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Biomedical subjects

L Lu

Publications and source records attributed to L Lu.

At least 379 records · Page 21Linked to original sources
PubMed1996

Retroviral transfer of the recombinant human erythropoietin receptor gene into single hematopoietic stem/progenitor cells from human cord blood increases the number of erythropoietin-dependent erythroid colonies.

To test whether an enforced expression of a lineage-specific cytokine receptor would influence the proliferation/differentiation of hematopoietic stem/progenitor cells, retroviral vectors containing the human erythropoietin receptor (hEpoR) gene were used to transduce the hEpoR gene into phenotypically sorted subsets of cells. CD34 , CD34++CD33-, and CD34++CD33+ populations of human cord blood, highly enriched for hematopoietic stem/progenitor cells, were sorted and plated as single cells per well in methylcellulose culture medium containing early acting growth factors in the presence or absence of Epo. The hEpoR gene was efficiently transduced into single high proliferative potential colony-forming cells (HPP-CFC) and multipotential (colony-forming unit granulocyte, erythroid, monocyte, megakaryocyte [CFU-GEMM]), erythroid (burst-forming unit-erythroid [BFU-E]), and granulocyte-macrophage (colony-forming unit-granulocyte-macrophage [CFU-GM]) progenitor cells. As expected in cultures grown in the absence of Epo, no BFU-E or CFU-GEMM colonies grew. In the presence of Epo, the hEpoR-gene transduced cells formed significantly more CFU-GEMM and BFU-E colonies than did the controls. A significant decrease in HPP-CFC colonies was also observed under these conditions. Little or no effect of hEpoR gene transduction was apparent in the numbers of CFU-GM colonies formed in the presence or absence of Epo. All of the above results were similar whether the cell populations assessed were CD34 or their CD33- or CD33+ subsets plated in the presence of growth factors at 200 cells/mL or after limiting dilution at 2 cells/well. These results suggest that the profile of detectable stem/progenitors can be altered by retrovirus-mediated expression of the hEpoR gene.

Antigens, CD↗
PubMed1996

Hematopoietic stem cells in the mouse embryonic yolk sac.

The yolk sac is the first site of hematopoiesis during mammalian development. The yolk sac is also the first site of blood vessel development. Development of the blood islands in the yolk sac is an integrated process in which these two developmental events, hematopoiesis and vasculogenesis, proceed in concert. This review focuses on mouse yolk sac hematopoietic stem cells (YS-HSC), describing their differentiation in vitro and in vivo. YS-HSC go through a progressive series of changes prior to the initiation of lineage-specific differentiation. Experiments tracing their origins from postulated hemangioblasts, and the subsequent interaction between these stem cells and yolk sac endothelial cells are described. Differences between the extraembryonic YS-HSC and HSC found later within the embryo, perinatally or in adults, are described. YS-HSC have greater reproductive capability than HSC obtained from fetal liver, umbilical cord blood or adult bone marrow; they do not yet express major histocompatibility complex-associated antigens and they are able to reconstitute adult immunocompromised animals even when introduced in small numbers (< 100 cells/mouse). With recent results demonstrating the feasibility of expanding YS-HSC in vitro as well as of introducing new genes into these cells by transfection, the YS-HSC shows promise both as a means of achieving long-term restitution of hematopoiesis across histocompatibility barriers and as a self-renewing vehicle for gene transfer.

Animals↗
PubMed1996

Identification of a novel missense mutation in the cardiac beta-myosin heavy chain gene in a Chinese patient with sporadic hypertrophic cardiomyopathy.

The exons 13, 16, 21 and 23 of cardiac beta-myosin heavy chain (MHC) gene from 32 Chinese patients with hypertrophic cardiomyopathy were analyzed by the polymerase chain reaction and the DNA single strand conformation polymorphism (PCR-SSCP) procedure. The results showed an altered SSCP in exon 13 of one patient. Sequencing analysis revealed that the patient had a G to T transversion in codon 383, resulting in the substitution of Lys by Asn. The missense mutation was also confirmed by Southern blot hybridization with an allele-specific oligonucleotide probe. Because it was found at a residue highly conserved through evolution, this mutation is likely to be the cause of hypertrophic cardiomyopathy in the patient. Because her parents and child were neither clinically nor genetically affected, it was concluded that the mutation in this patient arose de novo and was not passed to her child. This is the first report of a mutant cardiac beta-MHC gene in the Chinese population. Also, it is a novel missense mutation of the cardiac beta-MHC gene.

Adult↗
PubMed1996

Parametric modelling for electrical impedance spectroscopy system.

Three parametric modelling approaches based on the Cole-Cole model are introduced. Comparison between modelling only the real part and modelling both the real and imaginary parts is carried out by simulations, in which random and systematic noise are considered, respectively. The results of modelling the in vitro data collected from sheep are given to reach the conclusions.

Animals↗
PubMed1996

Effects of chlorotrifluoroethylene oligomer fatty acids on recombinant GABA receptors expressed in Xenopus oocytes.

GABA-activated Cl- current was expressed in Xenopus oocytes after injecting cRNA that had been transcribed in vitro from complementary DNA (cDNA) coding for a single GABA rho i-subunit cloned from human retina. The expressed current was insensitive to 100 microM bicuculline, but was activated by the GABA analogue trans-4-aminocrontonic acid (TACA). Anion-selective permeability of the expressed rho 1-subunit was determined by isotonically replacing the extracellular Cl- with different anions. The anion permeability was very similar to the native GABAA receptor/channel following a sequence of SCN- > I- > NO3- > Br- > or = Cl-. Halogenated fatty acids, such as chlorotrifluoroethylene (CTFE) and perfluorinated oligomer acids inhibited the GABA-induced current in oocytes expressing the human retinal GABA rho 1-subunit or rat brain GABAA receptor alpha 1,beta 2,gamma 2 subunits. The inhibitory effect of halogenated fatty acids demonstrated a carbon chain length-dependent manner of: C10 > C8 > C6 > C4. Perfluorinated C8-oligomer acid (PFOA) was less effective at blocking this channel than the C8-CTFE oligomer acid. Radiolabeled GABA binding assay indicated that CTFE oligomer acids do not interfere at the GABA binding site of the receptor. Furthermore, the C8-CTFE oligomer fatty acid did not compete with picrotoxin for binding sites within the pore of the channel. These studies demonstrated that the heterologous expression system is useful for studying the molecular interaction between potential neurotoxic agents and neuroreceptors. Our results provide detailed information that should contribute to our understanding of the structure and function of retinal GABA receptors.

Animals↗
PubMed1996

Macrophage-stimulating protein, a ligand for the RON receptor protein tyrosine kinase, suppresses myeloid progenitor cell proliferation and synergizes with vascular endothelial cell growth factor and members of the chemokine family.

Macrophage-stimulating protein (MSP), originally identified as an inducer of murine resident macrophage responsiveness to chemoattractants, is a ligand for human RON/murine STK receptor protein tyrosine kinases. Since STK was cloned from populations enriched for hematopoietic stem cells, we initiated studies on the effects of MSP on colony formation by granulocyte-macrophage (CFU-GM), erythroid (BFU-E), and multipotential (CFU-GEMM) myeloid progenitor cells. MSP alone had no colony stimulating activity. However, MSP caused about a 50% suppression of CFU-GM colony formation induced by synergistic combinations of SLF or Flt-L plus GM-CSF, G-CSF, or IL-3 and of BFU-E and CFU-GEMM colonies induced by SLF or Flt3-L plus Epo or Epo and IL-3. In contrast, MSP had no effect on progenitors stimulated by one growth factor. MSP also suppressed colony formation by stimulated cord blood progenitors, but only after preinduction to a rapidly cycling state. It was previously reported that several members of the chemokine family synergistically suppress myeloid progenitor proliferation. Likewise, synergistic suppression was observed when MSP was paired with VEGF, MIP-1 alpha, IL-8, PF4, MCP-1, IP-10, or ENA-78, or when VEGF was paired with the chemokines; and the required MSP concentration was more than 100-fold less than for MSP alone. Additionally, MSP or VEGF inhibited proliferation of the human myeloid growth factor-dependent cell line, M07e, but a sustained effect required multiple additions over time. At the least, some of the MSP suppressive effects on myeloid progenitors, as assessed on single isolated CD34 marrow cells, appeared to be directly on the progenitors; sustained additions of MSP were required to see this effect. The suppressive action of MSP and its synergism with proteins of the chemokine family may be of relevance to regulation of blood cell production.

Bone Marrow Cells↗
PubMed1996

Stem cells from bone marrow, umbilical cord blood and peripheral blood for clinical application: current status and future application.

Bone marrow transplantation (BMT) has progressed rapidly during the past two decades to that of a treatment of choice as a therapeutically effective modality for the treatment of selected patients with malignant disease and non-malignant hematological disorders. However, its use is limited by availability of human leukocyte antigens (HLA)-matched donor cells, engraftment and graft-versus-host disease (GVHD). Prevention of GVHD, improvement in the speed and quality of marrow reconstitution, and screening of new immunomodulating agents which improve engraftment and augment hemopoiesis are intense areas of investigation. To this end there has clearly been progress in purification and characterization of human stem cells from different tissue sources. Discussed in this review are: (a) stem cell purification, characterization and ex vivo expansion; (b) bone marrow stem cell transplantation; (c) cord blood stem cell transplantation; (d) peripheral blood stem cell transplantation; (e) fetal liver stem cell transplantation; (f) in utero stem cell transplantation; and (g) evaluation of the capacity of stem cells to serve as targets for gene therapy.

Blood Cells↗
PubMed1996

Low-dose inotropic stimulation during left ventricular ischaemia does not worsen post-ischaemic dysfunction.

OBJECTIVE: Inotropic agents are used clinically to improve ventricular function during ischaemia. The goal of this study was to determine whether inotropic stimulation during moderate left ventricular (LV) ischaemia exacerbated post-ischaemic LV dysfunction. METHODS: In 18 open-chest, anesthetized pigs, LV pressure versus subendocardial segment length loops were used to generate regional preload-recruitable stroke work (PRSW) and LV end-diastolic pressure (EDP) versus end-diastolic segment length (EDL) relations. Ischaemia was produced by constant, partial constriction of the mid anterior descending coronary artery for 90 min. Nine pigs received dobutamine (4 micrograms.kg-1.min-1, i.v.) during the final 60 min of ischaemia (Group 2), while 9 other pigs did not (Group 1). RESULTS: During unstimulated ischaemia, anterior subendocardial blood flow (Group 1, 0.27 +/- .05; Group 2, 0.30 +/- .07 ml.g-1.min.-1, mean +/- s.e.m.) and steady-state PRSW (Group 1, 30 +/- 4%; Group 2, 27 +/- 5% of baseline) were similar in both groups. Dobutamine stimulation during ischaemia increased heart rate, mean arterial pressure, subendocardial blood flow, oxygen consumption and steady-state PRSW of the ischaemia zone, but not lactate release. After 60 min reperfusion, steady-state ischaemic zone PRSW remained markedly and nearly equally reduced in both groups (Group 1, 28 +/- 4%; Group 2, 23 +/- 5% of baseline). Reduced PRSW after reperfusion was due primarily to persistent rightward shift of the PRSW intercept with only a modest contribution from reduced PRSW slope. CONCLUSIONS: Low-dose inotropic stimulation during moderate regional LV ischaemia increases aerobic, but not anaerobic energy metabolism, and does not worsen post-ischaemic dysfunction.

Animals↗
PubMed1996

TGF-beta 1 pretreatment impairs the allostimulatory function of human bone marrow-derived antigen-presenting cells for both naive and primed T cells.

Transforming growth factor-beta (TGF-beta) exhibits strong antiproliferative effects upon lymphocytes and inhibits many of the effector functions of activated immune cells. However, its influence on the inductive phase of immune responses, and in particular its effect on antigen-presenting cells (APC), has not been well studied. In this investigation, we examined the influence of human TGF-beta 1 on the antigen-presenting function of human bone marrow (BM)-derived APC propagated in liquid culture for 11-17 days in response to granulocyte/macrophage colony-stimulating factor (GM-CSF). These cells were predominantly macrophages, accompanied by a minor population of dendritic cells. TGF-beta 1 had no effect upon the allostimulatory function of vertebral body whole BM cells cultured for 3-5 days in GM-CSF. However, it markedly reduced the allostimulatory capacity of BM-derived APC exposed to the cytokine for the last 3 days of culture. This inhibitory action could not be ascribed to cytokine 'carry-over', or to any consistent changes in the expression of cell surface molecules implicated in antigen presentation (HLA-DR), intercellular adhesion (ICAM-1; CD54), or costimulatory activity (B7-1; CD80). Mechanisms that may underlie the inhibitory action of TGF-beta on APC function and the immunologic and possible clinical implications of the findings are discussed.

Antigen-Presenting Cells↗
PubMed1996

Impact of donor MHC class I or class II antigen deficiency on first- and second-set rejection of mouse heart or liver allografts.

The influence of donor major histocompatibility complex (MHC) class I- or class II-deficiency on the initiation of first- and second-set rejection of mouse heart and liver allografts was examined. C3H (H-2k) mice received heterotopic cardiac or orthotopic liver grafts from unmodified B10 (H-2b), B6 (H-2b), b2m (H-2b; class I deficient) or AB0 (H-2b; class II deficient) donors. Organ survival was also investigated in C3H recipients that had been presensitized by a normal B10 skin graft 2-3 weeks before heart or liver transplantation. The absence of cell surface MHC class I or class II resulted in significant prolongation of primary cardiac allograft survival. Three of seven (43%) MHC class I-deficient, and two of five (40%) class II-deficient heart grafts were accepted indefinitely (survival time > 100 days). Thus both MHC class I and class II molecules appear to be important for the elicitation of first-set rejection in the heart allograft model. All liver allografts survived > 100 days in normal recipients. In C3H recipients that had been presensitized by a B10 skin graft, however, both heart and liver grafts from AB0 (class II deficient) donors underwent accelerated rejection (median survival time [MST] 3 and 4 days, respectively). In contrast, liver grafts from class I-deficient mice (b2m) were still accepted indefinitely by B10 skin-presensitized C3H recipients, whereas class I-deficient hearts survived significantly longer than those from class II-deficient or normal donors. These data demonstrate that the expression of donor MHC class I, and not class II is crucial in initiating second-set organ allograft rejection. In vitro monitoring revealed that at the time of organ transplant, both splenocytes and serum of the skin-presensitized animals displayed high cytotoxicity against AB0 (class II-deficient) but not against b2m (class I-deficient) targets.

Animals↗
PubMed1996

EITS changes following oleic acid induced lung water.

We present the results of using electrical impedance tomographic spectroscopy (EITS) to follow the changes in lung water induced by oleic acid. Measurements were made on three goats before and after the injection of oleic acid. In addition to the EITs measurements, lung water was also measured using a double-indicator technique. Large falls in lung electrical impedance were seen as a result of the increase in lung water but the size of the fall was a function of the frequency at which the measurements were made. These changes have been modelled using the Cole equation. Four-electrode measurements were also made on two extracted porcine lungs and Cole equation modelling carried out following the introduction of saline into the lungs. Results were similar in the two sets of animal experiments.

Animals↗
PubMed1996

Inhibitory effects of interleukin 12 on retroviral gene transduction into CD34 cord blood myeloid progenitors mediated by induction of tumor necrosis factor-alpha.

Interleukin 12 (IL-12), a heterodimeric cytokine with potent biologic activity, was evaluated for effects on retroviral-mediated gene transduction into human myeloid progenitor cells in vitro. Cord blood CD34 cells were prestimulated with Steel factor (SLF), IL-3, GM-CSF, and erythropoietin (Epo) in the presence and absence of 5-80 ng/ml IL-12 for 40 hr in suspension culture prior to gene transduction using viral supernatant collected from a packaging cell line containing the pLNL6 vector encoding Neo sequences. After gene transduction, cells were assayed for colony formation stimulated by Epo, GM-CSF, IL-3, and SLF, and gene transduction efficiency was determined by the percentage of G418 resistant (R) colonies and confirmed by PCR analysis. IL-12 dose-dependently inhibited retroviral-mediated gene transduction into human cord blood CD34 granulocyte-macrophage (CFU-GM) and erythroid (BFU-E) progenitors. These suppressive effects could be neutralized by incubation of IL-12 with polyclonal antihuman IL-12. IL-12 had no inhibitory effects directly on colony formation. To understand the possible mechanisms for this suppression, ELISA assays were used to detect the release of interferon (IFN)-gamma and tumor necrosis factor (TNF)-alpha, which could potentially have been induced by IL-12 from CD34 cells. TNF-alpha protein release was significantly increased in CD34 cells incubated with IL-12. No detectable levels of IFN-gamma were noted. Anti-TNF-alpha, but not anti-IFN-gamma, blocked the inhibitory effects of IL-12 on gene transduction. Moreover, TNF-alpha, but not IFN-gamma, suppressed gene transfer to the same degree as IL-12. No change of amphotropic receptor mRNA expression was noted by Northern blot analysis in cells treated with or without IL-12. The results suggest that the suppressive effects of IL-12 on retroviral gene transduction are, at least in part, mediated by IL-12 induction of the release of TNF-alpha.

Antigens, CD↗
PubMed1996

A quantitative trait locus in major histocompatibility complex determining latent period of mouse lymphomas.

The effects of two host genes on retrovirus-induced murine lymphoma were evaluated by studying 114 F2 intercross mice between SL/Kh and AKR/Ms mice. Out of 47 T-lymphoma-bearing F2 mice, 45 had the AKR-derived dominant allele at Tism-1. The length of the lymphoma latent period was not related to type of tumor. Instead, it was significantly shortened by a recessive SL/Kh-derived allele at a major histocompatibility complex (MHC)-linked locus on Chr. 17. A quantitative trait analysis of the latent period yielded a maximal logarithm of likelihood ratio for linkage (LOD) score of 7.06 at a class II gene within MHC. The SL/Kh-derived recessive gene was named lla (lymphoma latency acceleration).

Alleles↗
PubMed1996

Effects of cycloheximide on pancreatic endonuclease activity, apoptosis, and severity of acute pancreatitis.

The factors that determine the severity of acute pancreatitis are unknown, but a close inverse correlation between that severity and the extent of acinar cell apoptosis that follows the triggering signal has been previously noted [A. M. Kaiser, A. K. Saluja, A. Sengupta, M. Saluja, and M. L. Steer. Am. J. Physiol. 269 (Cell Physiol. 38): C1295-C1304, 1995]. In the present studies, we have evaluated internucleosomal DNA fragmentation and apoptosis within the pancreas and the effects of inhibiting protein synthesis by cycloheximide (CHX) on these phenomena as well as on the severity of pancreatitis. We report the constitutive presence of a Ca(2+)- and Mg(2+)-dependent endonuclease activity within pancreatic nuclei that is dependent on continued protein synthesis. Furthermore, we have found that CHX administration reduces the extent of apoptosis but significantly worsens the severity of pancreatitis that follows ligation of the rat common bile-pancreatic duct. These observations are consistent with the hypothesis that apoptosis is a teleologically beneficial response to acinar cell injury during acute pancreatitis.

Animals↗
PubMed1996

Induction of human myeloblastic ML-1 cell G1 arrest by suppression of K+ channel activity.

Our previous studies have shown that a voltage-gated K+ channel is highly expressed in proliferating human myeloblastic ML-1 cells and is suppressed in the early stages of 12-O-tetradecanoylphorbol-13-acetate-induced ML-1 cell differentiation. In the present study, we report that inhibition of the K+ channel activity by 4-aminopyridine (4-AP) suppressed ML-1 cell proliferation, as measured by DNA synthesis. Cell cycle mapping indicated that ML-1 cells were arrested in G1 phase after 24-h treatment with 4-AP. Blockade of ML-1 cells at the G1/S boundary of the cell cycle with aphidicolin revealed that ML-1 cells past the G1 checkpoint were capable of entering S phase and synthesizing DNA independently of the channel blockade. ML-1 cell differentiation, measured by CD14 marker protein expression, revealed that the effect of 4-AP was to cause growth arrest and that it did not cause differentiation. Dephosphorylation of retinoblastoma protein accompanied inhibition of ML-1 cell proliferation and suggested that suppression of K+ channel activity by 4-AP is associated with retinoblastoma protein-mediated G1 arrest in ML-1 cells. Moreover, we found that ML-1 cell volume increased 35 +/- 7% after 4-AP treatment, which could be an early event triggering inhibition of ML-1 cell proliferation. These findings suggest that a 4-AP-sensitive K+ channel may play an important role in the transduction of mitogenic signals in ML-1 cells.

4-Aminopyridine↗
PubMed1996

Catechol-O-methyltransferase inhibition increases the uptake of 11C-3-(3,4-dihydroxyphenyl)-L-alanine in the rat pancreas.

BACKGROUND: The objective of the present investigation was to evaluate the uptake and metabolism of 3-(3,4-dihydroxyphenyl-L-alanine) (L-DOPA) in the rat pancreas. METHODS: The procedure included intravenous injection of the positron-emitting radiotracer L-[beta-11C] DOPA (DOP) into unanaesthetized male Sprague-Dawley rats and evaluation of uptake of radioactivity in organs in animals only given the tracer and in animals given therapeutic doses of three different catechol-O-methyltransferase (COMT) inhibitors, OR-486, OR-611, or Ro 41-0960. Selected pancreati were homogenized, and the chemical form bearing the radioactivity was analysed with high-performance liquid chromatography (HPLC). RESULTS: The main finding was that the tracer uptake in the pancreas increased fourfold when the rats were pretreated with COMT inhibitors. Half maximum effect of OR-486 was found at a dose of 0.2 mg/kg. HPLC analysis showed that with COMT inhibitor, the radioactivity in the pancreas consisted of 90% DOPAC. When administering MAO-A and COMT inhibitor together, the pancreas radioactivity corresponded to dopamine. Also in the pig pancreas a significant increase of DOP was observed after COMT inhibition. CONCLUSIONS: This study has shown a high turnover of L-DOPA in the rat pancreas, which can be modulated to give enhanced levels of DOPAC or dopamine by COMT and MAO inhibition.

Analysis of Variance↗