Biomedical subjects

M Li

Publications and source records attributed to M Li.

At least 325 records · Page 18Linked to original sources

PubMed2000

Tandem mass spectrometry studies of green tea catechins. Identification of three minor components in the polyphenolic extract of green tea.

Liquid chromatography/electrospray ionization mass and tandem mass spectrometry (MS/MS) techniques were used to identify two minor components and one new compound in the polyphenolic extract of green tea (Camellia sinensis). Identification and structure assignments were based on previously reported sub-structural features in the MS/MS product, precursor and neutral loss scans of reference samples. The structures of two minor components, related to the known green tea components epicatechin gallate (ECG, 5) and epigallocatechin gallate (EGCG, 6), are formed by methylation at the 3"-O-position of the gallic acid moiety. The new compound contained a gallic acid ester group, but had only one phenolic group in either the A- or B-ring, relative to the structure of 5. High-resolution mass measurements supported the empirical formula assigned to the new compounds. An important fragmentation for defining the position of methylation of the ester function involves ionization of the phenolic group at the 4"-position of the gallic acid, followed by elimination of the ester function as a neutral with concomitant formation of the m/z 169 ion. If the 4"-position is blocked by methylation, the formation of m/z 169 incorporating the gallic acid group would be blocked. Thus, the presence of an ion representing the ester group indicates a free 4"-phenol and the absence of this ion would signify the 4"-position as a site of methylation. The operation of this mechanism should be general and useful in assigning the site of methylation of any polyphenolic ester group in natural products. A similar conclusion can be drawn concerning alkylation or esterification of the 4'-position of the catechins, i. e. blocking the 4'-phenol would prevent formation of the m/z 125 ion common to all of the catechin compounds thus far examined. Therefore, mass spectral data are of considerable importance in deducing the sites of alkylation or esterification in the structures of the components of green tea.

Catechin↗

PubMed2000

Synectin, syndecan-4 cytoplasmic domain binding PDZ protein, inhibits cell migration.

Syndecan-4, a member of the syndecan gene family of proteoglycans, is an important regulator of bFGF signaling. In particular, bFGF-dependent regulation of cell growth and migration has been linked to syndecan-4 cytoplasmic domain-mediated interactions. Screening of a yeast two-hybrid library with a cytoplasmic domain of rat syndecan-4 identified a novel binding partner, here termed synectin. Synectin is highly homologous to semaphorin F binding protein semcap1, glucose 1 transporter binding protein glut1cbp, and RGS-GAIP/neuropilin-1 binding protein GIPC. Overexpression of synectin in ECV304 cells in culture led to a dose-dependent inhibition of migration while not affecting cell adhesion or growth rate. We conclude that synectin is involved in syndecan-4-dependent interactions and may play a role in the assembly of syndecan-4 signaling complex.

Amino Acid Sequence↗

PubMed2000

Genetic engineering of Helicoverpa armigera single-nucleocapsid nucleopolyhedrovirus as an improved pesticide.

The Helicoverpa armigera single-nucleocapsid nucleopolyhedrovirus (HearNPV) has been registered and is commercially produced in China as a biopesticide to control the bollworm in cotton. However, the virus has a relatively slow speed of action. To improve its efficacy, recombinant HearNPVs were generated by deleting the ecdysteroid UDP-glucosyltransferase (egt) gene (HaCXW1 and HaLM2) or by inserting the insect-specific toxin gene AaIT in the egt locus (HaCXW2) of HearNPV using conventional recombination strategies in insect cell culture. The various recombinants remained genetically stable when cultured in HzAM1 insect cells. Bioassay data showed a significant reduction in the time required for all HearNPV recombinants to kill second instar H. armigera larvae. The LT(50) of the egt deletion recombinants HaCXW1 and HaLM2 was about 27% faster than that of wild-type HearNPV. The largest reduction in LT(50) was achieved by inserting the gene for the insect-specific neurotoxin, AaIT, in the egt locus, giving a reduction in LT(50) of 32% compared to wild-type HearNPV. The ability to genetically improve the properties of HearNPV as a biopesticide provides a further opportunity to develop this virus into a commercially viable product to control the bollworm in China.

Animals↗

PubMed2000

Patterning of the "distal esophagus" in esophageal atresia with tracheo-esophageal fistula: is thyroid transcription factor 1 a player?

BACKGROUND: We have recently proposed that the "distal esophagus" in esophageal atresia with tracheo-esophageal fistula (EA/TEF) is actually embryologically derived from the middle branch of a trifurcation of the embryonic lung bud, which subsequently grows caudally in the foregut to connect with the developing stomach. We hypothesized that differential mRNA expression of the lung-specific patterning transcription factor, thyroid transcription factor 1 (TTF-1), in the developing fistula tract in TEF relative to the bronchi (the other branches of the lung bud trifurcation) might explain the unique nonbranching pattern of growth of the fistula tract. MATERIALS AND METHODS: EA/TEF was induced in Sprague-Dawley rat embryos via intraperitoneal injection of 2.2 mg/kg adriamycin into pregnant dams on Days 6-9 of gestation. The foregut from embryos developing EA/TEF and from control embryos (no adriamycin) were isolated on Gestational Days 13.5, 15.5, and 17.5 (term = 21 days). Some were processed for whole-mount in situ hybridization for TTF-1, while others were embedded and sectioned for histologic analysis via in situ hybridization for TTF-1. RESULTS: The expression of the respiratory-specific transcription factor TTF-1 is conserved in the epithelium of the developing fistula tract in TEF. The pattern of expression of TTF-1 in the fistula tract mirrors the expression in the large airways of the developing lungs, despite the fact that the fistula tract does not form secondary branches to give rise to a lung. CONCLUSIONS: The fistula tract in TEF is a respiratory-derived structure that expresses the lung-specific transcription factor TTF-1 throughout its development in the foregut. Contrary to the patterning role that it normally plays in the developing lung, TTF-1 does not induce branching morphogenesis in the fistula tract. Thus, the nonbranching pattern of growth of the fistula tract may be attributable to local mesenchymal-epithelial interactions that override TTF-1 patterning activity.

Animals↗

PubMed2000

Resonance Rayleigh scattering method for the determination of trace amounts of cadmium with iodide-basic triphenylmethane dye systems.

In dilute phosphoric acid solution, cadmium (II) reacts with a large excess of I- to form [CdI4]2- which reacts further with basic triphenylmethane dyes such as crystal violet (CV), ethyl violet (EV), methyl violet (MV), brilliant green (BG) or malachite green (MG) to form an ion-association complex. This results in a significant enhancement of resonance Rayleigh scattering (RRS) intensity and the appearance of new RRS spectra. The characteristics of RRS spectra of the ion-association complexes, the influencing factors and the optimum conditions of these reactions have been investigated. The intensity of RRS is directly proportional to the concentration of cadmium from 0 to 60 ng mL(-1) for EV and MV systems, 0 to 80 ng mL(-1) for CV system, and 0 to 100 ng mL(-1) for BG and MG systems. The methods exhibit high sensitivities and the detection limits for cadmium are between 0.35 and 2.00 ng mL(-1) depending on the different reaction systems. The new RRS method was applied to the direct determination of traces of cadmium in pure zinc and synthetic water samples.

Journal Article↗

PubMed2000

Visual event-related potentials in progressive supranuclear palsy, corticobasal degeneration, striatonigral degeneration, and Parkinson's disease.

To determine whether there are characteristic changes in event-related potentials (ERPs) in parkinsonian syndromes we studied 8 patients with progressive supranuclear palsy (PSP), 10 patients with corticobasal degeneration (CBD), 9 patients with striatonigral degeneration (SND), and 16 patients with idiopathic Parkinson's disease (PD) with a mean duration of illness shorter than 5 years in each group. A visual oddball paradigm was employed to elicit P300. P300 to the rare target and rare nontarget stimuli and reaction time (RT) to rare target stimuli in each group were compared with those in the corresponding age-matched normal control group and to each other after age correction. The correlation of P300 and RT to motor disability score was also studied. In PSP P300 amplitude was markedly reduced while in CBD P300 latency was prolonged. P300 amplitude to rare nontargets in SND and PD was attenuated. The mean RT in the PSP and the CBD group was significantly longer than in the other two groups. The mean RT in PD and P300 amplitude to rare nontargets in both CBD and PD showed significant correlation with the severity of motor disability. Simultaneous measurement of P300 and RT may yield useful supplementary information in facilitating diagnosis of parkinsonian syndromes in addition to clinical criteria.

Aged↗

PubMed2000

Genomic organization of Helicoverpa armigera single-nucleocapsid nucleopolyhedrovirus.

The genome organization of the Helicoverpa armigera single-nucleocapsid nucleopolyhedrovirus (HearNPV) was investigated and compared to that of other baculoviruses. A detailed physical map was constructed for the restriction enzymes BamHI, BglII, EcoRI, HindIII, KpnI, PstI, SacI and XhoI. The 130.1-kilobase pairs (kb) long viral genome was cloned as restriction fragments into a plasmid library, which covered 97.5% of the viral genome. From this plasmid library about 45 kb of dispersed sequence information was generated. Fifty-three putative open reading frames (ORFs) with homology to ORFs of other baculoviruses were identified and their location on the genome of HearNPV was determined. The arrangement of the ORFs along the HearNPV genome is significantly different from the multiple-nucleocapsid NPVs, AcMNPV, BmNPV and OpMNPV, which have a highly collinear genome, and the granulovirus XcGV. In contrast the genomes of HearNPV and SeMNPV are highly collinear. This close relatedness between an MNPV and an SNPV is supported by the phylogeny of specific genes of these two viruses and suggests that the morphotype (S or M) is only a taxonomic and not a phylogenetic denominator. The data presented here also give further support to the view that the gene distribution along baculovirus genomes can be used as a character to describe baculovirus relatedness independent of gene phylogeny. Five homologous regions (hrs) were located on the genome of HearNPV. This is also the first report of the existence of hrs in SNPVs and this observation suggests that hrs are a common feature of baculovirus genomes.

Animals↗

PubMed2000

In-vitro and in-vivo antibiotic susceptibilities of Lyme disease Borrelia isolated in China.

The antibiotic susceptibilities of seven Borrelia burgdorferi sensu lato isolates from Ixodes persulcatus in China were examined by in-vitro microdilution minimum inhibition concentration (MIC) and macrodilution minimum bactericidal concentration (MBC) methods. All isolates tested were susceptible to amoxicillin, erythromycin, and minocycline. The MICs of these drugs for the Chinese isolates were 0.025-0.1 microg/ml, <0.012-0.05 microg/ml, and <0.012-0.05 microg/ml, respectively. The MBCs were 0.1-0.39 microg/ml, <0.012-0.2 microg/ml, and 0.025-0.39 microg/ml, respectively. The in-vivo antimicrobial susceptibilities of the Chinese Borrelia isolates to two test drugs, amoxicillin and minocycline, were evaluated using ddY mice. Mice were infected by subcutaneous inoculation into the right hind footpad. When infection was confirmed, the mice were treated by subcutaneous injection of the test drugs into the back. Amoxicillin and minocycline, which possessed high in-vitro activities against Lyme disease Borrelia, provided good protection against borreliosis in this animal model. Higher doses of these drugs resulted in elimination of the Lyme disease spirochete from all animals receiving this course of treatment. The 50% curative doses (CD50) of amoxicillin and minocycline were 8.7 mg/kg and 3.1 mg/kg, respectively. This suggested that amoxicillin and minocycline could be useful for the treatment of Chinese Borrelia infection.

Amoxicillin↗

PubMed2000

Biological features and preoperative evaluation of mediastinal nodal status in non-small cell lung cancer.

BACKGROUND: To examine whether biological features of primary tumor can help preoperative evaluation of mediastinal nodal status in non-small cell lung cancer. METHODS: A total of 450 patients who underwent tumor resection and mediastinal dissection were reviewed. p53 status and proliferative fraction (PI) were evaluated immunohistochemically. RESULTS: The accuracy of preoperative evaluation of mediastinal nodal status with computed tomography (CT) was 72.2%; mediastinal nodal metastases had not been revealed until operation in 59 patients (13.1%) (false-negative), and no metastasis was revealed in 66 patients (14.7%) although mediastinal nodal enlargement had been demonstrated by CT (false-positive). The number of false-negative patients was significantly larger when p53 aberrant expression was positive or when PI was higher. Combined with p53 status and PI, there were 27 false-negatives (24.1%) among patients with aberrant p53 expression and higher PI, whereas only two false-negatives (1.5%) among those with negative p53 expression and lower PI. CONCLUSIONS: Mediastinoscopy may be recommended for tumor showing aberrant p53 expression and higher PI, even when CT demonstrates no mediastinal nodal enlargement.

Aged↗

PubMed2000

Cloning and functional expression of a synthetic gene encoding huwentoxin-I, a neurotoxin from the Chinese bird spider (Selenocosmia huwena).

Cloning and functional expression of a synthetic gene encoding huwentoxin-I, a neurotoxin from the Chinese bird spider Selenocosmia huwena. A gene encoding huwentoxin-I, a peptide neurotoxin consisted of 33 amino acid residues from the venom of the Chinese bird spider Selenocosmia huwena, was designed, synthesized and expressed in Escherichia coli as a hybrid protein fused with glutathione S-transferase at the N-terminal. The fusion protein was purified by GSH-Sepharose 4B affinity column chromatography and cleaved by thrombin to release the toxin peptide. The amino acid sequence of the recombinant toxin was consistent with the designed one by sequence determination and MALDI-TOF mass analysis, suggesting that the recombinant huwentoxin-I produced the same expression product as the native one. After reduction and renaturation, the biological activity of the recombinant toxin was identical with that of the native huwentoxin-I by electrophysiological method.

Amino Acid Sequence↗

PubMed2000

Tissue distribution of PACAP27 and -38 in oligochaeta: PACAP27 is the predominant form in the nervous system of Lumbricus polyphemus.

The levels of pituitary adenylate cyclase-activating polypeptide (PACAP)27 and -38 were measured in the nervous, intestinal, excretory, and reproductive systems of Lumbricus polyphemus by radioimmunoassay. Although both PACAP27 and -38 were significantly detectable in all of the examined tissues, the distribution of the peptides was very heterogeneous. Their highest concentrations were found in the cerebral ganglia and the ventral cord, followed by the alimentary tract and the nephridial system, respectively. Moreover, the reproductive system also contained a substantial amount of PACAP. The dominant form of the peptide discovered in the majority of tissues was PACAP27. Interestingly, about 10 times more PACAP27 than PACAP38 was found, with the latter representing only a fraction of PACAP-like immunoreactivity in the tissues of Lumbricus polyphemus.

Animals↗

PubMed2000

Functional role and therapeutic implications of neuronal caspase-1 and -3 in a mouse model of traumatic spinal cord injury.

Evidence indicates that both necrotic and apoptotic cell death contribute to tissue injury and neurological dysfunction following spinal cord injury. Caspases have been implicated as important mediators of apoptosis following acute central nervous system insults. We investigated whether caspase-1 and caspase-3 are involved in spinal cord injury-mediated cell death, and whether caspase inhibition may reduce tissue damage and improve outcome following spinal cord injury. We demonstrate a 17-fold increase in caspase-1 activity in traumatized spinal cord samples when compared with samples from sham-operated mice. Caspase-1 and caspase-3 activation were also detected by western blot following spinal cord injury, which was significantly inhibited by the broad caspase inhibitor N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone. By immunofluorescence or in situ fluorogenic substrate assay, caspase-1 and caspase-3 expression were detected in neuronal and non-neuronal cells following spinal cord injury. N-Benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone treated mice, and transgenic mice expressing a caspase-1 dominant negative mutant, demonstrated a significant improvement of motor function and a reduction of lesion size compared with vehicle-treated mice. Our results demonstrate for the first time that both caspase-1 and caspase-3 are activated in neurons following spinal cord injury, and that caspase inhibition reduces post-traumatic lesion size and improves motor performance. Caspase inhibitors may be one of the agents to be used for the treatment of spinal cord injury.

Amino Acid Chloromethyl Ketones↗

PubMed2000

Effect of extrusion temperature on the solubility and molecular weight of lentil bean flour proteins containing low cysteine residues.

Lentil flour was extruded at die temperatures of 135, 160, and 175 degrees C. The soluble protein content in the extrudates decreased by 40.1% in the extracting buffer (1% sodium dodecyl sulfate in 50 mM sodium phosphate buffer, pH 6.9) as the extrusion die temperature was increased to 175 degrees C. The most insoluble proteins in the extrudates extruded at die temperatures of up to 175 degrees C could be resolubilized by using sonication. The total disulfide content and sulfhydryl content in the extrudates decreased. The SDS-PAGEs showed that the molecular weight distribution of proteins in the lentil flour changed little before and after extrusion as well as during reduction. The results from this study show that the extrusion temperature had less effect on the solubility and molecular weight of the lentil proteins, which contain a lower level of cysteine residues than wheat proteins.

Cysteine↗

PubMed2000

Constituents of the roots of Salvia prionitis.

From the roots of Salvia prionitis, a novel alkaloid named prioline (1) and a new diterpene, prineoparaquinone (2), were isolated together with taxodione; microstegiol; 8,11,13-dehydroabietane; and 2-isopropyl-8-methyl-3,4-phenanthraquinone. The structures of the new compounds were established by spectroscopic means.

Magnetic Resonance Spectroscopy↗

PubMed2000

Temporal expression of mRNAs for neuropoietic cytokines, interleukin-11 (IL-11), oncostatin M (OSM), cardiotrophin-1 (CT-1) and their receptors (IL-11Ralpha and OSMRbeta) in peripheral nerve injury.

The mRNA expression pattern of the neuropoietic cytokines, interleukin-11 (IL-11), oncostatin M (OSM) and cardiotrophin-1 (CT-1), and their receptor components (IL-11Ralpha and OSMRbeta) was examined in peripheral nerves on two different types of injury, crush and transection. The IL-11 mRNA increased after nerve damage and immediately returned to control levels. The OSM mRNA expression increased rapidly after nerve injury and relatively high expressions were maintained for at least 14 days. The CT-1 mRNA was not expressed in any time before and after the injury. Interestingly, IL-11Ralpha was expressed in the intact nerve and decreased after injury. The expression of OSMRbeta increased slightly after the injury. Moreover, temporal mRNA expression pattern of these neuropoietic cytokines and receptors was similar between the crushed and transected models. Each neuropoietic cytokine of IL-11, OSM and CT-1 has its own specific temporal mRNA expression pattern, which is also different from those of ciliary neuro-trophic factor (CNTF), leukemia inhibitory factor (LIF) and interleukin-6 (IL-6). These results suggest that all neuropoietic cytokines have distinctive functions in nerve degeneration and repair process in response to peripheral nerve injury.

Animals↗

PubMed2000

Nitric oxide (NO), methylation and TIMP-1 expression in BL6 melanoma cells transfected with MHC class I genes.

We have previously found that transfection of BL6-8 melanoma cells with the H-2K, but not H-2D/L genes resulted in loss of their metastatic ability that was associated with decrease in their invasiveness and up-regulation of TIMP-1 expression. In the present study using the methylation-specific PCR (MSP) we found that lack of TIMP-1 expression in BL6-8 is associated with methylation in the TIMP-1 5' regulatory area. In the H-2Kb transfected CL8-1 melanoma cells up-regulation of TIMP-1 was in parallel with loss of TIMP-1 gene methylation. Treatment of BL6-8 with 5-azacytidine or with an inhibitor of histone deacetylase trichostatin A resulted in up-regulation of TIMP-1 expression. These results indicate that methylation and histone deacetylation play an important role in transcription repression of TIMP-1 in BL6 melanoma cells. Some data showed that nitric oxide (NO) could affect methylation and expression of various gene. Therefore we analyzed NO production in B16 melanoma cell lines with different expression of TIMP-1. We have found that B16F10 and BL6-8 melanoma cells do not express TIMP-1 and do not produce nitric oxide (NO) even after stimulation with IFN-gamma and LPS. However, BL6-8 cells transfected with H-2Kb or H-2Kd, but not H-2Dd or H-2Ld gene expressed TIMP-1 and produced NO constitutevely. NO production in these cells was further stimulated by IFN-gamma and LPS. Northern blot analysis showed that expression of iNOS was paralleled with TIMP-1 expression in the tested melanoma cells. However, NO produced by SNAP or inhibition of NO production by NMA did not affect TIMP-1 expression in the tested melanoma cells. Thus, TIMP-1 expression and NO production in BL6 melanoma cells transfected with MHC class I gene coincides but it remains unclear whether NO is responsible for the change in TIMP-1 methylation and expression.

Antimetabolites, Antineoplastic↗

PubMed2000

Upregulation of BiP and CHOP by the unfolded-protein response is independent of presenilin expression.

Presenilin 1 (PS1), a polytopic membrane protein, has a critical role in the trafficking and proteolysis of a selected set of transmembrane proteins. The vast majority of individuals affected with early onset familial Alzheimer's disease (FAD) carry missense mutations in PS1. Two studies have suggested that loss of PS1 function, or expression of FAD-linked PS1 variants, compromises the mammalian unfolded-protein response (UPR), and we sought to evaluate the potential role of PS1 in the mammalian UPR. Here we show that that neither the endoplasmic reticulum (ER) stress-induced accumulation of BiP and CHOP messenger RNA, nor the activation of ER stress kinases IRE1alpha and PERK, is compromised in cells lacking both PS1 and PS2 or in cells expressing FAD-linked PS1 variants. We also show that the levels of BiP are not significantly different in the brains of individuals with sporadic Alzheimer's disease or PS1-mediated FAD to levels in control brains. Our findings provide evidence that neither loss of PS1 and PS2 function, nor expression of PS1 variants, has a discernable impact on ER stress-mediated induction of the several established 'readouts' of the UPR pathway.

Alzheimer Disease↗

PubMed2000

PR39, a peptide regulator of angiogenesis.

Although tissue injury and inflammation are considered essential for the induction of angiogenesis, the molecular controls of this cascade are mostly unknown. Here we show that a macrophage-derived peptide, PR39, inhibited the ubiquitin-proteasome-dependent degradation of hypoxia-inducible factor-1alpha protein, resulting in accelerated formation of vascular structures in vitro and increased myocardial vasculature in mice. For the latter, coronary flow studies demonstrated that PR39-induced angiogenesis resulted in the production of functional blood vessels. These findings show that PR39 and related compounds can be used as potent inductors of angiogenesis, and that selective inhibition of hypoxia-inducible factor-1alpha degradation may underlie the mechanism of inflammation-induced angiogenesis.

Animals↗