Biomedical subjects

D Luo

Publications and source records attributed to D Luo.

At least 37 records · Page 2Linked to original sources

PubMed2000

Characterization and transcriptional profiles of two rice MADS-box genes.

The plant MADS-box gene family plays a key role in plant development, especially in flower development. We designed degenerate primer according to the MADS-box conserved region and isolated two cDNA from rice, FDRMADS6 and FDRMADS7, which are homologous to AP1. RT-PCR expression analyses by using total RNA isolated from root, shoot and flower showed that the FDRMADS6 transcript was detectable only in flower while FDRMADS7 was expressed in all three tissues. In situ hybridization experiments indicated that at the early stage of rice flower development, the transcripts of FDRMADS6 and FDRMADS7 were detected in the spikelet apical meristem, which were same as AP1. At the late stage, when flower organ primordia started differentiating, the expression of FDRMADS6 appeared to be specifically localized in developing stamens and the pistil primordia, while the transcripts of FDRMADS7 were detectable abundantly throughout the organ primordia. Our results suggest the two MADS-box genes may be members of the AP1 family, but may have different functions.

Journal Article↗

PubMed2000

In vitro expression of hepatitis C virus non-structure 5 antigen in the HepG2 cell line.

To establish a cell line as a model system for HCV infection and propagation in vitro, a human HepG2 cell line was incubated with a HCV RNA positive serum. The sABC immunological techniques and gold-labeled colloid electron microscopy method were employed to examine the viral proteins in those cells. The HCV non-structure 5 antigen was first detected in the HepG2 cells 72 h after incubation. The antigen was continuously observed in the cytoplasm as well on the membrane of the HepG2 cells even after 1, 2, 3 and 4 weeks after incubation. The observation of HCV non-structure 5 antigen continuously expressed in the HepG2 cells strongly indicates that the cells may have been infected by HCV virus. Therefore, the HepG2 cell line may serve as a potential host for establishment of HCV infection and propagation in vitro.

Animals↗

PubMed2000

Study on biologic activity for membrane of normal bone marrow cells with infection of epidemic hemorrhagic fever virus.

Using DPH fluorescence probe, the membrane of normal bone marrow cells with infection of epidemic hemorrhagic fever virus (EHFV) was labeled. The membrane lipid fluidity was obviously decreased from the membrane lipid fluorescence polarization. The membrane lipid fluidity of lymphocyte, monocyte and neutrophilic granulocyte was dynamically observed. After culturing the cells for 1, 6, 24 and 72 h, it was found that all the membrane lipid fluidity of the infected cells was decreased obviously with the longer the culturing time, the more obvious it. Compared with the normal control groups, there was a significant difference statistically (P < 0.05-0.01). It was suggested that the decrease of the membrane lipid fludity of normal bone marrow cell with infection of EHFV had correlation with the degree of virus invading and cell-function injury.

Bone Marrow Cells↗

PubMed2000

Effects of three different Ca(2+) pump ATPase inhibitors on evoked contractions in rabbit aorta and activities of Ca(2+) pump ATPases in porcine aorta.

Using vascular smooth muscle, we describe the actions of three pharmacological tools, cyclopiazonic acid (CPA), thapsigargin (TG) and 2,5-di-(tert-butyl)-1,4-benzohydroquinone (tBHQ), which are presumed to act as selective inhibitors of the sarco-endoplasmic reticulum Ca(2+)-ATPases (SERCAs). In porcine aortic smooth muscle microsomes two Ca(2+)-ATPase activities have been described, one vanadate-sensitive and one vanadate-resistant, representing the Ca(2+)-ATPase activities of the plasma membrane and SERCAs, respectively. In agreement, CPA, TG and tBHQ, in the concentration range 0.1 microM to 0.1 mM, dose-dependently inhibit the Ca(2+)-ATPase activity only in the vanadate-resistant microsomes. However, 0.1 mM tBHQ also significantly inhibited the Ca(2+)-ATPase activity of vanadate-sensitive microsomes. In rabbit aortic rings, all three SERCA inhibitors produced a dose-dependant inhibition of contractions evoked by 20 mM caffeine or 1 microM phenylephrine (PE) in a Ca(2+)-free physiological solution. However, in PE-contracted rings, tBHQ (> or =30 microM) also significantly inhibited the ability of cromakalim to induce relaxation. In conclusion, the data suggest that CPA, TG and tBHQ can all act as selective SERCA inhibitors in both porcine and rabbit aortic smooth muscle. However, in contrast to CPA and TG, high concentrations of tBHQ can exhibit some nonspecific effects, which include inhibition of the plasma membrane Ca(2+)-ATPase and possibly K(+) channels regulated by cromakalim.

Animals↗

PubMed2000

Synthetic DNA delivery systems.

The ability to safely and efficiently transfer foreign DNA into cells is a fundamental goal in biotechnology. Toward this end, rapid advances have recently been made in our understanding of mechanisms for DNA stability and transport within cells. Current synthetic DNA delivery systems are versatile and safe, but substantially less efficient than viruses. Indeed, most current systems address only one of the obstacles to DNA delivery by enhancing DNA uptake. In fact, the effectiveness of gene expression is also dependent on several additional factors, including the release of intracellular DNA, stability of DNA in the cytoplasm, unpackaging of the DNA-vector complex, and the targeting of DNA to the nucleus. Delivery systems of the future must fully accommodate all these processes to effectively shepherd DNA across the plasma membrane, through the hostile intracellular environment, and into the nucleus.

Animals↗

PubMed2000

Enhancement of transfection by physical concentration of DNA at the cell surface.

Efficient DNA transfection is critical for biological research and new clinical therapies, but the mechanisms responsible for DNA uptake are unknown. Current nonviral transfection methods, empirically designed to maximize DNA complexation and/or membrane fusion, are amenable to enhancement by a variety of chemicals. These chemicals include particulates, lipids, and polymer complexes that optimize DNA complexation/condensation, membrane fusion, endosomal release, or nuclear targeting, which are the presumed barriers to gene delivery. Most chemical enhancements produce a moderate increase in gene delivery and a limited increase in gene expression. As a result, the efficiency of transfection and level of gene expression after nonviral DNA delivery remain low, suggesting the existence of additional unidentified barriers. Here, we tested the hypothesis that DNA transfection efficiency is limited by a simple physical barrier: low DNA concentration at the cell surface. We used dense silica nanoparticles to concentrate DNA-vector (i.e. DNA-transfection reagent) complexes at the surface of cell monolayers; manipulations that increased complex concentration at the cell surface enhanced transfection efficiency by up to 8.5-fold over the best commercially available transfection reagents. We predict that manipulations aimed at optimizing DNA complexation or membrane fusion have a fundamental physical limit; new methods designed to increase transfection efficiency must increase DNA concentration at the target cell surface without adding to the toxicity.

Animals↗

PubMed2000

Molecular mimicry of human tumor antigen by heavy chain CDR3 sequence of the anti-idiotypic antibody.

We isolated and characterized an anti-idiotype monoclonal antibody (AR42.1) which is capable of mimicking a distinct and specific epitope of MUC-1 antigen. The cDNA sequences coding for the AR42.1 variable regions were determined. We found significant amino acid homology between complementary determining regions 3 (CDR3) in the heavy chain of AR42.1 and the determinant epitope sequence of MUC-1. This 10 amino acid sequence may represent an "internal image" of the anti-idiotype antibody to the MUC-1 antigen, and could be used for development of a MUC-1 surrogate for immunotherapy.

Animals↗

PubMed2000

Effects of Bcl-2 and Bcl-XL protein levels on chemoresistance of hepatoblastoma HepG2 cell line.

The ratio between apoptotic promoters and repressors in the Bcl-2 family determines the chemosensitivity of cells to apoptotic stimuli. This study examines the chemoresistance of a transfected human hepatoblastoma HepG2 cell-line during Taxol and Doxorubicin application. Sense bcl-2, and anti-sense bcl-XL gene fragments were separately inserted into HepG2 cells via stable transfection. The expression profile of the Bcl-2 family proteins was determined by Western blot analysis. Chemosensitivity of the transfected cells was measured by Trypan blue exclusion assay and XTT reduction assay during drug application. In the absence of Bax protein, HepG2 cells with elevated Bcl-2 protein levels did not exhibit any significant increase in chemosensitivity towards the drugs. Transfected cells with reduced Bcl-XL levels became more sensitive to the drugs, and a significant difference in IC50 values was observed. The chemosensitivity of HepG2 cells to Taxol and Doxorubicin was not affected by Bcl-2 levels, while reduction of Bcl-XL levels rendered the cells more sensitive to the drugs. This suggests that the Bcl-2 protein alone could not protect HepG2 cells from drug-induced apoptosis, and that the Bcl-XL protein may be a target for gene therapy in hepatoblastoma treatment.

Antineoplastic Agents↗

PubMed2000

Measuring continuity of elders' posthospital care.

Continuity of care is a critical component of quality patient care, yet the paucity of reliable and valid measures of continuity of care make it difficult to ascertain the extent to which continuity has been achieved. The purpose of this article is to describe the development of an instrument to measure continuity of care that incorporates the perspectives of elders hospitalized for a chronic illness and their family caregivers. The instrument was used, and its reliability and validity examined, in a series of studies related to elders' posthospital transition. Elders in the studies ranged in age from 55 to 94 years. The findings supported content and construct validity, internal consistency reliability, and ability to detect changes in the same subjects at different points in time for the care management and services subscales. With further refinement, the continuity of provider and conflicting information subscales might also facilitate assessment of care continuity.

Aftercare↗

PubMed2000

[Mutations of Q20L and G247D improved the specific-activity and optimum pH of glucose isomerase].

The mutants of Q20L and G247D of glucose isomerase (GI) were constructed by in vitro site-directed mutagenesis of GI gene with double-primersmethod. The recombinant plasmids pTKD-GIQ20L and pTKD-GIG247D were expressed in E. coli K38 strain. The comparison experiments of mutant enzymes with wild-type GI showed that: (1) the optimum temperature of GIQ20L was decreased by 5 degrees C. Its thermostability was only 78% half-time of the wild type. But its substrate affinity was enhanced. (2) The specific-activity of GIG247D was increased by 33%, and the optimum pH was lowered by 0.6 unit. However, the thermostability of GIG247D was decreased. We supposed, based on the above facts and 0.19 nm resolution crystal structure of SM33GI, that Gln20 locates between alpha 0-helix and alpha 1-helix, the substitution of hydrophobic side chain of Leu for hydrophilic side chain of Gln may enhance the hydrophobic interaction of the molecular surface, leading to the decrease of the stability and thermostability of GIQ20L. Gly247 which is the last amino acid of a beta-sheet from 242 to 247 residues locates in the active core of GI. After replacement, Asp247 which has strong negative electricity may change the electrostatic distribution and influence the charge transfer processes of the active core. So the specific-activity of GIG247D was increased. The introduced charge could alter the pKa of dissociable groups and make the optimum pH lower. In addition, the side chain of Asp247 seems to be very crowded in the surrounding space conformation and is easy to exclude with the other side chains, therefore influences the stability of beta-sheet. Furthermore, Asp247 is in the vicinity of the interface of subunits, so it could interfere with the stability of the interaction between subunits. Thus, the GIG247D decreased the thermostability of SM33GI. The higher enzyme activity and the lower optimum pH will be very useful for industrial production of GI.

Aldose-Ketose Isomerases↗

PubMed2000

Anti-hepatoma activity of taxol in vitro.

AIM: To investigate the in vitro anti-hepatoma activity of taxol against SMMC-7721 human hepatoma cells. METHODS: The hepatoma cell growth was measured by MTT-microculture tetrazolium assay. Cell-cycle kinetics and apoptosis were analyzed by flow cytometry and microscopic examination. RESULTS: Taxol inhibited the hepatoma cell growth in concentration- and time-dependent manners with IC50 of 18.96 nmol.L-1. Marked cell accumulation in G2/M phase and multinucleated cells were also observed after treatment with taxol 10 nmol.L-1. In addition, taxol at 10 nmol.L-1 could induce the apoptosis of hepatoma cells. CONCLUSION: Taxol suppresses the growth of SMMC-7721 human hepatoma cells in vitro by causing cell-cycle arrest, aberrant mitosis, and apoptosis of the human hepatoma cells.

Antineoplastic Agents, Phytogenic↗

PubMed2000

Caries inhibition efficacy of an antiplaque/antigingivitis dentifrice.

PURPOSE: To evaluate the efficacy of a fluoride dentifrice containing a fixed combination of essential oils (Thymol, Menthol, Eucalyptol, and Methyl Salicylate) in preventing caries in Sprague Dawley rats. MATERIALS AND METHODS: The dentifrice contains 0.76% sodium monofluorophosphate (SMFP) as the fluoride source and a silica abrasive system. A fluoride-free placebo and a clinically proven USP dentifrice reference standard for SMFP/silica were included as controls. Three groups of 45 SDV-free Sprague Dawley weanlings were infected by a cariogenic strain of Streptococcus sobrinus and fed cariogenic diet NIH 2000 ad libitum. Animals were treated twice daily (once on weekends) with the assigned dentifrice using a cotton-tipped applicator, for 5 wks, after which they were terminated and caries scored using Larson's modification of the Keyes method. RESULTS: Analyses of variance were used to compare inter-group means, the total E lesion score was the primary efficacy variable. Compared with the fluoride-free vehicle control, the experimental dentifrice and USP reference standard dentifrice produced a statistically significant reductions of 18.3% and 12.2% respectively for total caries score (P<0.001). Compared with the clinically tested USP positive control dentifrice, the experimental dentifrice produced a statistically significant reduction in the total caries score of 6.9% (P=0.028). The results of this study show that 1) both the new dentifrice containing essential oils and USP dentifrice are statistically significantly effective in reducing caries in the rat model, 2) the anticaries activity of the SMFP dentifrice is not adversely affected with the addition of essential oils.

Analysis of Variance↗

PubMed2000

Stain removal efficacy of two new fluoride dentifrices containing essential oils.

PURPOSE: To assess in vitro the stain removal efficacy of two new antiplaque/antigingivitis dentifrices utilizing a modification of a previously validated Stookey method. MATERIALS AND METHODS: The modifications to the original Stookey method are the following: (1) study design; three 5 x 5 Latin Squares were employed to minimize bias stemming from position or test run in the study. (2) statistical success criteria; a test formulation was judged to be effective if the lower one-sided 95% confidence limit was "equal to or higher than" 50 since a minimum PCR (pellicle cleaning ratio) score of 50 is needed for a dentifrice to show clinical efficacy. The two test dentifrice formulations contained a fluoride source, a silica abrasive system, and four essential oils. The ADA reference abrasive material (calcium pyrophosphate) and placebo toothpaste were included as positive and negative controls, respectively. RESULTS: Compared to the negative control, the positive control exhibited a statistically higher PCR score; therefore, the validity of this modified Stookey method was confirmed. Additionally, the lower limits of the one-sided 95% confidence interval for the two dentifrice formulations were above the threshold PCR of 50; therefore, this modified Stookey method should predict that both essential oil-containing dentifrices possess acceptable stain removal power.

Analysis of Variance↗

PubMed2000

Molecular epidemiologic study of Mycoplasma genitalium infection in high risk populations of sexually transmitted diseases in China.

OBJECTIVE: To detect Mycoplasma genitalium (Mg) infection in high risk populations of sexually transmitted diseases (STDs) from several cities in China and to clarify the possible role of Mg in the pathogenesis of non-gonococcal urethritis. METHODS: Polymerase chain reaction (PCR) based on 2 pairs of primers, one for Mg-Pa (adhesion protein) and the other for 16S-rRNA (Mycoplasma genera) was used to detect Mg infection. Urogenital specimens of different high risk populations and urethritis patients, were collected from the Guangdong, Kunming, Shanghai, Nanjing, and Changzhou areas. RESULTS: The positive detection rate of Mg-DNA in high risk populations of STDs was significantly higher than that of the control group (chi 2 = 7.82, P < 0.01). The positive detection rates in Guangdong STD clinics and promiscuous persons from Kunming were higher than those from the Shanghai, Nanjing, and Changzhou areas (chi 2 = 8.54, P < 0.01 and chi 2 = 5.89, P < 0.05). Mg DNA could be detected in those patients without other relevant pathogens. Some patients were simultaneously infected with Mg and other microbes, such as Chlamydia trachomatis and/or Ureaplasma urelyticum. The positive Mg-DNA detection rate in patients with urethritis symptoms was higher than in patients without the symptoms (chi 2 = 11.68, P < 0.01). CONCLUSION: Mg infection exists in high risk populations of STDs in China, and the Mg infection rate is different among different high risk groups.

Adolescent↗

PubMed1999

Transcriptional induction of stromelysin-3 in mesodermal cells is mediated by an upstream CCAAT/enhancer-binding protein element associated with a DNase I-hypersensitive site.

Stromelysin-3 (ST3) is a matrix metalloproteinase whose synthesis is markedly increased in stromal fibroblasts of most invasive human carcinomas. In the present study, we have investigated the molecular mechanisms by which high levels of ST3 expression can be induced. In contrast to the early and transient induction of interstitial collagenase by 12-O-tetradecanoylphorbol-13-acetate (TPA), the fibroblastic induction of ST3 was found to be delayed and to require protein neosynthesis. We demonstrated that this induction is transcriptional and does not result from changes in RNA stability. By looking next to promoter regions accessible to DNase I upon gene induction, we have identified two distal elements and have characterized their role in the transcriptional regulation of ST3. The first one is a TPA-responsive element that controls the base-line ST3 promoter activity but is not required for its activation. We demonstrate that ST3 gene induction is actually mediated by the second element, a C/EBP-binding site, by showing: (i) that this element becomes accessible in cells induced to express ST3, (ii) that endogenous C/EBPbeta binds to the ST3 promoter, and (iii) that this binding leads to ST3 transcriptional activation. Our study provides new insights into the regulation of ST3 and suggests an additional role for C/EBP transcription factors in tissue remodeling processes associated with this MMP.

CCAAT-Enhancer-Binding Proteins↗

PubMed1999

Control of organ asymmetry in flowers of Antirrhinum.

Organ asymmetry is thought to have evolved many times independently in plants. In Antirrhinum, asymmetry of the flower and its component organs requires cyc and dich gene activity. We show that, like cyc, the dich gene encodes a product belonging to the TCP family of DNA-binding proteins that is first expressed in the dorsal domain of early floral meristems. However, whereas cyc continues to be expressed throughout dorsal regions, expression of dich eventually becomes restricted to the most dorsal half of each dorsal petal. This correlates with the effects of dich mutations and ectopic cyc expression on petal shape, providing an indication that plant organ asymmetry can reflect subdomains of gene activity. Taken together, the results indicate that plant organ asymmetry can arise through a series of steps during which early asymmetry in the developing meristem is progressively built upon.

Amino Acid Sequence↗

PubMed1999

Muscarinic receptor-mediated calcium signaling in spiral ganglion neurons of the mammalian cochlea.

Using indo-1 microspectrofluorometry, we examined the effects of cholinergic agonists on the concentration of intracellular Ca(2+) ions ([Ca(2+)](i)) in spiral ganglion neurons, isolated from rat cochleae at different stages of post-natal development (from P3 to P30). Extracellular application of acetylcholine (ACh) or carbamylcholine generated a rapid and transient increase in [Ca(2+)](i). The ACh concentration-response curve indicated an apparent dissociation constant (K(d)) of 8 microM and a Hill coefficient of 1.0. Removing extracellular free Ca(2+) did not suppress the ACh-induced Ca(2+) responses suggesting an intracellular Ca(2+)-release mechanism. When we compared the cholinergic response at different stages of postnatal development, there were no significant differences on the aspect of the Ca(2+) response and the percentage of responsive neurons, which ranged between 50 and 65% per cochlear preparation. The application of muscarine triggered reversible Ca(2+) responses similar to those observed with ACh, with an apparent K(d) of 10 microM and a Hill coefficient of 1.0. The cholinergic-induced Ca(2+)pirenzepine. Nicotine (10 to 100 microM) did not evoke Ca(2+) responses and the nicotinic antagonist curare (10 microM) did not block the ACh-evoked responses. The present study is the first direct demonstration of functional muscarinic receptors (mAChRs) in spiral ganglion neurons. These mAChRs activated by the cholinergic lateral efferent system may participate in the regulation of the electrical activity of the afferent auditory fibers contacting the inner hair cells.

Acetylcholine↗

PubMed1999

Smoking hygiene: a study of attitudes to passive smoking.

AIM: To study the attitudes and knowledge of adults in the Wellington area about the effects of passive smoking and measures to reduce exposure to smoke. METHODS: A sample of 200 people, randomly selected in the Wellington area, answered a telephone survey on passive smoking. RESULTS: Of the 200 respondents, 160 (80%) were males, 40 (20%) were females and approximately one-third (30%) were smokers. Most people (85.5%) thought public and private areas should be smoke-free when there were children around, but only half (53.5%) thought that smoking should be banned in cars when there are passengers. Most people (92.5%) correctly defined passive smoking. Half were aware that passive smoking negatively contributed to all the following diseases (asthma, cancer, heart disease, respiratory problems) and cot death but a higher percentage identified cancer (75.5%) and cot deaths (68.5%) specifically. Most smokers reported that they smoke at home or in their cars rather than in public places. Half the smokers (50.9%) did not smoke in front of children; a further 17.3% reported that they smoked less. CONCLUSIONS: In this sample there was a relatively low level of awareness of the effects of passive smoking on health and a high prevalence of smoking in the presence of children. Smokers and non-smokers were almost equally divided on whether there should be a law restricting smoking in private cars, although the majority agreed that cars carrying children should be smoke-free. Public health efforts to reduce the harm from passive smoking should be focused on discouraging smoking, in settings in which children are exposed, including private cars when children are passengers.

Attitude to Health↗