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Biomedical subjects

Y Zhao

Publications and source records attributed to Y Zhao.

At least 757 records · Page 42Linked to original sources
PubMed1997

Endocrine disorders associated with inappropriately high aromatase expression.

Aromatase P450 (P450arom) is responsible for conversion of C19 steroids to estrogens in a number of human tissues, such as the placenta, gonads, adipose tissue, skin and the brain. Aromatase expression in human tissues is regulated by use of alternative promoters in the placenta (promoter I.1), adipose tissue (promoters I.4, I.3 and II) and gonads (promoter II). Aromatase expression is absent in the disease-free adult liver, adrenal and uterine tissues. Excessive or inappropriate aromatase expression in adipose fibroblasts and endometriosis-derived stromal cells, as well as in testicular, hepatic, adrenal and uterine tumors, is associated with abnormally high circulating estrogen levels and/or with increased local estrogen concentrations in these tissues. Whether systemically delivered or locally produced, elevated estrogen levels will in turn promote the growth of hormone-responsive tissues. We recently studied aromatase expression in testicular tumor and adipose tissue samples from prepubertal boys with gynecomastia, in hepatocellular cancer and adrenocortical tumor samples from adult men with gynecomastia, in breast adipose tissue samples proximal to breast tumors, and in endometrial cancer, leiomyoma and endometriosis tissues. Excessive aromatase activity and P450arom transcript levels were found in these tissue samples or in cultured cells derived from these tissues. In these neoplastic or non-neoplastic tissues or cells, the regulation of aromatase expression was studied in terms of alternative promoter use, both in vivo and in response to various hormonal stimuli. Our results were suggestive of a common metabolic abnormality associated with activation of a cyclic AMP-dependent signalling pathway that gives rise to transcriptional transactivation of aromatase expression via promoters I.3 and II in all of the above tissues. This article describes the common pathophysiological and molecular features of excessive aromatase expression in these disease states.

Adolescent↗
PubMed1997

Genotyping by PCR-ELISA of a complex polymorphic region that contains one to four copies of six highly homologous human VH3 genes.

The Humhv3005 human VH gene is located in an intricate locus that encompasses for each haplotype a combination of one to four copies of six highly homologous VH3 genes. To assess the complexity of this region, we developed a polymerase chain reaction-enzyme-derived immunosorbent assay (PCR-ELISA) method capable of detecting each of the VH3 genes. The method consisted of amplification of selected germline VH3 genes with a biotinylated primer, covalent capture of the amplicons onto streptavidin-coated wells, and quantitative typing of the bound VH3 genes with diagnostic oligonucleotides. Pilot studies of two DNA samples with known presence or absence of hv3005 [according to a characteristic BamH1 restriction fragment-length polymorphism (RFLP)] yielded the expected results. Subsequent analysis of 100 additional DNA samples with the known EcoR1 RFLP of hv3005 showed a complete match between the absence of the 9.4-kb hybridizing band and lack of hv3005-like genes, as determined by PCR-ELISA. Importantly, the PCR-ELISA analyses of these 102 genomic DNA samples revealed two new haplotypes in the complex hv3005 region. Combined, these data demonstrate the usefulness and efficiency of this new technique to ascertain the presence or absence of six highly homologous genes in an unusually heterogeneous duplication-insertion-deletion region. In the future, a similar strategy may be used to dissect other similarly complex VH genetic loci.

Amino Acid Sequence↗
PubMed1997

[Improving patient's posture during nerve surgery].

The patient's posture for nerve surgery operation was improved in order to convenient to micro surgery procedure and offer cooperation further better for operators, as well as to decrease possibility of skin injury. The results indicated that emergence of skin injury in improved posture decreased 67.25% compared with that before and complications reduced significantly.

Humans↗
PubMed1997

[The dendritic cell differentiation and antigen-presenting function of the erythroleukemia cells induced by GM-CSF].

OBJECTIVE: To investigate the generation of dendritic cells and the change of antigen-presenting function during the differentiation of FBL-3 erythroleukemia cells induced by GM-CSF. METHODS: The effects of GM-CSF on the phenotype, ultrastructure and antigen-presenting function of FBL-3 erythroleukemia cells were observed by FACS, electromicroscopy and 51Cr-release assay. RESULTS: After treatment with 100 ng/ml GM-CSF for 3 days, the expressions of 33 D1 and NLDC 145 which are the specific markers on dendritic cells were increased significantly; MHC-II B7-1, B7-2, ICAM-1, VCAM-1 and CD40 were also upregulated. The membrane of FBL-3 cells was changed into villous surface with dendritic projections. There were plenty of mitochondria in cytoplasm, the nucleus became lobulated. The GM-CSF-treated FBL-3 cells could apparently stimulate the proliferation of allogeneic T lymphocytes, induce the production of IL-2 and improve the specific cytotoxic activity of CTL on FBL-3 cells. CONCLUSION: Erythroleukemia cells were induced to differentiate into the dendritic cells by GM-CSF and obtained the antigen-presenting function.

Animals↗
PubMed1997

[A pharmacokinetic study of lidocaine in patients undergoing liposuction with tumescent technique].

The purpose of this study was to evaluate the pharmacokinetics of lidocaine in the patients undergoing liposuction after subcutaneous infiltration of 0.06% lidocaine. It was found that the absorption of lidocaine was slow. The mean peak concentration of lidocaine that was 1.16 ug/mg with a range of 0.67 to 2.84 ug/mg occurred 4-13 hours after lidocaine administration. The peak concentration (Y) was correlated with the dose (X) of lidocaine, which was drawn as Y = -0.494 + 0.071X (r = 0.934, P < 0.001). We concluded that the tumescent technique is an effective and safe method for the patients undergoing liposuction.

Adult↗
PubMed1997

[Clinical significance of determining serum soluble IL-6 receptor concentration in plasma cell dyscrasias].

It has been proven that interleukin 6 (IL-6) is the key growth factor for myeloma cells in vitro and in vivo. Binding of serum soluble IL-6 receptor (sIL-6R) with IL-6 can promote the biological effects of IL-6. To investigate the significance of serum sIL-6R in plasma cell dyscrasias (PCD), we determined serum sIL-6R concentrations in 62 patients with multiple myeloma (MM), 5 with macroglobulinemia, 1 with mu heavy chain disease and 15 healthy controls by using ligand immunoenzyme assay. The results showed that serum sIL-6R concentrations in macroglobulinemia and MM at stage II and stage III were significantly higher than these in MM at stage I and healthy controls (P < 0.01). Morever, serum sIL-6R concentrations in MM at stage III were higher than those in MM at stage II (P < 0.01). But there were no statistic difference in serum sIL-6R concentrations between normal controls and MM at stage I (P > 0.05). And there were also no difference in serum sIL-6R concentrations among various M-protein classes (P > 0.05). Our results indicated that serum sIL-6R concentration is a useful marker in reflecting disease severity in MM. Its clinical significance in other PCD needs further investigation.

Aged↗
PubMed1997

[HLA-DRB1 alleles genotyping in patients with rheumatoid arthritis in Chinese].

To explore the role of HLA-DRB1 genes in the development of rheumatoid arthritis (RA) and the correlations between HLA-DR alleles and clinical manifestations of patients with RA we studied 86 patients and 106 race matched controls in whom HLA-DR typing was performed by the method of DNA amplification with sequence-specific primers (PCR-SSP). The subtypes of HLA-DR4 were determined by the method of hybridization of PCR products with sequence-specific oligonucletides (PCR-SSO). The absence or presence of HLA-DR4 and its subtypes was evaluated with the clinical and serological characteristics of the patients. Compared with controls, an increased gene frequency of HLA-DR4 (48.8% vs 17.9%, P < 0.001) and a decreased frequency of HLA-DR5 (16.3% vs 27.4%, P = 0.06) were found. The DRB1 * 0405 accounted for 61.9% of DR4+ RA patients and 21.1% of DR+4 controls (P < 0.01). There was no difference between the DR4+ and DR4- patients with respect to age, sex, duration of disease, extra-articular manifestations including secondary Sjogren's syndrome. But rheumatoid factor (RF) was associated with HLA-DR4 (P < 0.05). According to the X-ray stage, the patients of DR4+ were more severe than those of DR4- (P < 0.05). HLA-DR4 and DR4 subtype of DRB1 * 0405 were related to the development of RA in Chinese. HLA-DR4 can be a useful prognostic marker in the patients with RA.

Adult↗
PubMed1997

Telomerase activity in normal and neoplastic breast.

Telomerase activity is detected in the majority of human tumors and provides a mechanism to escape from proliferative limitations due to telomere loss. Similar to other studies, telomerase activity was detected with a modified telomeric repeat amplification protocol in the majority (76%) of 49 human breast cancer specimens, including most (75%) ductal carcinoma in situ specimens. There were no correlations between telomerase activity and tumor stage or estrogen/progesterone receptor status. In four of seven invasive tumors, telomerase expression seemed to be heterogeneous because not all microdissected regions were telomerase positive. Low levels of telomerase activity were also detected in a minority (17%) of breast specimens from patients without evidence of cancer. These findings suggest that telomerase activation can occur early in breast cancer progression and may be periodically down-regulated during subsequent progression.

Biomarkers, Tumor↗
PubMed1996

Effect of the apolipoprotein A-I and surface lipid composition of reconstituted discoidal HDL on cholesterol efflux from cultured fibroblasts.

Five series of reconstituted discoidal HDL (LpA-I) particles have been prepared, and their constituents, apolipoprotein A-I (apoA-I), 1-palmitoyl-2-oleoylphosphatidylcholine (POPC), unesterified cholesterol (UC), phosphatidylinositol (PI), or sphingomyelin (SM), have been systematically varied to elucidate the relationship between HDL composition and cholesterol efflux from non-cholesterol-loaded human skin fibroblasts. The physical properties, such as hydrodynamic diameters, alpha-helix contents, and surface potentials, of these LpA-I have been measured and related to the ability of the LpA-I to accept cellular cholesterol. The results show that for LpA-I particles containing 2, 3, or 4 apoA-I per particle, Lp4A-I are the best acceptors of cellular cholesterol, followed by Lp3A-I and then Lp2A-I particles. Discoidal Lp2A-I with variations in POPC content, from 121 to 266 mol/particle; show no difference in their abilities to promote cholesterol efflux. Similarly, inclusion of 7 and 15 mol of free cholesterol to Lp2A-I also does not affect their ability to accept cellular cholesterol. However, increasing the content of either PI or SM, up to 20 mol/particle, is associated with significantly increased abilities of the LpA-I to promote cholesterol efflux. The efflux of cellular cholesterol to discoidal LpA-I particles is independent of specific changes in apoA-I conformation and charge, but appears to be positively related to major changes in the size of the lipoprotein particle. The study suggests that in contrast to interlipoprotein cholesterol transfers, the efflux of cholesterol from cultured fibroblasts is less sensitive to factors that affect the frequency of molecular collisions and more dependent on the ability of an HDL particle to absorb and retain cholesterol molecules. Since SM and PI appear to modulate this adsorption/desorption of cholesterol to HDL, variations in the concentration of these lipids within HDL would be expected to affect plasma cholesterol homeostasis.

Apolipoprotein A-I↗
PubMed1996

Regeneration of broken tip links and restoration of mechanical transduction in hair cells.

A hair cell's tip links are thought to gate mechanoelectrical transduction channels. The susceptibility of tip links to acoustic trauma raises questions as to whether these fragile structures can be regenerated. We broke tip links with the calcium chelator 1,2-bis(O-aminophenoxy) ethane-N,N,N',N'-tetraacetic acid and found that they can regenerate, albeit imperfectly, over several hours. The time course of tip-link regeneration suggests that this process may underlie recovery from temporary threshold shifts induced by noise exposure. Cycloheximide does not block tip-link regeneration, indicating that new protein synthesis is not required. The calcium ionophore ionomycin prevents regeneration, suggesting regeneration normally may be stimulated by the reduction in stereociliary Ca2+ when gating springs rupture and transduction channels close. Supporting the equivalence of tip links with gating springs, mechanoelectrical transduction returns over the same time period as tip links; strikingly, adaptation is substantially reduced, even 24 hr after breaking tip links.

Animals↗
PubMed1996

Identification and developmental expression of two activin receptors in baboon lung.

Activins are members of the transforming growth factor-beta (TGF-beta) superfamily that exert their effects through interacting with specific cell surface TGF-beta superfamily receptors (TSRs). To determine whether activins are involved in lung development, we used a reverse transcription polymerase chain reaction (RT-PCR)-based approach to identify members of the activin receptors from baboon fetal lung mRNAs. Two partial cDNA sequences encoding serine/threonine kinase domains of baboon TSR type I (bTSR1) and type II (bTSR2) were identified by sequencing analysis. bTSR1 displays 96% identity to human activin type I receptor TSR1, whereas bTSR2 shows 80% identity to human activin type II receptor ActRIIB over the kinase domain region. Northern analysis revealed the expression of a 2.1 kb bTSR1 transcript and a 5.0 kb bTSR2 transcript in baboon lung tissues. Both bTSR1 and bTSR2 were expressed throughout embryonic lung development and in adult lung. The expressions of bTSR1 and bTSR2 were developmentally regulated and each had a distinct expression pattern. Furthermore, the expressions of bTSR1 and bTSR2 in fetal baboon lung were altered by oxygen exposure. This study for the first time identifies the presence of the activin receptors in the baboon lung and provides evidence that both bTSR1 and bTSR2 are regulated during lung development, suggesting that activins might play an important role during lung development.

Activin Receptors↗
PubMed1996

Regulation and interaction of pp90(rsk) isoforms with mitogen-activated protein kinases.

Each of the three known mammalian 90-kDa S6 kinase (pp90(rsk)) isoforms (RSK1, RSK2, and RSK3) was expressed in transfected cells and further characterized. The kinase activity (immunocomplex toward S6 peptide) of each isoform was activated by in vivo growth factor (epidermal growth factor (EGF)) stimulation; RSK1 was more responsive (10-15-fold) versus RSK2 and RSK3 (2-4-fold). Pretreatment with PD98059 (MEK1 inhibitor) partially (80%) blocked EGF-mediated ERK1 activation and had similar effects on EGF stimulation of each ribosomal S6 kinase (RSK). Cotransfection with dominant-negative MEK1 inhibited activation of each RSK; furthermore, the kinase activity of RSK1, RSK2, and RSK3 was markedly increased by cotransfection with constitutively active MEK1. A specific association between mitogen-activated protein kinases (MAPKs) (ERK1 and ERK2) and RSK isoforms was tested by MAPK immunoblotting after immunoprecipitation of RSKs. ERK1 and ERK2 were present in RSK3 (and to a lesser extent, RSK2) immunoprecipitates, but were absent in RSK1 immunoprecipitates. Both dephosphorylated (from quiescent cells) and phosphorylated (from stimulated cells) MAPKs were associated with RSK2 and RSK3. Deletion mutants of RSK3 were characterized: the C terminus (33 residues) was shown to be required for association with MAPKs. The kinase activity of RSK1 or RSK2 was enhanced by in vitro incubation with ERK1. In contrast, RSK3 activity was not affected by exposure to ERK1. Furthermore, MAPKs in RSK3 immunoprecipitates were phosphorylated by purified MEK1; however, RSK3 kinase activity was unaffected. We conclude that 1) the MEK1-MAPK signaling pathway is both necessary and sufficient for in vivo growth factor-mediated activation of all three RSK isoforms; 2) RSK isoforms differ with respect to growth factor responsiveness and their physical association with MAPK; and 3) formation of the MAPK.RSK complex is mediated by the RSK C terminus.

Animals↗
PubMed1996

Specific phospholipid association with apolipoprotein A-I stimulates cholesterol efflux from human fibroblasts. Studies with reconstituted sonicated lipoproteins.

To understand how the lipid composition of high density lipoprotein mediates the efflux of cellular cholesterol, we have characterized the effects of variations in the lipid composition of well defined model sonicated apolipoprotein A-I (apoA-I)-containing lipoprotein (LpA-I) particle on cholesterol efflux from cultured human skin fibroblasts. LpA-I particles with varying content of phosphatidylcholine (POPC), phosphatidylinositol, sphingomyelin, cholesterol ester, and triolein were prepared by co-sonication. Association of as little as 5 mol of phosphatidylcholine with apoA-I is sufficient to transform lipid-free apoA-I into a distinct lipoprotein-like particle that is a significantly better acceptor of cellular cholesterol. Increasing the ratio of POPC/apoA-I from 5/1 to 35.5/1 in the sonicated LpA-I is associated with a significant increase in the release of cellular cholesterol. At low POPC/apoA-I ratios, native gradient gel electrophoresis of the LpA-I shows these lipoproteins to be small complexes (around 5-6 nm), with only 1 molecule of apoA-I (Lp1A-I). At a POPC/apoA-I ratio above 11/1, LpA-I form well defined complexes that contain 2 molecules of apoA-I (Lp2A-I) and range in size from 7.6 to 7.7 nm. Inclusion of sphingomyelin into an Lp1A-I further stimulates cholesterol efflux significantly. In contrast, inclusion of either sphingomyelin or phosphatidylinositol into a sonicated Lp2A-I has no effect on cholesterol efflux. Incorporation of cholesterol ester and/or triolein into an Lp2A-I particle is associated with a small reduction in cholesterol efflux to these lipoproteins. Therefore, cholesterol efflux from human fibroblasts is directly proportional to the amount and type of phospholipid in a sonicated LpA-I particle. Changes in the conformation and charge of apoA-I that result from changes in the lipid composition of a sonicated LpA-I particle appear to directly affect the ability of the lipoprotein to bind and retain cholesterol molecules. These data therefore suggest that the adsorption/desorption of cholesterol molecules to/from a sonicated LpA-I complex may be less sensitive to interfacial lipid-lipid interactions, but may depend on a conformation-dependent ability of apoA-I to bind cholesterol.

Apolipoprotein A-I↗
PubMed1996

The chick alpha2(I) collagen gene contains two functional promoters, and its expression in chondrocytes is regulated at both transcriptional and post-transcriptional levels.

Embryonic chick cartilages contain transcripts derived from the alpha2(I) collagen gene, although type I collagen is not normally found in these tissues; most of these RNAs are alternative transcripts initiating within intron 2. Use of the internal start site results in replacement of exons 1 and 2 with a previously undescribed exon and a change in the translational reading frame; thus, the alternative transcript cannot encode alpha2(I) collagen. We have demonstrated that production of the alternative transcript is due to activation of an internal promoter in chondrocytes and have identified a 179-base pair domain that is required for its activity. Furthermore, we have shown that the alternative transcript resulting from activation of the internal promoter turns over relatively rapidly; thus, the steady-state level of this transcript is less than predicted based on the transcription rate. The upstream promoter is only partially repressed in chondrocytes, suggesting that the lack of authentic alpha2(I) collagen mRNA may also be due in part to decreased mRNA stability. Thus, repression of alpha2(I) collagen synthesis in cartilage involves both transcriptional and post-transcriptional mechanisms. In contrast, repression of alpha1(I) collagen synthesis appears to be mediated primarily at the level of transcription.

Alternative Splicing↗