Biomedical subjects

M L Liou

Publications and source records attributed to M L Liou.

8 recordsLinked to original sources

PubMed2006

Association of serum protein levels with egg productivity in Taiwan red-feathered country chickens.

This study investigated the relationship between serum protein levels and egg productivity in Taiwan red-feathered country chickens (TRFCC). The total egg numbers of TRFCC (n=157) were recorded from 25 to 48 weeks of age. Serum samples were collected at 24 and 35 weeks of age, then classified by total egg number into four groups according to mean+/-1S.D. Serum X protein levels were evaluated by protein chip technology and with an insulin-like growth factor-I (IGF-I) immunoassay. Other serum proteins (apolipoprotein A-I, ovotransferrin and vitellogenin) were found at different levels between the most productive and the least productive groups of TRFCC, were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and were quantified by age. The results showed that levels of vitellogenin were positively correlated with total egg number at 24 and at 35 weeks old (p<0.01). Levels of apolipoprotein A-I and an IGF-1-related marker (termed X protein) in serum at 35 weeks old were correlated with total egg number (p<0.01). Serum ovotransferrin levels remained constant regardless of total egg number. To investigate the concentration differences among the four groups of TRFCC, serum protein levels of each group were analyzed by one-way ANOVA. The results showed that those protein levels, except for ovotransferrin, in the least productive group significantly differed from the other three groups (p<0.05). Although the correlation between those protein levels and the total egg number was not significant at the time of initial egg production, the selection strategy of those protein levels at later stages of egg production should provide a screening model to improve selection.

Aging↗

PubMed1999

The ubiquitin-homology protein, DAP-1, associates with tumor necrosis factor receptor (p60) death domain and induces apoptosis.

The tumor necrosis factor receptor, p60 (TNF-R1), transduces death signals via the association of its cytoplasmic domain with several intracellular proteins. By screening a mammalian cDNA library using the yeast two-hybrid cloning technique, we isolated a ubiquitin-homology protein, DAP-1, which specifically interacts with the cytoplasmic death domain of TNF-R1. Sequence analysis reveals that DAP-1 shares striking sequence homology with the yeast SMT3 protein that is essential for the maintenance of chromosome integrity during mitosis (Meluh, P. B., and Koshland, D. (1995) Mol. Biol. Cell 6, 793-807). DAP-1 is nearly identical to PIC1, a protein that interacts with the PML tumor suppressor implicated in acute promyelocytic leukemia (Boddy, M. N., Howe, K., Etkin, L. D., Solomon, E., and Freemont, P. S. (1996) Oncogene 13, 971-982), and the sentrin protein, which associates with the Fas death receptor (Okura, T., Gong, L., Kamitani, T., Wada, T., Okura, I., Wei, C. F., Chang, H. M., and Yeh, E. T. (1996) J. Immunol. 157, 4277-4281). The in vivo interaction between DAP-1 and TNF-R1 was further confirmed in mammalian cells. In transient transfection assays, overexpression of DAP-1 suppresses NF-kappaB/Rel activity in 293T cells, a human kidney embryonic carcinoma cell line. Overexpression of either DAP-1 or sentrin causes apoptosis of TNF-sensitive L929 fibroblast cell line, as well as TNF-resistant osteosarcoma cell line, U2OS. Furthermore, the dominant negative Fas-associated death domain protein (FADD) protein blocks the cell death induced by either DAP-1 or FADD. Collectively, these observations highly suggest a role for DAP-1 in mediating TNF-induced cell death signaling pathways, presumably through the recruitment of FADD death effector.

Amino Acid Sequence↗

PubMed1999

c-Rel is crucial for lymphocyte proliferation but dispensable for T cell effector function.

The TCR signals are essential for T cell activation and proliferation, primarily through the induction of cytokine and cytokine receptors. Several transcription factor families, including NF-kappaB/Rel, have been implicated in the regulation of cytokine gene expression in T cells in response to antigen, cytokine and mitogenic stimulation. In this study, we show that the mice with a null mutation in the lymphoid-specific c-Rel gene have normal development of lymphoid tissues and T cell compartment. However, T cells derived from the c-Rel knockout mice have several functional abnormalities. The c-Rel-deficient T lymphocytes fail to respond to activation and proliferation signals mediated by the TCR and mitogens in vitro. This is attributed to an impaired production of cytokines IL-2, IL-3 and granulocyte macrophage colony stimulating factor. In addition, the induction of IL-2R alpha chain is impaired in the c-Rel(-/-) T cells. The poor expression of cytokines and IL-2R alpha chain correlates with a reduced nuclear translocation of NF-kappaB components in c-Rel(-/-) T cells. Since activation is prerequisite for differentiation into effector cells, c-Rel(-/-) T cells failed to differentiate into cytotoxic T cells or Th cells without rescuing cytokines. However, upon supplement with exogenous IL-2, the c-Rel(-/-) cytotoxic T lymphocytes are able to execute cytotoxicity and the c-Rel(-/-) Th cells are capable of providing help to normal B cells. These data suggest that c-Rel is important for inducible cytokine and cytokine receptor expression, and a key regulator of early activation and proliferation in T cells.

Animals↗

PubMed1998

c-Rel is essential for B lymphocyte survival and cell cycle progression.

c-Rel is a lymphoid-specific member of the NF-kappaB/Rel family of transcriptional factors. To investigate the role of c-Rel in B lymphocyte function, we generated a c-Rel(-/-) mouse via a gene targeting approach. Although early lymphocyte development is normal in c-Rel(-/-) mice, there are significantly fewer B cells displaying a memory (IgM/IgD-) phenotype. Upon immunization, c-Rel(-/-) mice generate fewer B cells with a germinal center (PNAhi) phenotype. In vitro, c-Rel(-/-) B cells proliferate poorly upon ligation of their surface IgM or CD40 receptors or when stimulated with either lipopolysaccharide (LPS) or T cell help. Early molecular events that precede proliferation, such as increases in RNA synthesis as well as IL-2 receptor alpha chain expression, are greatly diminished in c-Rel(-/-) B cells. Furthermore, c-Rel(-/-) B cells are impaired in the ability to receive survival signals generated by anti-IgM or LPS. In contrast, CD40-mediated cell survival is normal in c-Rel(-/-) B cells, suggesting the involvement of a survival-signaling pathway that is independent of c-Rel. When c-Rel (-/-) B cells are co-stimulated with either anti-IgM and CD40 or LPS and CD40, they are rendered capable of progressing through the cell cycle. Finally, co-culture experiments suggest that the defects observed in c-Rel(-/-) B cells are intrinsic to the cell and can not be rescued through either cell-cell contact or addition of soluble factors. Thus, c-Rel is requisite for differentiation to the germinal center and memory B cells in vivo and is required for the transduction of survival and cell cycle progression signals mediated by anti-IgM and LPS in vitro. Furthermore, while c-Rel is involved in CD40-induced proliferation, it is apparently dispensable for the survival signals transduced by CD40.

Animals↗

PubMed1998

Japanese encephalitis virus is transported across the cerebral blood vessels by endocytosis in mouse brain.

Japanese encephalitis (JE) virus principally infects neuron systems of animals and causes severe encephalitis. The mechanism by which the virus enters the central nervous system (CNS) from the circulatory system remains elusive. In this study, electron-microscopic techniques have been used to determine these sequential events in the suckling mouse brain. The results indicate that (1) endocytosis is employed when JE virus is transported across the cerebral blood vessels (CBV) and breaches the blood-brain barrier (BBB). (2) Uncoated vesicles, which may be caveolae, and coated vesicles are involved in the endocytic and transcytotic vesicles of capillary endothelium and pericytes. (3) The JE virus is transported in endocytic vesicles across the endothelial cells and pericytes. (4) Endocytosis and transportation of JE virus in pericytes seems to be the same as that in endothelial cells. (5) The interaction of the viral envelope and cell membrane of endothelial cells and pericytes plays an important role in the endocytosis. This study elucidates the infectious processes of JE virus entering the CNS from the circulatory system in the mouse brain.

Animals↗

PubMed1996

CD30/TNF receptor-associated factor interaction: NF-kappa B activation and binding specificity.

CD30 is a member of the tumor necrosis factor (TNF) receptor superfamily. CD30 is expressed on normal activated lymphocytes, on several virally transformed T- or B-cell lines and on neoplastic cells of Hodgkin's lymphoma. The interaction of CD30 with its ligand induces pleiotropic effects on cells resulting in proliferation, differentiation, or death. The CD30 cytoplasmic tail interacts with TNF receptor-associated factors (TRAFs), which have been shown to transduce signals mediated by TNF-R2 and CD40. We demonstrate here that TRAF2 also plays an important role in CD30-induced NF-kappa B activation. We also show that TRAF2-mediated activation of NF-kappa B plays a role in the activation of HIV transcription induced by CD30 cross-linking. Detailed site-directed mutagenesis of the CD30 cytoplasmic tail reveals that there are two independent binding sites for TRAF, each interacting with a different domain of TRAF. Furthermore, we localized the TRAF-C binding site in CD30 to a 5-7 amino acid stretch.

Amino Acid Sequence↗

PubMed1993

cAMP analogs prevent activation-induced apoptosis of T cell hybridomas.

Activation of T cell hybridomas through their TCR leads to secretion of IL-2, inhibition of proliferation, and apoptosis. The identification of various inhibitors that prevent activation-induced T cell death (AICD) has helped identify several essential events in apoptosis. For example, inhibition of AICD by dexamethasone indicates a connection between these two programmed death pathways. In this study, we have investigated the interaction between the cAMP signal transduction pathway and the activation- or glucocorticoid-induced cell death. cAMP induced DNA fragmentation in thymocytes. T cell hybridomas displayed different sensitivity to cAMP. Regardless of its cAMP sensitivity, programmed cell death promoted by anti-CD3 or Ag in hybridoma was prevented by the presence of cAMP analogs. In contrast, cAMP had no effect on glucocorticoid-induced T cell death. The inhibitory effect of cAMP on AICD was unlikely to be due to quenching of T cell activation signals, because cAMP added 1 h after T cell activation could still prevent cell death. In addition, the increased binding of AP-1, NF-AT, and NF-kappa B during T cell activation was not significantly affected by cAMP. The presence of the inhibitory cAMP-mediated signals, together with the glucocorticoid-induced pathway, suggest there are at least two distinct mechanisms regulating AICD in immature lymphocytes.

Amino Acid Sequence↗

PubMed1992

Isolation and characterization of nuclear proteins that bind to T cell receptor V beta decamer motif.

TCR V beta promoter contains a highly conserved decamer homologous to cAMP response element (CRE). Recent studies have identified this CRE decamer as the dominant transcription-activating element within the TCR V beta promoter. We have isolated cDNA clones, TCR-ATF1 and TCR-ATF2, encoding DNA-binding proteins that recognize this CRE motif. The nucleotide sequence of TCR-ATF1 has not previously been reported, whereas that of TCR-ATF2 was homologous to CRE-BP1, ATF-2, and mXBP. Both TCR-ATF1 and TCR-ATF2 shared a conserved leucine zipper and DNA binding motif with other CRE-binding proteins. TCR-ATF1 and TCR-ATF2 were expressed in all cell lines examined and in mouse embryos as early as 12.5 days. Despite binding to the same CRE motif, TCR-ATF1 and TCR-ATF2 were different from CREB in the fine nucleotide specificity. TCR-ATF bound methylated CRE and CRE mutant M4 (4C----G) that were not recognized by CREB. Additionally, TCR-ATF1 weakly recognized two other single nucleotide mutants of V beta-CRE that were not bound by TCR-ATF2 and CREB. We have further demonstrated that TCR beta-chain expression was immediately activated by cAMP. Such induction is likely mediated through V beta-CRE sequence, because the inclusion of V beta-CRE in a vector with minimum promoter (pBLCAT2) conferred the cAMP inducibility of CAT activity.

Amino Acid Sequence↗