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L Li

Publications and source records attributed to L Li.

At least 1,027 records · Page 57Linked to original sources
PubMed1998

Inducible expression of the alpha1-acid glycoprotein by rat and human type II alveolar epithelial cells.

Alpha1-acid glycoprotein (AGP) is a major acute phase protein in rat and human. AGP has important immunomodulatory functions that are potentially important for pulmonary inflammatory response. The liver is the main tissue for AGP synthesis in the organism, but the expression of AGP in the rat lung has not been investigated. We show that AGP mRNA was induced in the lung of dexamethasone-, turpentine-, or LPS-treated rats, whereas AGP mRNA was not detected in the lung of control rats. In the lung of animals treated intratracheally with LPS, in situ hybridization showed that AGP gene expression was restricted to cells located in the corners of the alveolus, consistent with an alveolar type II (ATII) cell localization. The inducible expression of the AGP gene was confirmed in vitro with SV40 T2 cells and rat ATII cells in primary culture: maximal expression required the presence of dexamethasone. IL-1 and the conditioned medium of alveolar macrophages acted synergistically with dexamethasone. Rat ATII cells secreted immunoreactive AGP in vitro when stimulated with dexamethasone or with a combination of dexamethasone and the conditioned medium of alveolar macrophages. In vivo, in the human lung, we detected immunoreactive AGP in hyperplastic ATII cells, whereas we did not detect AGP in the normal lung. We conclude that AGP is expressed in the lung in cases of inflammation and that ATII cells are the main source of AGP in the lung.

Acute-Phase Proteins↗
PubMed1998

MALDI mass spectrometry combined with avidin-biotin chemistry for analysis of protein modifications.

A general mass spectrometric method that combines purification and analysis in one step is described for the rapid and sensitive determination of protein modification that involves covalent attachment of a modifying group. In this method, the modifying group is first labeled with a biotin moiety, and the covalent interaction of this group with the targeted protein results in a biotinylated product. The modified protein can then be subjected to enzymatic digestion, followed by the isolation of the biotinylated peptide based on a previously described MALDI method incorporating the avidin-biotin interaction (Schriemer, D. C.; Li, L. Anal. Chem. 1996, 68, 3382-3387). To illustrate the validity of the method, a study of a model system was undertaken, involving the interaction between avian skeletal muscle troponin C and a sulfhydryl-specific biotinylation reagent. It is shown that isolation of a modified peptide with an immobilized avidin product could be achieved, even in the presence of an excess of contaminating protein. Exoproteases could be added to the crude tryptic digest to generate peptide ladders, each containing biotin, which could be analyzed by the avidin-biotin/MALDI method for sequence information. Complementary sequence information could be obtained from the application of this technique in a tandem sector/time-of-flight mass spectrometer for MALDI MS/MS analysis, which allowed for the identification of the modification site.

Animals↗
PubMed1998

Effects of K+ channel inhibitors on the basal tone and KCl- or methacholine-induced contraction of mouse trachea.

The present study examined the effects of K+ channel inhibitors on the basal tone and on KCl- or methacholine-induced contraction of the mouse-isolated trachea. Glibenclamide and iberiotoxin, procaine, quinine and tetraethylammonium did not induce any contraction of the indomethacin-treated mouse trachea. 4-Aminopyridine induced concentration-dependent contraction. This action of 4-aminopyridine was abolished by atropine and reduced by tetrodotoxin and nifedipine. Glibenclamide failed to modify KCl- or methacholine-induced contraction. Iberiotoxin and 4-aminopyridine potentiated KCl- and methacholine-induced contractions. Nifedipine, procaine, quinine and tetraethylammonium inhibited KCl- and methacholine-induced contractions. These data suggest that the closure of large Ca2+-dependent K+ channels can potentiate KCI- and methacholine-induced contraction. The effects of 4-aminopyridine on the mouse trachea reflect chiefly activation of muscarinic receptors. Procaine, quinine and tetraethylammonium inhibit depolarization-induced and receptor-mediated contractions of the mouse-isolated trachea.

Animals↗
PubMed1998

[Sequencing analysis of human K-ras oncogene exon 1 in Chinese people].

OBJECTIVE: To investigate the mutation of human K-ras oncogene in the blood of patients with lung cancer. METHODS: PCR and sequencing methods were used to analyse the exon 1. Twelve patients'blood samples and 31 normals' blood samples were detected. RESULTS: In all 43 samples, the K-ras codon 11 was CCT (proline), and the opposite strand sequenced was AGG. It was different from the standard GCT(Alanine) sequenced by foreign authors. CONCLUSION: The 11th codon of the human K-ras oncogene in Chinese is CCT (Proline). As the K-ras codon 12 is a hot spot, this finding may be of importance to clinical genetic diagnosis.

Asian People↗
PubMed1998

Proteolytic processing of the Aplysia egg-laying hormone prohormone.

By using matrix-assisted laser desorption/ionization time-of-flight MS, individual peptidergic neurons from Aplysia are assayed. A semiquantitative method is developed for comparing single-cell profiles by using spectral normalization, and peptides are localized to specific cells by mass spectrometric cell mapping. In addition to all previously identified products of the egg-laying hormone (ELH) gene, other peptides are formed from proteolytic hydrolysis of Leu-Leu residues within ELH and acidic peptide (AP). AP exhibits further processing to yield AP1-20 and AP9-27. These peptides appear to be colocalized in vesicles with ELH, transported to specific neuronal targets, and released in a Ca2+-dependent manner. A differential peptide distribution is observed at a specific target cell, and a low-frequency variation of AP, [Thr21]AP, is detected in a single animal.

Animals↗
PubMed1998

A long-lifetime Ru(II) metal-ligand complex as a membrane probe.

A luminescent metal-ligand complex, [Ru(bpy)2(dppz)]2+, (where dppz is dipyrido[3,2-a:2',3'-c] phenazine), was used as a photoluminescence probe for investigating submicrosecond lipid dynamics in a dipalmitoyl-L-alpha-phosphotidylglycerol (DPPG) model bilayer system. The luminescence of [Ru(bpy)2(dppz)]2+ in buffer is completely quenched but becomes luminescent when intercalated into DPPG vesicles. The experimental results show that the emission intensity of [Ru(bpy)2(dppz)]2+ intercalated into DPPG vesicles increases dramatically as temperature is increased towards the lipid phase transition temperature. This effect is abolished in bilayers containing a high concentration (> 30 mol%) of cholesterol, suggesting this probe is sensitive to the membrane composition. Frequency-domain emission intensity decays, measured as a function of increasing temperature towards the lipid phase transition temperature (2 to 57 degrees C), display two major lifetime components. The short lifetime disappears at temperatures well above the phase transition temperature. A comparison of oxygen quenching with iodide quenching suggests the heterogeneity of probe location at temperatures well below the lipid phase transition temperature and the homogeneity of probe location at temperature well above the lipid phase transition temperature. [Ru(bpy)2(dppz)]2+ displays polarized emission, enabling the study of membrane dynamics. The long decay time displayed by this probe allows measurement of the overall rotational correlation time of lipid vesicles on the microsecond time-scale. Because of the long lifetime, polarized emission, and background free nature of the photoluminescence measurements, [Ru(bpy)2(dppz)]2+ has numerous applications in the biophysical studies of membranes.

Anisotropy↗
PubMed1998

The roles of individual gamma-carboxyglutamate residues in the solution structure and cation-dependent properties of conantokin-T.

The solution structure of the Ca2+-loaded conantokin-T (con-T), a gamma-carboxyglutamate (Gla)-containing 21-residue peptide (NH2-G1EgammagammaY5QKMLgamma10NLRgammaA15EVKKN20A-CONH2,gam ma = Gla), has been elucidated by use of distance geometry calculations with experimental distances derived from two-dimensional 1H NMR spectroscopy. An end-to-end alpha-helix was the dominant conformation in solution, similar to that of apo-con-T, except that reorientation of several side chains occurred in the Ca2+-coordinated complex. The most notable examples of this were those of Gla10 and Gla14, which were more optimally positioned for complexation with Ca2+. In addition to the stabilization offered to the alpha-helix by Ca2+ binding, hydrophobic clustering of the side chains of Tyr5, Met8, Leu9, and Leu12, and ionic interactions between Lys7 and Gla3/Gla10 and between Arg13 and Gla14, along with hydrogen bonding between Gln6 and Gla10, were among the side chain interactions likely playing a significant role in maintenance of the alpha-helical conformation. Docking of Ca2+ in the con-T structure was accomplished using genetic algorithm-molecular dynamics simulation approaches. The results showed that one Ca2+ ion is most likely coordinated by four side chain oxygen atoms, two each from Gla10 and Gla14. Another bound Ca2+ ion has as its donor sites three oxygen atoms, two from Gla3 and one from Gln6. To examine the functional roles of the individual Gla residues, a series of variant peptides have been synthesized with Ala substituted for each Gla residue, and several properties of the resulting variants have been examined. The data obtained demonstrated the importance of Gla10 and Gla14 in stabilizing binding of the highest affinity Ca2+ site and in governing the conformational change induced by Ca2+. The critical nature of Gla3 and Gla4 in inhibition of the spermine-induced potentiation of the binding of MK-801 to open ion channels of the N-methyl-D-aspartate receptor was established, as well as the role of Gla4 in stabilizing the apo-con-T alpha-helical conformation.

1-Carboxyglutamic Acid↗
PubMed1998

Alzheimer's disease and heparan sulfate proteoglycan.

Alzheimer's disease (AD) is a debilitating neurodegenerative disorder. Cardinal histopathologic changes of AD are neurofibrillary tangles (NFTs) and deposits of beta-amyloid protein (A-beta) in the form of neuritic plaques (NPs). Several different mutations found in patients with familial AD have been demonstrated to increase A-beta production, resulting in a common pathological cascade of beta-amyloidosis in the brain. Heparan sulfate proteoglycan (HSPG) has been co-localized with both A-beta in the NPs and NFTs. The proteoglycans are a family of complex macromolecules consisting of a protein core to which glycosaminoglycan (GAG) chains are covalently attached. HSPG has been shown to bind to A-beta, accelerate its fibril formation, and maintain its fibril stability. In AD and other neurodegenerative disorders, tau becomes hyperphosphorylated hence it is unable to bind to microtubules which results in the production of paired helical filaments, a building unit of NFTs. It has been shown in vitro that sulfated GAGs induce the formation of paired helical-like filaments under physiological conditions from tau. Furthermore, an interaction between HSPG and apolipoprotein E (a potent risk factor of AD) has been shown to be involved in neurodegeneration. Thus, substantial evidence exists to underscore important roles of HSPG in the etiology of AD.

Alzheimer Disease↗
PubMed1998

Cell cycle-dependent subcellular localization of the TSG101 protein and mitotic and nuclear abnormalities associated with TSG101 deficiency.

TSG101 is a recently discovered tumor susceptibility gene whose functional inactivation in mouse fibroblasts results in cell transformation and the ability to form metastatic tumors in nude mice. Although restoration of TSG101 activity reverses tumorigenesis, neoplasia is irreversible in some cells, suggesting that permanent genetic alteration can occur during TSG101 inactivation. Here we describe studies that support this notion. We find that localization of TSG101 is cell cycle-dependent, occurring in the nucleus and Golgi complex during interphase, and in mitotic spindles and centrosomes during mitosis; cells made neoplastic by a deficiency in TSG101 expression show a series of mitosis-related abnormalities, including multiple microtubule organizing centers, aberrant mitotic spindles, abnormal distribution of metaphase chromatin, aneuploidy, and nuclear anomalies. Our findings suggest that TSG101 deficiency may lead to genome instability in addition to previously reported reversible neoplastic transformation.

Aneuploidy↗
PubMed1998

Distribution of the pressure-regulated operons in deep-sea bacteria.

DNA regions corresponding to portions of two different pressure-regulated operons previously identified in two deep-sea barophilic bacteria were separately PCR amplified from a variety of deep-sea microorganisms and sequenced. With the two sets of primers employed, amplification was particularly successful from the more barophilic bacteria examined. 16S rRNA sequence analysis revealed that these bacteria are all phylogenetically related and belong in a sub-branch of the genus Shewanella containing only the deep-sea Shewanella barophilic bacteria. We define this sub-branch as the 'Shewanella barophile branch' containing at least two different species. Our results suggest that the DNA sequences of the pressure-regulated operons can be regarded as marker sequences to identify the Shewanella barophilic strains.

Amino Acid Sequence↗
PubMed1998

Genistein inhibits the growth of human-patient BPH and prostate cancer in histoculture.

BACKGROUND: There is strong epidemiological evidence that prostate disease is significantly less prevalent in the Orient, where the intake of soy products is very high, than in the United States. We therefore undertook a study of the effects of genistein, a major component of soy, on growth of human-patient benign prostatic hypertrophy (BPH) and prostate cancer tissue in three-dimensional collagen gel-supported histoculture. METHODS: Surgical specimens of human BPH and cancer were histocultured for 5 days to study the effects of genistein on growth, as measured by inhibition of 3H-thymidine incorporation per microgram protein on day 5. RESULTS: Genistein in doses of 1.25-10 micrograms/ml decreased the growth of BPH tissue in histoculture in a dose-dependent manner, with little additional effect at higher doses. Prostate cancer tissue in histoculture was similarly inhibited by these doses of genistein. CONCLUSIONS: Genistein decreases the growth of both BPH and prostate cancer tissue in histoculture. The data suggest that genistein has potential as a therapeutic agent for BPH and prostate cancer.

Antineoplastic Agents↗
PubMed1998

Use of a long-lifetime Re(I) complex in fluorescence polarization immunoassays of high-molecular-weight analytes.

We describe a new class of fluorescence polarization immunoassays based on the luminescence from a Re(I) metal-ligand complex. Re(I) complexes are extremely photostable and possess useful photophysical properties including long lifetimes, high quantum yields, and high emission polarization in the absence of rotational diffusion. In the present study, a conjugatable, highly luminescent Re(I) metal-ligand complex, [Re(bcp)(CO)3(4-COOHPy)](ClO4), where bcp is 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline and 4-COOHPy is isonicotinic acid, has been evaluated for use in fluorescence polarization immunoassays (FPIs) with high-molecular-weight antigens. This Re(I) complex (Re) displays highly polarized emission (with a maximum anisotropy near 0.3) in the absence of rotational diffusion and a long average lifetime (2.7 microseconds) when bound to human serum albumin (HSA) in oxygenated aqueous solution. The emission polarization of the Re-HSA conjugate is sensitive to the binding of anti-HSA, resulting in a significant increase in anisotropy. The labeled HSA was also used in a competition immunoassay where unlabeled HSA was also used as an antigen. These experimental results, combined with theoretical predictions, demonstrate the potential of this Re(I) metal-ligand complex as a luminescence probe in FPIs of high-molecular-weight analytes (10(5)-10(8) Da).

Antigens↗
PubMed1998

Conversion of pancreas allograft rejection to acceptance by liver transplantation.

BACKGROUND: Liver allografts of PVG(RT1c)-->DA(RT1a) are spontaneously accepted, whereas pancreas, heart, and kidney allografts are rejected. Our previous studies have shown that simultaneous liver and pancreas transplantation prevents pancreas allograft rejection. The aim of this study was to examine the effect of liver transplantation on subsequent pancreas allografts and on ongoing pancreas rejection. METHODS: Heterotopic, duct-ligated segmental pancreas grafts were transplanted into streptozotocin-induced diabetic recipients (60 mg/kg body weight i.p.) with or without orthotopic liver grafting at different times. Experimental design was as follows. Group 1 received PVG-->PVG pancreas syngrafts (n=6); group 2, PVG-->DA pancreas allografts (n=7); groups 3-5, PVG-->DA pancreas allografts followed by liver transplantation on day 2 (n=6), on day 4 (n=5), and on day 6 (n=5), respectively, group 6, PVG-->DA pancreas allografts after liver transplantation at 4 weeks (n=6). RESULTS: The results showed that pancreas allografts in group 2 were rejected from postoperative day 7 to 13. Liver transplantation prevented subsequent pancreas allograft rejection in group 6. Ongoing pancreas rejection was reversed by liver transplantation with subsequent graft acceptance in groups 3-5. Significant graft-infiltrating lymphocyte apoptosis was demonstrated at 2 weeks in pancreas transplants associated with liver grafting. Graft-versus-host disease was not detected in the pancreas recipients. CONCLUSIONS: We conclude that pancreas allografts in the PVG-->DA combination are rejected rapidly with median survival time of 9 days. Liver transplantation can protect subsequent pancreas grafts from rejection and reverse ongoing pancreas graft rejection with subsequent pancreatic acceptance. Graft-infiltrating lymphocyte apoptosis may be associated with the process of graft acceptance.

Animals↗
PubMed1998

Apoptosis in the absence of cytochrome c accumulation in the cytosol.

Cytochrome c release from mitochondria to and subsequent accumulation in the cytosol has been considered a prerequisite for apoptosis. In this study, we present evidence for apoptosis induction without accumulation of cytochrome c in the cytosol. U937 lymphoma cells treated with staurosprine released cytochrome c from mitochondria to cytosol prior to PARP cleavage and DNA fragmentation. However, U937 cells treated with BMD188 (a hydroxamic acid and a potent apoptosis inducer) did not demonstrate any cytochrome c accumulation in the cytosol during apoptosis induction. This different pattern of cytochrome c alterations was also observed with these two inducers on leukemic HL60 cells and epithelial PC3 cells. Furthermore, when PC3 cells were treated with a panel of apoptosis-inducing agents, it was found that camptothecin, bleomycin, VP16 and TNF-alpha induced varying amounts of cytosolic accumulation of cytochrome c either prior to or concurrent with PARP cleavage while vinblastine and BHPP did not. Taken together, the present results suggest that cytochrome c accumulation in the cytosol during apoptosis is a cell type- and inducer-dependent phenomenon.

Antibiotics, Antineoplastic↗
PubMed1998

Peripheral target regulation of the development and survival of spinal sensory and motor neurons in the chick embryo.

Unilateral limb-bud removal (LBR) before the outgrowth of sensory or motor neurons to the leg of chick embryos was used to examine the role of limb (target)-derived signals in the development and survival of lumbar motoneurons and sensory neurons in the dorsal root ganglia (DRG). After LBR, motor and sensory neurons underwent normal initial histological differentiation, and cell growth in both populations was unaffected. Before their death, target-deprived motoneurons also expressed a cell-specific marker, the homeodomain protein islet-1. Proliferation of sensory and motor precursor cells was also unaffected by LBR, and the migration of neural crest cells to the DRG and of motoneurons into the ventral horn occurred normally. During the normal period of programmed cell death (PCD), increased numbers of both sensory and motor neurons degenerated after LBR. However, whereas motoneuron loss increased by 40-50% (90% total), only approximately 25% more sensory neurons degenerated after LBR. A significant number of the surviving sensory neurons projected to aberrant targets in the tail after LBR, and many of these were lost after ablation of both the limb and tail. Treatment with neurotrophic factors (or muscle extract) rescued sensory and motor neurons from cell death after LBR without affecting precursor proliferation of either population. Activity blockade with curare failed to rescue motoneurons after LBR, and combined treatment with curare plus muscle extract was no more effective than muscle extract alone. Treatment with the antioxidant N-acetylcysteine rescued motoneurons from normal cell death but not after LBR. Two specific inhibitors of the interleukin beta1 converting enzyme (ICE) family of cysteine proteases also failed to prevent motoneuron death after LBR. Taken together these data provide definitive evidence that the loss of spinal neurons after LBR cannot be attributed to altered proliferation, migration, or differentiation. Rather, in the absence of limb-derived trophic signals, the affected neurons fail to survive and undergo PCD. Although normal cell death and cell death after target deprivation share many features in common, the intracellular pathways of cell death in the two may be distinct.

Acetylcysteine↗
PubMed1998

Cyclophosphamide given after active specific immunization augments antitumor immunity by modulation of Th1 commitment of CD4+ T cells.

BACKGROUND AND OBJECTIVES: In order to evaluate the regulatory effect of cyclophosphamide (CPA) on active specific immunization (ASI)-induced antitumor immunity, we examined the timing of CPA (100 mg/kg) with ASI, and focused on whether CPA given after ASI augments antitumor immunity by modulation of Th1 commitment of CD4+ T cells. METHODS: We examined the effect of CPA combined with ASI using sonicated tumor supernatant (SS) and recombinant interleukin-1 beta (rIL-1 beta). RESULTS: Survival of i.p. tumor inoculated mice after ASI (days -12, -9, and -6) followed by 100 mg/kg CPA (day -3) (ASI-CPA) was significantly prolonged compared with that of mice treated with ASI alone, whereas CPA (day -15) treatment before ASI (CPA-ASI) completely abrogated the survival prolongation by ASI alone. In early stage (day 0) after ASI-CPA treatment, the CD4+ T cells were determined to play an important role in the protective immunity for the following reasons: 1) the CD4+/CD8+ ratio of spleen cells from immunized mice was higher than that of the control or CPA alone treated group; and 2) the tumor neutralizing activity of fresh spleen cells was abrogated by CD4+ T-cell depletion in vitro. CD4+ T cells of mice treated with ASI-CPA produced more interferon (IFN)-gamma and IL-2 and less IL-4 than those of the ASI alone group. CONCLUSIONS: These results suggest that the protective immunity induced by ASI was augmented through the modification of the Th1 and Th2 balance by CPA injection after ASI.

Animals↗
PubMed1998

Investigation of spectral reproducibility in direct analysis of bacteria proteins by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

Matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectrometry (TOFMS) can be used for rapid detection of bacteria proteins in a crude mixture. It can potentially be used as a tool for bacterial identification based on the mass spectral patterns or the appearance of some characteristic mass peaks. However, there are many experimental parameters that can potentially have a strong effect on the observed mass spectra. The objective of this work is to address the mass spectral reproducibility issue. Several experimental parameters that may affect the MALDI spectra are systematically investigated. Results of spectral comparison from two laboratories with different operators and instrumentation are presented. It is demonstrated that minor variations in the sample/matrix preparation procedures for MALDI and in the experimental conditions used for bacterial protein extraction can result in a significant change in the observed spectra, though a number of peaks are conserved in the spectra obtained under different experimental conditions from the same bacterial sample. These conserved peaks may potentially be used as the biomarkers for bacterial identification. It is stressed that this type of investigation on spectral reproducibility should be carried out for different bacterial species in order to identify the mass spectral peaks that are consistently detected regardless of operator and nominal variations in sample preparation approach.

Bacillus thuringiensis↗