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Biomedical subjects

Y Yang

Publications and source records attributed to Y Yang.

At least 541 records · Page 30Linked to original sources
PubMed1999

Ex vivo culture of cord blood CD34+ cells expands progenitor cell numbers, preserves engraftment capacity in nonobese diabetic/severe combined immunodeficient mice, and enhances retroviral transduction efficiency.

Ex vivo culture of hematopoietic stem/progenitor cells could potentially improve the efficacy of human placental/umbilical cord blood (CB) in clinical hematopoietic stem cell (HSC) transplantation and allow gene transduction using conventional retroviral vectors. Therefore, we first examined the effects of a 7-day period of ex vivo culture on the hematopoietic capacity of CB CD34+ cells. Medium for the ex vivo cultures contained either serum and six recombinant human hematopoietic growth factors (GFs), including Flt-3 ligand (FL), Kit ligand (KL = stem cell factor), thrombopoietin (Tpo), interleukin 3 (IL-3), granulocyte colony-stimulating factor (G-CSF), and interleukin 6 (IL-6), or a serum-free medium containing only FL, KL, and Tpo. After culture under both ex vivo conditions, the total numbers of viable cells, CD34+ cells, colony-forming cells (CFCs), and long-term culture initiating cells (LTC-ICs) were increased. In contrast, the severe combined immunodeficiency (SCID) mouse engrafting potential (SEP) of cultured cells was slightly decreased, as compared with fresh cells. Nevertheless, cultured human CB CD34+ cells were able to generate engraftment, shown to persist for up to 20 weeks after transplantation. We next tested the efficacy of retroviral transduction of cultured cells. Transduced cultured human cells were able to engraft in NOD/SCID mice, as tested 4 weeks after transplantation, and EGFP+CD34+ cells and EGFP+ CFCs were isolated from the chimeras. Thus, although additional improvements in ex vivo culture are still needed to expand the numbers and function of human HSCs, the current conditions appear to allow gene transduction into hematopoietic SCID engrafting cells, while at least qualitatively preserving their in vivo engraftment potential.

Animals↗
PubMed1999

Impaired immunoproteasome assembly and immune responses in PA28-/- mice.

In vitro PA28 binds and activates proteasomes. It is shown here that mice with a disrupted PA28b gene lack PA28a and PA28b polypeptides, demonstrating that PA28 functions as a hetero-oligomer in vivo. Processing of antigenic epitopes derived from exogenous or endogenous antigens is altered in PA28-/- mice. Cytotoxic T lymphocyte responses are impaired, and assembly of immunoproteasomes is greatly inhibited in mice lacking PA28. These results show that PA28 is necessary for immunoproteasome assembly and is required for efficient antigen processing, thus demonstrating the importance of PA28-mediated proteasome function in immune responses.

Animals↗
PubMed1999

A 1-Mb PAC contig spanning the common eliminated region 1 (CER1) in microcell hybrid-derived SCID tumors.

We have developed an elimination test to identify chromosomal regions that contain tumor inhibitory genes. Monochromosomal human/mouse microcell hybrids are generated and passaged through SCID mice. Derived tumors are then analyzed for deletions on the transgenomic chromosome. Using this strategy, we have previously identified a 1.6-cM common eliminated region 1 (CER1) on human 3p21. 3. We now report that CER1 contains 14 markers that are deleted in 19 SCID-derived tumors. A 1-Mb PAC contig that spans CER1 was assembled. Five chemokine receptor genes (CCR1, CCR3, CCR2, CCR5, and CCR6) were localized in CER1 in a 225-kb cluster. The lactotransferrin gene (LTF, or lactoferrin, LF), which reportedly has tumor inhibitory activity, also maps to CER1. Our results create a basis for characterization and further functional testing of genes within CER1.

Animals↗
PubMed1999

Treatment of severe electrical burns.

In summary, electrical injury is a typical type of burn injury with a unique mechanism of systemic and local damage. Resuscitation is more complex in critical patients than that of thermal injury. Local management is more difficult, which could be eventually accomplished by sequential procedures of debridement and operation. Although the modern trend of performing early debridement and operation might be promising, traditional experiences are still being used in clinical care. Progress in clinical management has brought about an improvement in therapeutic outcome, resulting in a decrease of amputation rate and reduced disability. Some typical types of electrical injury demand special treatment, which might prove to be effective. Close observation and timely treatment of the injury itself and related complications will be lifesaving in caring for critical electrical injury. Some special therapeutic measures would be indicated and might be fruitful in proving their efficacy. New measures aimed at theoretical problems will be promising if electroporation could be effectively treated.

Accidents, Occupational↗
PubMed1999

TCR-Mediated internalization of peptide-MHC complexes acquired by T cells.

Peptide-major histocompatibility complex protein complexes (pMHCs) on antigen-presenting cells (APCs) are central to T cell activation. Within minutes of peptide-specific T cells interacting with APCs, pMHCs on APCs formed clusters at the site of T cell contact. Thereafter, these clusters were acquired by T cells and internalized through T cell receptor-mediated endocytosis. During this process, T cells became sensitive to peptide-specific lysis by neighboring T cells (fratricide). This form of immunoregulation could explain the "exhaustion" of T cell responses that is induced by high viral loads and may serve to down-regulate immune responses.

Animals↗
PubMed1999

Interpolymer complexation. I. Preparation and characterization of a polyvinyl acetate phthalate-polyvinylpyrrolidone (PVAP-PVP) complex.

Polyvinyl acetate phthalate (PVAP) and polyvinylpyrrolidone (PVP) readily reacted in ethanol and acidic aqueous solutions to produce an insoluble PVAP-PVP complex. The complex has a pK(a) of 3.8. It is practically insoluble in common organic solvents, but dissolves in dimethylsulfoxide, an alkali or ammonical solution, and a 4:1 (v/v) mixture of methylene chloride and methanol. The powder X-ray diffraction analysis revealed the complex to be an amorphous material. The Fourier-transform infrared spectrum of the complex exhibited characteristics carbonyl stretching vibrations at 1724 and 1657 cm(-1) due to phthalate and acetate moieties in PVAP and cyclic amide groups in PVP, respectively, and at 1632 cm(-1) (appeared as a shoulder) due to cyclic amide groups of PVP bound to PVAP. The proton and carbon-13 (solution and solid-state) nuclear magnetic resonance spectra of the complex showed peak profiles that were linear combinations of those of PVAP and PVP. No new peaks appeared and no change in chemical shifts was observed due to complexation. The spectral data suggest that the interaction between PVAP and PVP probably initially involves the formation of hydrogen bonds between carbonyl groups of PVP and carboxylic groups of PVAP at some point of the polymer chains, causing the hydrophilic parts of the two flexible polymer chains strongly hydrophobic. As a result, the two polymer chains coil up into a compact structure and, consequently, precipitate out from the solution as an insoluble complex.

Chemistry, Pharmaceutical↗
PubMed1999

Serum homocysteine levels in postmenopausal breast cancer patients treated with tamoxifen.

Adjuvant treatment of breast cancer with tamoxifen may be associated with reduced risk of cardiovascular disease. Serum homocysteine level has been suggested to be a risk factor for cardiovascular disease influenced by estrogenic hormones. We evaluated a subset of postmenopausal women who had participated in a longitudinal, double-blind, randomized, placebo-controlled toxicity study of tamoxifen 10 mg orally, twice daily. Twenty-seven treated subjects and 37 placebo subjects had measurements of serum homocysteine levels made on previously frozen samples obtained at baseline and after 12 months. After treatment with tamoxifen, we found lower levels of serum homocysteine of borderline statistical significance.

Administration, Oral↗
PubMed1999

Identification of a human histone acetyltransferase related to monocytic leukemia zinc finger protein.

We describe here the identification and functional characterization of a novel human histone acetyltransferase, termed MORF (monocytic leukemia zinc finger protein-related factor). MORF is a 1781-residue protein displaying significant sequence similarity to MOZ (monocytic leukemia zinc finger protein). MORF is ubiquitously expressed in adult human tissues, and its gene is located at human chromosome band 10q22. MORF has intrinsic histone acetyltransferase activity. In addition to its histone acetyltransferase domain, MORF possesses a strong transcriptional repression domain at its N terminus and a highly potent activation domain at its C terminus. Therefore, MORF is a novel histone acetyltransferase that contains multiple functional domains and may be involved in both positive and negative regulation of transcription.

3T3 Cells↗
PubMed1999

[A sero-epidemiological study of HCV and HBV infection among intravenous drug abusers].

OBJECTIVE: To investigate hepatitis B and C virus infection in drug addicts in Guangzhou. METHODS: Serum samples from drug users and normal control people were collected. Serum antibodies against hepatitis C virus (HCV) and hepatitis B virus (HBV) were detected by ELISA. RESULTS: The results showed that hepatitis prevalence is significantly higher among the drug users than that in normal control group (for HCV 67.49% to 3.75%, for HBV 90.48% to 55.63%, and for the mixed infections 62.73% to 3.75%). CONCLUSION: In Guangzhou, the very high infection rates of HBV and HCV were found in drug addicts. Our results emphasize intravenous drug use is the major risk factor for HBV and HCV infections.

Adult↗
PubMed1999

[Effect of exogenous lactase on the absorption of lactose and its intolerance symptoms].

The objective of this study was to evaluate the effects of lactase on lactose malabsorption and its intolerance symptoms, as well as the available way to improve lactose absorption. Healthy adults with a history of lactose intolerance were screened by 25 g lactose tolerance test. The individuals with higher H2 expired and/or lactose intolerance symptoms were selected as the subjects. Subjects were challenged twice with "400 ml low fat milk" and "400 ml low fat milk + 9000Fcc lactase" separately in 3 days interval. The breath H2 concentration and intolerance symptoms were tested in 4 hours after the challenge. The results showed that exogenous lactase can significantly decrease the incidence of lactose malabsorption (the abnormal expiration of H2 decreased from 100% to 48.9%) and milk intolerance symptoms(from 51.1% to 13.3%). The results from this study demonstrate that lactose malabsorption and intolerance symptoms are resulted from the reduced enzyme activities of individuals, and the exogenous lactase can improve lactose absorption and intolerance symptoms. Lactose supplementation may be an available way to increase the dairy consumption and promote health of people.

Adolescent↗
PubMed1999

Soluble member(s) of the mesothelin/megakaryocyte potentiating factor family are detectable in sera from patients with ovarian carcinoma.

mAb OV569 was made by immunizing mice with ovarian carcinoma cells. It binds to cells from ovarian carcinomas and, to a lesser extent, to cells from certain other carcinomas whereas the binding to normal tissues is low to nondetectable. It also binds to soluble molecule(s) in culture supernatants from antigen-positive carcinomas. OV569 recognizes a protein(s) of 42-45 kDa with the same N-terminal amino acid sequence as the membrane-bound portion of mesothelin and megakaryocyte potentiating factor (MPF). Binding assays with fusion proteins comprising either the N-terminal part of mesothelin/MPF (D1Ig), reported to be easily cleaved off, or a noncleavable, membrane-associated part (D2Ig) showed that OV569 only binds to D2hIg. A new member of the mesothelin/MPF family was discovered, which has an 82-bp insert in the membrane-associated part, leading to a frameshift of 212 bp, and whose predicted molecular structure indicates that it is soluble. To test patient sera for soluble tumor antigen, antigen was isolated from cell-free tumor culture supernatants via immunoadsorption with OV569 and used to generate murine mAbs to an epitope different from the one to which OV569 binds, after which mAbs to two different epitopes were used to develop a "sandwich ELISA." Using this assay, the level of circulating antigen was elevated significantly in 23 of 30 sera from patients with ovarian carcinoma, as compared with 0 of 68 sera from healthy controls, 0 of 3 sera from patients with nonneoplastic diseases, and 25 of 75 sera from patients with other tumors. Soluble molecules of the mesothelin/MPF family may provide useful new marker(s) for diagnosis of ovarian carcinoma and/or monitoring its response to therapy.

Amino Acid Sequence↗
PubMed1999

Sequence analysis and expression of the aspartokinase and aspartate semialdehyde dehydrogenase operon from rifamycin SV-producing amycolatopsis mediterranei.

A approximately 4.8 kb KpnI fragment, from the upstream region of the methylmalonyl-CoA mutase gene (mutAB) of rifamycin SV-producing Amycolatopsis mediterranei, was cloned and partially sequenced. Codon preference analysis showed three complete ORFs. ORF2 is internal to ORF1, and encodes a polypeptide corresponding to 172 amino acids, whereas ORF1 encodes a polypeptide of 421 amino acids. They were identified as the encoding genes of aspartokinase alpha- and beta-subunits by comparing the amino acid sequences with those in the database. The downstream ORF3, whose start codon was overlapped with the stop codon of both ORF1 and ORF2 by 1 bp, was identified as the aspartate semialdehyde dehydrogenase gene (asd), encoding a polypeptide of 346 amino acids. Subclones containing either the ask gene or the asd gene were constructed, in which the genes could be expressed under Lac promoters. Two subclones could transform E. coli CGSC 5074 (ask-) and E. coli X6118 (asd-) to prototrophy, supporting the functional assignments. Southern hybridisation indicated that the approximately 4.8 kb sequenced region represented a continuous segment in the A. mediterranei chromosome. It is concluded that ask and asd genes are present in an operon in A. mediterranei, and therefore that organisation of these two genes is the same as in most gram-positive bacteria, such as Mycobacteria, Corynebacterium glutamicum and Bacillus subtilis, but is different from Streptomyces akiyoshiensis.

Actinobacteria↗
PubMed1999

Involvement of the SHP-1 tyrosine phosphatase in regulation of T cell selection.

The selection events shaping T cell development in the thymus represent the outcome of TCR-driven intracellular signaling cascades evoked by Ag receptor interaction with cognate ligand. In view of data indicating TCR-evoked thymocyte proliferation to be negatively modulated by the SHP-1 tyrosine phosphatase, a potential role for SHP-1 in regulating selection processes was investigated by analysis of T cell development in H-Y TCR transgenic mice rendered SHP-1 deficient by introduction of the viable motheaten mutation or a dominant negative SHP-1-encoding transgene. Characterization of thymocyte and peripheral T cell populations in H-Y TCR-viable motheaten mice revealed TCR-evoked proliferation as well as the positive and negative selection of H-Y-specific thymocytes to be enhanced in these mice, thus implicating SHP-1 in the negative regulation of each of these processes. T cell selection processes were also augmented in H-Y TCR mice carrying a transgene driving lymphoid-restricted expression of a catalytically inert, dominant-negative form of SHP-1. SHP-1-negative effects on thymocyte TCR signaling were not influenced by co-cross-linking of the CD28 costimulatory and/or CTLA-4 inhibitory receptors and appear, accordingly, to be realized independently of these comodulators. These observations indicate that SHP-1 raises the signaling threshold required for both positive and negative selection and reveal the inhibitory effects of SHP-1 on TCR signaling to be cell autonomous. The demonstrated capacity for SHP-1 to inhibit TCR-evoked proliferation and selection indicate SHP-1 modulatory effects on the magnitude of TCR-generated signal to be a key factor in determining the cellular consequences of TCR-ligand interaction.

Abatacept↗
PubMed1999

Evidence for an important role of serine 16 and its phosphorylation in the stabilization of c-Mos.

The c-Mos serine/threonine protein kinase is an essential component of cytostatic factor (CSF), which is required for metaphase II arrest of eggs in vertebrates. Previously, we showed that c-Mos residue Ser-16 is phosphorylated in the ts110 Mo-MuSV-encoded Gag-Mos fusion protein. Here we provide evidence that Mos is phosphorylated at Ser-16 in transfected COS-1 cells. To investigate the role of this phosphorylation, Ser-16 was substituted with alanine or glutamic acid in full-length v-Mos (an Env-Mos fusion protein that contains 31 additional amino acids at the amino terminus of c-Mos), its mouse c-Mos equivalent version (v-Mos residues 32-374, hereafter referred to as Mos), and mouse c-Mos. Constructs expressing mutant versions of Mos were transfected into COS-1 and NIH3T3 cells in a transient and stable manner, respectively. Synthesis and proteolysis of Mos were evaluated by pulse-chase analysis of 35S-methionine-labeled proteins. Our findings indicate that the S16A mutant of Mos was highly unstable. It accumulated to approximately 10% of the level of wild-type Mos or its S16E mutant. In addition, the S16A mutation but not the S16E mutation inhibited Mos interaction with a cellular protein, p35, suggesting that phosphorylation at Ser-16 may promote Mos interaction with p35. As expected from its destabilizing effect, the S16A mutation caused a dramatic decrease in the cellular transforming activity of Mos (determined by soft-agar colony-formation assay with the stably transfected NIH3T3 cells), which is known to correlate with its CSF function. Efficient ubiquitin-mediated proteolysis of c-Mos requires proline as the second residue from the amino-terminus. In contrast to Mos, neither the stability nor protein kinase activity of v-Mos (in which c-Mos residue Pro-2 becomes Pro-33) was affected by the S16A mutation. To provide further proof that, similar to c-Mos, the S16A mutant is recognized by the proteolysis system through Pro-2, we show that the effect of the S16A mutation is reversed by the Pro-2-Ala mutation. Thus, our results indicate that Ser-16 has an important role in the regulation of c-Mos and that phosphorylation at Ser-16 may inhibit proteolysis of c-Mos.

3T3 Cells↗
PubMed1999

Integrators of the cytoskeleton that stabilize microtubules.

Sensory neurodegeneration occurs in mice defective in BPAG1, a gene encoding cytoskeletal linker proteins capable of anchoring neuronal intermediate filaments to actin cytoskeleton. While BPAG1 null mice fail to anchor neurofilaments (NFs), BPAG1/NF null mice still degenerate in the absence of NFs. We report a novel neural splice form that lacks the actin-binding domain and instead binds and stabilizes microtubules. This interaction is functionally important; in mice and in vitro, neurons lacking BPAG1 display short, disorganized, and unstable microtubules defective in axonal transport. Ironically, BPAG1 neural isoforms represent microtubule-associated proteins that when absent lead to devastating consequences. Moreover, BPAG1 can functionally account for the extraordinary stability of axonal microtubules necessary for transport over long distances. Its isoforms interconnect all three cytoskeletal networks, a feature apparently central to neuronal survival.

Actin Cytoskeleton↗
PubMed1999

In vivo ligand specificity of E-selectin binding to multivalent sialyl Lewisx N-linked oligosaccharides.

The in vivo specificity for E-selectin binding to a panel of N-linked oligosaccharides containing a clustered array of one to four sialyl Lewisx (SLex; NeuAcalpha2-3Gal[Fucalpha1-3]beta1-4GlcNAc) determinants was studied in mice. Following intraperitoneal dosing with lipopolysaccharide, radioiodinated tyrosinamide N-linked oligosaccharides were dosed i.v. and analyzed for their pharmacokinetics and biodistribution. Specific targeting was determined from the degree of SLex oligosaccharide targeting relative to a sialyl oligosaccharide control. Oligosaccharides targeted the kidney with the greatest selectivity after a 4-h induction period following lipopolysaccharide dosing. Unique pharmacokinetic profiles were identified for SLex biantennary and triantennary oligosaccharides but not for monovalent and tetraantennary SLex oligosaccharides or sialyl oligosaccharide controls. Biodistribution studies established that both SLex biantennary and triantennary oligosaccharides distributed to the kidney with 2-3-fold selectivity over sialyl oligosaccharide controls, whereas monovalent and tetraantennary SLex oligosaccharides failed to mediate specific kidney targeting. Simultaneous dosing of SLex biantennary or triantennary oligosaccharide with a mouse anti-E-selectin monoclonal antibody blocked kidney targeting, whereas co-administration with anti-P-selectin monoclonal antibody did not significantly block kidney targeting. The results suggest that SLex biantennary and triantennary are N-linked oligosaccharide ligands for E-selectin and implicate E-selectin as a bivalent receptor in the murine kidney endothelium.

Animals↗
PubMed1999

Evidence of an interaction between Mos and Hsp70: a role of the Mos residue serine 3 in mediating Hsp70 association.

c-Mos is a germ cell-specific MAP kinase kinase kinase (MAPKKK) that plays an essential role during meiotic divisions of oocytes. c-Mos is a key component of an activity, cytostatic factor, required for metaphase II arrest of unfertilized eggs in vertebrates. To understand the regulation of c-Mos, we are investigating c-Mos-interacting proteins. We provide evidence that mouse c-Mos binds to Hsp70, a molecular chaperone. Hsp70 was found to associate with Mos ectopically expressed in COS-1 cells. Mos-Hsp70 complexes could be immunoprecipitated with both Mos and Hsp70 antibodies. Despite a low-abundance of Mos, the Hsp70 antibody immunoprecipitated Mos as the major protein. Of importance, the Mos protein present in anti-Hsp70 immunoprecipitates functioned as an active MAPKKK indicating that it is not grossly misfolded. It is known that c-Mos protein kinase activity in cell extracts of transfected COS-1 or NIH3T3 cells is labile. We found that the inclusion of adenosine triphosphate (ATP) in cell extracts protected against the loss of Mos kinase activity. In the absence of ATP from cell extracts, protein kinase activity of Mos was lost within 6 h on ice even though the Mos protein was not degraded and remained bound to Hsp70. Based on our identification of c-Mos-Hsp70 interaction, one of the roles of ATP may be to assist the regulation of c-Mos via ATP involvement in the protein-folding function of Hsp70 and possibly other molecular chaperones. We also detected by coimmunoprecipitation a physical association between endogenous c-Mos and Hsp70 in Xenopus eggs. To provide further evidence for the functional significance of Hsp70 interaction to Mos function, we show that the residue serine 3 in Mos, which is important for the regulation of protein kinase activity of Mos is also important for Hsp70 association.

Animals↗