Biomedical subjects

H L Li

Publications and source records attributed to H L Li.

At least 37 records · Page 2Linked to original sources

PubMed2001

Suppression of autoimmune neuritis in IFN-gamma receptor-deficient mice.

Experimental autoimmune neuritis (EAN) is an animal model of the human disease Guillain-Barré syndrome. In this autoimmune inflammatory disease, CD4(+) T cells mediate demyelination in the peripheral nervous system (PNS). Infiltrating macrophages and T cells as well as cytokines like interferon (IFN)-gamma are intimately involved in causing pathogenic effects. To investigate the role of IFN-gamma in cell-mediated EAN, IFN-gamma receptor-deficient mutant (IFN-gammaR(-/-)) C57BL/6 mice and corresponding wild-type mice were immunized with P0 peptide 180-199, a purified component of peripheral nerve myelin, and Freund's complete adjuvant. IFN-gammaR(-/-) mice exhibited later onset of clinical disease. The disease was also less severe than in wild-type mice. Fewer IL-12-producing but more IL-4-producing cells were found in sciatic nerve sections from IFN-gammaR(-/-) mice than from wild-type mice on day 24 postimmunization, i.e., at the peak of clinical EAN. At the same time, IFN-gammaR(-/-) mice had less infiltration of inflammatory cells, including macrophages, CD4(+) T cells, and monocytes, into sciatic nerve tissue and less demyelination. However, numbers of IFN-gamma-secreting cells from the spleen were significantly augmented in the IFN-gammaR(-/-) mice, reflecting a failure of negative feedback circuits. The IFN-gammaR deficiency did not affect the production of anti-P0 peptide 180-199-specific antibodies. These results indicate that IFN-gamma contributes to a susceptibility for EAN in C57BL/6 mice by promoting a Th1 cell-mediated immune response and suppressing a Th2 response.

Animals↗

PubMed2001

Effect of heparin on apoptosis in human nasopharyngeal carcinoma CNE2 cells.

In order to study the mechanism of the effect of heparin on apoptosis in carcinoma cells, the nasopharyngeal carcinoma cell line CNE2 was used to identify the effect of heparin on apoptosis associated with the expression of c-myc, bax, bcl-2 proteins by use of Hoechst 33258 staining, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL), agarose gel electrophoresis, and flow cytometry, as well as Western blot analysis. The results showed that heparin induced apoptosis of CNE2 cells including the morphologic changes such as reduction in the volume, and the nuclear chromatin condensation, as well as the "ladder pattern" revealed by agarose gel electrophoresis of DNA in a concentration-dependent manner. The number of TUNEL-positive cells was dramatically increased to 33.6+/-1.2% from 2.8+/-0.3% by treatment with heparin in different concentrations (10 to approximately 40 kU/L). The apoptotic index was increased to 32.5% from 3.5% by detecting SubG1 peaks on flow cytometry. Western blot analysis showed that levels of bcl-2, bax and c-myc were significantly overexpressed by treatment with the increase of heparin concentrations. These results suggest that heparin induces apoptosis of CNE2 cells, which may be regulated by differential expression of apoptosis-related genes.

Antineoplastic Agents↗

PubMed2001

Differential-pulse voltammetric determination of trace formaldehyde using magnetic microspheres and magnetic electrode.

A new type of magnetic polymer microsphere containing acylhydrazine groups on the surface was synthesized. They can be reacted with formaldehyde to produce an electroactive adduct. Reduction of these derivatives following aggregation on a magnetic electrode is possible and is effective in the indirect determination of formaldehyde. The experimental conditions and electrode structure are discussed. Under the optimum conditions, it was found that the peak potential (Ep) of formaldehyde is -1.01 V (vs. Ag/AgCl). Formaldehyde in the range 1-1000 micrograms l-1 can be determined. The detection limit for formaldehyde is 0.3 microgram l-1 and the relative standard deviation for the determination of 100 micrograms l-1 formaldehyde was 2.26%. The method was applied to the determination of formaldehyde in environmental samples with satisfactory results.

Air Pollutants, Occupational↗

PubMed2001

Pharmacology of caspase inhibitors in rabbit cardiomyocytes subjected to metabolic inhibition and recovery.

Protection of ischemic myocardium is an important unmet need in reperfusion therapy of acute myocardial infarction. Myocardial ischemia and reperfusion induce necrosis and apoptosis in cardiomyocytes. Caspase processing and activation are critical steps in most receptor and nonreceptor pathways of apoptosis. Caspase inhibitors have been shown to reduce ischemia reperfusion injury in cardiac muscle. Information about dose response and time of administration are needed to optimize the design of preclinical studies. We used isolated adult rabbit cardiomyocytes subjected to metabolic inhibition (MI) and recovery to examine the role of caspases and caspase inhibitors, the dose response, and the timing of administration. In vitro inhibitory concentrations (Ki) were determined for purified caspases. Cardiomyocytes subjected to MI were treated with peptidomimetic fluoromethyl ketone inhibitors of caspases before or during MI, or at recovery. Caspase inhibitors were most effective when added before MI and included throughout recovery, but were partially protective if added after MI. The optimal concentration of the inhibitors tested was approximately 10 microM. Protection was sustained when cells were allowed to recover for 4 or 24 h. These results suggest that caspase activation is an important component of myocyte injury mediated by MI and recovery. Low doses of caspase inhibitors were identified that reduce injury in this model system, and further investigations using in vivo models are warranted.

Animals↗

PubMed2001

[Identification and cloning of a novel full ORF gene of P. falciparum PDZ domain containing protein].

OBJECTIVE: To identify and clone a novel full ORF gene of P. falciparum PDZ domain containing protein (PfPCP) and study its expression at the erythrocytic stage. METHODS: The primers were designed according to the sequences from P. falciparum genomic database. The full ORF gene of PfPCP was amplified from mRNA of the erythrocytic stage of P. falciparum Hainan strain by RT-PCR. Bio-informatics software were used to analyze PfPCP; PfPCP expression at the erythrocytic stage was studied with Western Blotting. RESULTS: The full ORF gene of PfPCP was 2,076 bp and encoded 691 amino acids. PfPCP contained the typical PDZ domain. Western blotting showed that PfPCP was expressed at the schizont sub-stage of P. falciparum erythrocytic stage. CONCLUSIONS: The novel full ORF gene of PfPCP is cloned. As a PDZ domain containing protein, PfPCP is expressed at the schizont sub-stage of P. falciparum.

Amino Acid Sequence↗

PubMed2001

[Weekly cyclophosphamide pulse therapy combined with corticosteroids in the treatment of pemphigus].

OBJECTIVE: To investigate the better regimen of combined cyclophosphamide pulse therapy with corticosteroids in the treatment of Pemphigus. METHODS: Intravenous cyclophosphamide was given weekly in a dosage of 600 mg to those Pemphigus patients whose conditions couldn't be improved by corticosteroids (oral prednisone 1.2-1.5 mg/kg/d) alone. RESULTS: Ten patients with Pemphigus received weekly cyclophosphamide therapy in addition to corticosteroid. Patients conditions improved quickly, without side effects. CONCLUSIONS: Cyclophosphamide weekly pulse therapy combined with corticosteroids is a good regimen in the treatment of Pemphigus.

Adrenal Cortex Hormones↗

PubMed2000

TRANCE, a tumor necrosis factor family member, enhances the longevity and adjuvant properties of dendritic cells in vivo.

Mature dendritic cells (DCs) are powerful antigen presenting cells that have the unique capacity to migrate to the T cell zone of draining lymph nodes after subcutaneous injection. Here we report that treatment of antigen-pulsed mature DCs with tumor necrosis factor (TNF)-related activation-induced cytokine (TRANCE), a TNF family member, before immunization enhances their adjuvant capacity and elicits improved T cell priming in vivo, such that both primary and memory T cell immune responses are enhanced. By enumerating migratory DCs in the draining lymph nodes and by studying their function in stimulating naive T cells, we show that one of the underlying mechanisms for enhanced T cell responses is an increase in the number of ex vivo antigen-pulsed DCs that are found in the T cell areas of lymph nodes. These results suggest that the longevity and abundance of mature DCs at the site of T cell priming influence the strength of the DC-initiated T cell immunity in situ. Our findings have the potential to improve DC-based immunotherapy; i.e., the active immunization of humans with autologous DCs that have been pulsed with clinically significant antigens ex vivo.

Adjuvants, Immunologic↗

PubMed2000

Modulation of early immune responses and suppression of Trypanosoma brucei brucei infections by surgical denervation of the spleen.

OBJECTIVE: To examine critical interactions between the nervous system and the immune system during experimental African trypanosomiasis. METHODS AND RESULTS: Inoculation of Trypanosoma brucei brucei resulted in early interferon (IFN)-gamma production, elevated corticosterone and prostaglandin E(2) (PGE(2)) levels and increased splenocyte proliferation, as measured by enzyme-linked immunospot assay, radioimmunoassay and thymidine incorporation assay, respectively. Splenic denervation suppressed IFN-gamma, corticosterone and PGE(2) production, enhanced splenocyte proliferation, and significantly reduced parasitemia and prolonged rat survival. CONCLUSIONS: Our data show substantial effects of the nervous system on early immune responses that may influence the outcome of this disease. These effects were not dependent on cytokine inhibitory mediators such as prostaglandins or stress hormones. More investigations are required to understand the evident neural control over the immune system during infectious challenges, which may assist in novel therapeutic approaches.

Animals↗

PubMed2000

Ontogenesis of proopiomelanocortin and its processing to beta-endorphin by the fetal and neonatal rat brain.

A number of reports suggest that beta-endorphin (beta-END) may play an important role in the regulation of cell proliferation and neuronal differentiation. Proopiomelanocortin (POMC), the common precursor ofadrenocorticotropic hormone and beta-END, is detected very early in embryonic life in hypothalamic neurons of the developing rat. However, very little is known about the degree to which POMC is processed to beta-END during fetal and early postnatal life. Thus, it was the objective of the present study to estimate the hypothalamic content of POMC mRNA, as well as the biosynthesis and posttranslational processing of POMC by hypothalamic neurons on fetal day 20 and on days 1, 8 and 22 of postnatal life. Hypothalamic POMC mRNA, as determined by Northern blot analysis, was higher on fetal day 20 than on postnatal days 1, 8 and 22. A higher rate of incorporation of [(3)H]phenylalanine into beta-END immunoreactive peptides was observed on fetal day 20 than on postnatal day 1. However, the rate of incorporation was significantly increased by day 8 of postnatal life and was similar to that on day 22. POMC was processed to beta-lipotropin (beta-LPH) and beta-END at all ages examined, but the relative proportions of POMC:beta-LPH:beta-END changed during development. Thus, beta-END accounted only for 34.89 +/- 6.14% of the total [(3)H]phenylalanine-labeled beta-END immunoreactive peptides on fetal day 20, while it accounted for 57. 37 +/- 5.20, 62.81 +/- 1.38 and 79.25 +/- 6.57% on days 1, 8 and 22 of postnatal life, respectively. Thus, POMC is processed to a considerable extent into beta-END-sized peptides by the fetal hypothalamus and may influence brain development. Furthermore, the rate of processing of hypothalamic POMC into beta-END increases with development, probably due to the increased activity of the enzymes specific for POMC processing.

Animals↗

PubMed2000

[Effect of jiaweiyiguanjian decoction on hypothalamus-pituitary-thyroid gland (HPT) in rat model with Yin-deficiency of liver and kidney induced by slow irritation].

OBJECTIVE: To explore the mechanism of Jiaweiyiguanjian decoction in nourishing the liver and kidney. METHOD: A rat model with Yin-deficiency of liver and kidney was made by way of slow irritation. Thyrotropin-releasing-hormone(TRH) of thyron and blood, TSH of pituitary and blood, thyroxine, 3,5,3',5-tetraiodothyronine(FT4) and 3,3',5-traiodothyronine(FT4), 3,3',5-traiodothyronine(rT3) were used as indexes to study the effect of the decoction on HPT. RESULT: The TRH Secretion from hypothalamus increased (P < 0.05), TSH of pituitary and blood reduced(P < 0.05), FT3 and FT4 of blood decreased at the same time and rT3 of blood, increased. The indexes of the treatment group were found almost the same as the those of the normal control group. CONCLUSION: Jiaweiyiguanjian Decoction could adjust HPT.

Animals↗

PubMed2000

[Effect of L-dicentrine on contraction of rat stomach muscle strips].

OBJECTIVE: To study the effect of L-dicentrine on the contraction of rat stomach muscle strips induced by 5-HT, histamine K+ and Ca2+. METHOD: In-vitro experimenting on rat stomach muscle strips. RESULTS: The contraction of the strips induced by 5-HT histamine K+ and Ca2+ after high K+ depolarization was markedly inhibited by L-dicentrine or papaverine, showing a non-competitive antagonism. The contraction induced by 5-HT was inhibited by L-dicentrine in Ca2+ free solution. L-Dicentrine inhibited the contraction induced by 5-HT, depending on Ca2+ released from the intracellular store. When the Ca2+ concentration in both solutions was restored, L-dicentrine did not influence the contraction significantly. CONCLUSION: L-Dicentrine could relax the rat stomach smooth muscle. In rat stomach smooth muscles there exist 5-HT receptors.

Animals↗

PubMed1999

The tyrosine kinases Syk and Lyn exert opposing effects on the activation of protein kinase Akt/PKB in B lymphocytes.

The protein kinase Akt/PKB is a crucial regulator of cell survival in response to mitogenic signals. The increased kinase activity of v-akt, an oncogenic form of Akt/PKB, causes mouse T cell lymphoma, and overexpression of Akt/PKB is associated with progression of several tumor types in human. In this study, we demonstrate that ligation of B cell antigen receptor (BCR) leads to activation of Akt/PKB in B lymphocytes. BCR-induced activation of Akt/PKB required the tyrosine kinase Syk, which was not previously known to regulate Akt/PKB. In contrast, BCR crosslinking of Lyn-deficient B cells resulted in markedly enhanced hyperphosphorylation and activation of Akt/PKB compared with wild-type B cells, indicating that this Src-family kinase acts as an endogenous antagonist of BCR-induced Akt/PKB activation. Lyn inhibited Akt/PKB additively with an okadaic acid-sensitive endogenous phosphatase(s). Expression of exogenous Lyn in mutant cells restored normal BCR-induced phosphorylation of Akt/PKB. Negative regulation of Akt/PKB by Lyn was not dependent on the protein phosphatases SHP-1, SHP-2, or SHIP. Our results show that Lyn provides a mechanism for negative regulation and opposes the effect of Syk on BCR-mediated activation of Akt/PKB. Deregulation of Akt/PKB correlates with the hyperresponsiveness of B cells from Lyn-deficient mice stimulated by BCR crosslinking and may contribute to the autoimmune syndrome that develops in Lyn-deficient animals.

3-Phosphoinositide-Dependent Protein Kinases↗

PubMed1999

The distribution of substance P receptor (NK1)-like immunoreactive neurons in the newborn and adult human spinal cord.

Substance P receptor (i.e. NK1)-like immunoreactive (SPR-LI) neurons were observed in the newborn and adult human spinal cord. Substance P receptor-like immunoreactive neuronal cell bodies were seen most frequently in lamina I, and were scattered throughout the remaining laminae of the dorsal horn and the area around the central canal. Some neurons in the intermediolateral nucleus also showed weak immunoreactivity. The pattern of distribution of SPR-LI neurons in the adult spinal cord was essentially the same as that in the newborn spinal cord. However, SPR-LI neurons cell bodies were seen much more frequently in the newborn than in the adult dorsal horn, especially in lamina II.

Adult↗

PubMed1999

Suboptimal cross-linking of antigen receptor induces Syk-dependent activation of p70S6 kinase through protein kinase C and phosphoinositol 3-kinase.

Ligation of the B cell antigen receptor (BCR) induces a cascade of signaling pathways that lead to clonal expansion, differentiation, or abortive activation-induced apoptosis of B lymphocytes. BCR-mediated cross-linking induces the rapid phosphorylation of protein tyrosine kinases. However, the pathways leading to the activation of downstream serine/threonine kinases such as mitogen-activated protein kinase, p90(Rsk), and p70S6 kinase (p70(S6k)) that mediate reorganization of the actin cytoskeleton, cell cycle progression, gene transcription, and protein synthesis have not been delineated. We recently demonstrated that cross-linking of BCR leads to activation of p70(S6k) in B lymphocytes. In this report, we demonstrate that multiple protein tyrosine kinase-dependent signal transduction pathways induced by BCR lead to the activation of p70(S6k). These distinct pathways exhibit different thresholds with respect to the extent of receptor cross-linking required for their activation. Activation of p70(S6k) by suboptimal doses of anti-Ig is Syk-dependent and is mediated by protein kinase C and phosphoinositol 3-kinase. Moreover, the activation of p70(S6k) results in phosphorylation of S6 protein which is important for ribosomal protein synthesis and may be coupled to BCR-induced protein and DNA synthesis in primary murine B cells.

Animals↗

PubMed1999

TRANCE, a TNF family member, is differentially expressed on T cell subsets and induces cytokine production in dendritic cells.

TNF-related activation-induced cytokine (TRANCE) is a member of the TNF family recently identified in activated T cells. We report here that TRANCE mRNA is constitutively expressed in memory, but not naive, T cells and in single-positive thymocytes. Upon TCR/CD3 stimulation, TRANCE mRNA and surface protein expression are rapidly up-regulated in CD4+ and CD8+ T cells, which can be further enhanced on CD4+ T cells by CD28-mediated costimulation. However, TRANCE induction is significantly suppressed when cells are stimulated in the presence of IL-4, but is not modified in the presence of IFN-alpha, IFN-gamma, TGF-beta, TNF-alpha, or IL-2. High levels of TRANCE receptor expression are found on mature dendritic cells (DCs). In this study we show that activated T and B cells also express TRANCE receptor, but only at low levels. TRANCE, however, does not exert any significant effect on the proliferation, activation, or survival of those cells. In DCs, TRANCE induces the expression of proinflammatory cytokines (IL-6, IL-1) and T cell growth and differentiation factors (IL-12, IL-15) in addition to enhancing DC survival. Moreover, TRANCE cooperates with CD40 ligand or TNF-alpha to further increase the viability of DCs, suggesting that several TNF-related molecules on activated T cells may cooperatively regulate the function and survival of DCs to enhance T cell-mediated immune responses.

Animals↗

PubMed1999

Activation of the JNK pathway is important for cardiomyocyte death in response to simulated ischemia.

Multiple signaling pathways, including the c-Jun N-terminal kinase (JNK) pathway, are activated in myocardial ischemia and reperfusion (MI/R) and correlate with cell death. However, the role of the JNK pathway in MI/R-induced cell death is poorly understood. In a rabbit model, we found that ischemia followed by reperfusion resulted in JNK activation which could be detected in cytosol as well as in mitochondria. To address the functional role of the JNK activation, we examined the consequences of blockade of JNK activation in isolated cardiomyocytes under conditions of simulated ischemia. The JNK activity was stimulated approximately sixfold by simulated ischemia and reperfusion (simulated MI). When a dominant negative mutant of JNK kinase-2 (dnJNKK2), an upstream regulator of JNK, and JNK-interacting protein-1 (JIP-1) were expressed in myocytes by recombinant adenovirus, the activation of JNK by simulated MI was reduced 53%. Furthermore, the TNFalpha-activated JNK activity in H9c2 cells was completely abolished by dnJNKK2 and JIP-1. In correlation, when dnJNKK2 and JIP-1 were expressed in cardiomyocytes, both constructs significantly reduced cell death after simulated MI compared to vector controls. We conclude that activation of the JNK cascade is important for cardiomyocyte death in response to simulated ischemia.

Adenoviridae↗

PubMed1999

Proteolysis of synaptobrevin, syntaxin, and SNAP-25 in alveolar epithelial type II cells.

Synaptobrevin-2, syntaxin-1, and SNAP-25 were identified in rat alveolar epithelial type II cells by Western blot analysis. Synaptobrevin-2 was localized in the lamellar bodies, and syntaxin-1 and SNAP-25 were found in 0.4% Nonidet P40-soluble and -insoluble fractions, respectively, of the type II cells. When the isolated type II cells were stimulated for secretion with calcium ionophore A23187 or with phorbol 12-myristate 13-acetate, these proteins were found to have been proteolyzed. Preincubation of cells with calpain inhibitor II (N-acetylleucylleucylmethionine), however, prevented the proteolysis. Treatment of the cell lysate with exogenous calpain resulted in a time-dependent decrease of these proteins. The data suggest that synaptobrevin, syntaxin, and SNAP-25 are subject to proteolytic modification by activated calpain in intact type II cells stimulated for secretion.

Animals↗

PubMed1999

Characterization of anergic anti-DNA B cells: B cell anergy is a T cell-independent and potentially reversible process.

Anti-single stranded DNA (ssDNA) and anti-double stranded DNA (dsDNA) B cells are regulated in non-autoimmune mice. In this report we show that while both anti-ssDNA and anti-dsDNA B cells are blocked in their ability to differentiate into antibody-secreting cells, other phenotypic and functional characteristics distinguish them from one another. Splenic anti-ssDNA B cells are found distributed throughout the B cell follicle, and are phenotypically mature and long-lived. On the other hand, splenic anti-dsDNA B cells are short-lived, exhibit an immature and antigen-experienced phenotype, and localize to the T-B interface of the splenic follicle. Functionally, anti-ssDNA B cells proliferate, albeit suboptimally, in response to anti-IgM, lipopolysaccharide (LPS) and CD40L/IL-4 + anti-IgM stimulation, and tyrosine phosphorylate intracellular proteins upon mIgM cross-linking. Anti-dsDNA B cells, on the other hand, are functionally unresponsive to anti-IgM and LPS stimulation, and do not phosphorylate intracellular proteins, including Syk, upon mIg stimulation. Importantly, anti-DNA B cell anergy is maintained in the absence of T cells since both anti-ssDNA and anti-dsDNA B cells are as efficiently regulated in RAG2(-/-) mice as in their RAG2(+/+) counterparts. Interestingly, the severely anergic state of anti-dsDNA B cells is partially reversible upon stimulation with CD40 ligand and IL-4. In response to these signals, anti-dsDNA B cells remain viable, up-regulate cell surface expression of B7-2 and IgM, and restore their ability to proliferate and phosphorylate Syk upon mIg cross-linking. Collectively, these data suggest that anti-DNA B cell anergy encompasses distinct phenotypes which, even in its most severe form, may be reversible upon stimulation with T cell-derived factors.

Animals↗