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Biomedical subjects

L Lu

Publications and source records attributed to L Lu.

At least 415 records · Page 23Linked to original sources
PubMed1995

Immobilized liposome chromatography for analysis of interactions between lipid bilayers and peptides.

Liposomes were sterically immobilized in gel beads to be used for isocratic chromatographic analysis of interactions between lipid bilayers, amino acids, and water-soluble peptides. Tryptophan was more retarded on the immobilized liposomes than were other amino acids, and peptides with C-terminal cysteine were much more retarded than were peptides with serine or aminobutyric acid instead of the cysteine. Peptide sequences could affect the peptide-liposome interactions. For peptides corresponding to polypeptide segments of a membrane protein, the human red cell glucose transporter (Glut1), the retention volumes increased with decreasing water-to-oil transfer free energy of the peptides and were related to the transfer free energy distribution within the peptides as shown by hydropathy plots and to the presence of cysteine. Among these peptides, the partially hydrophobic peptides 125GRFIIGVYCG134 and 201CIVLPFCPES210 and the hydrophilic peptide 421CFQYVEQLC429 were most strongly retarded on immobilized phosphatidylcholine liposomes. The results indicated that the peptide-liposome interactions were mainly of hydrophobic nature and that the structure of the interfacial head-group region of the lipid bilayers was important.

Amino Acid Sequence↗
PubMed1995

Growth of donor-derived dendritic cells from the bone marrow of murine liver allograft recipients in response to granulocyte/macrophage colony-stimulating factor.

Allografts of the liver, which has a comparatively heavy leukocyte content compared with other vascularized organs, are accepted permanently across major histocompatibility complex barriers in many murine strain combinations without immunosuppressive therapy. It has been postulated that this inherent tolerogenicity of the liver may be a consequence of the migration and perpetuation within host lymphoid tissues of potentially tolerogenic donor-derived ("chimeric") leukocytes, in particular, the precursors of chimeric dendritic cells (DC). In this study, we have used granulocyte/macrophage colony-stimulating factor to induce the propagation of progenitors that give rise to DC (CD45+, CD11c+, 33D1+, nonlymphoid dendritic cell 145+, major histocompatibility complex class II+, B7-1+) in liquid cultures of murine bone marrow cells. Using this technique, together with immunocytochemical and molecular methods, we show that, in addition to cells expressing female host (C3H) phenotype (H-2Kk+; I-E+; Y chromosome-), a minor population of male donor (B10)-derived cells (H-2Kb+; I-A+; Y chromosome+) can also be grown in 10-d DC cultures from the bone marrow of liver allograft recipients 14 d after transplant. Highly purified nonlymphoid dendritic cell 145+ DC sorted from these bone marrow-derived cell cultures were shown to comprise approximately 1-10% cells of donor origin (Y chromosome+) by polymerase chain reaction analysis. In addition, sorted DC stimulated naive, recipient strain T lymphocytes in primary mixed leukocyte cultures. Evidence was also obtained for the growth of donor-derived cells from the spleen but not the thymus. In contrast, donor cells could not be propagated from the bone marrow or other lymphoid tissues of nonimmunosuppressed C3H mice rejecting cardiac allografts from the same donor strain (B10). These findings provide a basis for the establishment and perpetuation of cell chimerism after organ transplantation.

Animals↗
PubMed1995

Cloning and expression of a second photoreceptor-specific membrane retina guanylyl cyclase (RetGC), RetGC-2.

One of the membrane guanylyl cyclases (GCs), RetGC, is expressed predominantly in photoreceptors. No extracellular ligand has been described for RetGC, but it is sensitive to activation by a soluble 24-kDa protein (p24) and is inhibited by Ca2+. This enzyme is, therefore, thought to play a role in resynthesizing cGMP for photoreceptor recovery or adaptation. By screening a human retinal cDNA library at low stringency with the cytoplasmic domains from four cyclases, we cloned cDNAs encoding a membrane CG that is most closely related to RetGC. We have named this GC RetGC-2, and now term the initially described RetGC RetGC-1. By in situ hybridization, mRNA encoding RetGC-2 is found only in the outer nuclear layer and inner segments of photoreceptor cells. By using synthetic peptide antiserum specific for each RetGC subtype, RetGC-2 can be distinguished from RetGC-1 as a slightly smaller protein in immunoblots of bovine rod outer segments. Membrane GC activity of recombinant RetGC-2 expressed in human embryonic kidney 293 cells is stimulated by the activator p24 and is inhibited by Ca2+ with an EC50 value of 50-100 nM. Our data reveal a previously unappreciated diversity of photoreceptor GCs.

Amino Acid Sequence↗
PubMed1995

Involvement of SH2-containing phosphotyrosine phosphatase Syp in erythropoietin receptor signal transduction pathways.

Erythropoietin (Epo) regulates the proliferation and differentiation of erythroid precursors. The phosphorylation of proteins at tyrosine residues is critical in the growth signaling induced by Epo. This mechanism is regulated by the activities of both protein-tyrosine kinases and protein tyrosine phosphatases. The discovery of phosphotyrosine phosphatases that contain SH2 domains suggests roles for these molecules in growth factor signaling pathways. We found that Syp, a phosphotyrosine phosphatase, widely expressed in all tissues in mammals became phosphorylated on tyrosine after stimulation with Epo in M07ER cells engineered to express high levels of human EpoR. Syp was complexed with Grb2 in Epo-stimulated M07ER cells. Direct binding between Syp and Grb2 was also observed in vitro. Furthermore, Syp appeared to bind directly to tyrosine-phosphorylated EpoR in M07ER cells. Both NH2-terminal and COOH-terminal SH2 domains of Syp, made as glutathione S-transferase fusion proteins, were able to bind to the tyrosine-phosphorylated EpoR in vitro. These results suggest that Syp may be an important signaling component downstream of the EpoR and may regulate the proliferation and differentiation of hematopoietic cells.

Adaptor Proteins, Signal Transducing↗
PubMed1995

In vitro propagation and homing of liver-derived dendritic cell progenitors to lymphoid tissues of allogeneic recipients. Implications for the establishment and maintenance of donor cell chimerism following liver transplantation.

Dendritic cell (DC) progenitors were propagated in liquid culture from nonparenchymal cells resident in normal mouse (B10.BR; H-2k, I-E+) liver in response to granulocyte-macrophage colony stimulating factor (GM-CSF). The liver-derived DC progenitors were MHC class II-/dim and did not express counter receptors for CTLA-4, a structural homologue of the T cell activation molecule CD28. Following subcutaneous or intravenous injection, these liver-derived cells migrated to T cell-dependent areas of lymph nodes and spleen of unmodified, allogeneic (B10; H-2b; I-E-) recipients, where they were identified 1-5 days, and 1 and 2 months after injection by their strong surface expression of donor MHC class II (I-Ek) and their dendritic morphology. Maximal numbers of liver-derived DC in the spleen were recorded 5 days after injection. Both clusters of strongly donor MHC class II+ cells--and (more rarely) dividing cells--could also be identified, suggesting cell replication in situ. Using the same techniques employed to generate DC progenitors from normal liver, GM-CSF-stimulated cells were propagated for 10 days from the bone marrow and spleen of nonimmunosuppressed mice sacrificed 14 days after orthotopic liver transplantation (B10;H-2b-->C3H;H-2k). Immunocytochemical staining for recipient and donor MHC class II phenotype revealed the growth both of host cells with DC characteristics, and of cells expressing donor alloantigens (I-Ab). These results are consistent with the growth, in response to GM-CSF, of donor-derived DC from progenitors seeded from the liver allograft to recipient lymphoid tissue. The functional activity of the progenitors of chimeric DC and the possible role of these cells in the establishment and maintenance of donor-specific tolerance following liver transplantation remain to be determined.

Animals↗
PubMed1995

Application of immunostaining for muscle specific actin in detection of myoepithelial cells in breast fine-needle aspirates.

Myoepithelial cells play an important role in the interpretation of breast fine-needle aspiration biopsy, since these cells are believed to be a component of a benign process in breast lesions. Myoepithelial cells are usually easy to recognize, however, other cells can morphologically simulate myoepithelial cells and make the distinction difficult. To assess the feasibility of immunostaining as an adjunct to identify myoepithelial cells, we have used immunocytochemistry using monoclonal antibody against muscle specific actin (MSA) in our breast fine-needle aspirates. Herein, we report our experience in immunocytochemical detection of myoepithelial cells using labeled Streptavidin Biotin Detection System on destained Papanicolaou stained smears and cell block preparations obtained from breast aspirates.

Actins↗
PubMed1995

Microchimerism, dendritic cell progenitors and transplantation tolerance.

The recent discovery of multilineage donor leukocyte microchimerism in allograft recipients up to three decades after organ transplantation implies the migration and survival of donor stem cells within the host. It has been postulated that in chimeric graft recipients, reciprocal modulation of immune responsiveness between donor and recipient leukocytes may lead, eventually, to the induction of mutual immunologic nonreactivity (tolerance). A prominent donor leukocyte, both in human organ transplant recipients and in animals, has invariably been the bone marrow-derived dendritic cell (DC). These cells have been classically perceived as the most potent antigen-presenting cells but evidence also exists for their tolerogenicity. The liver, despite its comparatively heavy leukocyte content, is the whole organ that is most capable of inducing tolerance. We have observed that DC progenitors propagated from normal mouse liver in response to GM-CSF express only low levels of major histocompatibility complex (MHC) class II antigen and little or no cell surface B7 family T cell costimulatory molecules. They fail to activate resting naive allogeneic T cells. When injected into normal allogeneic recipients, these DC progenitors migrate to T-dependent areas of host lymphoid tissue, where some at least upregulate cell surface MHC class II. These donor-derived cells persist indefinitely, recapitulating the behavior pattern of donor leukocytes after the successful transplantation of all whole organs, but most dramatically after the orthotopic (replacement) engraftment of the liver. A key finding is that in mice, progeny of these donor-derived DC progenitors can be propagated ex vivo from the bone marrow and other lymphoid tissues of nonimmunosuppressed spontaneously tolerant liver allograft recipients. In humans, donor DC can also be grown from the blood of organ allograft recipients whose organ-source chimerism is augmented with donor bone marrow infusion. DC progenitors cannot, however, be propagated from the lymphoid tissue of nonimmunosuppressed cardiac-allografted mice that reject their grafts. These findings are congruent with the possibility that bidirectional leukocyte migration and donor cell chimerism play key roles in acquired transplantation tolerance. Although the cell interactions are undoubtedly complex, a discrete role can be identified for DC under well-defined experimental conditions. Bone marrow-derived DC progenitors (MHC class II+, B7-1dim, B7-2-) induce alloantigen-specific hyporesponsiveness (anergy) in naive T cells in vitro. Moreover, costimulatory molecule-deficient DC progenitors administered systemically prolong the survival of mouse heart or pancreatic islet allografts. How the regulation of donor DC phenotype and function relates to the balance between the immunogenicity and tolerogenicity of organ allografts remains to be determined.

Animals↗
PubMed1995

Myeloid progenitor cell regulatory effects of vascular endothelial cell growth factor.

Vascular endothelial cell growth factor (VEGF) is a ligand for the tyrosine kinase receptor Flk-1/KDR and Flt1 and is considered to be an endothelial cell specific mitogen that plays an important role in angiogenesis. Since Flk-1 mRNA has been detected in primitive and more mature hematopoietic cells, recombinant human VEGF was evaluated for its influence on hematopoiesis, which was assayed as in vitro colony formation by myeloid progenitor cells from human bone marrow. VEGF enhanced colony formation by mature subsets of granulocyte-macrophage and erythroid progenitor cells that had been stimulated with a colony stimulating factor. In contrast, VEGF inhibited colony formation by more immature subsets of granulocyte-macrophage, erythroid and multipotential progenitor cells synergistically stimulated to proliferate with a colony stimulating factor and either steel factor or the ligand for the Flt-3 receptor tyrosine kinase. VEGF produced effects similar to those given above on purified CD34 progenitor cells from bone marrow and VEGF effects were neutralized by VEGF antibodies. However, when assessed for effects on single sorted CD34 cells, VEGF only enhanced or suppressed colony formation by granulocyte-macrophage progenitor cells and the amplitude of the response was less than that observed when populations of these cells were tested. In the single cell assays, VEGF had no effect on colony formation by erythroid or multipotential progenitors. These results suggest that the effects of VEGF, which were not species specific, are mediated by both direct and indirect actions on the progenitors and thereby identify new activities for this important factor.

Animals↗
PubMed1995

Life events, social support, and depression among Taiwanese female homemakers.

Eighty-five female homemakers in a Taiwanese city were surveyed. Multiple regression analysis indicated that age, life events, and social support were related to depression symptomatology. Younger homemakers reported more depressive symptoms than their older counterparts did. Life events were related to depression, and social support acted as a buffer against depression.

Adaptation, Psychological↗
PubMed1995

The relationship between subjective well-being and psychosocial variables in Taiwan.

Psychosocial factors that may influence subjective well-being were examined. A random sample of 581 Chinese adults living in a metropolitan Taiwanese city completed questionnaires concerning demographic variables, personality traits, life stress, and social support. The results of multivariate analyses indicated that (a) extraversion and social support were related to better mental health, whereas neuroticism and stress were related to poorer mental health; (b) older age, better education, and social support were related to higher life satisfaction, whereas neuroticism and stress were related to lower life satisfaction; and (c) older age, extraversion, and social support were related to higher happiness, whereas neuroticism was related to lower happiness.

Adult↗
PubMed1995

A fast parametric modelling algorithm with the Powell method.

This paper presents a model that comprises only two parameters (R/S, fr) and the application of three function minimization algorithms (simplex, Powell and modified Powell) to this model to obtain parametric images. Comparisons among the three algorithms in terms of efficiency and reliability were carried out. It was found that, with proper initialization by taking the shape of the modelled data into consideration, the minimization function can be approximated by a quadratic function near the minimum point, therefore the iteration times can be minimized in the modified Powell method. The results show that with the modified Powell method a substantial reduction of computation time can be achieved in the parametric imaging. This makes it possible to obtain a 16 x 16 parametric image in 1 s.

Algorithms↗
PubMed1995

Measured and expected Cole parameters from electrical impedance tomographic spectroscopy images of the human thorax.

Electrical impedance tomographic spectroscopy (EITS) images have been recorded from a group of 12 normal subjects using frequencies from 9.6 kHz to 1.2 MHz. The impedance changes with frequency have been modelled on a pixel by pixel basis to produce parametric images as a means of characterizing tissue. The modelling was based on the Cole equation. The lungs are seen as areas of high characteristic frequency and low time constants SC and RS. The R/S images are much less uniform over the region of the lungs. Values characterizing the lung and cardiac regions are given. The results appear to be consistent with a model for the lungs whereby the model parameters can be related to alveolar structure and composition.

Adult↗
PubMed1995

Eicosapentaenoic acid-induced changes in membrane fluidity and cell adhesion molecules in cultured human keratinocytes.

The effects of eicosapentaenoic acid (EPA, 20:5n-3) on the lipid dynamics of cultured epidermal keratinocytes and their expression of cell adhesion molecules were investigated, and were compared with those of arachidonic acid (AA, 20:4n-6). When keratinocytes were treated with 3 micrograms/ml of EPA or AA for 72 h, these compounds were found to be incorporated into the cells. EPA-induced lipid changes were distinguished by a significant increase in the cellular content of n-3 polyunsaturated fatty acids, whereas AA treatment resulted in an increase in the cellular content of n-6 arachidonic acid. These changes in fatty acid composition were accompanied by an increase in cellular membrane fluidity, which was evaluated by the diffusion coefficient, using the method of fluorescence recovery after photobleaching (FRAP) [from 1.77 +/- 0.34 x 10(-8) cm2/s untreated to 2.23 +/- 0.35 x 10(-8) cm2/s EPA-treated (P < 0.001), and 2.16 +/- 0.35 x 10(-8) cm2/s AA-treated (P < 0.001)]. Intercellular adhesion molecule-1 (ICAM-1) was induced on the keratinocyte membrane in the presence of tumour necrosis factor-alpha and interferon-gamma, and pretreatment with EPA or AA further enhanced the expression, almost to an equal degree, as estimated by flow cytometry (P < 0.05). These results indicate that the modulation of ICAM-1 expression does not seem to be EPA-specific, but is presumably a consequence of increased membrane fluidity due to the increased levels of unsaturated fatty acids of both the n-3 and n-6 series in the membrane.

Arachidonic Acid↗
PubMed1995

Comparison of characteristics of Q beta replicase-amplified assay with competitive PCR assay for Chlamydia trachomatis.

In order to study infections due to Chlamydia trachomatis, we have compared semiquantitative PCR and Q beta replicase-amplified assays for detection of this organism. The PCR assay was directed against the C. trachomatis 16S rRNA gene. Quantitation was accomplished by adding known amounts of a plasmid containing a truncated segment of the 16S rRNA gene target to chlamydia-containing samples and then amplifying with a common primer set. The Q beta replicase assay consisted of reversible target capture of C. trachomatis 16S rRNA, which was followed by amplification of an RNA detector probe in the presence of the enzyme Q beta replicase. In a clinical matrix, the lower limit of detection of both the PCR and Q beta replicase assays was five elementary bodies. The Q beta replicase and PCR assays were quantitative over 10,000- and 1,000-fold ranges of organisms, respectively. Analysis of the effects of endocervical matrix on amplification was accomplished by examining 94 endocervical specimens by each technique. Both assays detected five of six culture-confirmed specimens as well as three culture-negative specimens. PCR inhibitors were detected in 13 specimens. The Q beta replicase assay, in contrast, showed no evidence of sample inhibition. The Q beta replicase and PCR assays should allow quantitative investigation of infections due to C. trachomatis. In addition, because it targets highly labile RNA, the Q beta replicase assay may facilitate investigations into the role of active persisting infection in culture-negative inflammatory conditions.

Base Sequence↗