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Biomedical subjects

A Meng

Publications and source records attributed to A Meng.

At least 19 recordsLinked to original sources
PubMed2003

Cell death in irradiated prostate epithelial cells: role of apoptotic and clonogenic cell kill.

Dose-escalated conformal radiotherapy is increasingly being used to radically treat prostate cancer with encouraging results and minimal long-term toxicity, yet little is known regarding the response of normal or malignant prostate cells to ionizing radiation (IR). To clarify the basis for cell killing during prostate cancer radiotherapy, we determined the IR-induced expression of several apoptotic- (bax, bcl-2, survivin and PARP) and G1-cell cycle checkpoint- (p53 and p21(WAF1/Cip1)) related proteins, in both normal (PrEC-epithelial and PrSC-stromal) and malignant (LNCaP, DU-145 and PC-3; all epithelial) prostate cells. For these experiments, we chose doses ranging from 2 to 10 Gy, to be representative of the 1.8-2 Gy daily clinical fractions given during curative radiotherapy and the 8-10 Gy single doses given in palliative radiotherapy. We observed that IR-induced bax and p21(WAF1/Cip1) protein expression were attenuated selectively in normal stromal and epithelial cell cultures, yet maintained their p53-dependency in malignant cell lines. For each cell culture, we also determined total apoptotic and overall radiation cell kill using a short-term nuclear morphologic assay and a long-term clonogenic survival assay, respectively. Clonogenic survival, as measured by the surviving fraction at 2 Gy (SF2), ranged from 0.05 (PrEC) to 0.55 (DU-145), suggesting that malignant prostate cells are more radioresistant than normal prostate cells, for this series. IR-induced apoptotic cell kill was minimal (less than 6% cell after a dose of 10 Gy at times of 24-96 h) and was not dose-dependent. Furthermore, apoptotic kill was not correlated with either molecular apoptotic response or clonogenic cell kill. Using a flow cytometric proliferation assay with the PrSC (stromal) and DU-145 (epithelial) representative cultures, we observed that a senescent-like phenotype (SLP) emerges within a sub-population of cells post-irradiation that is non-clonogenic. Terminal growth arrest was dose-responsive at 96 h following irradiation and associated with long-term expression of both p21(WAF1/Cip1) and p16(INK4a) genes. Future strategies for prostate radiotherapy prediction or novel treatments should additionally focus on terminal growth arrest as an important endpoint in prostate cancer therapy.

Apoptosis↗
PubMed2001

The nuclear localization signal of zebrafish terra is located within the DM domain.

Zebrafish Terra is a member of the DM domain-containing transcription factor family and is involved in somitogenesis. The other known members of this family play a role in sex differentiation across species from Caenorhabditis elegans to human. Using the green fluorescence protein-Terra fusion constructs, we have identified the nuclear localization signal (NLS) of terra by transfecting human HeLa cells. The terra NLS is located between the two intertwined zinc-binding sites of the DNA-binding domain. However, the nuclear translocation of terra is independent of the structure required for DNA binding. Mutational analysis demonstrates that basic residues K77 and R78 within the DM domain are absolutely required for the translocation of Terra into the nuclei. Sequence comparison discloses that the NLS of Terra is also present in the other known members of the DM family, indicating the conservative nature of the NLS of this family during evolution.

Amino Acid Sequence↗
PubMed2001

DNA methyltransferases of the cyanobacterium Anabaena PCC 7120.

From the characterization of enzyme activities and the analysis of genomic sequences, the complement of DNA methyltransferases (MTases) possessed by the cyanobacterium ANABAENA PCC 7120 has been deduced. ANABAENA has nine DNA MTases. Four are associated with Type II restriction enzymes (AVAI, AVAII, AVAIII and the newly recognized inactive AVAIV), and five are not. Of the latter, four may be classified as solitary MTases, those whose function lies outside of a restriction/modification system. The group is defined here based on biochemical and genetic characteristics. The four solitary MTases, DmtA/M.AVAVI, DmtB/M.AVAVII, DmtC/M. AVAVIII and DmtD/M.AVAIX, methylate at GATC, GGCC, CGATCG and rCCGGy, respectively. DmtB methylates cytosines at the N4 position, but its sequence is more similar to N6-adenine MTases than to cytosine-specific enzymes, indicating that it may have evolved from the former. The solitary MTases, appear to be of ancient origin within cyanobacteria, while the restriction MTases appear to have arrived by recent horizontal transfer as did five now inactive Type I restriction systems. One Mtase, M.AVAV, cannot reliably be classified as either a solitary or restriction MTase. It is structurally unusual and along with a few proteins of prokaryotic and eukaryotic origin defines a structural class of MTases distinct from all previously described.

Algal Proteins↗
PubMed2001

Double-stranded RNA injection produces nonspecific defects in zebrafish.

We have investigated the ability of dsRNA to inhibit gene functions in zebrafish using sequences targeted to the maternal gene pouII-1, the transgene GFP, and an intron of the zebrafish gene terra. We found that embryos injected with all of these dsRNAs at approximately 7.5 pg/embryo or higher had general growth arrest during gastrulation and displayed various nonspecific defects at 24 h postfertilization, although embryonic development was unaffected before the midblastula stage. Reducing dsRNA concentration could alleviate the global defects. Injection of GFP dsRNA (7.5-30 pg/embryo) did not inhibit GFP expression in transgenic fish, although abnormal embryos were induced. Co-injection of GFP mRNA with either GFP or non-GFP dsRNA caused reduction of GFP expression. Whole-mount in situ hybridization clearly showed that embryos injected with dsRNA degraded co-injected and endogenous mRNA without sequence specificity, indicating that dsRNA has a nonspecific effect at the posttranscriptional level. It appears that RNAi is not a viable technique for studying gene function in zebrafish embryos.

Abnormalities, Multiple↗
PubMed2001

The zygotic expression of zebrafish trebf during embryogenesis is restricted to the embryonic shield and its derivatives.

We have identified a zebrafish gene trebf that shows an overall similarity of 51.5% and 55.1% in amino acid sequence with human and mouse TREB5/hXBP-1/HTF, respectively. Northern hybridization reveals that trebf mRNA is expressed throughout the life cycle of zebrafish. Whole-mount in situ hybridization detects an expression pattern of trebf in zebrafish that is very different from that of mammalian TREB5. Just before the onset of gastrulation, trebf transcripts are accumulated in the dorsal blastoderm margin and subsequently in the forming organizer. During gastrulation, the trebf-positive cells in the organizer migrate toward the animal pole and form two distinct domains. The cells in the anterior leading expression domain ultimately differentiate into hatching gland, whereas those in the following domain form the notochord.

Amino Acid Sequence↗
PubMed2000

Activation of peroxisome proliferator-activated receptor-gamma pathway inhibits osteoclast differentiation.

The nuclear receptor and transcription factor, peroxisome proliferator-activated receptor-gamma (PPAR-gamma), regulates the activity of other transcription factors in the adipogenic differentiation and inflammatory response pathways. We examined the possible function of the PPAR-gamma pathway in osteoclast (Ocl) formation from CD34(+) hematopoietic stem cells (CD34(+) HSCs), using a co-culture system comprised of human mesenchymal stem cells (hMSCs) and CD34(+) HSCs, both derived from bone marrow. Ocl formation in this co-culture system is enhanced by the addition of exogenous osteoprotegerin ligand (OPGL), an essential Ocl differentiation factor, and macrophage-colony stimulating factor (M-CSF). The data indicate that soluble OPGL (sOPGL) and M-CSF stimulate Ocl formation in the co-cultures up to 4-fold compared with CD34(+) HSCs alone treated with sOPGL and M-CSF. CD34(+) HSCs, but not hMSCs, express PPAR-gamma, and 15-deoxy-Delta(12, 14)-prostaglandin-J2 (15d-PG-J2), a PPAR-gamma agonist, completely blocked the effects of sOPGL and M-CSF on Ocl formation and activity. The inhibitory effect of 15d-PG-J2 is specific to the Ocl lineage in both human and mouse models of osteoclastogenesis. Accordingly, parallel experiments demonstrate that sOPGL activates the NF-kappaB pathway within mouse Ocl progenitors, and this effect was abolished by 15d-PG-J2. These data establish a link between PPAR-gamma and OPGL signaling within Ocl progenitors, and support a role for PPAR-gamma pathway in the modulation of osteoclastogenesis.

Animals↗
PubMed2000

[Acupuncture in neurology].

Acupuncture is a reflex therapy with the aim of rearranging an imbalance of the organism. Acupuncture is a regulatory therapy. At first, there have to be diagnosis and indication according to the rules of western modern medicine. With that, we carry on with a standard program and standard exciting needle technique. We will report about acupuncture in neurology in three chapters: neuro-orthopedics, neuropsychiatry and somatopsychic diseases.

Acupressure↗
PubMed2000

[Principles of traditional Chinese medicine].

The beginnings of traditional Chinese medicine (TCM) can be related to the three most important philosophic and religious personalities. Modern Western medicine (MM), which was already sensationally successful at that time, was brought to China by business men, missionaries and soldiers. Compared to MM, the theories of TCM seem abstract, its concept unusual. Historical hallmarks of TCM influenced by culture are the following: the medical system is philosophical, oriented towards humanism. TCM is a medical system without strict structural relationships (without anatomy).

Acupuncture Therapy↗
PubMed2000

[Cytocompatible evaluation for skin reproducing membrane of medical fibroin].

This study was intended to evaluate the cytocompatibility of skin reproducing membrane of medical fibroin. Cell growth rate test and hemolysis test were conducted to investigate the cytotoxicity and hemolysis reaction for skin reproducing membrane. The results showed there was no obvious cytotoxicity for this kind of membrance. The hemolysis rate was 1.15%. In conclusion, skin reproducing membrane is a material of good cytocompatibility.

Animals↗
PubMed2000

A school-based asthma clinic: a partnership model for managing childhood asthma.

Childhood asthma is a major public health problem. It is the leading cause of childhood hospitalizations and school absences despite recent advances in management. Current standards of care call for client education as partners in disease management. In pediatrics, this calls for shared decision making between health care provider, parent, and child. Traditional care delivery systems often fall short of meeting this standard. This article describes a nurse practitioner-run school-based asthma clinic, designed as a pilot study, to fill these gaps. Characteristics of the community that affected outcomes are described.

Asthma↗
PubMed1999

Positive and negative cis-acting elements are required for hematopoietic expression of zebrafish GATA-1.

GATA-1 is a transcription factor required for development of erythroid cells. The expression of GATA-1 is tightly restricted to the hematopoietic lineage. Using transgene constructs containing zebrafish GATA-1 genomic sequences and the green fluorescent protein (GFP) reporter gene, we previously showed that a 5.6-kb enhancer/promoter fragment is sufficient to direct erythroid-specific expression of the GFP. In this study, we used enhancer/promoter fragments containing various deletion and point mutations to further characterize the cis-acting elements controlling tissue-specific GATA-1 expression. We report here the identification of distinct cis-acting elements that cooperate to confer on GATA-1 its hematopoietic expression pattern. A CACCC box, located 142 bp upstream of the translation start codon, is critical for the initiation of GATA-1 expression. A distal double GATA element is required for maintaining and enhancing the hematopoietic expression of GATA-1. The erythroid-specific activity of the GATA-1 promoter is also enhanced by a 49-bp sequence element located 218 bp upstream of the CACCC element and a CCAAT box adjacent to the double GATA motif. Finally, the hematopoietic specificity of the GATA-1 promoter is secured by a negative cis-acting element that inhibits expression in the notochord.

Animals↗
PubMed1999

Human mesenchymal stem cells promote human osteoclast differentiation from CD34+ bone marrow hematopoietic progenitors.

Interactions between osteoclast progenitors and stromal cells derived from mesenchymal stem cells (MSCs) within the bone marrow are important for osteoclast differentiation. In vitro models of osteoclastogenesis are well established in animal species; however, such assays do not necessarily reflect human osteoclastogenesis. We sought to establish a reproducible coculture model of human osteoclastogenesis using highly purified human marrow-derived MSCs (hMSCs) and CD34+ hematopoietic stem cells (HSCs). After 3 weeks, coculture of hMSCs and HSCs resulted in an increase in hematopoietic cell number with formation of multinucleated osteoclast-like cells (Ocls). Coculture of hMSCs with HSCs, transduced with a retroviral vector that expresses enhanced green fluorescent protein, produced enhanced green fluorescent protein+ Ocls, further demonstrating that Ocls arise from HSCs. These Ocls express calcitonin and vitronectin receptors and tartrate-resistant acid phosphatase and possess the ability to resorb bone. Ocl formation in this assay is cell contact dependent and is independent of added exogenous factors. Conditioned medium from the coculture contained high levels of interleukin (IL)-6, IL-11, leukemia inhibitory factor (LIF), and macrophage-colony stimulating factor. IL-6 and LIF were present at low levels in cultures of hMSCs but undetectable in cultures of HSCs alone. These data suggest that coculture with HSCs induce hMSCs to secrete cytokines involved in Ocl formation. Addition of neutralizing anti-IL-6, IL-11, LIF, or macrophage-colony stimulating factor antibodies to the coculture inhibited Ocl formation. hMSCs seem to support Ocl formation as undifferentiated progenitor cells, because treatment of hMSCs with dexamethasone, ascorbic acid, and beta-glycerophosphate (to induce osteogenic differentiation) actually inhibited osteoclastogenesis in this coculture model. In conclusion, we have developed a simple and reproducible assay using culture-expanded hMSCs and purified HSCs with which to study the mechanisms of human osteoclastogenesis.

Acid Phosphatase↗
PubMed1999

A Drosophila doublesex-related gene, terra, is involved in somitogenesis in vertebrates.

The Drosophila doublesex (dsx) gene encodes a transcription factor that mediates sex determination. We describe the characterization of a novel zebrafish zinc-finger gene, terra, which contains a DNA binding domain similar to that of the Drosophila dsx gene. However, unlike dsx, terra is transiently expressed in the presomitic mesoderm and newly formed somites. Expression of terra in presomitic mesoderm is restricted to cells that lack expression of MyoD. In vivo, terra expression is reduced by hedgehog but enhanced by BMP signals. Overexpression of terra induces rapid apoptosis both in vitro and in vivo, suggesting that a tight regulation of terra expression is required during embryogenesis. Terra has both human and mouse homologs and is specifically expressed in mouse somites. Taken together, our findings suggest that terra is a highly conserved protein that plays specific roles in early somitogenesis of vertebrates.

Amino Acid Sequence↗
PubMed1999

[Study on correlation between in vivo and in vitro tests of biomaterials--correlation between leukocyte chemotaxis test and muscular implant test in rabbits].

The purpose of this study was to investigate the correlation between the results of in vivo and in vitro tests of biomaterials. With muscular implant test and leukocyte chemotaxis test, the levels of tissue toxicity of seven biomaterials were evaluated. The samples with high-level toxicity showed weak leukocyte chemotaxis, which would influence the anti-inflammatory reaction to foreign bodies. By the method of Spearman rank correlation, the coefficient was between 0.89286-0.98198 indicating that the correlation of the two tests is excellent.

Animals↗
PubMed1999

[A comparative study on cytocompatibility of medical PVA and intelligent PVA-g-NIPAAm hydrogels].

"Intelligent" Polymers which resonse with large property changes to small physical or chemical stimuli are attracting more and more attention in the field of medical science. One trend in the area is to modify some conventional medical polymers to form intelligent biomaterials. This investigation was designed to evaluate and compare in vitro cytocompatibility of PVA hydrogel, which could be used as a kind of solid support with good biomcompatibility, and PVA-g-NIPAAm, which was produced by irradiation grafting of NIPAAm onto the said PVA hydrogel support. Cytotoxicity test was carried out with a modified Cell Relative Growth Rate test (RGR test). On the day 2, day 4 and day 7, the RGRs of the PVA hydrogel were 82%, 90% and 102% respectively while the RGRs of the PVA-g-NIPAAm were 77%, 86% and 100%. The grades of the cytotoxicity of the PVA and PVA-g-NIPAAm hydrogels were 0, so they had no cytotoxicity as judged by our tests. After 24 hours, cells in direct contact with the two kinds of samples were observed morphologically through the Olympus inverted microscope and had a normal development. The conclusion suggests that irradiation grafting is a good way to modify conventional medical polymers to produce intelligent biomaterials.

Acrylamides↗
PubMed1999

[Evaluation on cytotoxicity of gallium alloy].

Cytotoxicity is an important indicator to the biocompatibility of biomaterials. In this study, the cytotoxicity of Gallium alloy was evaluated by the method of cell relative growth rate in vitrousing L-929 mouse fibroblast. The cell relative growth rate of Gallium alloy was the absorbency ratio between the solution of Gallium alloy and negative control. The relative growth rates of Gallium aloy were converted into the scores of cytotoxicity. It was found from the results that Gallium alloy had no cytotoxicity.

Alloys↗
PubMed1999

Transgenesis.

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Animals↗