Biomedical subjects

P Yang

Publications and source records attributed to P Yang.

At least 181 records · Page 10Linked to original sources

PubMed1999

[Atomic/ionic fluorescence in microwave plasma torch discharge excited by high current microsecond pulsed hollow cathode lamp-europium atomic/ionic fluorescence spectrometry].

Eu atomic and ionic fluorescence spectrometry in microwave plasma torch discharge excited by high current microsecond pulsed hollow cathode lamp (HCMP HCL-MPT AFS/IFS) was studied. Operating conditions were optimized. The best detection limits for AFS and IFS obtained with a desolvated ultrasonic nebulization system were 42.0 ng/mL for Eu I 462.7 nm and 21.8 ng/mL for Eu II 381.97 nm, respectively, both were better than those given by the instruction manual of a Baird ICP AFS-2000 spectrometer using pneumatic concentric nebulizer with desolvation for AFS, but were significantly higher than those obtained by using the Baird spectrometer with a mini-monochromator and a ultrasonic nebulzer system.

English Abstract↗

PubMed1998

Hierarchically ordered oxides

Porous silica, niobia, and titania with three-dimensional structures patterned over multiple length scales were prepared by combining micromolding, polystyrene sphere templating, and cooperative assembly of inorganic sol-gel species with amphiphilic triblock copolymers. The resulting materials show hierarchical ordering over several discrete and tunable length scales ranging from 10 nanometers to several micrometers. The respective ordered structures can be independently modified by choosing different mold patterns, latex spheres, and block copolymers. The examples presented demonstrate the compositional and structural diversities that are possible with this simple approach.

Journal Article↗

PubMed1998

Negative regulation of mitosis in fission yeast by the shk1 interacting protein skb1 and its human homolog, Skb1Hs.

We previously provided evidence that the protein encoded by the highly conserved skb1 gene is a putative regulator of Shk1, a p21(Cdc42/Rac)-activated kinase (PAK) homolog in the fission yeast Schizosaccharomyces pombe. skb1 null mutants are viable and competent for mating but less elongate than wild-type S. pombe cells, whereas cells that overexpress skb1 are hyperelongated. These phenotypes suggest a possible role for Skb1 as a mitotic inhibitor. Here we show genetic interactions of both skb1 and shk1 with genes encoding key mitotic regulators in S. pombe. Our results indicate that Skb1 negatively regulates mitosis by a mechanism that is independent of the Cdc2-activating phosphatase Cdc25 but that is at least partially dependent on Shk1 and the Cdc2 inhibitory kinase Wee1. We provide biochemical evidence for association of Skb1 and Shk1 with Cdc2 in S. pombe, suggesting that Skb1 and Shk1 inhibit mitosis through interaction with the Cdc2 complex, rather than by an indirect mechanism. These results provide evidence of a previously undescribed role for PAK-related protein kinases as mitotic inhibitors. We also describe the cloning of a human homolog of skb1, SKB1Hs, and show that it can functionally replace skb1 in S. pombe. Thus, the molecular functions of Skb1-related proteins have likely been substantially conserved through evolution.

Amino Acid Sequence↗

PubMed1998

D-serine added to antipsychotics for the treatment of schizophrenia.

BACKGROUND: Hypofunction of N-methyl-D-aspartate (NMDA) subtype glutamate receptor has been implicated in the pathophysiology of schizophrenia. D-serine is a full agonist of the glycine site of NMDA receptor, an endogenous cotransmitter enriched in corticolimbic regions and distributed in parallel with NMDA receptor. Supplementation of D-serine may improve the symptoms of schizophrenia. METHODS: Thirty-one Taiwanese schizophrenic patients enrolled in a 6-week double-blind, placebo-controlled trial of D-serine (30 mg/kg/day), which was added to their stable antipsychotic regimens. Of these, 28 completed the trial. Measures of clinical efficacy, side effects, and serum levels of amino acids and D-serine were determined every other week. Wisconsin Card Sorting Test (WCST) was performed at the beginning and end of the trial. RESULTS: Patients who received D-serine treatment revealed significant improvements in their positive, negative, and cognitive symptoms as well as some performance in WCST. D-serine levels at week 4 and 6 significantly predicted the improvements. D-serine was well tolerated and no significant side effects were noted. CONCLUSIONS: The significant improvement with the D-serine further supports the hypothesis of NMDA receptor hypofunction in schizophrenia. Given the effects of D-serine on positive symptoms, a trial of D-serine alone in schizophrenia should be considered.

Adult↗

PubMed1998

The histidine kinase dhkC regulates the choice between migrating slugs and terminal differentiation in Dictyostelium discoideum.

An early decision that a newly formed aggregate of Dictyostelium cells must make is whether to form a migrating slug or to proceed through culmination, the process of forming the mature fruiting body. The choice between these alternative morphological pathways is influenced by external and internal cues. dhkC was identified as a potential hybrid sensor kinase possessing domains homologous to the histidine kinase and receiver motifs of two-component signaling systems. Null strains of dhkC show a rapidly developing phenotype for aggregation through finger formation, and culmination commences immediately thereafter and proceeds at a normal rate to generate typical fruiting bodies. Ammonia, an endogenous regulator of the slug versus culmination choice, results in a prolonged slug stage for wild-type strains while the dhkC- strain bypasses the slug stage in the presence or absence of ammonia. Conversely, expression in wild-type cells of a modified DHKC protein composed of only the histidine kinase domain results in normal timing through early aggregation, but subsequent development is significantly delayed. The resulting fingers, once formed, readily convert to slugs that do not undergo culmination but instead migrate until their energy sources are depleted. The slugger phenotype is dependent on the presence of a functional response regulator REGA, and it is rescued by exogenously supplied cAMP. Together, the results indicate that DHKC contributes to the integration of environmental and cellular signals so that the appropriate choice is made between slug formation and culmination. We suggest that DHKC may function as a sensor for ammonia, and that it is the initial component of a phosphorelay signaling system that may modulate the activity of cAMP-dependent protein kinase to either inhibit or promote culmination. Additionally, dhkC- spores were found to be defective in germination, indicating a role for the DHKC signaling pathway in activating spore germination.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed1998

Cse4p is a component of the core centromere of Saccharomyces cerevisiae.

Histones are fundamental structural components of chromatin and are expected to play important roles in chromosome dynamics. Here, we present direct evidence that Cse4p, a histone H3 variant, is a structural component of the core centromere of S. cerevisiae. In histone H4 and Cse4p mutants, the core centromere chromatin structure is disrupted at restrictive temperature. Overexpression of Cse4p suppresses this defect in the H4 mutant, implying that the two proteins act together in centromere structure. We show by chromatin immunoprecipitation experiments that Cse4p is specifically cross-linked to centromeric DNA. Furthermore, by immunofluorescence microscopy, Cse4p is found in discrete foci consistent with that expected for centromeres. These results suggest the kinetochore is assembled on a specialized centromeric nucleosome containing Cse4p.

Centromere↗

PubMed1998

Inhibition of tumor necrosis factor alpha decreases inflammation and prolongs adenovirus gene expression in lung and liver.

The clinical application of adenoviral gene therapy currently is impeded by the potent host immune response to the virus, which limits the duration of its effects. In these studies, we investigated the role of TNF-alpha and of a soluble TNF receptor (TNF-bp) in the inflammatory response and expression of a lacZ-expressing adenovirus (AdCMVlacZ) in the liver and lung of mice. The expression of the recombinant adenovirus was studied in mouse liver and lung by determining the activity of the lacZ gene product of the adenovirus. The mononuclear cell inflammatory response was determined histologically at different times after intravenous or intranasal administration of AdCMVlacZ. The cytotoxic T cell and antibody response to the adenovirus was determined. Treatment with TNF-bp reduced circulating levels of TNF-alpha, greatly reduced the inflammatory response, and resulted in prolonged expression of lacZ for up to 30 days in the liver and lung after either intravenous or intranasal administration of adenovirus. Treatment with TNF-bp had no effect on anti-adenovirus antibodies and induction of cytotoxic T cells 30 days after administration of AdCMVlacZ. These results indicate that TNF-alpha is the primary factor driving the early inflammatory response leading to elimination of adenovirus-infected cells in the liver and lung and that TNF-bp is capable of inhibiting these effects.

Adenoviridae↗

PubMed1998

PTEN/MMAC1 mutations identified in small cell, but not in non-small cell lung cancers.

A putative tumor suppressor, PTEN/MMAC1 gene at 10q23 was recently identified and found to be mutated in many different human tumors. To determine the role of the PTEN/MMAC1 gene in lung cancer, we screened 34 small cell lung cancer (SCLC) cell lines, 10 SCLC tumors, 13 non-small cell lung cancer (NSCLC) cell lines and 10 NSCLC tumors using Denaturing HPLC (DHPLC) and direct sequencing methods. In SCLC, six (18%) of the cell lines and one of the primary tumor samples (10%) showed alterations of the PTEN/MMAC1 gene including point mutations, small fragment deletions, and homozygous deletions. All of the point mutations and small fragment deletions were observed in hemizygously deleted cell lines. In contrast to SCLC, none of the NSCLC tumors or cell lines had mutations in the PTEN/MMAC1 gene. These data indicate that PTEN/MMAC1 mutations contribute to the pathogenesis and neoplastic evolution in SCLC but not in NSCLC.

Carcinoma, Non-Small-Cell Lung↗

PubMed1998

Cloning and characterization of shk2, a gene encoding a novel p21-activated protein kinase from fission yeast.

We describe the characterization of a novel gene, shk2, encoding a second p21(cdc42/rac)-activated protein kinase (PAK) homolog in fission yeast. Like other known PAKs, Shk2 binds to Cdc42 in vivo and in vitro. While overexpression of either shk2 or cdc42 alone does not impair growth of wild type fission yeast cells, cooverexpression of the two genes is toxic and leads to highly aberrant cell morphology, providing evidence for functional interaction between Cdc42 and Shk2 proteins in vivo. Fission yeast shk2 null mutants are viable and exhibit no obvious phenotypic defects. Overexpression of shk2 restores viability and normal morphology but not full mating competence to fission yeast cells carrying a shk1 null mutation. Additional genetic data suggest that Shk2, like Cdc42 and Shk1, participates in Ras-dependent morphological control and mating response pathways in fission yeast. We also show that overexpression of byr2, a gene encoding a Ste11/MAPK kinase kinase homolog, suppresses the mating defect of cells partially defective for Shk1 function, providing evidence of a link between PAKs and mitogen-activated protein kinase signaling in fission yeast. Taken together, our results suggest that Shk2 is partially overlapping in function with Shk1, with Shk1 being the dominant protein in function.

Amino Acid Sequence↗

PubMed1998

Autocrine and paracrine apoptosis are mediated by differential regulation of Fas ligand activity in two distinct Jurkat T cell populations.

Fas ligand (FasL) produced by activated T cells mediates autocrine-induced apoptosis to limit T cell expansion. To investigate the regulation of FasL activity, Jurkat cells were stably transfected with a 2.3-kb fragment of human FasL promoter that controlled the expression of a GFP reporter gene. Two populations of Jurkat cells with different levels of GFP expression were obtained. One population constitutively expressed high levels of GFP (GFP+), while the other population expressed low levels of GFP (GFP-). The level of GFP expression in the two populations correlated with their levels of FasL transcription and its functional activity. Autocrine regulation of apoptosis was demonstrated by increased FasL activity after stimulation of GFP- cells with anti-CD3, phorbyl myristyl acetate plus ionomycin, or Con A. Paracrine regulation of apoptosis was suggested by the induction of apoptosis of GFP- cells after coculture with unstimulated GFP+ cells. GFP+ cells exhibited a decreased sensitivity to FasL-mediated apoptosis compared with GFP- cells. Furthermore, the cell surface expression of Fas and CD4 was lower on GFP+ cells than GFP- cells, whereas the expression of CD45RO was higher. A decreased level of IL-2 was produced by GFP+ cells after phorbyl myristyl acetate and ionomycin stimulation. Our results indicate that a subpopulation of T cells that express low levels of FasL and IL-2, which are responsive to up-regulation of these molecules after activation, can undergo apoptosis either by suicide after activation or by a paracrine pathway mediated by T cells that constitutively express higher levels of FasL.

Apoptosis↗

PubMed1998

Activation of p73 silent allele in lung cancer.

p73, a first p53 relative, has recently been identified and demonstrated to be monoallelically expressed. This protein shows significant amino acid sequence and functional similarities to p53. However, it is unclear whether this protein functions as a tumor suppressor. To elucidate the role of p73 in tumor development, we investigated the expression of the p73 gene in lung cancer. In a comparison between normal lung and tumor tissues, p73 was more highly expressed in tumors. Moreover, using a C/T polymorphism in exon 2 for allele-specific expression analysis in 21 pairs of lung tumors and matched normal tissues, we found that five heterozygous samples exclusively expressed both alleles in tumors while showing monoallelic expression in matched normal tissues. This result was confirmed by single-nucleotide primer extension analysis. Mutation analysis of all 13 coding exons of the gene in 21 lung tumor DNAs revealed several polymorphisms, but no tumor-specific mutations were detected. These findings strongly suggest that p73 may play an important role in lung tumorigenesis through activation of a silent allele and overexpression of wild-type p73 rather than as a tumor suppressor.

Alleles↗

PubMed1998

Fas/Fas ligand signaling during gestational T cell development.

Most thymocytes express high levels of Fas Ag (Apo-1/CD95); however, the role of Fas/Fas ligand-mediated apoptosis in thymocyte development remains unclear. During gestational development of thymocytes in C57BL/6(B6) +/+ mice, the highest levels of Fas ligand mRNA and Fas ligand protein expression were detected at gestational day (GD) 15, and there was a ninefold decrease in Fas ligand mRNA expression between GD 15 and 17 accompanied by a sixfold increase in Fas mRNA. Apoptotic thymocytes were first detected in the medulla at GD 15, and increasing numbers of cortical clusters and scattered, single apoptotic cells were present on GD 16 and 17. Thus, early apoptosis correlated with high expression of Fas ligand. High levels of Fas ligand mRNA were maintained throughout gestational development in thymocytes of Fas-deficient B6-lpr/lpr mice, but cortical clusters and scattered apoptotic cells were decreased relative to B6 +/+ mice before GD 17. Kinetic analysis of fetal thymic organ cultures treated with anti-Fas Ab demonstrated that thymocytes become sensitive to Fas-mediated apoptosis during the transition from the CD4-CD8- to the CD4+CD8+ phenotype. More mature CD4+CD8+ thymocytes and CD4+ and CD8+ thymocytes became resistant to Fas-mediated apoptosis after GD 17, despite high expression of Fas. However, low avidity engagement of the TCR on Fas-sensitive CD4+CD8+ thymocytes before GD 17 induced resistance to Fas-mediated apoptosis. The present results indicate that Fas plays a critical role in mediating apoptosis during early gestational thymocyte development and that thymocytes that receive a survival signal through TCR/CD3 become resistant to Fas-mediated apoptosis.

Animals↗

PubMed1998

Genetic dissection of SLE pathogenesis. Sle1 on murine chromosome 1 leads to a selective loss of tolerance to H2A/H2B/DNA subnucleosomes.

One of the hallmarks of SLE is the loss of tolerance to chromatin. The genes and mechanisms that trigger this loss of tolerance remain unknown. Our genetic studies in the NZM2410 lupus strain have implicated genomic intervals on chromosomes 1 (Sle1), 4 (Sle2), and 7 (Sle3) as conferring strong lupus susceptibility. Interestingly, B6 mice that are congenic for Sle1 (B6.NZMc1) have elevated IgG antichromatin Abs. This study explores the antinuclear antibody fine specificities and underlying cellular defects in these mice. On the B6 background, Sle1 by itself is sufficient to generate a robust, spontaneous antichromatin Ab response, staining Hep-2 nuclei homogeneously, and reacting primarily with H2A/H2B/DNA subnucleosomes. This targeted immune response peaks at 7-9 mo of age, affects both sexes with equally high penetrance (> 75%), and interestingly, does not "spread" to other subnucleosomal chromatin components. Sle1 also leads to an expanded pool of histone-reactive T cells, which may have a role in driving the anti-H2A/H2B/DNA B cells. However, these mice do not exhibit any generalized immunological defects or quantitative aberrations in lymphocyte apoptosis. We hypothesize that Sle1 may lead to the presentation of chromatin in an immunogenic fashion, or directly impact tolerance of chromatin-specific B cells.

Animals↗

PubMed1998

Risk factors for primary central nervous system lymphoma: a case-control study.

BACKGROUND: The incidence of primary central nervous system lymphoma (PCNSL) has increased over time in both immunocompetent and immunodeficient individuals. The reasons for the increase among immunocompetent patients are unclear. METHODS: The authors conducted a case-control study of PCNSL at the Mayo Clinic based on cases from local community and referral practices. Cases were all PCNSL patients without immunodeficiency diagnosed between 1975 and 1994 (n = 109). Two groups of controls were selected from the same referral practice, namely, patients with other cancer (cancer controls; n = 101), and patients with a different neurologic disease (neurologic controls; n = 109) seen at our institution during the same time period. RESULTS: PCNSL was significantly associated with lower education when cases were compared with cancer controls but only suggestively when cases were compared with neurologic controls. PCNSL cases were less likely to have had a history of tonsillectomy or oral contraceptive use compared with both control groups. The findings regarding autoimmune disorders and cardiovascular diseases were inconsistent for the two control groups. Neither farming nor prior personal or family history of cancer appeared to be risk factors for PCNSL. CONCLUSIONS: The findings of this study warrant further investigation of tonsillectomy and oral contraceptives as possible factors for PCNSL.

Adolescent↗

PubMed1998

Dual-colour fluorescence in situ hybridization analysis of synovial sarcoma.

Mounting cytogenetic evidence indicates that synovial sarcomas, regardless of histological conformation, share the specific reciprocal chromosomal translocation t(X;18)(p11.2;q11.2). Application of dual-colour fluorescence in situ hybridization (FISH) on interphase nuclei isolated from archival paraffin-embedded material to identify the specific translocation is of diagnostic importance for pathological practice and retrospective study. Five cases of well-characterized biphasic synovial sarcomas, two monophasic fibrous synovial sarcomas, one embryonal rhabdomyosarcoma, one fibrosarcoma, and one malignant peripheral nerve sheath tumour were analysed. To visualize the translocated chromosomal fragments and their topographic relationships with centromeres of chromosomes X and 18, nuclei from each case were hybridized concurrently with chromosome X centromeric and chromosome 18 painting probes, and chromosome 18 centromeric and chromosome X painting probes, respectively. Six out of seven synovial sarcomas showed chromosomal alterations consistent with t(X;18). One biphasic synovial sarcoma had trisomy 18 and lacked the chromosomal translocation t(X;18). The other three spindle cell sarcomas and the normal control tissues showed the normal numerical and structural composition for chromosomes X and 18. It is indicated from the present study that when histological differential diagnosis is difficult, FISH would be a crucial aid in detecting a known specific chromosomal alteration and that dual-colour FISH is an efficient stable diagnostic tool for pathological research and daily diagnosis. The results also suggest that rare synovial sarcomas may lack the chromosomal translocation t(X;18). 1998 John Wiley & Sons, Ltd.

Adult↗

PubMed1998

Reduction of arthritis and pneumonitis in motheaten mice by soluble tumor necrosis factor receptor.

OBJECTIVE: To determine the effects of anti-tumor necrosis factor (anti-TNF) therapy in the inflammatory and autoimmune disease in motheaten (me/me) mice, which exhibit a Fas apoptosis signaling defect. METHODS: Arthritis, pneumonitis, and mortality were analyzed in me/me mice treated with a novel, soluble, dimeric TNF receptor I (sTNFRI) molecule capable of high-affinity binding and neutralization of TNFalpha. RESULTS: Soluble TNFRI reduced serum levels of TNFalpha and led to a 2-fold increase in the lifespan of me/me mice, compared with the control treatment group. The treatment also reduced the development of the "motheaten" skin patches and alleviated pneumonitis and inflammatory lesions in the extremities of me/me mice compared with controls. However, the serum levels of IgM and IgM anti-double-stranded DNA autoantibody were comparable to those of untreated control mice. CONCLUSION: TNFalpha is an important cytokine involved in the pathogenesis of inflammatory disease in me/me mice, resulting in tissue damage and early mortality. Therapies directed at blocking TNF/TNFR interactions, such as the sTNFRI used in these experiments, may be effective in diseases associated with apoptosis defects leading to overutilization of the TNF/TNFR pathway.

Alopecia↗

PubMed1998

Accumulation of splenic B1a cells with potent antigen-presenting capability in NZM2410 lupus-prone mice.

OBJECTIVE: In order to shed light on the role of splenic B1 cells in disease pathogenesis in lupus-prone mice, this study was undertaken to determine how efficiently these cells can serve as antigen-presenting cells (APC) and to ascertain which murine lupus susceptibility loci dictate the expansion of these cells. METHODS: Spleens and peritoneal cavities (PerC) of NZM2410 lupus-prone mice, as well as of control B6 and New Zealand white mice, were examined for the prevalence, surface phenotype, and possible anatomic location of B1 cells. The antigen-presenting ability of fluorescence-sorted splenic B1a cells was assessed. Levels of B1 cells were examined in B6 mice congenic for 4 different lupus susceptibility intervals. RESULTS: NZM2410 lupus mice showed an expansion of splenic and PerC B1a cells at all ages. These cells expressed high levels of B71, B72, CD24, lymphocyte function-associated antigen 1, and intercellular adhesion molecule 1, and had the functional capability to serve as APC. Among the lupus susceptibility intervals studied, Sle2, but not Sle1, Sle3, or the H2 locus, affected the expansion of B1 cells. CONCLUSION: These findings raise the possibility that the genetically determined expansion of splenic B1a cells in lupus-prone mice might contribute to disease pathogenesis by augmenting the presentation of autoantigens to pathogenic T cells.

Animals↗

PubMed1998

Implications of quantal motor action in biological systems.

We demonstrate in this paper that quantal behavior is a central feature of biological motile and contractile systems. Step-like behavior has been demonstrated in the interaction between single molecules and filaments both in the kinesin-microtubule system and in the myosin-actin filament system. We show here that the step-like molecular features appear also in the single intact sarcomere. We studied single sarcomeres of single bumble-bee myofibrils, both in the unactivated and activated states. Myofibril-length changes induced by a motor-imposed ramp were accompanied by corresponding sarcomere-length changes. However, the sarcomere-length changes were stepwise. Computer analysis of the stepwise shortening patterns revealed a step-size distribution containing multiple peaks. In the activated state, the peaks were separated by 2.7 nm per half-sarcomere which is the linear actin-subunit spacing. Thus, translation steps are an integer multiple of the actin-subunit spacing. This result parallels the one observed in the kinesin-tubulin spacing, where step size is a multiple of the tubulin-subunit spacing. In the muscle system, however, the steps are preserved on a macroscopic scale, implying high synchrony. The quantal steps are easily explained by a model in which the actin filament propels itself over stationary cross-bridges: if actin binds to the cross-bridges between steps, then the observed quantal result is inevitable. As probes of contractile phenomena approach the molecular level, the discrete unitary events underlying contraction begin to emerge. Thus, step-like behavior is observed as the single kinesin molecule translates along the microtubule, as the single myosin molecule translates over the actin filament, and as the single isolated titin molecule is stretched.

Actins↗