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Biomedical subjects

Y Liu

Publications and source records attributed to Y Liu.

At least 847 records · Page 47Linked to original sources
PubMed2000

Development of a noninvasive reporter system for gene expression in Porphyromonas gingivalis.

Several reports have supported the association of Porphyromonas gingivalis with periodontal disease. Genetic studies are vital for understanding the relative importance of virulence factors in this organism. Thus, gene reporters may prove useful for the study of gene expression in this organism. We have investigated the use of the green fluorescent protein (GFP), bacterial luciferase, and bifunctional xylosidase/arabinosidase enzyme (XA) as reporters of gene expression in P. gingivalis. Fusion cassettes containing the promoterless tetracycline resistant gene [tetA(A)Q2] and the promoterless gfp, luxAB, or xa gene were placed under the control of the rgpA promoter in P. gingivalis W83 using recombinational allelic exchange. The rgpA gene encodes for an arginine-specific protease in P. gingivalis. No GFP activity was detected in P. gingivalis isogenic mutants carrying the rgpA::gfp-tetA(Q)2 fusion construct. Luciferase activity in P. gingivalis mutants carrying the rgpA::luxAB-tetA(Q)2 fusion was only detected in the presence of exogenous FMNH(2). xa gene expression in P. gingivalis with the rgpA::xa-tetA(Q)2 fusion construct was detected in crude extracts using rho-nitrophenol derivatives as substrate and on agar plates with methylumbelliferyl derivatives under long-wave ultraviolet light. This indicates that both luxAB and xa genes can be used as reporters of gene expression in P. gingivalis. However, only the xa gene can be used as a noninvasive reporter gene.

Artificial Gene Fusion↗
PubMed2000

Changes of cytokines levels in peritoneal fluids of patients with endometriosis and its effect on reproductive activity.

To study the changes of cytokines in peritoneal fluids of patients with endometriosis and their effects on reproductive activity, levels of tumor necrosis factor (TNF) and interleukin 6 (IL-6) in peritoneal fluids and peritoneal macrophages' culture supernatant were studied by using enzyme linked immunoassay (ELISA) in 14 infertile patients with endometriosis (EMT group) and 11 infertile women with normal pelvis (control group). The effects of peritoneal fluids in patients with endometriosis in vitro on sperm motility and development of 2-cell mouse embryos were also studied. The results showed that the levels of TNF and IL-6 in peritoneal fluids and peritoneal macrophages' supernatant in EMT group were elevated significantly as compared with those in the control group (P < 0.01). The percent of sperm straight line movement and total sperm motility were decreased significantly in EMT group (P < 0.01). The percent of 2-cell mouse embryos developing to 16-cells was 32.5% in EMT group, while 47.6% in control group after 48 h co-culture with peritoneal fluid (P < 0.01). It is likely that the elevation of peritoneal fluid cytokines in patients with endometriosis may play a role in infertility associated with endometriosis.

Adult↗
PubMed2000

Study on gastric empty disorder after the gastric ulcer healing and therapeutic effect of cisapride.

Gastric emptying time of liquid meal was detected by using ultrasonography in 28 gastric ulcer patients with continual or recurrent dyspepsia symptoms after the ulcer healing. Sixteen out of 28 patients (57.1%) with a delay of gastric emptying time (T1/2) were randomly divided into two groups: 8 cases were treated with cisapride 5 mg three times a day and 8 cases with cisapride 10 mg three times a day respectively. The results showed that cisapride could relieve the symptoms with the effective rate being 68.8% in the two groups. T1/2 in the patients after treatment with cisapride was significantly shorter than before treatment (P < 0.001). It was concluded that there is a delay of T1/2 in some patients with gastric ulcer healing. Cisapride could promote gastric empty of liquid meal and relieve the symptoms efficiently. The effect of lower dose of cisapride is similar to that of higher dose.

Adult↗
PubMed2000

Cloning and expression of rat transforming growth factor beta 1 cDNA in osteoblasts.

Rat transforming growth factor beta 1 (rTGF beta 1) cDNA from rat lymphocytes was cloned by RT-PCR and inserted into pcDNA3 to construct an eukaryotic expression vector, which was named pcDNA3-TGF beta 1. The cloned gene was confirmed to code rat TGF beta 1 by restriction enzyme analysis. pcDNA3-TGF beta 1 plasmid was transfected into rat osteoblasts by using liposome-mediated gene transfer technique and the expression of TGF beta 1 was detected by using immunohistochemical staining assay. It was found that the rat TGF beta 1 expression product was obviously detectable in the transfected osteoblasts in 48 h. High expression of TGF beta 1 was obtained in the rat osteoblasts in which the constructed TGF beta 1 expression vector was transfected.

Animals↗
PubMed2000

Effect of absorbable hydroxyapatite/poly-DL-lactide rods on experimental fracture healing.

In order to investigate the effect of a new institute-designed absorbable hydroxyapatite microparticles/poly-DL-lactide (HA/PDLLA) fracture fixation devices on experimental fracture healing, 25 rabbits with a transverse transcondylar osteotomy of the distal femur were fixed intramedullary by a HA/PDLLA rod (4.5 mm in diameter, 30-40 mm in length). The follow-up time lasted 1, 2, 4, 6 and 12 week(s). Roentgenographic, histological and ultrastructural analyses were conducted. The results showed that all osteotomies united within 6 weeks without delay. No accumulation of inflammatory cells was seen. Ultrastructural studies showed that polymorphonuclear neutrophils and macrophages were observed mainly at the 1st week, but only few were noted at the 2nd week. The inflammatory and debridement stages were not prolonged. Large amount of active fibroblasts and some chondroblasts were observed at the 2nd week, suggesting a fibrous callus stage. The main cellularity at 4th week was osteoblasts and osteocytes. Part of osteocytes had already entered the static stage at the 6th week. Our experiment showed that the HA/PDLLA had good biocompatibility, sufficient mechanical strength and caused no delay to the fracture healing.

Animals↗
PubMed2000

The effect of hyperthermia on DNA in mouse HepA cells--an analysis with computer and observation with EM.

A computer analysis system, automated imaging cytometry (AIC), flow cytometry (FCM) and EM, were used to study the relationship of apoptosis and the change of DNA in mouse HepA cells subjected to hyperthermia. Our results showed that pyknotic rate in the 44 degrees C group was significantly increased (P < 0.01) when compared with that in the 37 degrees C group, both the diploid rate and aneuploid rate in the 44 degrees C group were significantly decreased (P < 0.01) when compared with that in the 37 degrees C group. The pyknotic rate determined by ALC was in conformity with the apoptotic index (AI) determined by FCM. Under EM, ultrastructures of HapA cells appeared typical apoptosis changes in the 44 degrees C group. We are led to conclude that (1) when the temperature is 42 degrees C or 44 degrees C for 2 h, it did not promote the necrosis of HepA cells; (2) when the temperature is 42 degrees C for 2 h, it did not obviously induce the apoptosis of HepA cells, and the 44 degrees C for 2 h obviously induced the apoptosis of HepA cells; (3) AIC method can be used as an aid for the measurement of apoptotic index. Further study is needed to established it as a novel, simple and convenient method for determining the apoptosis.

Animals↗
PubMed2000

Characterization of a Saccharomyces cerevisiae homologue of Schizosaccharomyces pombe Chk1 involved in DNA-damage-induced M-phase arrest.

Chk1 is an evolutionarily conserved protein kinase that plays an essential role in mediating G2 arrest in response to DNA damage in Schizosaccharomyces pombe and human cells. It functions by maintaining the inhibition (by phosphorylation of a specific tyrosine residue) of the cyclin-dependent kinase Cdc2 that initiates the G2/M transition. Here, we characterize a structural homologue of Chk1 in the budding yeast Saccharomyces cerevisiae. In this organism, G2/M arrest following DNA damage is considered to be independent of tyrosine phosphorylation of the Cdc2 homologue Cdc28. Nevertheless, a partial defect in G2/M-phase arrest following treatment with ionizing radiation, but not UV radiation, is associated with deletion of CHK1. The fact that such an effect remains detectable in cells synchronized with the microtubule inhibitor nocodazole prior to gamma irradiation implies the existence of a CHK1-dependent checkpoint in M phase. We conclude from epistasis analysis that Chk1 participates in the Pds1-dependent subpathway of M-phase arrest. In spite of the partial checkpoint defect of the chk1 mutant, the survival of colony-forming cells is not notably decreased following UV and gamma irradiation. In two-hybrid screens, we identified a heme-binding stress protein (encoded by the yeast ORF YNL234W), a protein involved in genomic silencing (Sas3) and Chk1 itself as interacting partners of Chk1.

Amino Acid Sequence↗
PubMed2000

Effect of retinoic acid and its complexes with transition metals on human bladder cancer cell line EJ in vitro.

The aim of this study was to investigate the effect of retinoic acid (RA) and its complexes with transition metals on the bladder cancer cell line EJ. Retinoic acid complexes with transition metals Cu, Co, Zn, and Ni were prepared. Cell proliferation was tested by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay in the presence of RA or its complexes with transition metals Cu, Co, Zn, and Ni ¿Cu(RA)2.3H2O, Co(RA)2.3H2O, Zn(RA)2.4H2O, and Ni(RA)2.3H2O¿. Colony formation in soft agar culture, A agglutination reaction, and lactic acid dehydrogenase isoenzyme assay were performed in the cells treated with these drugs to estimate the induced differentiation. p53 or c-Ha-ras expression in drug-treated cells was assayed by ABC immunocytochemistry technique. The results demonstrate that EJ cells treated with the drugs become less confluent and tend to exhibit normal characteristics. Although RA and its complexes showed inhibition to proliferation of EJ cells at the concentrations of 10(-6) mmol/l, the inhibition induced by Ni(RA)2.3H2O was much more marked than that by RA. EJ cells were growth inhibited by RA or Ni(RA)2.3H2O from 48 to 96 h at the concentration of 10(-8) mol/l. The levels of LDH4 and LDH5 in the cells were greatly increased by RA. Nevertheless, Ni(RA)2.3H2O did not affect LDH isoenzyme in EJ cells. The number of colony formations of EJ cells in soft agar culture was decreased by RA or Ni(RA)2.3H2O. The percentage of colony formation in soft agar culture was much lower in EJ cells treated with Ni(RA)2.3H2O than with RA. The required concentration of A agglutination reaction was more increased for EJ cells treated with RA or Ni(RA)2.3H2O than for the control and was further increased in cells treated with Ni(RA)2.3H2O. Mutant p53 expression was more decreased in the EJ cells treated with RA or Ni(RA)2.3H2O than in the control. Although RA at the concentration of 10(-6) mmol/l caused lower p21 expression, Ni(RA)2.3H2O did not affect p21 expression in EJ cells. Therefore, RA and its transition metal complexes have a potential use in the treatment of bladder cancer.

Agar↗
PubMed2000

Reduced Growth Yield of Activated Sludge in Organic Protonophore-Containing Batch Culture.

The effects of organic protonophores 2,4-dinitrophenol (dNP) and para-nitrophenol (pNP) on the observed growth yield (Y(obs)) was studied using batch cultures of activated sludge microorganisms. A growth yield model was proposed in relation to the ratio of initial protonophore concentration (C(u)) to initial biomass concentration (X(0)) and was verified with experimental data. It was found that Y(obs) decreased with the increase of the C(u)/X(0) ratio, while the specific rate of glucose consumption was increased. Results showed that the C(u)/X(0) ratio could more reasonably reflect the real strength of organic protonophore exerted to activated sludge than using C(u) only. Based on the concept of growth yield, a model describing the uncoupling degree between energy generated via electron transport system and energy used for growth was further developed for protonophore-containing batch culture. It was shown that more than 60% of glucose was consumed through a futile cycle of energy rather than for growth at higher C(u)/X(0) ratios. This research usefully shows that the dissipation of energy via uncoupling biochemical processes can reduce excessive production of activated sludge markedly.

Journal Article↗
PubMed2000

Fruiting body production in Basidiomycetes.

Mushroom cultivation presents an economically important biotechnological industry that has markedly expanded all over the world in the past few decades. Mushrooms serve as delicacies for human consumption and as nutriceuticals, as "food that also cures". Mushrooms, the fruiting bodies of basidiomycetous fungi, contain substances of various kinds that are highly valued as medicines, flavourings and perfumes. Nevertheless, the biological potential of mushrooms is probably far from exploited. A major problem up to now is that only a few species can be induced to fruit in culture. Our current knowledge on the biological processes of fruiting body initiation and development is limited and arises mostly from studies of selected model organisms that are accessible to molecular genetics. A better understanding of the developmental processes underlying fruiting in these model organisms is expected to help mushroom cultivation of other basidiomycetes in the future.

Agaricales↗
PubMed2000

SM5-1: a new monoclonal antibody which is highly sensitive and specific for melanocytic lesions.

Antibodies such as HMB-45 and anti-S100 protein have been widely used as markers of malignant melanoma despite evidence that HMB-45 has a sensitivity of only 67-93% and S100 is nonspecific for melanoma. Using a subtractive immunization protocol in a mouse model of human melanoma, we have generated several monoclonal antibodies with putative specificity for melanoma. After initial screenings, the antibody SM5-1 was chosen because of its intriguing reactivity with melanocytic tumors in both frozen and paraffin sections. The immunohistochemical staining of SM5-1 was studied in paraffin-embedded specimens of 401 melanomas (n = 401; 250 primary melanomas, 151 metastases), melanocytic nevi of the skin (n = 16), nonmelanocytic neoplasms (n = 84). The results were compared with HMB-45 and anti-S100 staining. All antibodies reacted with nevi and 97-99% with primary melanomas. Whereas both SM5-1 and anti-S100 stained 96% (146/151) of melanoma metastases, HMB-45 correctly identified only 83% (126/151). All HMB-45-negative metastases were positive for SM5-1. Whereas neither SM5-1 nor HMB-45 stained any of 84 specimens from 40 different nonmelanocytic neoplasms, anti-S100 was positive in 21/84 (25%). While the staining pattern of SM5-1 was mostly homogeneous, small tumor areas in some metastases remained unstained. Staining with SM5-1 was also observed in perivascular dendritic cells, in plasma cells, some myofibroblasts and the secretion of eccrine sweat glands. Nonactivated epidermal melanocytes, keratinocytes, endothelial cells, smooth muscle cells and peripheral nerves were all negative for SM5-1. These results suggest that SM5-1 is highly specific, as well as sensitive, for melanocytic lesions and is useful in the immunohistochemical evaluation of melanoma.

Animals↗
PubMed2000

Up-regulation of AT(1) and AT(2) receptors in postinfarcted hypertrophied myocytes and stretch-mediated apoptotic cell death.

To determine whether up-regulation of AT(1) and AT(2) receptors occurred in hypertrophied myocytes after infarction and whether AT(2) played a role in stretch-mediated apoptosis, left ventricular myocytes were dissociated from the surviving portion of the wall 8 days after coronary occlusion and cardiac failure in rats. Control cells were obtained from sham-operated animals. Myocytes were stretched in an equibiaxial stretch apparatus and angiotensin II (Ang II) formation and cell death were measured 3 and 12 hours later. AT(1) and AT(2) proteins were evaluated in freshly isolated myocytes and after stretch. The effects of AT(1) and AT(2) antagonists on stretch-induced Ang II synthesis and apoptosis were also established. Myocardial infarction increased AT(1) and AT(2) in myocytes and stretch further up-regulated these receptors. Ang II levels were higher in postinfarcted myocytes and this peptide increased with the duration of stretch in both groups of cells. Similarly, apoptosis increased with time in control and postinfarcted myocytes. Absolute values of Ang II and apoptosis were greater in myocytes from infarcted hearts at 3 and 12 hours after stretch. Addition of AT(1) blocker to cultures inhibited stretch-activated apoptosis in both myocyte populations as well as the generation of Ang II in postinfarcted myocytes. In contrast, AT(2) antagonists had no impact on these cellular events. In conclusion, Ang II stimulated cell death through AT(1) receptor activation, whereas ligand binding to AT(2) receptor did not alter Ang II concentration and apoptosis in normal and postinfarcted hypertrophied myocytes.

Angiotensin II↗
PubMed2000

Pulmonary artery perfusion with protective solution reduces lung injury after cardiopulmonary bypass.

BACKGROUND: The inflammatory response and higher temperature of lung tissue during cardiopulmonary bypass can result in lung injury. This study was to evaluate the protective effect of pulmonary perfusion with hypothermic antiinflammatory solution on lung function after cardiopulmonary bypass. METHODS: Twelve adult mongrel dogs were randomly divided into two groups. The procedure was carried out through a midline sternotomy, cardiopulmonary bypass was established using cannulas placed in the ascending aorta, superior vena cava, and right atrium near the entrance of the inferior vena cava. After the ascending aorta was clamped and cardioplegic solution infused, the right lung was perfused through a cannula placed in the right pulmonary artery with 4 degrees C lactated Ringer's solution in the control group (n = 6) and with 4 degrees C protective solution in the antiinflammation group (n = 6). Antiinflammatory solution consisted of anisodamine, L-arginine, aprotinin, glucose-insulin-potassium, and phosphate buffer. Plasma malondialdehyde, white blood cell counts, and lung function were measured at different time point before and after cardiopulmonary bypass; lung biopsies were also taken. RESULTS: Peak airway pressure increased dramatically in the control group after cardiopulmonary bypass when compared with the antiinflammation group at four different time points (24 +/- 1, 25 +/- 2, 26 +/- 2, 27 +/- 2 cm H2O versus 17 +/- 2, 18 +/- 1, 17 +/- 1, 18 +/- 1 cm H2O; all p < 0.01). Pulmonary vascular resistance increased significantly in the control group than in the antiinflammation group at 5 and 60 minutes after cardiopulmonary bypass (1,282 +/- 62 dynes x s x cm(-5) versus 845 +/- 86 dynes x s x cm(-5) and 1,269 +/- 124 dynes x s x cm(-5) versus 852 +/- 149 dynes x s x cm(-5), p < 0.05). Right pulmonary venous oxygen tension (PvO2) in the antiinflammation group was higher than in the control group at 60 minutes after cardiopulmonary bypass (628 +/- 33.3 mm Hg versus 393 +/- 85.9 mm Hg, p < 0.05). The ratio of white blood cells in the right atrial and the right pulmonary venous blood was lower in the antiinflammation group than in the control group at 5 minutes after the clamp was removed (p < 0.05). Malondialdehyde were lower in the antiinflammation group at 5 and 90 minutes after the clamp was removed (p < 0.01 and p < 0.05, respectively). Histologic examination revealed that the left lung from both groups had marked intraalveolar edema and abundant intraalveolar neutrophils, whereas the right lung in the control group showed moderate injury and the antiinflammation group had normal pulmonary parenchyma. CONCLUSIONS: Pulmonary artery perfusion using hypothermic protective solution can reduce lung injury after cardiopulmonary bypass.

Animals↗
PubMed2000

Computer-aided ergonomics: a case study of incorporating ergonomics analyses into workplace design.

One of the primary goals of computer-aided ergonomics is to develop software tools that allow ergonomics information to be accessed at the earliest stages of design. This case study discusses a PC-based software program that allows a designer to quantify a worker's biomechanical risk for injury based on a proposed workplace design. The program couples an established software tool for biomechanical analysis, the Three-Dimensional Static Strength Prediction Program (3DSSPP), with a widely used computer-aided design software package, AutoCAD. The use of this "3DSSPP/AutoCAD interface" in the proactive analysis of an automotive assembly task is described and the results compared with an independent assessment using observations of workers performing the same task. Both studies yield similar conclusions, suggesting that proactive use of software such as the 3DSSPP/AutoCAD interface may be a valid tool in evaluating proposed workplace designs. In this context, issues in the analysis of workplace designs regarding the use of supporting ergonomic tools, assumptions, and posture selection are discussed.

Accidents, Occupational↗
PubMed2000

Alteration of tropomyosin function and folding by a nemaline myopathy-causing mutation.

Mutations in the human TPM3 gene encoding gamma-tropomyosin (alpha-tropomyosin-slow) expressed in slow skeletal muscle fibers cause nemaline myopathy. Nemaline myopathy is a rare, clinically heterogeneous congenital skeletal muscle disease with associated muscle weakness, characterized by the presence of nemaline rods in muscle fibers. In one missense mutation the codon corresponding to Met-8, a highly conserved residue, is changed to Arg. Here, a rat fast alpha-tropomyosin cDNA with the Met8Arg mutation was expressed in Escherichia coli to investigate the effect of the mutation on in vitro function. The Met8Arg mutation reduces tropomyosin affinity for regulated actin 30- to 100-fold. Ca(2+)-sensitive regulatory function is retained, although activation of the actomyosin S1 ATPase in the presence of Ca(2+) is reduced. The poor activation may reflect weakened actin affinity or reduced effectiveness in switching the thin filament to the open, force-producing state. The presence of the Met8Arg mutation severely, but locally, destabilizes the tropomyosin coiled coil in a model peptide, and would be expected to impair end-to-end association between TMs on the thin filament. In muscle, the mutation may alter thin filament assembly consequent to lower actin affinity and altered binding of the N-terminus to tropomodulin at the pointed end of the filament. The mutation may also reduce force generation during activation.

Actins↗
PubMed2000

Job strain, Type A behavior pattern, and the prevalence of coronary atherosclerosis in Japanese working men.

OBJECTIVE: To examine the relation of type A behavior pattern and job strain to angiographically documented coronary stenosis. METHODS: Subjects were 197 male Japanese patients with a full-time job. A questionnaire-based interview elicited psychosocial and other factors. Type A behavior pattern was measured by 12 questions, and job strain by the method of Karasek. Significant coronary stenosis was defined when a 75% or greater luminal narrowing occurred at one or more major coronary arteries or when a 50% or greater narrowing occurred at the left main artery. Logistic regression analysis was used to calculate odds ratio (OR) and 95% confidence interval (CI) with adjustment for traditional coronary risk factors and job type. RESULTS: Type A behavior pattern was related to a statistically non-significant lower prevalence of the coronary stenosis especially in the absence of job strain (adjusted OR 0.6, 95% CI 0.3-1.2). Job strain was non-significantly associated with a modestly increased prevalence of coronary stenosis (OR 1.7, 95% CI 0.6-5.2). CONCLUSION: These findings suggest that both the behavioral pattern and psychosocial work environment may be related to coronary artery stenosis.

Adult↗
PubMed2000

Biochemical responses of the mycorrhizae in Pinus massoniana to combined effects of Al, Ca and low pH.

Biochemical responses of Pinus massoniana, with and without the inoculation mycorrhizal fungus Pisolithus tinctorius at the root, to artificial acid rain (pH 2.0) and various Ca/Al ratios were investigated. Some enzymes associated with the nutritive metabolism, such as acid phosphatase, alkaline phosphatase, nitrate reductase, mannitol dehydrogenase and trehalase, in the roots, stems and leaves of plant were obviously inhibited by the artificial acid rain and Al. After treatment with pH 2.0 + Ca/Al (0/1 or 1/10) artificial acid rain, the protein content in the organs was decreased. However, the activities of superoxide dismutase (SOD) and peroxidase (POD) and glutathione (GSH) concentrations were induced. It demonstrated that acid rain and Al could induce oxygen radicals in plant. Compared with the treatments with lower pH or Al, respectively, the combination of lower pH and Al concentration was more toxic to P. massoniana. Al toxicity could be ameliorated by the addition of Ca and the amelioration was the most when the ratio was 1/1 among the various Ca/Al ratio. Infection with mycorrhizal fungus P. tinctorius at the root of P. massoniana increased the ability of the plant to resist the toxicity of artificial acid rain and Al stress.

Acid Phosphatase↗