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Biomedical subjects

R Yang

Publications and source records attributed to R Yang.

At least 109 records · Page 6Linked to original sources
PubMed2000

[Morphological changes of cultured rabbit retinal cells after injury].

PURPOSE: To investigate the morphological changes of cultured rabbit retinal cells after injury. METHODS: Mechanical scratch was done in nenatol rabbit retinal cell culture and in Schwann Cell(SC)/retinal cell colculture. The morphological changes of different sorts of cells after the injury were observed under the phase contrast microscope for 24 h. RESULTS: About 30 min after injury, many glial cells moved to the blank region and proliferated to form gliosis. Axons of retinal neurons began to regenerate 6 h post injury. The direction of regrowth was influenced by the environment. In the coculture, regeneration of axons was discerned only 3 h after injury. CONCLUSION: Axons of retinal neurons had strong capability of regeneration; Gliosis was not the absolute obstacle of regeneration; SC played a role in promoting the axon regeneration.

Animals↗
PubMed2000

[The preparations and spectroscopic studies of infrared radiating materials].

ZrO2 and ZrO2-Al2O3 samples have been prepared by precipitation method, and characterized by FTIR, NIR FT-Raman, XRD and IR emission spectra, respectively. The result showed that these samples are the better infrared radiating materials, which have high efficiency and excellent properties. When compared with pure ointment, ZrO2-Al2O3 prepared has more strong infrared emission peaks. The application of infrared radiating materials in ointment may have a good effect on thermal infrared absorption vibration and absorption of medicine by sick part of body.

Aluminum Oxide↗
PubMed2000

[Vibrational frequencies study of the hydroxy-benzoquinones].

In this paper, we report the Ab initio calculation and experimental investigation of the vibrational frequencies of 4,5-dihydroxy-1,2-benzoquinone and 2,5-dihydroxy-1,4-benzoquinone. The main IR and Raman absorption bands of them have been assigned, learned from other strong points to offset one weakness, by combination the program Gaussian 94 and MOPAC. The difference in absorption bands between them has been discussed.

Benzoquinones↗
PubMed2000

[The synthesis and spectral study of multicomponent heteropoly compounds with Keggin structure].

The Multicomponent heteropoly compounds [Me4N]3 + x[PVxMoyW12-x-yO40]. n(H2O) with Keggin structure have been synthesized, and have been characterized by FTIR and NIR FT-Raman. The vibrational regularity of oxygen-containing bonds (P-Oa, M = Od, M-Ob-M and M-Oc-M) in these heteropoly compounds have been studied. The vibrational frequencies nu as (M = Od) and nu as (M-Ob-M) was shown to prove the reason why the acidity of the heteropoly compounds descended and the oxidization increased by the substitution of V atoms.

English Abstract↗
PubMed2000

[Determination of the composition distribution of polymer blend films by using microscopic FTIR].

In this paper, PS/PC blend film (about 120 microns thick) and PS/PMMA (about 90 microns thick) blend film were prepared by evaporation the solvent very slowly from polymer blend solution. Different FTIR methods were used to determine the composition distribution along the vertical direction of the films. PS/PC film was firstly sectioned by ultramicrotomy, then the vertical section was measured to determine the composition of every 16 microns width unit from the surface-side to the bottom-side by Microscopic transmission-FTIR. The results showed that the concentration of PS was significantly greater in the vicinity of the surface of the film than that in the bulk, i.e., the component of PS enriched to the surface. Focusing the reflecting infrared light on different layer of the film, we can detect the composition of the different depth region in the PS/PMMA blend film. As the result, PMMA aggregated to the bottom of the film. It was considered that this effect was related to the different affinity and wetting prosperities of the blend component to the substrate or air.

English Abstract↗
PubMed2000

[Synthesis and characterization of the oxidation product of the 1, 2, 3-trihydroxybenzene and its metallic complexes].

The oxidation reaction mechanism of the 1,2,3-trihydroxybenzene was studied by the Ab initio calculation of the quantum chemistry. The derivative of the hydrazine and THBO(the reaction product of the 1,2,3-trihydroxybenzene and H2O2) and its metal complexes were synthesized and characterized by the IR, Raman spectrum and thermogravimetric analysis. The composition of these complexes and the possible structure of THBO were confirmed.

Chelating Agents↗
PubMed2000

Effects of VEGF on hemodynamics and cardiac function: characterization and mechanisms.

Vascular endothelial growth factor (VEGF), a mitogen specific for endothelial cells, produces beneficial angiogenesis in animal models of ischemic diseases; however, its side effects on hemodynamics and cardiac function may limit clinical use for some indications. This review focuses on the VEGF-induced hemodynamic profile, including hypotension, tachycardia, decreases in cardiac output and stroke volume, and changes in preload and afterload. The hemodynamic effects of VEGF are due to vasodilation and vascular hyperpermeability, which are mainly mediated by nitric oxide. Finally, the regimen or strategy for attenuation or prevention of these side effects is discussed.

Journal Article↗
PubMed1999

c-myb transactivates the human cyclin A1 promoter and induces cyclin A1 gene expression.

Cyclin A1 differs from other cyclins in its highly restricted expression pattern. Besides its expression during spermatogenesis, cyclin A1 is also expressed in hematopoietic progenitor cells and in acute myeloid leukemia. We investigated mechanisms that might contribute to cyclin A1 expression in hematopoietic cells. Comparison of cyclin A1 and cyclin A promoter activity in adherent and myeloid leukemia cell lines showed that the cyclin A1 promoter is preferentially active in myeloid cell lines. This preferential activity was present in a small, 335-bp cyclin A1 promoter fragment that contained several potential c-myb binding sites. Coexpression of a c-myb expression vector with the cyclin A1 promoter constructs significantly increased the reporter activity in adherent CV-1 as well as in myeloid U937 cells. Gel-shift assays demonstrated that c-myb could bind to the cyclin A1 promoter at a binding site located near the transcription start site. Site-directed mutagenesis of this site decreased promoter transactivation by 50% in both KCL22 cells that express high levels of c-myb and in CV-1 cells that were transfected with c-myb. In addition, transfection of primary human embryonic fibroblasts with a c-myb expression vector led to induction of the endogenous cyclin A1 gene. Taken together, c-myb can directly transactivate the promoter of cyclin A1, and c-myb might be involved in the high-level expression of cyclin A1 observed in acute myeloid leukemia. These findings suggest that c-myb induces hematopoiesis-specific mechanisms of cell cycle regulation.

Base Sequence↗
PubMed1999

Molecular cloning of transferrin receptor 2. A new member of the transferrin receptor-like family.

Transferrin receptor (TfR) plays a major role in cellular iron uptake through binding and internalizing a carrier protein transferrin (Tf). We have cloned, sequenced, and mapped a human gene homologous to TfR, termed TfR2. Two transcripts were expressed from this gene: alpha (approximately 2.9 kilobase pairs), and beta (approximately 2.5 kilobase pairs). The predicted amino acid sequence revealed that the TfR2-alpha protein was a type II membrane protein and shared a 45% identity and 66% similarity in its extracellular domain with TfR. The TfR2-beta protein lacked the amino-terminal portion of the TfR2-alpha protein including the putative transmembrane domain. Northern blot analysis showed that the alpha transcript was predominantly expressed in the liver. In addition, high expression occurred in K562, an erythromegakaryocytic cell line. To analyze the function of TfR2, Chinese hamster ovary TfR-deficient cells (CHO-TRVb cells) were stably transfected with FLAG-tagged TfR2-alpha. These cells showed an increase in biotinylated Tf binding to the cell surface, which was competed by nonlabeled Tf, but not by lactoferrin. Also, these cells had a marked increase in Tf-bound (55)Fe uptake. Taken together, TfR2-alpha may be a second transferrin receptor that can mediate cellular iron transport.

Amino Acid Sequence↗
PubMed1999

Cloning of the cyclin A1 genomic structure and characterization of the promoter region. GC boxes are essential for cell cycle-regulated transcription of the cyclin A1 gene.

Cyclin A1 is a recently cloned cyclin with high level expression in meiotic cells in the testis. However, it is also frequently expressed at high levels in acute myeloid leukemia. To elucidate the regulation of cyclin A1 gene expression, we cloned and analyzed the genomic structure of cyclin A1. It consists of 9 exons within 13 kilobase pairs. The TATA-less promoter initiates transcription from several start sites with the majority of transcripts beginning within a 4-base pair stretch. A construct containing a fragment from -190 to +145 showed the highest transcriptional activity. Transfection of cyclin A1 promoter constructs into S2 Drosophila cells demonstrated that Sp1 is essential for the activity of the promoter. Sp1, as well as Sp3, bound to four GC boxes between nucleotides -130 and -80 as observed by gel shift analysis. Mutations in two or more of the four GC boxes decreased promoter activity by >80%. The promoter was found to be cell cycle-regulated with highest activities found in late S and G2/M phase. Further analyses suggested that cell cycle regulation was accomplished by periodic repression of the GC boxes in G1 phase. Taken together, our data show that cyclin A1 promoter activity critically depends on four GC boxes, and members of the Sp1 family appear to be involved in directing expression of cyclin A1 in both a tissue- and cell cycle-specific manner.

Base Sequence↗
PubMed1999

Cyclin A1 expression in leukemia and normal hematopoietic cells.

Human cyclin A1 is a newly cloned, tissue-specific cyclin that is prominently expressed in normal testis. In this study, we showed that cyclin A1 was highly expressed in a subset of leukemia samples from patients. The highest frequency of cyclin A1 overexpression was observed in acute myelocytic leukemias, especially those that were at the promyelocyte (M3) and myeloblast (M2) stages of development. Cyclin A1 expression was also detected in normal CD34(+) progenitor cells. The expression of cyclin A1 increased when these cells were stimulated to undergo myeloid differentiation in vitro. Taken together, our observations suggest that cyclin A1 may have a role in hematopoiesis. High levels of cyclin A1 expression are especially associated with certain leukemias blocked at the myeloblast and promyelocyte stages of differentiation.

Antigens, CD34↗
PubMed1999

Gene expression analysis by transcript profiling coupled to a gene database query.

We describe an mRNA profiling technique for determining differential gene expression that utilizes, but does not require, prior knowledge of gene sequences. This method permits high-throughput reproducible detection of most expressed sequences with a sensitivity of greater than 1 part in 100,000. Gene identification by database query of a restriction endonuclease fingerprint, confirmed by competitive PCR using gene-specific oligonucleotides, facilitates gene discovery by minimizing isolation procedures. This process, called GeneCalling, was validated by analysis of the gene expression profiles of normal and hypertrophic rat hearts following in vivo pressure overload.

Animals↗
PubMed1999

Functions of cyclin A1 in the cell cycle and its interactions with transcription factor E2F-1 and the Rb family of proteins.

Human cyclin A1, a newly discovered cyclin, is expressed in testis and is thought to function in the meiotic cell cycle. Here, we show that the expression of human cyclin A1 and cyclin A1-associated kinase activities was regulated during the mitotic cell cycle. In the osteosarcoma cell line MG63, cyclin A1 mRNA and protein were present at very low levels in cells at the G0 phase. They increased during the progression of the cell cycle and reached the highest levels in the S and G2/M phases. Furthermore, the cyclin A1-associated histone H1 kinase activity peaked at the G2/M phase. We report that cyclin A1 could bind to important cell cycle regulators: the Rb family of proteins, the transcription factor E2F-1, and the p21 family of proteins. The in vitro interaction of cyclin A1 with E2F-1 was greatly enhanced when cyclin A1 was complexed with CDK2. Associations of cyclin A1 with Rb and E2F-1 were observed in vivo in several cell lines. When cyclin A1 was coexpressed with CDK2 in sf9 insect cells, the CDK2-cyclin A1 complex had kinase activities for histone H1, E2F-1, and the Rb family of proteins. Our results suggest that the Rb family of proteins and E2F-1 may be important targets for phosphorylation by the cyclin A1-associated kinase. Cyclin A1 may function in the mitotic cell cycle in certain cells.

Animals↗