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L Li

Publications and source records attributed to L Li.

At least 37 records · Page 2Linked to original sources
PubMed2002

Identification and characterization of the feeding circuit-activating peptides, a novel neuropeptide family of aplysia.

We use a multidisciplinary approach to identify, map, and characterize the bioactivity of modulatory neuropeptides in the circuitry that generates feeding behavior in Aplysia. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry of the cerebral-buccal connective (CBC), a nerve containing axons of many interneurons that control feeding behavior of Aplysia, was used to identify neuropeptides that may participate in generation and shaping of feeding motor programs. Using this functionally oriented search, we identified a novel family of peptides that we call the feeding circuit-activating peptides (FCAPs). Two peptides with masses identical to those observed in the CBCs (molecular weight 1387 and 1433) were purified from buccal ganglia and partially sequenced using mass spectrometry. The amino acid sequence was then used to clone the FCAP precursor, which encodes multiple copies of eight different FCAPs. The two FCAPs present in highest copy number correspond to those observed in the CBC. The distribution of FCAP expression was mapped using Northern analysis, whole-mount in situ hybridization, and immunocytochemistry. Consistent with our initial findings, FCAP-immunopositive axons were observed in the CBC. Furthermore, we found that FCAP was present in some cerebral-buccal and buccal-cerebral interneurons. As their name suggests, FCAPs are capable of initiating rhythmic feeding motor programs and are the first neuropeptides with such activity in this circuit. The actions of FCAPs suggest that these peptides may contribute to the induction and maintenance of food-induced arousal. FCAPs were also localized to several other neuronal systems, suggesting that FCAPs may play a role in the regulation of multiple behaviors.

Amino Acid Sequence↗
PubMed2002

Incomplete inactivation of voltage-dependent K+ channels in human B lymphoma cells.

The voltage-dependent K (KV) channel in Daudi human B lymphoma cells was characterized by using patch-clamp techniques. Whole-cell voltage-clamp experiments demonstrated that cell membrane depolarization induced a transient (time-dependent) outward current followed by a steady-state (time-independent) component. The time-dependent current resembled behavior of the type n channel, such as use dependence and a unique blockade by tetraethylammonium (TEA). Both time-dependent and time-independent currents were blocked by quinine with a similar IC50 (14.2 mM and 12.6 mM). Treatment with antisense oligonucleotide of human Kv1.3 gene significantly reduced both currents by 80%. Single-channel experiments showed that only one type of KV channel was recorded with a unitary conductance of approximately 19 pS. Consistent with whole-cell recordings, the channel activity in cell-attached patches remained in response to prolonged depolarization, and the remaining channel activity was blocked by quinine, but not TEA. Channel activity was scarcely seen in cell-attached patches after antisense treatment. Whole-cell current-clamp data showed that TEA, which blocks only the time-dependent current, caused a slight decrease in the membrane potential. In contrast, quinine and antisense, which block both time-dependent and -independent currents, strongly reduced the membrane potential. These data together suggest that the KV channel in Daudi cells does not completely inactivate and that the remaining channel activity due to this incomplete inactivation appears to be primarily responsible for maintaining the membrane potential.

Electric Conductivity↗
PubMed2002

Impaired eyeblink conditioning and decreased hippocampal volume in PDAPP V717F mice.

We examined heterozygous transgenic (Tg) mice that overexpress V717F amyloid precursor protein (APP) for delay eyeblink conditioning (EBC) and hippocampal volume with magnetic resonance imaging (MRI). Platelet-derived APP mice were significantly impaired on EBC relative to wild type (WT) litter-mate controls. T2-weighted spin echo images (62.5 x 125 x 500 microm) of the same mice were acquired under anesthesia using a 9.4T magnet. Tg mice had hippocampal to brain volume ratios that were significantly smaller than WT controls (31% smaller in the rostral dorsal hippocampus, 13-22% smaller among equal dorsal-ventral thirds of a caudal section). These results indicate that overexpression of APP or beta amyloid profoundly affects learning and memory and hippocampal volume. The results also indicate that eyeblink conditioning and quantitative MRI in mice may be useful assays to follow the progression of disease-related changes, and to test the effectiveness of potential therapeutics against Alzheimer's disease.

Alzheimer Disease↗
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↗