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Biomedical subjects

L Li

Publications and source records attributed to L Li.

At least 163 records · Page 9Linked to original sources
PubMed2002

A novel amino acid position in hemagglutinin glycoprotein of measles virus is responsible for hemadsorption and CD46 binding.

Three recent isolates of measles virus Fu, IMA, and SMD obtained by using B95a cells did not exhibit hemadsorption with African green monkey red blood cells (AGM-RBC). After long-term passage in Vero cells, these Vero cell-adapted strains derived from three isolates obtained the activity to agglutinate AGM-RBC. The primary sequences of the hemagglutinin (H protein) and fusion glycoproteins (F protein) from these two types of viruses were compared and revealed that several important amino acid residues in the H protein do not converge. After adaptation, Fu strain has an Asn to Tyr substitution at position 481 and IMA strain has two substitutions--an Asp to Asn at position 14 and a Ser to Gly at position 546, SMD strain also has a Ser to Gly substitution at position 546. Since the sequences of the F protein were identical between both types of viruses, the hemadsorption alteration from negative to positive might be the result of these substitutions. Site-directed mutagenesis of the H genes were performed to confirm that the substitution of Ser --> Gly at position 546 and Asn --> Tyr at position 481 in the H protein were responsible for hemadsorption alteration. Anti-CD46 monoclonal antibody (M75 and M160) study made clear that these two substitutions also governed the MV H protein's interaction with CD46 receptor. Our results showed that two important amino acid residues in MV H protein govern the binding to CD46 receptor and hemadsorption. In this paper, we reported a novel amino acid residue at position 546 in MV H protein, which was critical for hemadsorption and CD46 binding.

Amino Acid Substitution↗
PubMed2002

Age-related changes in the calcium homeostasis of adherent neutrophils.

The elderly are susceptible to infections and show a decline in neutrophil (PMN) functions that are regulated by cytosolic calcium [Ca2+]i. This study measures [Ca2+]i in suspended and adherent PMN of young and elderly individuals by using flow cytometry, confocal microscopy, the bacterial peptide fMLP, and the fluorescent Ca2+ indicator fluor-3/acettoxymethyl ester. PMN from both age groups show a steep and transient fMLP-induced Ca2+ increase. This increase is independent of external divalent cations and is desensitized by a subsequent exposure to the same agonist. Adherent PMN of the elderly express elevated [Ca2+]i before (basal) and after fMLP activation but show reduced ability to mobilize Ca2+ into and from the cytosol. PMN of the elderly take longer (13.7 +/- 3 s) to attain the maximal response compared to those of young adults (5.7 +/- 0.8 s). PMN from both age groups show heterogeneity in the time and magnitude of this response. However, PMN of the elderly show a decrease in the proportion of cells with prompt and effective reaction and an increase in the representation of a cell subpopulation manifesting delayed response. We conclude that age-related delayed and reduced PMN response to a bacterial peptide could hamper functional activities that are essential in host protection against infections.

Adult↗
PubMed2002

Gastrointestinal involvement in paroxysmal nocturnal hemoglobinuria: first report of electron microscopic findings.

Thrombotic complications, particularly microthrombi involving intraabdominal veins leading to intestinal ischemia, have remained a major cause of morbidity in patients with paroxysmal nocturnal hemoglobinuria (PNH). While intestinal ischemia has been postulated to be the cause of recurrent bouts of abdominal pain in this population, direct antemortem evidence for this complication is scarcely documented in the literature. We describe a case of PNH in a patient who presented with abdominal distress three years after the initial diagnosis was established. Clinical features and a combination of diagnostic modalities, including radiography, endoscopy, and histology were used to make the prompt diagnosis of intestinal ischemia. This is the first case in which the electronic microscopy of the gastrointestinal lesion is described. Our patient was successfully treated with conservative measures and anticoagulation.

Abdominal Pain↗
PubMed2002

An improved resazurin-based cytotoxicity assay for hepatic cells.

A simple resazurin-based cytotoxicity assay is presented for screening of cytotoxicity in hepatocytes and liver cell lines. Human hepatoma (HepG2) cells in 96-well culture plates were exposed to known toxic (cisplatin, 5-fluorouracil, ethionine, flufenamic acid, and diflunisal) and control (transplatin, 5-chlorouracil, methionine, and acetylsalicylic acid) compounds for 1-3 days, and resazurin (5 micromol/L) was added. A conventional short-term (1 h) assay was first performed, where cytotoxicity is indicated by decreased reduction of resazurin to its fluorescent product resorufin. Our improved assay consists of additionally measuring fluorescence 2-4 days later, when cytotoxicity is indicated by a striking increase in the concentration of resorufin, resulting from two distinct processes. First, viable liver-derived cells slowly convert resorufin to nonfluorescent metabolites. Fluorescence of control cell wells decreased to background during a 2- to 4-day exposure to resazurin. This metabolism of resorufin was largely blocked by dicumarol and to lesser extents by disulfiram and SKF525a. Second, dead or dying cells slowly convert resazurin to resorufin but do not further metabolize resorufin; thus this fluorescent metabolite accumulates to high levels in wells with dead cells by 2 to 4 days. A similar increase in fluorescence associated with cytotoxicity was observed in primary cultures of rat hepatocytes using the long-term resazurin-based assay. In addition to an improved signal relative to the short-term assay, the inversion of the fluorescent signal from high = alive short-term to high = dead long-term allows determination of two independent cytotoxicity endpoints after addition of one innocuous vital dye.

Animals↗
PubMed2002

Description of fourteen new DRB alleles found in a stem cell donor registry.

Fourteen DRB alleles, DRB1*0705, DRB1*11014, DRB1*1134, DRB1*1136, DRB1*1141, DRB1*1335, DRB1*1337, DRB1*1338, DRB1*1342, DRB1*1343, DRB1*1349, DRB1*1510, DRB3*0105, and DRB5*0103, are described. Among them, eleven are variants which differ by only one nucleotide from previously described alleles, including one silent variant (DRB1*11014). Alleles, DRB1*0705, DRB1*1335 and DRB3*0105, display unique sequence motifs that have never been observed in DRB alleles.

Alleles↗
PubMed2002

Soluble Fas gene therapy protects against Fas-mediated apoptosis of hepatocytes but not the lethal effects of Fas-induced TNF-alpha production by Kupffer cells.

The elevation of soluble Fas (sFas) in the sera of patients with liver disease suggests a role for sFas in the disease process; whether it is protective or not is controversial. To determine the effects of sFas on Fas-induced liver apoptosis, we manipulated mice to produce sFas by transfecting them in vivo with different amounts of an adenovirus that produces mouse sFas driven by the CMV promoter (AdsFas). Fas-mediated apoptosis was induced by administration of anti-mouse Fas (Jo2; 10 microg/mouse) one week later. The administration of AdsFas (10(3), 10(7), or 10(9) pfu/mouse), which was associated with only minimal side-effects, resulted in a significant reduction in the liver transaminase levels and mortality of the mice on challenge with Jo2, as compared to control mice treated with AdLacZ. However, the protective effect of AdsFas was not complete. The possibility that Jo2-induction of TNF-alpha in the Kupffer cells of the liver contributes to the pathology was therefore tested. Although administration of soluble TNF receptor (sTNFRI) alone did not protect the mice from the lethal effects of Jo2, administration of sTNFRI (200 microg/mouse) after infection with AdsFas (10(9) pfu/mouse) resulted in 100% survival of the mice on challenge with Jo2. To confirm that the production of TNF-alpha by Kupffer cells produce the lethal effects of Jo2 that remained after treatment with AdsFas, these cells were selectively ablated by treatment of the mice with gadolinium chloride prior to challenge with Jo2. This treatment greatly reduced early mortality and hepatocellular damage as well as TNF-alpha production 6 h after injection of Jo2. These results indicate that: (1) AdsFas prevents Jo2-induced apoptosis of hepatocytes; (2) In addition to mediating Fas-mediated apoptosis of hepatocytes, Jo2 can separately induce TNF-alpha production by Kupffer cells resulting in early mortality, and (3) Optimal protection from Jo2-induced mortality can be achieved by protection of liver cells by pretreatment with both AdsFas and sTNFRI.

Animals↗
PubMed2002

Characterization of the FcgammaRIIA promoter and 5'UTR sequences in patients with systemic lupus erythematosus.

FcgammaRIIA is a candidate gene involved in the predisposition to systemic lupus erythematosus (SLE). The presence of low binding alleles in patients with SLE is not sufficient to explain the lower phagocytic capacity observed in SLE patients. We considered the possibility that nucleotide polymorphisms in the FcgammaRIIA promoter that cause alterations in receptor expression might be present in SLE patients. In the present study, a 2.0 kb region of the human FcgammaRIIA 5'UTR from 20 normal donors and 53 SLE patients was examined. The results demonstrate that the sequence of the human FcgammaRIIA 5' region differs from the published sequence. Two novel SNPs have been identified in the distal region of the FcgammaRIIA promoter. The polymorphisms are present in both disease-free and SLE donors and do not associate with quantitative changes in FcgammaRIIa phagocytic function.

5' Untranslated Regions↗
PubMed2002

The effect of storage temperatures on the in vitro properties of a polyanhydride implant containing gentamicin.

Septacin is a biodegradable sustained-release implant containing 20% (w/w) gentamicin sulfate. The matrix of the implant is a polyanhydride copolymer composed of erucic acid dimer (EAD) and sebacic acid (SA) in a one-to-one weight ratio. The effect of storage temperatures (-15 degrees C and 25 degrees C) on the stability of Septacin was evaluated with respect to gentamicin potency, copolymer molecular weight, and in vitro drug release. The drug in polymer matrix was stable for at least 12 months when stored at 25 degrees C, but the molecular weight of the copolymer declined rapidly at this temperature. At -15 degrees C, there was no change in the molecular weight of the copolymer. However, the placebo (copolymer without gentamicin) exhibited a significant drop in copolymer molecular weight at both temperatures. The drug release profiles showed no change for samples stored at -15 degrees C for the duration of this study, while the release of drug slowed down significantly for samples stored at 25 degrees C for longer than one month. A pronounced difference in the morphology of the -15 degrees C samples and the 25 degrees C samples was observed during the in vitro dissolution test; cracking of the -15 degrees C samples was evident, but the 25 degrees C samples remained intact.

Anhydrides↗
PubMed2002

Cyanide induces different modes of death in cortical and mesencephalon cells.

A comparative study was conducted in rat primary cortical (CX) and mesencephalic (MC) neurons to investigate intracellular cascades activated during cyanide-induced injury and to determine the point at which the cascades diverge to produce either apoptosis or necrosis. Cyanide treatment (400 microM) for 24 h produced primarily apoptosis in CX cells, whereas the same concentration of cyanide induced predominantly necrosis in MC cells as indicated by increased propidium iodide staining and cellular lactate dehydrogenase efflux. Cyanide increased generation of cellular reactive oxygen species (ROS) in both CX and MC cells, but the rate of formation and nature of the oxidative species varied with cell type. Catalase decreased cyanide-induced ROS generation in CX but not in MC cells. Nitric oxide generation was more prominent after cyanide treatment of MC compared with CX cells. N-Methyl-D-aspartate receptors were more involved in CX apoptosis than in MC necrosis. Mitochondrial membrane potential decreased moderately in CX cells on exposure to cyanide, whereas MC cells responded with a more pronounced reduction in potential. In CX cells cyanide produced a concentration-dependent release of cytochrome c from mitochondria and increased caspase activity, whereas little change was seen in MC neurons. Thus, cyanide-induced necrosis of MC cells involved generation of excessive amounts of nitric oxide and superoxide accompanied by mitochondrial depolarization. In contrast cyanide causes a lower level of oxidative stress in CX cells, involving mainly hydrogen peroxide and superoxide, and a moderate change in mitochondrial membrane potential that lead to cytochrome c release, caspase activation, and apoptosis.

Animals↗
PubMed2002

Humoral immune response associated with lyme borreliosis in nonhuman primates: analysis by immunoblotting and enzyme-linked immunosorbent assay with sonicates or recombinant proteins.

The immune response to Borrelia burgdorferi, the causative agent of Lyme disease, is complex. We studied the immunoglobulin M (IgM) and IgG antibody response to N40Br, a sensu stricto strain, in the rhesus macaque(nonhuman primate [NHP]) model of infection to identify the spirochetal protein targets of specific antibody. Antigens used in enzyme-linked immunosorbent assays were whole-cell sonicates of the spirochete and recombinant proteins of B. burgdorferi. Immunoblotting with a commercially available strip and subsequent quantitative densitometry of the bands were also used. Sera from four different groups of NHPs were used: immunocompetent, transiently immunosuppressed, extended immunosuppressed, and uninfected. In immunocompetent and transiently immunosuppressed NHPs, there was a strong IgM and IgG response. Major proteins for the early IgM response were P39 and P41 and recombinant BmpA and OspC. Major proteins for the later IgG response were P39, P41, P18, P60, P66, and recombinant BmpA and DbpA. There was no significant response in the NHPs to recombinant OspA or to Arp, a 37-kDa protein that elicits an antibody response during infection in mice. Most antibody responses, except for that to DbpA, were markedly diminished by prolonged dexamethasone treatment. This study supports the hypothesis that recombinant proteins may provide a useful adjunct to current diagnostic testing for Lyme borreliosis.

Animals↗
PubMed2002

Identification of a haplosufficient 3.6-Mb region in human chromosome 11q14.3-->q21.

Cytogenetic deletions are almost always associated with phenotypic abnormality and are very rarely transmitted. We have located a hitherto undescribed, familial deletion involving the region 11q14.3-->q21 in five individuals in a three-generation kindred. Four of the deletion carriers show no phenotypic abnormality; the other, who is the proband, was investigated for short stature and poor academic progress. In view of the apparent innocuous nature of this genetic imbalance, the deletion was investigated in detail to determine its size (3.6 Mb) and location with reference to molecular markers and genetic content. The deleted region is described by a contig of 37 BACS including the flanking regions, which we have assembled. Several possible contributory factors are considered, which might explain the lack of clinical significance of this large deletion. It is notable that there are few genes in this region and none have known functions. All most likely have copies elsewhere in the genome and a number of other hypothetical genes appear to be members of certain gene families, i.e. none is unique. Part of the region (1 Mb) is also duplicated at the pericentromeric region 11p11. Given the very low proportion of the genome occupied by single copy genes and their uneven distribution, regions such as this, which appear to be functionally haplosufficient, may be more common than hitherto recognised.

Chromosome Banding↗
PubMed2002

Immunogenicity of a recombinant fusion protein of tandem repeat epitopes of foot-and-mouth disease virus type Asia 1 for guinea pigs.

In this study, the sequences of capsid protein VPI regions of YNAs1.1 and YNAs1.2 isolates of foot-and-mouth disease virus (FMDV) were analyzed and a peptide containing amino acids (aa) 133-158 of VP1 and aa 20-34 of VP4 of FMDV type Asia I was assumed to contain B and T cell epitopes, because it is hypervariable and includes a cell attachment site RGD located in the G-H loop. The DNA fragments encoding aa 133-158 of VP1 and aa 20-34 of VP4 of FMDV type Asia 1 were chemically synthesized and ligated into a tandem repeat of aa 133-158-20 approximately 34-133-158. In order to enhance its immunogenicity, the tandem repeat was inserted downstream of the beta-galactosidase gene in the expression vector pWR590. This insertion yielded a recombinant expression vector pAS1 encoding the fusion protein. The latter reacted with sera from FMDV type Asia 1-infected animals in vitro and elicited high levels of neutralizing antibodies in guinea pigs. The T cell proliferation in immunized animals increased following stimulation with the fusion protein. It is reported for the first time that a recombinant fusion protein vaccine was produced using B and T cell epitopes of FMDV type Asia 1 and that this fusion protein was immunogenic. The fusion protein reported here can serve as a candidate of fusion epitopes for design of a vaccine against FMDV type Asia 1.

Animals↗
PubMed2001

[Protective effect of human decay accelerating factor on mouse cells].

OBJECTIVE: To observe the protective effect of human decay accelerating factor (DAF) expressed in mouse myeloma cells against the injury of human serum complement. METHODS: Mouse myeloma cells were transfected with human DAF cDNA and then put into normal human serum culture to observe if they were injured. RESULTS: The mouse cells containing human DAF cDNA and expressing human DAF survived for more than 48 hours and passed on from generation to generation in the culture medium containing human normal serum. However, the control mouse cells died in 1 - 4 hours. CONCLUSION: Human DAF protects mouse cells from injuring by human complement.

Animals↗
PubMed2001

Bridged bis(beta-cyclodextrin)s possessing coordinated metal center(s) and their inclusion complexation behavior with model substrates: enhanced molecular binding ability by multiple recognition.

To investigate quantitatively the cooperative binding ability of several beta-cyclodextrin oligomers bearing single or multiligated metal center(s), the inclusion complexation behavior of four bis(beta-cyclodextrin)s (2-5) linked by 2,2'-bipyridine-4,4'-dicarboxy tethers and their copper(II) complexes (6-9) with representative dye guests, i.e., methyl orange (MO), acridine red (AR), rhodamine B (RhB), ammonium 8-anilino-1-naphthalenesulfonic acid (ANS), and sodium 6-(p-toludino)-2-naphthalenesulfonate (TNS), have been examined in aqueous solution at 25 degrees C by means of UV-vis, circular dichroism, fluorescence, and 2D NMR spectroscopy. The results obtained indicate that bis(beta-cyclodextrin)s 2-5 can associate with one or three copper(II) ion(s) producing 2:1 or 2:3 bis(beta-cyclodextrin)-copper(II) complexes. These metal-ligated oligo(beta-cyclodextrin)s can bind two model substrates to form intramolecular 2:2 host-guest inclusion complexes and thus significantly enhance the original binding abilities of parent beta-cyclodextrin and bis(beta-cyclodextrin) toward model substrates through the cooperative binding of two guest molecules by four tethered cyclodextrin moieties, as well as the additional binding effect supplied by ligated metal center(s). Host 6 showed the highest enhancement of the stability constant, up to 38.3 times for ANS as compared with parent beta-cyclodextrin. The molecular binding mode and stability constant of substrates by bridged bis- and oligo(beta-cyclodextrin)s 2-9 are discussed from the viewpoint of the size/shape-fit interaction and molecular multiple recognition between host and guest.

Algorithms↗
PubMed2001

[Identification of high-pathogenicity island-harboring Escherichia coli from children with diarrhea disease].

OBJECTIVE: To investigate the etiological status of high-pathogenicity island-harboring Escherichia coli (HPIEC) in diarrhea diseases among children. METHODS: Escherichia coli was Isolated and identified from the stool specimens of 1,032 children with diarrhea diseases by culturing, serotyping, PCR, and colony hybridization. RESULTS: 652 strains of E. coli were isolated from the 1,032 stool specimens and confirmed by colony hybridization out of which 225 were identified as diarrheagenic E. coli, including 20 EPEC, 81 ETEC, 47 SLTEC, 74 ESIEC, and 3 EIEC strans. 112 (17.2%) irp2 virulent gene positive E. coli strains were detected from the 652 strains, out of which 24 were from the 74 ESIEC strans and 17 from the 47 SLTEC stranis. The typical clinical symptoms of diarrhea caused by HPI-haboring E. coli included anorexia (87.5%), abdominal pain (58.0%), diarrhea (75.9%, over 6 episodes, mostly of mucous stool a day, 75.9%), and fever (50.9%). CONCLUSION: High-pathogenicity island-harboring E. coli is one of the important pathogens of diarrhea diseases in children.

Adolescent↗
PubMed2001

Novel erythromycin derivatives with aryl groups tethered to the C-6 position are potent protein synthesis inhibitors and active against multidrug-resistant respiratory pathogens.

A novel series of erythromycin derivatives has been discovered with potent activity against key respiratory pathogens, including those resistant to erythromycin. These compounds are characterized by having an aryl group tethered to the C-6 position of the erythronolide skeleton. Extensive structural modification of the C-6 moiety led to the discovery of several promising compounds with potent activity against both mef- and erm-mediated resistant Streptoccoccus pneumoniae. Preliminary mechanistic studies indicated that the new macrolides are potent protein synthesis inhibitors, which interact with methylated ribosomes isolated from resistant organisms. In experimental animal models, these compounds exhibited excellent in vivo efficacy and balanced pharmacokinetic profiles.

Animals↗