Search PubMed⌕ Search

Biomedical subjects

C Y Lu

Publications and source records attributed to C Y Lu.

At least 145 records · Page 8Linked to original sources
PubMed1989

Polyamines mediate the reversible opening of the blood-brain barrier by the intracarotid infusion of hyperosmolal mannitol.

The blood-brain barrier (BBB) can be opened transiently by infusing a hyperosmolal solution of a non-electrolyte into the internal carotid artery. We investigated the hypothesis that capillary polyamines and their rate-regulating synthetic enzyme, ornithine decarboxylase (ODC), may be involved in mediating BBB breakdown in this model, as they are in BBB breakdown by focal cold injury. The intracarotid infusion of 1.6 M mannitol induced a prompt (less than 2 min) increase in ODC activity and the levels of polyamines in the ipsilateral hemisphere. Isolated cerebral capillary preparations and neural elements showed similar increases in ODC activity. The rank order of increase at 2 min, ODC (170%) greater than putrescine (90%) greater than spermidine (15%) greater than spermine (7%), was consistent with an activation of the ODC-regulated pathway of polyamine synthesis. The specific ODC inhibitor alpha-difluoromethylornithine (DFMO) blocked the 1.6 M mannitol-induced increase in ODC activity and the accumulation of polyamines, and concurrently prevented BBB breakdown, monitored by transport of intravenously administered Evans blue and alpha-[3H]aminoisobutyrate into cerebral tissue. Exogenous putrescine, the product of ODC activity, replenished brain polyamines and negated DFMO protection allowing BBB breakdown by 1.6 M mannitol. These experiments support the hypothesis that BBB breakdown induced by the intracarotid infusion of hyperosmolal mannitol is mediated by rapid, ODC-regulated synthesis of microvascular polyamines. In addition, increases in ODC-controlled polyamine synthesis in nerve cells may play a significant role in the pathophysiology of the reversible neuronal dysfunction, e.g. diazepam-sensitive seizure-like activity, enhanced glucose utilization, evoked by the intracarotid infusion of hyperosmolal mannitol.

Blood-Brain Barrier↗
PubMed1989

Pregnancy as a natural model of allograft tolerance. Interactions between adherent macrophages and trophoblast populations.

From an immunologic viewpoint, the fetus with its paternal antigens may be considered a successful allograft in the maternal host. Understanding the basis of this host-allograft relationship remains a fundamental unsolved problem in transplantation immunobiology. We have previously demonstrated that local immunoregulation in the murine placenta prevented macrophage activities necessary for an effective response against the intracellular bacterium Listeria monocytogenes. Given the central role of macrophages both as antigen-presenting and cytolytic effector cells, such local immuno-regulation may ordinarily help prevent rejection of the fetoplacental unit with its paternal alloantigens by the maternal immune system. We therefore examined two types of interaction between macrophages and the placental cells that populate the maternal-fetal interface. (1) Upon activation to kill listeria efficiently, macrophages also acquire cytolytic capacities against some tumor and embryonic cells. We tested the hypothesis that macrophage activation in the placenta was inhibited to prevent macrophages from lysing fetal trophoblasts. We found, however, that trophoblasts isolated by dispase dispersion, differential isopyknic centrifugation, and adherence were not lysed by three different populations of cytolytic macrophages: (a) those activated in vivo during listeriosis, (b) peptone-elicited macrophages activated in vitro by recombinant interferon gamma and other lymphokines, and (c) the macrophage cell line RAW 264.7 activated in vitro. (2) Previous studies had demonstrated that cells from the placental region and their conditioned media inhibited a variety of lymphocyte functions. However, we found that these did not inhibit activation of adherent macrophages as assessed by induction of cell-surface Ia and acquisition of tumoricidal activity. In addition, under conditions where placental cells inhibited the proliferative response of a cloned CD4+ anti-Listeria T cell line to fixed, antigen-pulsed macrophages, the secretion of macrophage-activating lymphokines was not affected. These studies are important because they indicate that previously described suppressor systems in the murine placental region do not account for the profound local deficits in macrophage function seen during listeriosis.

Animals↗
PubMed1989

Polyamines and Ca2+ mediate hyperosmolal opening of the blood-brain barrier: in vitro studies in isolated rat cerebral capillaries.

We recently presented evidence that the reversible opening of the blood-brain barrier (BBB) by the infusion of 1.6 M mannitol into the rat internal carotid artery is mediated by a rapid stimulation of ornithine decarboxylase (ODC) activity and putrescine synthesis in cerebral capillaries. We have now investigated this hypothesis further, using isolated rat cerebral capillaries as an in vitro model of the BBB. The ODC activity of cerebral capillary preparations was enriched up to 15-fold over that of the cerebral homogenate. Hyperosmolal mannitol in physiological buffer evoked a rapid (less than 15 s), concentration- and time-dependent increase in capillary ODC activity and an accumulation of putrescine and spermidine which was blocked by the specific ODC inhibitor, alpha-difluoromethylornithine (DFMO, 10 mM). Mannitol (1 M), as well as 2 M urea, evoked a two- to fivefold increase in the temperature-sensitive influx of 45Ca2+ and uptake of horseradish peroxidase (HRP) and 2-deoxy-D-[1-3H]glucose (DG), but not alpha-[1-14C]aminoisobutyrate, during a 2-min incubation. DFMO (10 mM) abolished 1 M mannitol-mediated stimulation of 45Ca2+ influx and uptake of HRP and DG, whereas 1 mM putrescine replenished capillary polyamines and reversed the DFMO effects. Mannitol (1 M)-induced stimulation of ODC activity and membrane transport processes was Ca2+-dependent and verapamil- and nisoldipine-sensitive. Phorbol myristate acetate (PMA, 10 nM), a protein kinase C activator, also evoked a two- to threefold stimulation of 45Ca2+ transport and HRP and DG uptake. This PMA effect was abolished by DFMO, suggesting involvement of rapid, ODC-controlled polyamine synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Aminoisobutyric Acids↗
PubMed1989

Blood-brain barrier breakdown in cold-injured brain is linked to a biphasic stimulation of ornithine decarboxylase activity and polyamine synthesis: both are coordinately inhibited by verapamil, dexamethasone, and aspirin.

An early increase in ornithine decarboxylase (ODC) activity and polyamine levels in rat cerebral capillaries was previously implicated in the mediation of blood-brain barrier (BBB) breakdown in cold-injured brain. A time course study in rat cerebrum indicated that cold injury evokes a biphasic increase in ODC activity and polyamine levels in perilesional cortex. ODC activity rose sharply (fourfold) within 1 min, remained elevated for 5 min, and then returned to the basal level by 10 min. A transient rise in polyamine concentration followed in the rank order of putrescine greater than spermidine greater than spermine. A secondary rise in ODC activity commenced in perilesional tissue at 2-6 h and peaked (8.8-fold) at 48 h. Major increases in the content of putrescine (330%), spermidine (103%), and spermine (50%) developed at 48-72 h. alpha-Difluoromethylornithine (DFMO), a specific irreversible inhibitor of ODC, suppressed the evoked increase in ODC activity and abolished the associated increase in content of polyamines, findings indicating that the accumulation of polyamines in cryoinjured brain reflects enhanced synthesis resulting from an ODC-mediated increase in putrescine content. Cycloheximide and actinomycin D were without effect on the early increase in ODC activity but inhibited the delayed increase in ODC activity, an observation suggesting that the initial increase in activity reflects an activation of a cryptic ODC via a posttranslational process, whereas the delayed increase in activity results from ODC synthesis mainly under transcriptional control.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Polyamines mediate androgenic stimulation of calcium fluxes and membrane transport in rat heart myocytes.

The androgenic steroid hormone testosterone induced an early (less than 30-60 seconds) stimulation of endocytosis, hexose transport, and amino acid transport, monitored by the temperature-sensitive uptake of horseradish peroxidase, 2-deoxyglucose, and alpha-aminoisobutyrate, respectively, in rat ventricle cubes and acutely isolated ventricular myocytes. This stimulation was time- and concentration-dependent and was maximal at 10(-9) to 10(-8) M testosterone, consistent with androgen-receptor mediation. EGTA (2.5 mM), La3+ (1 mM), and verapamil (100 microM) ablated the hormonal response. The calcium ionophore A23187 (10 microM) induced an acute stimulation of endocytosis, amino acid transport, and hexose transport which was not further increased by testosterone (10(-8) M), suggesting a common effector pathway. Testosterone (10(-8) M) also evoked a rapid (less than 30 seconds) stimulation of 45Ca influx and efflux. Testosterone (10(-8) M) induced a rapid (less than 5 seconds) transient increase in ornithine decarboxylase (ODC) activity peaking (twofold to threefold) at 60 seconds, and an early (15 seconds) transient accumulation of polyamines peaking at 60 seconds in isolated myocytes. The specific, irreversible ODC inhibitor alpha-difluoromethylornithine (DFMO, 5-10 mM) blocked the testosterone-evoked increase in ODC activity and polyamine levels and the stimulation of Ca2+ fluxes, endocytosis, hexose transport, and amino acid transport. Putrescine (0.5-1 mM), the ODC product, reversed DFMO inhibition and restored the increase in polyamines, 45Ca fluxes, and Ca2+-dependent membrane transport processes. These results demonstrate that rapid, transient ODC-regulated polyamine synthesis is essential for androgenic stimulation of Ca2+ fluxes and membrane transport processes in ventricular myocytes. These findings support a model for signal transduction in which newly synthesized polyamines serve as intracellular messengers to regulate transmembrane Ca2+ movements, Ca2+-dependent membrane transport functions, and other Ca2+- and polyamine-sensitive processes in cardiac myocytes.

Amino Acids↗
PubMed1989

Localization of fetal major histocompatibility complex antigens and maternal leukocytes in murine placenta. Implications for maternal-fetal immunological relationship.

An immunohistochemical study of the days 14-19 murine placenta and uterus using a panel of antibodies specific for maternal and paternal class I major histocompatibility complex (MHC) antigens, specific leukocyte subsets, and other lineage-specific markers was performed to elucidate the nature of the maternal tolerance of the fetal implant in the uterus. Fetally derived trophoblast lining maternal blood spaces lacked MHC antigens, but other interstitial trophoblasts expressed fetally derived polymorphic class I MHC determinants. The latter class I MHC-bearing trophoblasts were most prominent in the maternal decidua basalis where they were mixed with maternal cells. Our results identify two factors that may be relevant for understanding why these alloantigen-bearing fetal cells are not rejected by the mother: a paucity of la-bearing antigen presenting cells, macrophages, and mature T and B lymphocytes and the presence of large numbers of Thy-1+ asialo-GM-1+ CD4- CD8- bone marrow-derived (CLA/Ly5+) cells of maternal origin in the decidua basalis. These latter cells correspond to previously described granulated metrial gland cells that may be involved in local immunoregulation.

Alkaline Phosphatase↗
PubMed1989

[The diagnostic value of quantitative atrial activation mapping for localization of cardiac accessory pathways].

The diagnostic value of quantitative atrial activation mapping for localization of cardiac accessory pathways (AP) was evaluated in 50 cases with histories of supraventricular tachycardia (SVT). Some possible quantitative criteria are proposed for the differential diagnosis of free wall and septal APs. The diagnostic criteria of septal AP during SVT are 1) Slightly earlier left or right atrium depolarization; 2) time difference between left and right atrial depolarizations (delta A less than or equal to 30 ms; 3) change rate of delta A (delta A%) greater than 50%; 4) delta A index less than 10; and 5) ratio of ventriculo-atrial conduction times between the two atria less than 1.22. The sensitivity of these criteria in the diagnosis of cardiac septal AP is 91.7%, the specificity is 91.5% and the accuracy is 92%.

Adult↗
PubMed1989

[Comparative study of transesophageal atrial pacing and intracardiac electrophysiology in patients with supraventricular tachycardia].

The diagnostic value of transesophageal atrial pacing in supraventricular tachycardia (SVT) has been discussed according to the comparison of the results of intracardiac and transesophageal electrophysiological study. Some quantitative criteria for the differential diagnosis of atrioventricular node reentrant tachycardia (RT-AVN) and atrioventricular reciprocating tachycardia (RT-AP) has been proposed. We found that RT-AVN and RT-AP could be separated by noninvasive transesophageal atrial pacing. We also suggested that induced SVT would be RT-AVN if (1) SR conductive curve was not continuous and SR jump greater than 70 ms, (2) AV interval less than 60 ms, and it would be RT-AP if (1) SR curve was continuous and there was no SR jump phenomenon, (2) VA interval greater than 100 ms. Thus, transesophageal atrial pacing was very helpful in distinguishing the mechanisms of SVT and could provide a simple clinical cardiac electrophysiological procedure in diagnosing SVTs.

Adolescent↗
PubMed1989

[Noninvasive locational diagnosis of concealed accessory pathways in the heart].

Concealed accessory pathways in the heart can be located by noninvasively mapping the left and right atrial potentials. The quantitative diagnostic criteria for locating the septal pathway are (1) the retrograde depolarization time difference between the two atria (delta A) = 0ms, (2) (delta A) less than 30 ms, (3) the change rate of delta A(delta A%) greater than 50%, (4) delta A index less than 10 and (5) the ratio of ventriculoatrial conduction time in the left to that in the right heart less than 1.2. These criteria have a diagnostic sensitivity of 100%, specificity of 87.5% and accuracy of 94.4%.

Adult↗
PubMed1988

Autoreactive T cells in MRL/Mpr-lpr/lpr mice. Characterization of the lymphokines produced and analysis of antigen-presenting cells required.

Lymph node cells from 4-wk-old MRL/Mp-lpr/lpr mice, but not from MRL/Mp-+/+ mice, when cultured in vitro for 5 to 7 days, will spontaneously proliferate and produce IL-2. We examined the expression of several cell surface Ag on lymph node cells from MRL/Mp-lpr/lpr mice before and after in vitro culture. There is an increase in the expression of Thy-1, L3T4, IL-2R, T cell activating protein, T cell receptor, and T3 complex on the surface of cultured cells. Cultured cells produced IL-3, IFN-gamma, and small but detectable amounts of IL-1 in addition to IL-2. Gamma irradiation of APC from young MRL/Mp-lpr/lpr mice or treatment of APC with a mAb (J11D) and C, completely abrogated their stimulatory capacity. These experiments suggest that B cells are the predominant APC responsible in the activation of autoreactive T cells in MRL/Mp-lpr/lpr mice. Lymph node cells from C57BL/6-lpr/lpr or C3H-lpr/lpr mice were unable to spontaneously proliferate or produce IL-2. Lymph node cells from (MRL/Mp-lpr/lpr x C57BL/6-lpr/lpr) F1 mice or (C3H-lpr/lpr x MRL/Mp-lpr/lpr) F1 mice did proliferate and produced IL-2 after in vitro culture. Using T cells from these F1 animals and APC from each parental haplotype, we found that APC from MRL/Mp-lpr/lpr mice induced more proliferation and greater amounts of IL-2, when compared to APC from F1 animals. APC from C57BL6-lpr/lpr mice or C3H-lpr/lpr were unable to induce spontaneous proliferation and IL-2 production. Therefore, B cells from MRL/Mp-lpr/lpr mice appear to possess unique features that enable them to activate autoreactive T cells more effectively than B cells from other mice bearing the lpr/lpr gene.

Animals↗
PubMed1988

High strength binding of P815 mastocytoma cells is not necessary for their lysis by macrophages which have been primed and triggered in vitro.

We have examined the hypothesis that binding of P815 mastocytoma cells is a necessary step in lysis of these cells by macrophages which are both "primed" and "triggered" in vitro, Macrophages "primed" by conditioned media containing IFN-gamma, or by rIFN-gamma have an increased ability to bind P815. However, adding either heat-killed Listeria or endotoxin to trigger the primed macrophages has opposite effects on lysis and binding of P815. Lysis is increased. Binding is dramatically decreased. This is true when centrifugal forces of 200 x g, 400 x g, and 800 x g are used to disrupt P815-macrophage binding. Although 100% of P815 cells bound by cytotoxic macrophages are lysed, a large additional population of unbound P815 is also lysed. Detailed kinetic studies indicate that macrophages do not rapidly bind and lyse several cycles of P815. There is an initial lag period of 4 to 6 h before P815 lysis can be detected, and completion of lytic events then occurs within 12 to 14 h. Lysis of P815 bound to cytotoxic macrophages is slightly slower than lysis of the total population of bound and unbound P815. In contrast, D3.1, a cloned CD4+ T cell line, is tightly bound to macrophages but not lysed efficiently. When macrophages are simultaneously confronted with P815 and macrophage-bound D3.1, only the former are lysed. Altogether, the data indicate that P815-macrophage binding, as operationally defined by our assay, is not a necessary step for lysis. These results, by use of macrophages primed and triggered in vitro, are in contrast to previously reported experiments examining P815 binding and lysis by macrophages activated in vivo by infection with bacillus Calmette-Guérin.

Animals↗
PubMed1988

Polyamines are intracellular messengers in the beta-adrenergic regulation of Ca2+ fluxes, [Ca2+]i and membrane transport in rat heart myocytes.

The beta-adrenergic agonist 1-isoproterenol (0.1 microM) evokes an acute (less than 5-10 sec) transient increase in the activity of ornithine decarboxylase (ODC), and the levels of polyamines (putrescine, spermidine, spermine) in acutely isolated rat ventricular myocytes. Isoproterenol rapidly (less than 15 sec) increases 45Ca influx and efflux, decreases [Ca2+]i, and stimulates Ca2+-dependent membrane transport (endocytosis, hexose transport, amino acid transport). The beta-adrenergic antagonist propranolol blocks isoproterenol-induced membrane transport. The ODC inhibitor alpha-difluoromethylornithine (DFMO, 5-10 mM) blocks the isoproterenol-evoked increase in ODC activity and polyamine levels and the changes in 45Ca fluxes, [Ca2+]i and membrane transport. Putrescine (0.5-1 mM) replenishes cellular polyamines and reverses the DFMO effect. These data exclude an increase in [Ca2+]i in stimulus-transport coupling, and support the hypothesis that polyamines are messengers in beta-adrenoceptor-mediated regulation of transmembrane Ca2+ fluxes, [Ca2+]i, and Ca2+-dependent membrane transport.

Amino Acids↗
PubMed1988

Specific defects in the anti-listerial immune response in discrete regions of the murine uterus and placenta account for susceptibility to infection.

Infection of the murine uteroplacental region by the intracellular pathogen Listeria monocytogenes results in uncontrolled local bacterial growth. In this paper we examined infected and noninfected uteroplacental tissues by immunocytochemistry to delineate the nature of the aberrant anti-listerial response. Overall the data support the hypothesis that local immunoregulation, which ordinarily prevents maternal anti-fetal, responses also prevents an effective anti-listerial response at the maternal-fetal interface. Different types of response were seen in different anatomic regions. Listeria first localized to the maternal decidua basalis, which contains a mixture of fetal class I MHC-bearing trophoblast and maternal cells. Here the listeria proliferated in an uncontrolled manner due to a striking inability of monocyte/macrophages and lymphocytes to reach foci of infection. A second type of abnormal response was seen in the fetal chorioallantoic plate, a nontrophoblastic region of the placenta. Although macrophages were present, they were not appropriately activated as evidenced by a lack of Ia Ag and the presence of extracellular listeria colonies. Purely maternal tissues adjacent to the placenta had a normal anti-listerial response. During listeriosis, class I MHC expression was augmented throughout the placenta on cells normally bearing these Ag: trophoblast in the decidua basalis and both fetal and maternal stromal cells. Class II MHC Ag were induced on maternal and fetal endothelial cells but never appeared on trophoblast.

Animals↗
PubMed1988

Effects of in vivo monoclonal anti-I-A antibody treatment in neonatal mice on intrathymic and peripheral class II antigen expression.

Intrathymic, Ia-bearing antigen-presenting cells (APC) are believed to play an important role in the development of a mature, functional T-cell repertoire. We used chronic in vivo treatment of neonatal mice with anti-I-A monoclonal Ab (MAb) to examine the expression of I-A and I-E antigens on intrathymic and peripheral APC. Three weeks after continuous treatment with anti-I-A MAb, FACS analysis of unfractionated spleen cells revealed a 75-90% reduction in the number of I-A bearing cells. Splenic antigen-presenting capacity measured by the ability of unseparated or density gradient-enriched APC to stimulate I-A- or I-E-reactive T-cell hybridomas was also greatly reduced. In contrast to the expression of I-A and I-E molecules in the splenic APC, anti-I-A MAb treatment resulted in decreased thymic APC I-A expression without significant changes in I-E as measured by FACS analysis. This was confirmed in functional studies in which allo-I-A- or auto-I-A-reactive T-cell hybridomas could not be stimulated by treated thymic APC. Unlike splenic APC, anti-I-A-treated thymic APC did not differ significantly from normals in their ability to stimulate allo-I-E-reactive T hybridomas. This lack of linkage or comodulation of I-A and I-E expression on thymic but not splenic APC may allow us to study the role of I-A molecules and I-E molecules on the development and expansion of functional, mature T-cell repertoires.

Animals↗
PubMed1988

Application of high-performance liquid chromatography for the study of the microheterogeneity changes of mouse alpha-fetoprotein in fetal development.

Changes in the microheterogeneity of mouse alpha-fetoprotein (MAFP) during fetal development were investigated by high-performance liquid chromatography (HPLC). A total of six distinct isoforms (Iso-1, Iso-2, Iso-3, Iso-4, Iso-5, Iso-6) of the heterogeneous MAFP were resolved from mouse amniotic fluid (MAF). Analysis of MAF collected at various times revealed that these isoforms were accumulated at different stages of the fetal development.

Animals↗
PubMed1988

Inhibition of antigen-specific activation of an L3T4+ T cell line by cyclosporine with maintenance of macrophage-mediated antigen presentation.

Cyclosporine has clearly been shown to directly inhibit T lymphocyte activation by monoclonal antibodies or mitogens where nominal antigen and accessory cells are not present. However, when T lymphocytes are stimulated by antigen, as occurs in allograft rejection, T lymphocytes and accessory cells must interact with one another. Under the latter circumstances, the issue of whether cyclosporine acts on T lymphocyte, accessory cell, or both is not resolved. This issue is addressed in this study. To assess the effect of cyclosporine on T cell activation, macrophages were incubated with heat-killed Listeria and then fixed in paraformaldehyde. These fixed macrophages retained their ability to present antigen to T cells but were not affected by subsequent treatment with cyclosporine. When cyclosporine and a L3T4+ T lymphocyte line were added simultaneously to fixed, antigen-pulsed macrophages, the drug inhibited antigen-specific T cell activation with a half maximal inhibitory concentration of 10 ng/ml. To our knowledge, this is the first evidence that low doses of cyclosporine inhibit antigen-specific T cell activation where the drug's effects on antigen-presenting cells have been excluded. To assess the effects of cyclosporine on macrophage-mediated antigen-presentation, macrophages were exposed simultaneously to cyclosporine and antigen, and then fixed. Antigen-presentation was not inhibited unless extremely large doses (9000 ng/ml) of cyclosporine were used. In our experimental system, any new inhibitory activity acquired by live cyclosporine-treated macrophages could be explained by residual drug. Finally, cyclosporine did not inhibit the induction of macrophage Ia expression nor antigen-presenting function after stimulation in vitro with lymphokine.

Animals↗