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Biomedical subjects

Y H Li

Publications and source records attributed to Y H Li.

At least 55 records · Page 3Linked to original sources
PubMed2001

Talectomy in patients with recurrent deformity in club foot. A long-term follow-up study.

We reviewed 24 feet in 15 patients who had undergone talectomy for recurrent equinovarus deformity; 21 were associated with arthrogryposis multiplex congenita, two with myelomeningocele and one with idiopathic congenital talipes equinovarus. The mean follow-up was 20 years. Good results were achieved in eight feet (33%) in which further surgery was not needed and walking was painless; a fair result was obtained in ten feet (42%) in which further surgery for recurrence of a hindfoot deformity had been necessary but walking was painless; the remaining six feet (25%) were poor, with pain on walking. All patients wore normal shoes and could walk independently, except one who was wheelchair-bound because of other joint problems. Recurrent deformity, the development of tibiocalcaneal arthritis and spontaneous fusion of the tibia to the calcaneum were all seen in these patients.

Child↗
PubMed2001

Rat tripeptidyl peptidase I: molecular cloning, functional expression, tissue localization and enzymatic characterization.

We purified tripeptidyl peptidase I (TPP I) to homogeneity from a rat kidney lysosomal fraction and determined its physicochemical properties, including its molecular weight, substrate specificity and partial amino acid sequence. The molecular weight of the enzyme was calculated to be 280,000 and 290,000 by non-denaturing PAGE and gel filtration, respectively, and to be 43 000 and 46 000 on SDS-PAGE in the absence and presence of beta-ME, respectively. These findings suggest that the enzyme is composed of six identical subunits. The Km, Vmax, kcat and kcat/Km values of TPP I at optimal pH (pH 4.0) were 680 microM, 3.7 micromol x mg(-1) x min(-1), 33.1 s(-1) and 4.87 x 10(4) s(-1) x M(-1) for Ala-Ala-Phe-MCA, respectively. TPP I was significantly inhibited by PCMBS and HgCl2, and moderately by DFP. These findings also suggest that TPP I is an exotype serine peptidase that is regulated by SH reagent. TPP I released the tripeptide Arg-Val-Tyr from angiotensin III more rapidly than from Ala-Ala-Phe-MCA, and also released Gly-Asn-Leu from neuromedin B with the same velocity as from Ala-Ala-Phe-MCA. Angiotensin III and neuromedin B have recently been found to be good natural substrates for lysosomal TPP I. Furthermore, we determined the rat liver cDNA structure and deduced the amino acid sequence. The cDNA, designated as lambdaRTI-1, is composed of 2485 bp and encodes 563 amino acids in the coding region. By Northern blot analysis, the order for TPP I mRNA expression was kidney > or = liver > heart > brain > lung > spleen >> skeletal muscle and testis. In parallel experiments, the TPP I antigen was detected in various rat tissues by immunohistochemical staining.

Amino Acid Sequence↗
PubMed2001

Efficacy trial of Vi polysaccharide vaccine against typhoid fever in south-western China.

OBJECTIVE: To test the efficacy of locally produced Vi vaccine over a time period of longer than one year. METHODS: A double-blinded, randomized field trial was performed in Guangxi Zhuang Autonomous Region in south-western China, using 30 micrograms doses of locally produced Vi. Enrolled subjects were 3-50 years of age, although the majority (92%) were school-aged children, who have the highest rate of typhoid fever in this setting. A total of 131,271 people were systematically allocated a single dose of 30 micrograms of Vi polysaccharide or saline placebo. The study population was followed for 19 months, with passive surveillance conducted in the Ministry of Health and the Regional Health and Anti-epidemic Centre (HAEC). Clinically suspected cases of typhoid fever were confirmed by blood culture, or by serological reaction with O-antigen (Widal tests). FINDINGS: After 19 months, there were 23 culture-confirmed cases of typhoid fever in the placebo group versus 7 cases in the Vi group (Protective efficacy (PE) = 69%; 95% CI = 28%, 87%). Most of the isolates were from school-aged children: 22 cases in the placebo group versus 6 in the Vi group (PE = 72%; 95% CI = 32%, 82%). No serious post-injection reactions were observed. The locally produced Vi polysaccharide vaccine showed levels of protective efficacy similar to those for Vi vaccine produced in industrial countries. CONCLUSION: The slightly higher dose of vaccine did not seem to alter efficacy significantly in China.

Adolescent↗
PubMed2001

Effects of simulated weightlessness on the release of PGE2 in rat calvarial osteoblasts induced by flow shear stress.

OBJECTIVE: To observe the effects of simulated weightlessness on the release of prostaglandin E2 in rat calvarial osteoblasts by flow shear stress (FSS). METHOD: Osteoblasts were isolated from neonatal rat calvariae and then were set to two groups. One was cultured in 1 G terrestrial gravitational environment. The other was cultured on a clinostat (simulating weightlessness environment) for 60 h, then the osteoblasts were treated with 0.5 Pa or 1.5 Pa FSS in a flow chamber for 1 h. Then release of PGE2 in the osteoblasts was determined. RESULT: 0.5 Pa and 1.5 Pa FSS treatments significantly increased the release of PGE2 in osteoblasts cultured in 1 G environment (P < 0.01) , but there was no remarkable difference between the responses of 0.5 Pa FSS treatment group and 1.5 Pa group (P > 0.05). By contrast, in cells cultured in simulated weightlessness environment, no detectable release of PGE2 was found with the treatment of 0.5 Pa FSS (P < 0.01). The release of PGE2 was delayed and the amount of PGE2 Production was remarkably decreased with 1.5 Pa FSS treatment (P < 0.01). CONCLUSION: These results demonstrated that the responsiveness of osteoblasts to FSS was down-regulated in simulated weightlessness.

Animals↗
PubMed2001

[Cloning and expression of human anti-colonic cancer single-chain Fv fragment].

We report a new strategy for the generation of human anticolon cancer monoclonal antibodies based on the molecular cloning and expression of immunoglobulin variable region cDNAs derived from peripheral blood mononuclear cells (PBMC) that were transformed by EBV. The immortalized B cells secreting tumor-specific antibodies were identified by HRT-18 cell ELISA and cloned by limiting dilution. Heavy- and light-chain VH-CH1 (gamma) and V kappa-C kappa cDNAs were rescued from ELISA-positive cells wells by RT-PCR. VH and V kappa were amplified by 2nd PCR and linked them together by 3rd PCR assembly with the use of a (Gly4Ser)3 linker. The ScFv cDNAs were then cloned into the fUSE 5 vector and displayed on phage. Phage clones were selected on HRT-18 cells and normal human PBMC. ELISA tested phage clones randomly picked after each panning step. > 80% of the clones showed a strong ELISA reaction, demonstrating the effectiveness of the panning procedure for selecting anticolon cancer antibodies. This approach offers an effective method by combining in vitro immunization, B-cell expansion for enrichment of specific B-lymphocytes, PCR gene cloning and phage display to make high-affinity human anticolon cancer monoclonal antibody molecules.

Antibodies, Monoclonal↗
PubMed2001

[Bone adaptation and response to mechanical stress in bone].

To review the progresses in the research of bone adaptation and its mechanisms. The Wolff's law represented early theory of bone adaptation, but the Frost's mechanostat theory developed in 1960s might be the more appropriate theory. Several studies showed that the bone cells including osteoblasts, osteocytes and bone lining cells are the mechanosensitive cells in bone tissue. Forces acting on the bone cells include compressive-tensile stress and shear stress. The shear stress is the main force which can be sensed by the bone cells. The effect of shear stress on bone cells is closely related to the basic structure of the bone, i.e., osteon. The main responses of bone cells to stress are changes of secretion of prostaglandins and nitric oxide.

Adaptation, Physiological↗
PubMed2001

[Mechanotransduction in bone].

This article reviewed the progresses in the research of mechanisms of bone adaptation. The process of mechanotransduction can be divided into four distinct steps: mechanocoupling; biochemical coupling; transmission of signal; effector cell response. Through these four steps, the loads acting on the bones are transduced into biochemical signals, and then change the function of bone cells, finally induce the changes of bone structures to adapt the mechanical environment.

Adaptation, Physiological↗
PubMed2001

[Determination of 4-chloro-3,5-dimethyl phenol in antiseptics and synthetic products by scanning thin-layer chromatography].

A new method of scanning thin-layer chromatography was established for the quantitative determination of the 4-chloro-3,5-dimethyl phenol by developing with 40% benzene in trichloromethane on GF254 silica gel plate. The results showed that the linear dynamic range of 4-chloro-3, 5-dimethyl phenol was 0.1858 g/L-7.4320 g/L in which the relative peak area obeyed the Lambert-Beer's law with a correlation coefficient of 0.9994 and recoveries of 98.31%-100.1%. The method is simple, rapid, sensitive and reproducible.

Anti-Infective Agents, Local↗
PubMed2001

[Effects of anti-idiotypic antibody NP30 on modulation of egg granuloma formation and hepatic fibrosis of schistosomiasis].

OBJECTIVE: To study the effects of the monoclonal anti-idiotypic antibody NP30 active immunization on egg granuloma formation and hepatic fibrosis in Schistosoma japonicum infection. METHODS: ICR mice were actively immunized with NP30 100 micrograms x 3 i.p. every 10 days while the mice in control group were injected with SP2/0 ascites i.p. simultaneously. After cercariae challenging, the mice were killed at the 4th, 8th, 12th, 16th, 20th and 24th week, respectively. Mouse livers were removed and stained histochemically with VG and subjected to immunohistochemical assay of collagen type I, III and fibronectin(FN). The volume of egg granulomas and the content of collagen type I, III and FN were determined quantitatively by NYD-1000 Image Analysis System. RESULTS: The volume of egg granulomas in NP30 immunized group was much smaller than that of control group from the 12th week after cercariae challenge. The cellular components of egg granulomas in NP30 immunized group were significantly different from those of the control group, exhibiting two types of atypical egg granulomas were found. VG stain revealed that the average optical density of collagen in hepatic granulomas of experimental group was lower than that of control group. Immunohistochemical assay revealed that the contents of collagen type I, III and fibronectin in egg granulomas of experimental group were lower than those of control group. CONCLUSION: NP30 vaccination may induce both cellular and humoral protective immunity to modulate egg granulomas and suppress liver fibrosis of schistosomiasis japonica.

Animals↗
PubMed2001

[Differential expression analysis and cloning of murine thymic aged-related genes].

OBJECTIVE: Differential expression analysis and cloning of murine thymic aged-related genes. METHODS: Different expressions of thymic mRNAs from 1- and 10-month old mice were analyzed via DDRT-PCR and different expression sequence tags (ESTs) were obtained, following by identification with Northern Blotting, DNA sequencing, as well as screening of cDNA library. RESULTS: It was found that there would be a significant difference of gene expression in murine thymuses. Gene expression of some genes were exclusive in thymus from 1 or 10-month old mice, while some expressed different with age. 108 differential display cDNA fragments were recovered, among which 31 were positive for hybridization by Northern blot. After sequenced, 14 ESTs were found to share high homology to known genes, whereas remaining 17 were novel. A murine thymic cDNA library was screened by using one cDNA fragment that expressed with higher level in total RNA of 1-month old murine thymic tissues than 10-month old. Finally, one 1,470 bp fragment was cloned and showed a 99% of homology to murine transketolase. CONCLUSION: Expression of murine thymic genes has displayed a marked difference with age. These genes might be participated in thymic atrophy.

Aging↗
PubMed2001

[Two-dimensional infrared correlation spectroscopy on dodecyloxy benzoic acid phase transition].

Thermal spectra of liquid crystal, dodecyloxy benzoic acid were collected over a temperature range of 26-150 degrees C by FTIR microspectroscopy. By taking investigations of temperature-induced changes in dodecyloxy benzoic acid by means of 2D infrared correlation spectroscopy, it was possible to clearly describe the molecular dynamic mechanism of dodecyloxy benzoic acid aggregates in the phase transitions. The analysis shows that p-dodecyloxy benzoic acid crystallized as multi-molecule aggregates through hydrogen bonds between the carboxylic groups, while the long polymethylene residues intermixed each other in solid state. Premelting phenomena in polymethylene residues were observed with temperature up to melting point. It seems that lots of oxy-benzoic acid part recrystallized to cycle dimer as supermolecular liquid crystal during alkyl chain melting in crystal-smectic phase transition. After temperature over 132 degrees C, oxy-benzoic acid part were melted to open dimer and separate molecule in liquid state.

Benzyl Compounds↗
PubMed2000

Alteration of rat dipeptidyl peptidase III by site-directed mutagenesis: cysteine(176) is a regulatory residue for the enzyme activity.

To comprehend the importance of cysteine residues for the regulation of enzyme activity, we replaced each of seven cysteine residues in rat dipeptidyl peptidase III cDNA with alanine, glycine, or glutamic acid residue using site-directed mutagenesis. Each mutated cDNA was expressed in E. coli (BL21), and each expressed DPP III was purified to apparent homogeneity on SDS-polyacrylamide gel electrophoresis. Six of the mutant proteins had similar activity to that of the wild-type enzyme, whereas the activity of the Cys(176) --> Ala mutant enzyme was only 25-35% of that of the wild-type enzyme activity. This mutant enzyme was resistant against both PCMB and NEM. Furthermore, both Cys(176) --> Gly and Cys(176) --> Glu mutated enzymes showed no DPP III activity. These seven mutated enzymes contained significant amounts of zinc, as determined by atomic absorption spectrometry. The results indicate that Cys(176) is essential for the regulation of DPP III activity.

Amino Acid Substitution↗
PubMed2000

Puromycin-sensitive alanyl aminopeptidase from human liver cytosol: purification and characterization.

A cytosolic alanyl aminopeptidase (AAP-S) was purified to homogeneity from human liver cytosol. The molecular weight of the purified enzyme was calculated to be approximately 98,000 on TOF-MS and 90,000 on SDS-PAGE in the presence of beta-ME. These findings suggest that the enzyme exists as a monomeric form in human liver cytosol. The enzyme rapidly hydrolyzed the substrates Ala-, Lys- and Phe-MCAs, and moderately hydrolyzed Met-, Leu-, Tyr- and Lys-Ala-MCAs at pH ranging from 7.5 to 8.0. The order of the K(cat)/K(m) values of AAP-S at the optimal pH was Arg->Arg-Arg->Met->Leu->Lys->Phe->Lys-Ala->Tyr->Ala-MCAs. It was strongly inhibited by bestatin, leuhistin, actinonin, amastatin, 1, 10-phenanthroline, DFP, PCMBS, Zn(2+), Cd(2+), Co(2+), Cu((2+)), Hg(2+) and puromycin. AAP-S was approximately 80 times more sensitive than human seminal plasma AAP (aminopeptidase N, membrane type). The amino acid sequence of the first 60 residues of AAP-S was highly homologous with the N-terminal amino acid sequence of the rat liver puromycin-sensitive enkephalin-degrading aminopeptidase. These physicochemical properties and findings indicate that AAP-S from human liver cytosol is identical to those of other puromycin-sensitive aminopeptidase(s). Furthermore, with immunohistochemistry the enzyme was strongly stained in the cytoplasm of liver cells and renal tubules, and was ubiquitously localized in various human tissues.

Aminopeptidases↗
PubMed2000

G-33A mutation in the promoter region of thrombomodulin gene and its association with coronary artery disease and plasma soluble thrombomodulin levels.

Thrombomodulin is an endothelial glycoprotein that decreases thrombin activity and activates protein C. A recent study has shown that G-33A promoter mutation of the thrombomodulin gene occurs particularly in Asians. In this study, we analyzed the distribution of G-33A mutation in the promoter region of the thrombomodulin gene in the Chinese population and determined whether the mutation might be a risk for coronary artery disease (CAD). In addition, the influence of this mutation on plasma soluble thrombomodulin levels in patients with CAD was also examined. We studied 320 consecutive patients (mean age 63 years; 73% men) with CAD and 200 age- and sex-matched control subjects. Screening for thrombomodulin G-33A promoter mutation was conducted using polymerase chain reaction, single-strand conformation polymorphism, and direct deoxyribonucleic acid sequencing. The frequency of the G-33A mutation (GA+AA genotypes) was significantly higher in the CAD group (23.8% vs 15.5%, odds ratio [OR] 1.70, p = 0.031). Multiple logistic regression analysis showed that the mutation was an independent risk factor (OR 1.81, p = 0.016) for CAD, as was hypertension (OR 1.44, p = 0.040), diabetes mellitus (OR 2.50, p <0.001), and smoking (OR 2.15, p <0.001). In CAD patients with GG genotype, the soluble thrombomodulin level increased with the extent of CAD (36 +/- 15 vs 47 +/- 18 vs 55 +/- 36 ng/ml in 1-, 2-, or 3-vessel CAD, p <0.001). However, in CAD patients with G-33A mutation, there was no difference between the levels of soluble thrombomodulin (39 +/- 17 vs 37 +/- 15 vs 42 +/- 18 ng/ml, p = NS) in 1-, 2-, or 3-vessel CAD. Our observations suggest that there is a significant association of the G-33A mutation in thrombomodulin gene with CAD, and this mutation may influence the soluble thrombomodulin levels in patients with CAD.

Asian People↗
PubMed2000

Correlation of homocytsteine levels with the extent of coronary atherosclerosis in patients with low cardiovascular risk profiles.

Elevation of homocysteine is now known as an independent risk factor for vascular diseases. However, influences of homocysteine to the extent of coronary atherosclerosis in patients with different coronary risk profiles have not been studied. In this study, we used angiographic "diffuse score" and "clinical vessel score" to evaluate the extent of coronary atherosclerosis, and examined the correlation between levels of serum total homocysteine and angiographic scores among patients with high- and low-risk profiles. Seventy consecutive patients (58 men and 12 women, mean age 50 years) undergoing selective coronary angiography for the first time were recruited for this study. Patients were divided into high-risk (risk factor > or =3, n = 35) and low-risk (risk factor <3, n = 35) groups. Linear regression analysis revealed that levels of serum homocysteine were only significantly correlated with diffuse (r = 0.217, p = 0.007) and clinical vessel (r = 0.078, p = 0.037) scores in low-risk patients. These correlations could not be observed in diffuse (r = 0.070, p = 0.319) and clinical vessel (r = -0.001, p = 0.970) scores in the high-risk group. In conclusion, levels of homocysteine correlated with the extent of coronary atherosclerosis only among patients with low cardiovascular risk profiles.

Coronary Angiography↗
PubMed2000

3Beta-hydroxy-6-aza-cholestane and related analogues as phosphatidylinositol specific phospholipase C (PI-PLC) inhibitors with antitumor activity.

6-Aza steroid analogues were synthesized as PI-PLC inhibitors. The most active compound, 3beta-hydroxy-6-aza-cholestane (1) showed potent PI-PLC inhibition (IC50 = 1.8 microM), similar to that of the commercially available steroid analogue U73122 (IC50 = 1-2.1 microM). Compound 1 exhibited significant growth inhibition effects (IC50 = 1.3 microM in each case) against MCF-7 and HT-29 cancer cells in in vitro cell culture. Compound 1 also inhibited the in vitro adhesion and transmigration of HT-1080 fibrosarcoma cells at 2.5 and 5.0 microM, respectively. In vivo, compound 1, at 1 mg/kg/day, reduced the volume of MCF-7 tumors in xenograft models, without weight loss in mice. Structure activity relationships of this series of compounds revealed that a hydrophobic cholesteryl side chain, 3beta-hydroxy group and a C-6 nitrogen containing a hydrogen atom at position-6 are crucial for activity. N-Maleic amidoacid derivative 11 also exhibited weak inhibition (IC50 = 16.2 microM).

Animals↗
PubMed2000

Regulation of urease gene expression by Streptococcus salivarius growing in biofilms.

The metabolism of urea by urease enzymes of oral bacteria profoundly influences oral biofilm pH homeostasis and oral microbial ecology. The purpose of this study was to gain insight into the regulation of expression of the low pH-inducible urease genes in populations of Streptococcus salivarius growing in vitro in biofilms and to explore whether urease regulation or the levels of urease expression in biofilm cells differed significantly from planktonic cells. Two strains of S. salivarius harbouring urease promoter fusions to a chloramphenicol acetyltransferase (cat) gene were used: PurelCAT, containing a fusion to the full-length, pH-sensitive promoter; or Pureldelta100CAT, a constitutively derepressed deletion derivative of the urease gene promoter. The strains were grown in a Rototorque biofilm reactor in a tryptone-yeast extract-sucrose medium with or without pH control. Both CAT and urease activities in biofilms were measured at 'quasi-steady state' and after a 25mM glucose pulse. The results showed that CAT expression in PurelCAT was repressed at relatively neutral pH values, and that expression could be induced by acidic pH after carbohydrate challenge. Biofilms of PurelCAT grown at low pH, without buffering, had about 20-fold higher CAT levels, and only a modest further induction could be elicited with carbohydrate pulsing. The levels of CAT in biofilms of PurelCAT grown in buffered medium were slightly higher than those reported for planktonic cells cultured at pH 7.0, and the levels of CAT in Purel-CAT growing at low pH or after induction were similar to those reported for fully induced planktonic cells. CAT activity in Pureldelta100CAT was constitutively high, regardless of growth conditions. Interestingly, urease activity detected in biofilms of the parent strain, S. salivarius 57.1, could be as much as 130-fold higher than that reported for fluid chemostat cultures grown under similar conditions. The higher level of urease activity in biofilms was probably caused by the accumulation of the stable urease enzyme within biofilm cells, low pH microenvironments and the growth phase of populations of cells in the biofilm. The ability of S. salivarius biofilm cells to upregulate urease expression in response to pH gradients and to accumulate greater quantities of urease enzyme when growing in biofilms may have a significant impact on oral biofilm pH homeostasis and microbial ecology in vivo. Additionally, S. salivarius carrying the pH-sensitive urease gene promoter fused to an appropriate reporter gene may be a useful biological probe for sensing biofilm pH in situ.

Artificial Gene Fusion↗