Biomedical subjects

Y L Li

Publications and source records attributed to Y L Li.

At least 55 records · Page 3Linked to original sources

PubMed1999

Anti-Trypanosoma brucei activity of nonprimate zoo sera.

Constitutive anti-Trypanosoma brucei subsp. brucei S 427 clone 1 and 22 activities were evaluated in sera from 22 species of nonprimate mammals. The sera fell into 5 categories. Sera from Cape buffalo, giraffe, and greater kudu showed a concentration-dependent inhibition of replication of the 2 clones of organisms, which was dependent on the presence of xanthine oxidase. Sera from warthog and springbok also severely limited trypanosome replication but lacked xanthine oxidase. Their antitrypanosome activity was inactivated by heating at 56 C for 30 min but not affected by absorbing with trypanosomes at 4 C. Sera from lion and leopard showed a concentration-dependent inhibition of the growth of T. brucei S427 clone 1 organisms, but not clone 22 organisms. These sera lacked xanthine oxidase. Their anti-T. brucei S 427 clone 1 activity was inactivated by heating at 56 C for 30 min but not removed by absorbing with trypanosomes. Serum from Grant's gazelle prevented replication of both T. brucei clones, lacked xanthine oxidase, and was not affected by heating at 56 C. Sera from waterbuck, Thompson's gazelle, sitatunga, Cape hartebeeste, gerenuk, Grant's zebra, cow, several cat, cougar, bobcat, and domestic cat were fully supportive of trypanosome replication irrespective of concentration tested up to a maximum of 48% v/v in culture medium. Sera from different individuals of the same mammal species had similar effects on trypanosomes, and samples collected from the same individual at different times also had similar activities indicating species-specific stable expression, or lack thereof, of constitutive serum antitrypanosome components.

Animals↗

PubMed1999

[SPE analysis of 4 rodenticides in whole blood and liver by HPLC].

A solid phase extraction (SPE) method has been developed for the analysis of 4 rodenticides: warfarin, couatetralyl, bromadiolone and brodifacoum, using reverse phase high performance liquid chromatograph (HPLC) as determination system. The recovery is 62.6-90.0% (RSD5.1-7.8%) and 37.5-67.7% (RSD5.4%-12.8%) in whole blood and liver sample respectively. The procedure is simple and stable. And the method was confirmed to be effective in the animal experiment.

Animals↗

PubMed1999

[The effect of EDTA with different density on adhesive power of casting post and its scanning electromicroscopy (SEM) observation]

OBJECTIVE:To evaluate the effect of EDTA with different density on adhesive power of casting post.METHODS:Four different density of EDTA(5%,10%,15%,17%)were used to rinse the smear layer of root canal for 60 extracted teeth before they were cemented with ZP;on the other,a SEM observation was made on the rinse of root canal and the combination of adhesive and root canal.Meanwhile,a comparison was also made, after the rinse of EDTA,of tensile strength of casting post after their cement.RESULTS:EDTA with different density have different effect in the rinse of smear layer of root canal,it was proved by both SEM observation and the records of tensile strength of casting post. CONCLUSION:EDTA with density 10% is more effective in both the rinse of smear layer of root canal and the enhancement of adhesive power of casting post.

Journal Article↗

PubMed1998

Selectivity of post-translational modification in biotinylated proteins: the carboxy carrier protein of the acetyl-CoA carboxylase of Escherichia coli.

Biotin-dependent enzymes contain a biotinyl-lysine residue in a conserved sequence motif, MKM, located in a surface hairpin turn in one of the two beta-sheets that make up the domain. A sub-gene encoding the 82-residue C-terminal biotinyl domain from the biotin carboxy carrier protein of acetyl-CoA carboxylase from Escherichia coli as a fusion protein with glutathione S-transferase was created and over-expressed in E. coli. The biotinyl domain was readily released by cleavage with thrombin. Five mutant domains were created in which the conserved MKM motif was systematically replaced: by MAK and KAM, in which the target lysine is moved one place; by KKM and MKK, in which a second potential site for biotinylation is introduced; and by DKA, the motif found in the correspondingly conserved site of lipoylation in the structurally related lipoyl domains of 2-oxo acid dehydrogenase multienzyme complexes. No biotinylation of the MAK or KAM mutants was observed in vivo or by purified biotinyl protein ligase in vitro; in the KKM and MKK mutants, only one lysine residue, presumed to be that in its native position in the hairpin turn, was found to be biotinylated in vivo and in vitro. The DKA mutant was not biotinylated in vivo, but was partly lipoylated and octanoylated. It was also a poor substrate for lipoylation in vitro catalysed by the E. coli lipoyl protein ligase encoded by the lplA gene. The flanking sequence in the MKM motif is important, but not crucial, and appears to have been conserved in part to be compatible with the subsequent carboxylation reactions of biotin-dependent enzymes. The DKA motif, displayed in the hairpin loop, is sufficient to address lipoylation in E. coli but probably by a pathway different from that mediated by the lplA-dependent ligase. The recognition of the structurally homologous lipoyl and biotinyl domains by the appropriate ligase evidently has a major structural component to it, notably the positioning of the target lysine residue in the exposed hairpin loop, but there appear to be additional recognition sites elsewhere on the domains.

Acetyl-CoA Carboxylase↗

PubMed1998

Identification and characterization of a novel member of the fibroblast growth factor family.

A new member of the fibroblast growth factor (FGF) family, FGF-13, has been molecularly cloned as a result of high throughput sequencing of a human ovarian cancer cell library. The open reading frame of the novel human gene (1419 bp) encodes for a protein of 216 a.a. with a molecular weight of 22 kDa. The FGF-13 sequence contains an amino-terminal hydrophobic region of 23 a.a. characteristic of a signal secretion sequence. FGF-13 is most homologous, 70% similarity at the amino acid level, to FGF-8. Northern hybridization analysis demonstrated prominent expression of FGF-13 in human foetal and adult brain, particularly in the cerebellum and cortex. In proliferation studies with BaF3 cells, FGF-13 preferentially activates cell clones expressing either FGF receptor variant, 3-IIIc or 4. The signal transduction pathways of FGF-13 and FGF-2 were compared in rat hippocampal astrocytes. The two FGFs induce an equivalent level of tyrosine phosphorylation of mitogen-activated protein kinase (MAPK) and c-raf activation. However, FGF-13 is more effective than FGF-2 in inducing the phosphorylation of phospholipase C-gamma (PLC-gamma). Treatment of neuronal cultures from rat embryonic cortex with FGF-13 increases the number of glutamic acid decarboxylase immunopositive neurons, the level of high-affinity gamma-aminobutyric acid (GABA) uptake, and choline acetyltransferase enzyme activity. The GABAergic neuronal response to FGF-13 treatment is rapid with a significant increase occurring within 72 h. We have identified a novel member of the FGF family that is expressed in the central nervous system (CNS) and increases the number as well as the level of phenotypic differentiation of cortical neurons in vitro.

Amino Acid Sequence↗

PubMed1997

Myocyte-specific enhancer binding factor 2C expression in fetal mouse brain development.

We have previously found that myocyte-specific enhancer binding factor 2C (MEF2C) is expressed in the brain, where it is found at high levels in the developing cerebral cortex. We have now examined MEF2C expression in fetal mouse brain by in situ hybridization and by immunohistochemistry from E11 to E17, the period when most cortical neurons are born. The distribution of MEF2C mRNA detected by in situ hybridization closely resembles that of MEF2C immunoreactivity. MEF2C is not present in proliferative zones in the brain. It is present at high levels in cells that have migrated to the subplate and cortical plate. MEF2C is also found in the olfactory blub at high levels and at lower levels in hippocampus, basal forebrain, striatum, cerebellum, and inferior colliculus, and in some nuclei of the hypothalamus, thalamus and brainstem. The pattern of expression suggests that MEF2C is expressed in a subset of postmitotic neurons in the brain and that it may therefore function to promote terminal differentiation of the cells that express it.

Animals↗

PubMed1997

Schistosoma japonicum, S. mansoni, S. haematobium, S. intercalatum, and S. rodhaini: cysteine-class cathepsin activities in the vomitus of adult worms.

Vomitus from adults of five Schistosoma species was screened for biochemical homologues of the mammalian cysteine proteinases cathepsins B, H, and L. Bovine cathepsin B and rat cathepsin L served as references. Using the substrate Arg-NMec, a schistosome cathepsin H-like activity was never detected. All species degraded the cathepsin B substrate Z-Arg-Arg-NMec, but distinct species differences were observed with respect to pH optima and buffer preferences. The cathepsin B and L substrate Z-Phe-Arg-NMec was similarly degraded by all species, and activity was abolished by the cysteine proteinase inhibitor E-64. Preferences by vomitus proteinase activities for Z-Phe-Arg-NMec over Z-Arg-Arg-NMec were similar to or higher than those found for bovine cathepsin B but well below those observed for rat cathepsin L; also, the preferential cathepsin L inhibitor Z-Phe-PheCHN2 only partially inhibited proteinolytic activity. The results suggest the possible presence in vomitus of a minor cathepsin L-like activity and demonstrate a major cathepsin B-like activity that is biochemically variable between schistosome species.

Animals↗

PubMed1997

Anthraquinones in Rheum palmatum and Rumex dentatus (Polygonaceae), and phorbol esters in Jatropha curcas (Euphorbiaceae) with molluscicidal activity against the schistosome vector snails Oncomelania, Biomphalaria and Bulinus.

Hot water extracts of Rheum plamatum and Rheum dentatus (from China) showed molluscicidal activity against the snails Oncomelania hupensis, Biomphalaria glabrata and Bulinus globosus, which are vectors of Schistosoma japonicum, S. mansoni and S. haematobium, respectively. Activity was correlated with antraquinones which were identified by HPLC: rhein and chrysophanol-anthron were most active (> 50% dead snails after 2 days in a 0.03% solution). Molluscicidal activity was intermediate with Rheum-emodin and physcion and was not detectable with cinnamic acid or Aloe-emodin. The snail O. hupensis tended to be more sensitive for several compounds than B. glabrata. Extracts of Jatropha curcas seeds (from Mali) showed molluscicidal activity against both B. glabrata and O. hupensis, the latter being the more sensitive snail. The activity was associated with phorbol esters extracted from Jatropha oil. Of the pure phorbol esters tested, 4 beta-phorbol-13-decanoate killed both snail species at a concentration of 0.001% (10 p.p.m). As Jatropha is locally grown in Mali for other purposes, it might potentially be exploited for schistosomiasis control.

Animals↗

PubMed1997

The trypanocidal Cape buffalo serum protein is xanthine oxidase.

Plasma and serum from Cape buffalo (Syncerus caffer) kill bloodstream stages of all species of African trypanosomes in vitro. The trypanocidal serum component was isolated by sequential chromatography on hydroxylapatite, protein A-G, Mono Q, and Superose 12. The purified trypanocidal protein had a molecular mass of 150 kDa, and activity correlated with the presence of a 146-kDa polypeptide detected upon reducing sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Amino acid sequences of three peptide fragments of the 146-kDa reduced polypeptide, ligand affinity and immunoaffinity chromatography of the native protein, and sensitivity to pharmacological inhibitors, identified the trypanocidal material as xanthine oxidase (EC 1.1.3.22). Trypanocidal activity resulted in the inhibition of trypanosome glycolysis and was due to H2O2 produced during catabolism of extracellular xanthine and hypoxanthine by the purine catabolic enzyme.

Africa↗

PubMed1997

Inhibitory effect of artemether on proteinase of Schistosoma japonicum.

AIM: To study the effect of artemether (Art) on the thio proteinase ("hemoglobinase", Hem) of Schistosoma japonicum. METHODS: Hem was extracted from S japonicum adults. The inhibitory effect of Art on the activity of Hem to degrade human hemoglobin (Hgb) was examined with UV-photometer at 280 nm, SDS-PAGE and scanning at 600 nm on a chromoscanner. RESULTS: Human Hgb was degraded at pH 4.0 by the Hem. The activities of Hem preincubated at 37 degrees C with Art 0.14, 1.4, and 14 mmol.L-1, were inhibited by 30.2%, 39.8%, and 45.0%, respectively. CONCLUSION: Art possesses an inhibitory effect to Hem of S japonicum.

Animals↗

PubMed1997

[Synthesis and biological activity of substance P analogs].

Substance P (SP) and its three analogs were synthesized through solid-phase procedure. The fully-protected peptide-resin was cleaved with anhydrous HF.--SH of Cys in [Cys5,9] SP(4-11) was protected with Acm, then deprotected through Iodine oxidation method, the disulfide bridge cyclization was formed subsequently. The crude product was purified on C18 RP-HPLC. The results of guinea-pig isolated ileum test (GPI) showed that the potency of the analogs was as follows: [AcGln5, Pro9] SP(5-11) > SP > SP(4-11) > [Cys5,9] SP(4-11). They induced GPI to contract very fast and showed the characteristics of tachykinin. On the writing test in mice, the results showed: [Cys5,9] SP(4-11) > SP > SP(4-11) > [AcGln5, Pro9] SP(5-11). The biological tests showed that the SP analogs have some extent of selectivity.

Animals↗

PubMed1997

[Effects of endothelin on electrophysiological and contractile activity of guinea pig papillary muscles].

Effects of endothelin on electrophysiological activity and contractility were examined in guinea pig papillary muscle using intracellular microelectrode and contractile tension recording technique. The results indicated that ET-1 prolonged APD, especially PPD and increased the contractile tension in a dose-dependent manner. The ET-induced effects were not influenced by K+ channel blocker TEA, but inhibited by L-type Ca2+ channel blocker nifedipine, ETA receptor selective antagonist BQ-123 and atriopeptin III in a concentration-dependent manner. It is suggested that the changes in electrophysiological activity and the positive inotropic effect induced by ET-1 in guinea pig muscles are due to the elevation of intracellular calcium, which may be mediated by ETA receptor.

Animals↗

PubMed1996

Affinity chromatography of trypsin using chitosan as ligand support.

Chitosan beads were prepared for use as affinity adsorbent carrier. The affinity ligand, chicken ovomucoid, was immobilized on the chitosan via a cross-linker, glutaraldehyde. The results showed that 60 mg chicken ovomucoid could be immobilized on l g chitosan, and the maximum binding capacity for trypsin was about 8.10(4) U/g dry adsorbent. The procedure for preparing the chitosan-based affinity adsorbents was much safer and simpler than when a Sepharose-based matrix was the support. Columns packed with the affinity adsorbents were employed for trypsin chromatography. The experimental results revealed that the affinity adsorbents possessed good mechanical strength and storage stability and could be also operated repeatedly. Chitosan was suitable for use as an affinity adsorbent support for laboratory-scale and large-scale purification.

Adsorption↗

PubMed1996

Preliminary report on treatment of bone tumors with microwave-induced hyperthermia.

Between July, 1992, and February, 1995, 62 patients with various bone tumors were treated with microwave-induced hyperthermia. The series had 47 cases of malignant tumors and 15 cases with benign tumors; most of the tumors occurred at or near knee joints (53/62 = 85.4%). The surgical procedure consisted of separating the tumorous segment from surrounding normal tissues with a safe margin, cooling the normal tissues (including the vital neurovascular bundle and the intrajoint structures) with a water circulation system while heating the tumor simultaneously with the microwave antenna array, and providing an adequate soft-tissue cover for the dead bone. The tumor core temperature and the surface temperature reached 108 and 65 degrees C, respectively. The duration of microwave irradiation was usually 40-50 minutes. Meanwhile, the temperature of the normal tissues was kept under 39 degrees C. The minimal and maximal periods of clinical observation were 3 months and 36 months, respectively, and the mean follow-up period was 17 months. The 62 cases were evaluated from both oncological and orthopedic points of view. Five cases had local recurrence and required amputation. The 57 other cases had excellent local control. Six malignancy cases died of lung metastasis during a period of 1-2 years. Pathological fracture occurred at devitalized bone in five cases. In most of the cases, the knee joints functioned well, were stable and painless, and had almost full range of motion. Single-photon emission-computed tomography study in 16 cases revealed that revascularization of the devitalized tumorous bone segment could be accomplished in 1 year or more. These results show that the use of microwave hyperthermia for the treatment of bone tumors can be considered to be a definitive operation procedure that is safe and is well tolerated by patients. The oncological and orthopedic results are very encouraging.

Adolescent↗

PubMed1996

Circulating antigens in schistosomiasis: detection of 31/32-kDa proteins in sera from patients infected with Schistosoma japonicum, S. mansoni, S. haematobium, or S. intercalatum.

A sandwich enzyme-linked immunosorbent assay (ELISA) was developed to detect 31/32-kDa schistosome proteins as circulating antigens in sera from schistosomiasis patients. A monoclonal antibody was used as a capture antibody and rabbit antiserum raised against purified 31/32-kDa proteins was the detecting antibody. Positive results were obtained with patients infected with Schistosoma japonicum (88%; n = 69), S. mansoni (80%; n = 56), S. haematobium (100%; n = 40), or S. intercalatum (94%; n = 65). Sera from uninfected Chinese and African individuals and from Chinese patients with trichinosis, cysticercosis, or paragonimiasis did not react in the assay. This ELISA appears to be valuable in diagnosing infections by all major human schistosome species.

Adolescent↗

PubMed1996

Phenolic and triterpenoid glycosides from Aster batangensis.

A new phenolic glycoside, asterbatanoside A [p-hydroxyacetophenone-4-O-beta-D-xylopyranosyl-(1-->6)-beta-D- glucopyranoside], and two new triterpenoid saponins, asterbatanoside B [2 alpha,3 beta,23-trihydroxyolean-12-en-28-oic acid-28-O-beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyranoside] and asterbatanoside C [3-O-beta-D-glucopyranosyl-2 beta,3 beta,23-trihydroxyolean- 12-en-28-oic acid-28-O-beta-D-glucopyranoside] were isolated from the roots of Aster batangensis. Their structures were determined by spectroscopic methods and chemical evidence. The total synthesis of asterbatanoside A is also reported.

Carbohydrate Conformation↗

PubMed1996

Evaluation of a monoclonal antibody-based sandwich-ELISA for detection of circulating Schistosoma japonicum antigen (Sj31/32) in an endemic area of China.

A sandwich-ELISA specific for 31/32 kDa schistosome proteins was used to trace infections in a Chinese population living in a low endemicity area for schistosomiasis japonica. The study population included 304 persons for whom records were available from 1992 onwards. In 1994, 2 individuals were positive in the miracidial hatching assay performed with 30 g of stools. The ELISA gave positive results for 8 individuals, including these 2 with active infections. Of the remaining 6 ELISA-positive, 5 had excreted eggs and received praziquantel in 1993 and may have harboured residual worms in 1994. It is concluded that this ELISA is able, in a low prevalence situation, to identify the few infected individuals.

Adolescent↗

PubMed1996

[Effects of endothelin on the electrical activity of sino-atrial pacemaker cells of rabbit].

The effects of endothelin-1 (ET-1) on the electrophysiological activity of pacemaker cells of rabbit sino-atrial node were examined by using intracellular microelectrode technique. The results obtained were as follows: (1) With superfusion of ET-1 (1-30 nmol/l), the velocity of diastolic depolarization (VDD) of pacemaker cells was significantly decreased in a concentration dependent manner, resulting in a reduced rate of pacemaker firing (RPF). (2) The decreases in RPF and VDD induced by ET-1 could be virtually blocked by pretreatment with ET(A) receptor blocker BQ-123 (20 or 100 micrograms/L). It was strongly suggested that the electrophysiological effects of ET-1 on the pacemaker cells were mediated by the ET(A) receptor. (3) The negative chronotropic action of ET-1 on the pacemaker cells was totally abolished by pretreatment with a kind of KATP channel blocker glibenclamide (10 mumol/L). On the basis of above results, it appears that the binding of ET-1 with ET(A) receptor may induce an activation of KATP channels with resultant increase in K+ current so as to decrease the velocity of diastolic depolarization in the pacemaker cells.

Animals↗