose distribution shows only small differences between the two methods. For all 5 patients, the Monte Carlo calculated treatment plans showed a slightly lower dose received by the 95% of target volume (D(95)) than the plans calculated with the pencil-beam algorithm. The average difference in the target volume encompassed by the prescription isodose line was less than 2.2%. The difference between the dose-volume histograms (DVHs) of the GTV was generally small. For the brainstem and chiasm, the DVHs of the two plans were similar. For the spinal cord, differences in the details of the DHV and the dose to 1 cc (D(1cc)) of the structure were observed, with Monte Carlo calculation generally predicting increased dose indices to the spinal cord. However, these changes are not expected to be clinically significant. CONCLUSION: For 6-MV photons, the effects of both normal tissue inhomogeneities and surgical air cavities on the target coverage were adequately accounted for by conventional pencil beam methods for all of the cases studied. Although differences in details of the DVHs of the normal structures were observed, depending on whether Monte Carlo or pencil-beam algorithm was used for calculation, these differences are not expected to be clinically significant. In general, the pencil-beam calculation corrected for primary attenuation by the equivalent pathlength is a sufficiently accurate method for head-and-neck treatment planning using 6-MV photons.

Air↗

PubMed2001

Transcriptional regulation of the p67phox gene: role of AP-1 in concert with myeloid-specific transcription factors.

We have investigated the myeloid-specific transcriptional regulation of p67(phox), an essential component of phagocyte respiratory burst NADPH oxidase. Analysis was carried out on the p67(phox) 5'-flanking region from -3669 to -4 (relative to ATG), including the first exon and intron and part of the second exon. The construct extending from -985 to -4 produced the highest luciferase activity in myeloid HL-60 cells but was not active in HeLa or Jurkat cells, indicating myeloid-specific expression. Four active elements were identified: Sp1/Sp3 at -694, PU.1 at -289, AP-1 at -210, and PU.1/HAF1 at -182, the latter three being in the first intron. These cis elements bound their cognate transacting factors both in vitro and in vivo. Mutation of the Sp1, PU.1, or PU.1/HAF1 site each decreased promoter activity by 35-50%. Mutations in all three sites reduced promoter activity by 90%. However, mutation of the AP-1 site alone nearly abolished promoter activity. The AP-1 site bound Jun and Fos proteins from HL-60 cell nuclear extract. Co-expression with Jun B in AP-1-deficient cells increased promoter activity by 3-fold. These data show that full p67(phox) promoter activity requires cooperation between myeloid-specific and nonmyeloid transcription factors, with AP-1 being the most critical for function.

Base Sequence↗

PubMed2001

Genomic and proteomic analysis of the myeloid differentiation program.

Although the mature neutrophil is one of the better characterized mammalian cell types, the mechanisms of myeloid differentiation are incompletely understood at the molecular level. A mouse promyelocytic cell line (MPRO), derived from murine bone marrow cells and arrested developmentally by a dominant-negative retinoic acid receptor, morphologically differentiates to mature neutrophils in the presence of 10 microM retinoic acid. An extensive catalog was prepared of the gene expression changes that occur during morphologic maturation. To do this, 3'-end differential display, oligonucleotide chip array hybridization, and 2-dimensional protein electrophoresis were used. A large number of genes whose mRNA levels are modulated during differentiation of MPRO cells were identified. The results suggest the involvement of several transcription regulatory factors not previously implicated in this process, but they also emphasize the importance of events other than the production of new transcription factors. Furthermore, gene expression patterns were compared at the level of mRNA and protein, and the correlation between 2 parameters was studied. (Blood. 2001;98:513-524)

Animals↗

PubMed2001

Cyclic AMP inhibits extracellular signal-regulated kinase and phosphatidylinositol 3-kinase/Akt pathways by inhibiting Rap1.

Cyclic AMP inhibited both ERK and Akt activities in rat C6 glioma cells. A constitutively active form of phosphatidylinositol 3-kinase (PI3K) prevented cAMP from inhibiting Akt, suggesting that the inactivation of Akt by cAMP is a consequence of PI3K inhibition. Neither protein kinase A nor Epac (Exchange protein directly activated by cAMP), two known direct effectors of cAMP, mediated the cAMP-induced inhibition of ERK and Akt phosphorylation. Cyclic AMP inhibited Rap1 activation in C6 cells. Moreover, inhibition of Rap1 by a Rap1 GTPase-activating protein-1 also resulted in a decrease in ERK and Akt phosphorylation, which was not further decreased by cAMP, suggesting that cAMP inhibits ERK and Akt by inhibiting Rap1. The role of Rap1 in ERK and Akt activity was further demonstrated by our observation that an active form of Epac, which activated Rap1 in the absence of cAMP, increased ERK and Akt phosphorylation. Inhibition of ERK and/or PI3K pathways mediated the inhibitory effects of cAMP on insulin-like growth factor-I (IGF-I) and IGF-binding protein-3 gene expression. Moreover, cAMP, as well as ERK and PI3K inhibitors produced equivalent stimulation and inhibition, respectively, of p27(Kip1) and cyclin D2 protein levels, potentially explaining the observation that cAMP prevented C6 cells from entering S phase.

Animals↗

PubMed2001

Screening for inborn errors of metabolism using gas chromatography-mass spectrometry.

Screening of newborns for inborn errors of metabolism (IEM) in China is both a challenging and undeveloped area for gynecologists and pediatricians. Since 1999, the Capital Institute of Pediatrics has been studied as regards screening for IEM using advanced gas chromatography-mass spectrometry (GC-MS) method in collaboration with the Matsumoto Institute of Life Science (MILS), Japan, and has successfully diagnosed 51 cases of IEM in a total of 393 patients. Galactosemia, phenylketonuria and methylmalonic acidemia were the most frequent disorders among 51 cases of IEM. Treatment by suitable drugs and/or diet therapy was very effective in the most cases.

Gas Chromatography-Mass Spectrometry↗

PubMed2001

Functional dynamics in the active site of the ribonuclease binase.

Binase, a member of a family of microbial guanyl-specific ribonucleases, catalyzes the endonucleotic cleavage of single-stranded RNA. It shares 82% amino acid identity with the well-studied protein barnase. We used NMR spectroscopy to study the millisecond dynamics of this small enzyme, using several methods including the measurement of residual dipolar couplings in solution. Our data show that the active site of binase is flanked by loops that are flexible at the 300-micros time scale. One of the catalytic residues, His-101, is located on such a flexible loop. In contrast, the other catalytic residue, Glu-72, is located on a beta-sheet, and is static. The residues Phe-55, part of the guanine base recognition site, and Tyr-102, stabilizing the base, are the most dynamic. Our findings suggest that binase possesses an active site that has a well-defined bottom, but which has sides that are flexible to facilitate substrate access/egress, and to deliver one of the catalytic residues. The motion in these loops does not change on complexation with the inhibitor d(CGAG) and compares well with the maximum k(cat) (1,500 s(-1)) of these ribonucleases. This observation indicates that the NMR-measured loop motions reflect the opening necessary for product release, which is apparently rate limiting for the overall turnover.

Endoribonucleases↗

PubMed2001

Molecular cloning and characterization of chemokine-like factor 1 (CKLF1), a novel human cytokine with unique structure and potential chemotactic activity.

Cytokines are small proteins that have an essential role in the immune and inflammatory responses. The repertoire of cytokines is becoming diverse and expanding. Here we report the identification and characterization of a novel cytokine designated as chemokine-like factor 1 (CKLF1). The full-length cDNA of CKLF1 is 530 bp long and a single open reading frame encoding 99 amino acid residues. CKLF1 bears no significant similarity to any other known cytokine in its amino acid sequence. Expression of CKLF1 can be partly inhibited by interleukin 10 in PHA-stimulated U937 cells. Recombinant CKLF1 is a potent chemoattractant for neutrophils, monocytes and lymphocytes; moreover, it can stimulate the proliferation of murine skeletal muscle cells. These results suggest that CKLF1 might have important roles in inflammation and in the regeneration of skeletal muscle.

Amino Acid Sequence↗

PubMed2001

Cross-talk between the ERK and p70 S6 kinase (S6K) signaling pathways. MEK-dependent activation of S6K2 in cardiomyocytes.

The alpha(1)-adrenergic agonist phenylephrine (PE) and insulin each stimulate protein synthesis in cardiomyocytes. Activation of protein synthesis by PE is involved in the development of cardiac hypertrophy. One component involved here is p70 S6 kinase 1 (S6K1), which lies downstream of mammalian target of rapamycin, whose regulation is thought to involve phosphatidylinositol 3-kinase and protein kinase B (PKB). S6K2 is a recently identified homolog of S6K1 whose regulation is poorly understood. Here we demonstrate that in adult rat ventricular cardiomyocytes, PE and insulin each activate S6K2, activation being 3.5- and 5-fold above basal, respectively. Rapamycin completely blocked S6K2 activation by either PE or insulin. Three different inhibitors of MEK1/2 abolished PE-induced activation of S6K2 whereas expression of constitutively active MEK1 activated S6K2, without affecting the p38 mitogen-activated protein kinase and JNK pathways, indicating that MEK/ERK signaling plays a key role in regulation of S6K2 by PE. PE did not activate PKB, and expression of dominant negative PKB failed to block activation of S6K2 by PE, indicating PE-induced S6K2 activation is independent of PKB. However, this PKB mutant did partially block S6K2 activation by insulin, indicating PKB is required here. Another hypertrophic agent, endothelin 1, also activated S6K2 in a MEK-dependent manner. Our findings provide strong evidence for novel signaling connections between MEK/ERK and S6K2.

Animals↗

PubMed2001

Treatment of stroke in rat with intracarotid administration of marrow stromal cells.

OBJECTIVE: To measure the therapeutic efficacy for the treatment of stroke with intra-arterial administration of bone marrow stromal cells (MSC). BACKGROUND: MSC have characteristics of stem and progenitor cells. The hypothesis that MSC injected into the internal carotid artery after stroke enter into ischemic brain and improve neurologic recovery was tested. METHODS: Twenty-five adult Wistar rats were subjected to transient (2-hour) middle cerebral artery occlusion alone (n = 9), or treated with intracarotid arterial injection of 200 microL phosphate-buffered saline (n = 8) or 2 x 10(6) MSC in 200 microL phosphate-buffered saline (n = 8) 1 day after ischemia. MSC were harvested and isolated from additional adult rats and then cultured and labeled with bromodeoxyuridine. Rats were subjected to neurologic functional tests (adhesive-removal, modified neurologic severity scores) before and at 1, 7, and 14 days after middle cerebral artery occlusion. Immunohistochemistry was used to identify cell-specific proteins of bromodeoxyuridine-reactive MSC. RESULTS: Bromodeoxyuridine-reactive cells ( approximately 21% of 2 x 10(6) injected MSC) distributed throughout the territory of the middle cerebral artery by 14 days after ischemia. Some bromodeoxyuridine-reactive cells expressed proteins characteristic of astrocytes and neurons. Rats with intra-arterial transplantation of MSC exhibited improvement on the adhesive-removal test (p < 0.05) and the modified neurologic severity scores (p < 0.05) at 14 days compared with controls. CONCLUSIONS: MSC injected intra-arterially are localized and directed to the territory of the middle cerebral artery, and these cells foster functional improvement after cerebral ischemia.

Animals↗

PubMed2001

Identification, classification and phylogeny of the Aspergillus section Nigri inferred from mitochondrial cytochrome b gene.

The partial mitochondrial cytochrome b gene from 32 strains of 12 species belonging to Aspergillus section Nigri was amplified by the polymerase chain reaction and sequenced directly. Using 402 nucleotide characters, nucleotide-based and amino acid-based phylogenetic trees were inferred and the genetic divergence among the species was evaluated. Based on analyses of the 402-bp nucleotide and 133-amino acid sequences, strains were divided into 11 DNA types and five amino acid types. Aspergillus niger and Aspergillus awamori showed different amino acid sequences. A. niger clade included A. niger var. niger and Aspergillus ficuum. A. awamori clade included A. awamori, Aspergillus phoenicis, Aspergillus pulverulentus, Aspergillus tubingensis, Aspergillus foetidus, and two varieties of A. niger, var. nanus and var. intermedius. Two varieties of A. niger will be reclassified. One strain of A. phoenicis and one strain of Aspergillus carbonarius were reidentified.

Aspergillus↗

PubMed2001

Biotin labeling of the symbiotically important succinoglycan oligosaccharides of Rhizobium meliloti for identification of putative plant receptors.

The symbiotically important trimer of the succinoglycan octasaccharide subunit was labeled with a biotin tag through coupling with a 6-biotinamidohexan hydrazide and subsequent reduction with borane. The acetyl and succinyl groups in the molecule were stable to the two-step sequence, while a small percentage of the ketal in the pyruvate groups was reduced to an ether-linked lactic acid moiety attached to either the O-4 or O-6 position of the sugar residue under the reaction conditions.

Biotin↗

PubMed2001

TEL contacts multiple co-repressors and specifically associates with histone deacetylase-3.

TEL (Translocation-ETS-Leukemia or ETV 6) is disrupted by multiple chromosomal translocations in acute leukemia. The loss of heterozygosity at the TEL locus in leukemias and the hemizygous deletion of TEL that is observed in various tumors, suggests that TEL is a tumor suppressor. Overexpression of TEL alters cellular morphology and represses the expression of the matrix metalloproteinase stromelysin-1. Based on these studies, deletion analysis was used to define the minimal repression domains of TEL. TEL-mediated repression required both the N-terminal pointed domain and a central region composed of amino acids 268-303. The mSin3A and N-CoR corepressors bind to the pointed domain and the central repression domain of TEL, respectively. Unexpectedly, histone deacetylase-3, but not other histone deacetylases, also associates with the central region of TEL. Histone deacetylase-3 interacts with a TEL mutant that cannot bind N-CoR, suggesting that this is a direct interaction with TEL. In addition, histone H3 was under-acetylated near the TEL-binding sites in the endogenous stromelysin-1 promoter when TEL was expressed. Furthermore, trichostatin A, a potent histone deacetylase inhibitor, impaired TEL-dependent repression of the stromelysin-1 promoter. Finally, while TEL-expression induced cellular aggregation of Ras-transformed cells, Trichostatin A reversed the TEL-induced cellular aggregation phenotype. Thus, the cumulative data suggests that histone deacetylase-3 activity is required for the transcriptional functions of TEL.

3T3 Cells↗

PubMed2001

Carbonyl sulfide derived from catalytic oxidation of carbon disulfide over atmospheric particles.

The formation of carbonyl sulfide (COS) by catalytic oxidization of carbon disulfide (CS2) over atmospheric particle catalysts was explored through FT-IR, MS (mass spectrometry), and a fixed-bed stainless steel reactor. Also the crystallizing conditions and specific surfaces (areas) of the catalysts were investigated by means of X-ray diffraction (XRD) and BET. Some oxides such as CaO, Fe2O3, Al2O3, and SiO2 were investigated under the conditions similar to the atmospheric particles as a comparison. The results showed that atmospheric particles and the oxide catalysts exhibited considerable oxidizing activity for CS2 at ambient temperature to form COS. Elemental sulfur as well as COS was one of the main products; even CO2 could be produced by a secondary reaction on some catalysts. Among the catalysts, CaO showed the strongest catalytic activity for oxidizing CS2. The catalytic activities of Fe2O3 and Al2O3 decreased considerably as compared with CaO, and SiO2 had the weakest catalytic activity. Atmospheric particles' catalytic activity is between Fe2O3's and Al2O3's. The atmospheric particles we collected mainly consist of Ca(Al2Si2O8).4H2O, which is also the main component of cement. COS, the main product, is formed by the catalytic oxidizing reaction of CS2 with adsorbed "molecular" oxygen overthe catalysts' surfaces. The concentration of adsorbed oxygen over catalysts' surfaces may be the key factor contributed to the oxidizing activities. This paper first revealed that CS2 could be catalytically oxidized over atmospheric particles to form COS. It induced that this reaction may be another important source of atmospheric COS from CS2.

Air Pollutants↗

PubMed2001

Vac8p release from the SNARE complex and its palmitoylation are coupled and essential for vacuole fusion.

Activated fatty acids stimulate budding and fusion in several cell-free assays for vesicular transport. This stimulation is thought to be due to protein palmitoylation, but relevant substrates have not yet been identified. We now report that Vac8p, a protein known to be required for vacuole inheritance, becomes palmitoylated when isolated yeast vacuoles are incubated under conditions that allow membrane fusion. Similar requirements for Vac8p palmitoylation and vacuole fusion, the inhibition of vacuole fusion by antibodies to Vac8p and the strongly reduced fusion of vacuoles lacking Vac8p suggest that palmitoylated Vac8p is essential for homotypic vacuole fusion. Strikingly, palmitoylation of Vac8p is blocked by the addition of antibodies to Sec18p (yeast NSF) only. Consistent with this, a portion of Vac8p is associated with the SNARE complex on vacuoles, which is lost during Sec18p- and ATP-dependent priming. During or after SNARE complex disassembly, palmitoylation occurs and anchors Vac8p to the vacuolar membrane. We propose that palmitoylation of Vac8p is regulated by the same machinery that controls membrane fusion.

Adenosine Triphosphatases↗

PubMed2001

Liver-derived DEC205+B220+CD19- dendritic cells regulate T cell responses.

Leukocytes resident in the liver may play a role in immune responses. We describe a cell population propagated from mouse liver nonparenchymal cells in IL-3 and anti-CD40 mAb that exhibits a distinct surface immunophenotype and function in directing differentiation of naive allogeneic T cells. After culture, such cells are DEC-205(bright)B220+CD11c-CD19-, and negative for T (CD3, CD4, CD8alpha), NK (NK 1.1) cell markers, and myeloid Ags (CD11b, CD13, CD14). These liver-derived DEC205+B220+ CD19- cells have a morphology and migratory capacity similar to dendritic cells. Interestingly, they possess Ig gene rearrangements, but lack Ig molecule expression on the cell surface. They induce low thymidine uptake of allogeneic T cells in MLR due to extensive apoptosis of activated T cells. T cell proliferation is restored by addition of the common caspase inhibitor peptide, benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone (zVAD-fmk). T cells stimulated by liver-derived DEC205+B220+D19- cells release both IL-10 and IFN-gamma, small amounts of TGF-beta, and no IL-2 or IL-4, a cytokine profile resembling T regulatory type 1 cells. Expression of IL-10 and IFN-gamma, but not bioactive IL-12 in liver DEC205+B220+CD19- cells was demonstrated by RNase protection assay. In vivo administration of liver DEC205+B220+CD19- cells significantly prolonged the survival of vascularized cardiac allografts in an alloantigen-specific manner.

Animals↗

PubMed2001

Human CARD12 is a novel CED4/Apaf-1 family member that induces apoptosis.

The CED4/Apaf-1 family of proteins functions as critical regulators of apoptosis and NF-kappaB signaling pathways. A novel human member of this family, called CARD12, was identified that induces apoptosis when expressed in cells. CARD12 is most similar in structure to the CED4/Apaf-1 family member CARD4, and is comprised of an N-terminal caspase recruitment domain (CARD), a central nucleotide-binding site (NBS), and a C-terminal domain of leucine-rich repeats (LRR). The CARD domain of CARD12 interacts selectively with the CARD domain of ASC, a recently identified proapoptotic protein. In addition, CARD12 coprecipitates caspase-1, a caspase that participates in both apoptotic signaling and cytokine processing. CARD12 may assemble with proapoptotic CARD proteins to coordinate the activation of downstream apoptotic and inflammatory signaling pathways.

Animals↗

PubMed2001

Sequence of the E. coli O104 antigen gene cluster and identification of O104 specific genes.

The Escherichia coli O104 polysaccharide is an important antigen, which contains sialic acid and is often associated with EHEC clones. Sialic acid is a component of many animal tissues, and its presence in bacterial polysaccharides may contribute to bacterial pathogenicity. We sequenced the genes responsible for O104 antigen synthesis and have found genes which from their sequences are identified as an O antigen polymerase gene, an O antigen flippase gene, three CMP-sialic acid synthesis genes, and three potential glycosyl transferase genes. The E. coli K9 group IB capsular antigen has the same structure as the O104 O antigen, and we find using gene by gene PCR that the K9 gene cluster is essentially the same as that for O104. It appears that the distinction between presence as group IB capsule or O antigen for this structure does not involve any difference in genes present in the O antigen gene cluster. By PCR testing against representative strains for the 166 E. coli O antigens and some randomly selected Gram-negative bacteria, we identified three O antigen genes which are highly specific to O104/K9. This work provides the basis for a sensitive test for rapid detection of O104 E. coli. This is important both for decisions on patient care as early treatment may reduce the risk of life-threatening complications and for a faster response in control of food borne outbreaks.

Antigens, Bacterial↗

PubMed2001

Suppression of skin tumorigenesis in c-Jun NH(2)-terminal kinase-2-deficient mice.

Previous studies have shown that c-Jun NH(2)-terminal kinase (JNK) belongs to the mitogen-activated protein kinase (MAPK) family of signal transduction components that are rapidly initiated and activated by many extracellular stimuli. However, the potential role of JNK in mediating tumor promotion and carcinogenesis is unclear. We show here that in JNK2-deficient (Jnk2(-/-)) mice, the multiplicity of papillomas induced by 12-O-tetradecanoylphorbol-13-acetate (TPA) was lower than that in wild-type mice. Papillomas on wild-type mice grew rapidly and were well vascularized compared with Jnk2(-/-) mice. After the 12th week of TPA treatment, the mean number of tumors per mouse was 4.13-4.86 in wild-type mice but only 1.13-2.5 in Jnk2(-/-) mice. TPA induced phosphorylation of extracellular signal-regulated kinases and activator protein-1 DNA binding activity in wild-type mice, but the phosphorylation of extracellular signal-regulated kinases and activator protein-1 DNA binding were inhibited in Jnk2(-/-) mice. These data suggest that JNK2 is critical in the tumor promotion process.

Animals↗