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Y Deng

Publications and source records attributed to Y Deng.

At least 127 records · Page 7Linked to original sources
PubMed1998

Identification of unfolding domains in large proteins by their unfolding rates.

Three unfolding domains in rabbit muscle aldolase destabilized in 3 M urea have been identified from their unfolding rate constants (0.10, 0.036, and 0.0064 min-1). The populations of folded and various, partially unfolded forms were determined by amide hydrogen exchange and mass spectrometry. Results of this study show that unfolding domains may include multiple, noncontiguous segments of the backbone and that different regions of helices may belong to different unfolding domains. In addition, these results show that the domain unfolding most rapidly is located distant from the subunit binding surfaces and has the greatest access to the denaturant. The bimodal intermolecular distributions of deuterium found in this study show that unfolding of these domains is cooperative. It is proposed that these unfolding domains are correlated with local energy minima in the free-energy folding surface of aldolase. In addition to the three unfolding domains, there are three short segments that do not unfold in 3 M urea. These segments, which are located in the subunit binding surface, identify the most stable regions of aldolase. This study also demonstrates that it is now possible to identify and characterize unfolding domains in relatively large (Mr 158 000) proteins.

Animals↗
PubMed1998

Thrombomodulin modulates growth of tumor cells independent of its anticoagulant activity.

Thrombomodulin (TM), recognized as an essential vessel wall cofactor of the antithrombotic mechanism, is also expressed by a wide range of tumor cells. Tumor cell lines subcloned from four patients with malignant melanoma displayed a negative correlation between TM expression and cell proliferation in vitro and in vivo. Overexpression of wild-type TM decreased cell proliferation in vitro and tumor growth in vivo. TM mutants with altered protein C activation capacity lead to a similar effect. In contrast, transfection of melanoma cells with mutant TM constructs, in which a portion of the cytoplasmic or lectin domain was deleted, abrogated the antiproliferative effect associated with overexpression of wild-type TM. Experiments performed with either peptide agonists/antagonists of the thrombin receptor, with hirudin, or with inhibitors of thrombin-TM interaction did not alter the growth inhibitory effect of TM overexpression. These data suggest that TM exerts an effect on cell proliferation independent of thrombin and the thrombin receptor, possibly related to the binding of novel ligands to determinants in the lectin domain which might trigger signal transduction pathways dependent on the cytoplasmic domain.

Animals↗
PubMed1998

Generation of reactive oxygen species accounts for cytotoxicity of an endogenous dopaminergic neurotoxin, (R)-N-methylsalsolinol, to differentiated dopaminergic SH-SY5Y cells.

The mechanism of the cytotoxicity of endogenous dopamine-derived (R)-1,2-dimethyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline [(R)-N-methylsalsolinol] to differentiated human dopaminergic neuroblastoma SH-SY5Y cells was studied using a reduction-oxidation indicator, Alamar Blue. N-Methylsalsolinol and its oxidation product, 1,2-dimethyl-6,7-dihydroxyisoquinolinium ion, were found to inhibit oxidative phosphorylation, as shown by the Redox capacity. Antioxidants, such as reduced glutathione, catalase, Tris and n-propyl gallate, reduced the cytotoxicity of N-methylsalsolinol, suggesting that hydroxyl radical was the major reactive oxygen species for the cytotoxicity. Deprenyl also protected the cells from the decrease of the Redox capavity by N-methylsalsolinol. However, antioxidants did not protect the cells from the cytotoxicity of the catechol isoquinolinium ion. The results suggest that oxidative stress induced by hydroxyl radical may be involved in the cell death of dopaminergic neurons by N-methylsalsolinol.

Cell Differentiation↗
PubMed1998

Adrenomedullin suppresses atrial natriuretic factor (ANF) secretion from isolated atrium.

Atrial natriuretic factor (ANF) secretion was studied using isolated perfused right atria prepared from rats. Adrenomedullin (ADM), a recently identified 52-amino acid peptide whose biological activity has a striking resemblance to that of ANF, was added to the perfusate at a concentration of 1 microg/ml. The concentration of ANF secreted into the perfusate was measured by radioimmunoassay, under basal conditions (atrial wall unstressed), and during atrial distention (intraluminal pressure raised to 4 and to 6 cm water). It was found that basal secretion of ANF was not altered by ADM. However, when intraluminal pressure was raised, there was a significantly smaller increase in ANF secretion in the ADM-infused atria than in the control atria. It is concluded that ADM significantly reduces stretch-induced secretion of ANF, while having only minimal effects on basal secretion. Such an inhibitory mechanism would ensure the necessary negative feedback mechanism to counter the previously-reported stimulatory actions of ANF on ADM secretion. Moreover, these results support the hypothesis that ADM could be responsible for the reduction in stretch-induced ANF release observed during pregnancy.

Adrenomedullin↗
PubMed1998

Deamination of methylamine and aminoacetone increases aldehydes and oxidative stress in rats.

Semicarbazide-sensitive amine oxidase (SSAO)-mediated deamination of methylamine and aminoacetone in vitro produces carbonyl compounds, such as formaldehyde and methylglyoxal, which have been proposed to be cytotoxic and may be responsible for some pathological conditions. An HPLC procedure was developed to assess different aldehydes, which were derivatized with 2,4-dinitrophenylhydrazine (DNPH). We have demonstrated in vivo deamination of methylamine and aminoacetone by examining the excretion of formaldehyde and methylglyoxal, respectively, in rats. Following chronic administration of methylamine, the urinary level of malondialdehyde (MDA), an end product of lipid peroxidation, was also found to be substantially increased. A selective SSAO inhibitor blocked the increase of MDA. The results support the idea that increased SSAO-mediated deamination of methylamine and aminoacetone can be a potential cytotoxic risk factor.

Acetaldehyde↗
PubMed1998

The human homolog of rat Jagged1 expressed by marrow stroma inhibits differentiation of 32D cells through interaction with Notch1.

A cDNA clone encoding the human homolog of rat Jagged1 was isolated from normal human marrow. Analyses of human stromal cell lines indicate that this gene, designated hJagged1, is expressed by marrow stromal cells typified by the cell line HS-27a, which supports the long-term maintenance of hematopoietic progenitor cells. G-CSF-induced differentiation of 32D cells expressing Notch1 was inhibited by coculturing with HS-27a. A peptide corresponding to the Delta/Serrate/LAG-2 domain of hJagged1 and supernatants from COS cells expressing a soluble form of the extracellular portion of hJagged1 were able to mimic this effect. These observations suggest that hJagged1 may function as a ligand for Notch1 and play a role in mediating cell fate decisions during hematopoiesis.

Adult↗
PubMed1998

TAP-independent delivery of antigenic peptides to the endoplasmic reticulum: therapeutic potential and insights into TAP-dependent antigen processing.

We have taken several approaches to investigate the capacity of the secretory pathway to liberate major histocompatibility complex (MHC) class I-restricted antigenic peptides from precursor polypeptides. Cells lacking the peptide transporter (TAP) are unable to deliver peptides from cytosolic antigens to class I molecules. TAP can be bypassed by targeting peptides directly to the endoplasmic reticulum (ER) using NH2-terminal signal sequences. This results in the generation of enormous numbers of MHC class I complexes (50,000 peptides/cell), and recombinant vaccinia viruses expressing such peptides are highly immunogenic. In contrast to signal sequence-targeted peptides, peptides are liberated very inefficiently from internal locations in ER-targeted full-length proteins, indicating that the secretory pathway has a limited capacity for generating antigenic peptides from most polypeptide contexts. We have, however, identified a location in proteins from which peptides can be liberated in numerous contexts in the secretory pathway. Placing a number of different peptides at the COOH termini of a secreted protein and two proteins with type II membrane anchors resulted in their TAP-independent presentation. These findings demonstrate that the secretory compartment possesses proteases able to liberate COOH-terminal antigenic peptides from virtually any context, entirely consistent with a role for these proteases in the processing of TAP-transported antigenic peptide precursors.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1998

Pregnancy-induced changes in central response to atrial distension mimicked by progesterone metabolite.

In virgin female rats, atrial distension (an index of blood volume expansion) causes an increase in c-fos expression in the paraventricular nucleus of the lateral hypothalamus. During pregnancy, this response is markedly attenuated. We tested the effects of 3alpha-hydroxy-5alpha-pregnan-20-one (3alpha-OH-DHP) on activation of central pathways following stimulation of the atrial volume receptors. Not only does this progesterone metabolite increase during pregnancy, but it has already been implicated in pregnancy-induced changes in the baroreflex. Female rats were prepared with indwelling venous cannulas and intracardiac balloons that, when inflated, caused a discrete localized stimulation of the atrial volume receptors in the absence of changes in cardiac hemodynamics. Seven days later, the rats were infused with 3alpha-OH-DHP dissolved in cyclodextrin and the intracardiac balloons were inflated. One hour later, the rats were killed and fixed by perfusion and the brains were prepared for visualization of c-fos activity. Infusion with 3alpha-OH-DHP significantly reduced the central response to atrial distension, i.e., it mimicked pregnancy. These results are consistent with the suggestion that this metabolite of progesterone may be an important factor in cardiovascular adaptation to pregnancy.

Animals↗
PubMed1998

[Protection of hypertonic saline/mannitol to thymic cell apoptosis induced by endotoxin (LPS) in mice].

To observe the effect of HSM (hypertonic saline/mannitol) on thymic cell apoptosis induced by endotoxin (LPS) in mice, twenty-four mice were divided into three groups (8 mice/each group): 1. Control group, each mouse was intraperitonealy injected with normal saline; 2. LPS group, each mouse was intraperitonealy injected with LPS; 3. LPS + HSM group, each mouse was intraperitonealy injected with HSM before and after injection of LPS. The results showed that the percentage of apoptosis of HSM + LPS group was lower than that of LPS group (P < 0.01); the ladder of nucleosomal DNA fragments by agarose gel eletrophoresis of HSM group was not typical as compared with that of LPS group. It is suggested that HSM might protect the apoptosis of mouse thymic cell induced by LPS and may improve the immune function.

Adjuvants, Immunologic↗
PubMed1998

[Mechanism of CD44V6 in human colorectal carcinoma metastasis].

OBJECTIVE: To study the mechanism of CD44V6 in human colorectal carcinoma (HCC) matastasis. METHODS: The effects of CD44V6 on HCC cell adhering to base membrane and vascular endothelium were investigated by human amniotic membrane invasion model and co-culturing HCC cell with vascular endothelium. The influence of CD44V6 variants on cytoskeleton and gap junctional intercellular communication (GJIC) was studied by immunofluorescent confocal 3-dimensional reconstruction and fluorescence recovery after photobleaching technique. RESULTS: CD44V6 antibody can decrease the ability of HCC cells to adhere to amniotic membrane and vascular endothelium. It also can affect the distribution, polymerization and depolymerization of actin of HCC cells, but does not significantly affect GJIC of HCC cells. CONCLUSIONS: CD44V6 may play an important role in promoting HCC cells to adhere to vascular endothelium and base membranes and may affect the distribution, polymerization and depolymerization of actin in HCC cells and facilitate HCC cell metastasis.

Coculture Techniques↗
PubMed1998

[Expression of CD44V6 and its effects on cytoskeleton in human colorectal carcinoma cell lines].

OBJECTIVE: To observe the expression of CD44V6 and its effects on cytoskeleton in human colorectal carcinoma(HCC) HT29 and LoVo cell lines. METHODS: Expression of CD44V6 variant in HCC HT29 and LoVo cell lines was investigated by in situ hybridization, immunohistochemistry and quantitative immunofluorescence technique. The effects of CD44V6 variants on cytoskeleton was studied by immunofluorescence and confocal 3 dimension reconstruction technique. RESULTS: CD44V6 was expressed at the mRNA and protein levels in both HT29 and LoVo cell lines, but the expression was higher in LoVo cells than in HT29 cells. When the HT29 cells and LoVo cells were blocked by monoclonal antibodies, it was found that changes developed in the cytoskeleton of these cells. CONCLUSIONS: The expression of CD44V6 is related to the metastatic potentiality of human colorectal carcinoma cells. CD44V6 may affect the distribution, polymerization and depolymerization of actin of HCC cells and promote HCC cell metastasis.

Actins↗
PubMed1998

[Clinical observation and anatomical analysis of middle turbinate and ethmoidal internal wall moved to external side after microsurgery].

OBJECTIVE: To assess the effect of middle turbinate (MT) and ethmoidal internal wall(EIW) moved externally after microsurgery. METHODS: Twenty-four cases (45 sides) were followed-up endoscopically for (16.3 +/- 9.3) months. Thirteen cases (24 sides) were observed by CT scans. Three cadaver heads were measured for anatomical analysis. RESULTS: Forty-one (91%) of 45 sides obtained better olfactory function after operation. Twenty-two (91%) of 24 sides were found to have better CT changes in sinus ventilation as compared with preoperative CT scans. The gap between the MT and EIW to the orbital wall was (12.0 +/- 1.0) mm, while that between the ethmoidal bulla and processus uncinatus was only (2.3 +/- 0.6) mm as revealed in the autopsy. CONCLUSION: MT and EIW moderately moved suitably to externally had no bad effect on sinus ventilation, and it improved olfaction.

Adolescent↗
PubMed1998

[Histopathology observations of the facial nerve on dehiscence of the facial nerve canal].

OBJECTIVE: To explore the possible histopathologic changes induced by the seriously defective epinurium on congenital dehiscent facial nerve canal. METHODS: The facial nerves at the dehiscent facial nerve canal of 885 human temporal bones from otopathology laboratory of the University of Minnesota, USA were observed histopathologically under light microscope. RESULTS: It showed that the seriously defective epineurium at the dehiscence was found in 48 ears. Of the 48 ears, the facial nerves in forty ears had herniated out from the dehiscence area, in thirteen ears on the outgrowing facial nerve had at the dehiscence areas and facial nerves in three ears with otitis media was obviously infiltrated with inflammatory cells. No similar pathologic change was found in all the 837 ears with the dehiscence covered by epineurium. CONCLUSION: The seriously defective epineurium at the dehiscencesite is a histological cause for the herniation of facial nerve and formation of outgrowing Schwannomas and inflammatory infiltration of facial nerve.

Facial Nerve↗
PubMed1998

[The responses of the microvasculature of the periodontal ligament to horizontal force].

OBJECTIVE: The purpose of this study is to examine the responses of the microvasculature in periodontal ligament(PDL) to horizontal force. METHODS: Using ink injections and celloidin embed, serial sections were cut, then observed by light micrascope, quantitative analysis was conducted by the picture-analysis instrument. Vascular corrosion casts were prepared and examined by scanning electron microscopy. The forth premolars of dogs were pulled by 200 g force in a mesial direction for two hours, and the pressure effects in different positions were demonstrated. RESULTS: The section area of the microvasculature per unit PDL area is obvious larger on the tension sides than on the pressure sides. There is not an obvious distinction on the pressure sides between the experiment groups and control groups. However, there are clear distinctions in the one-third of cervical, and apical segment on the tension sides between the experiment groups and control groups. CONCLUSION: The microvascular changes in PDL had importance to the cushioning effect of PDL when a teeth received a kind of force in a short-time.

Animals↗
PubMed1998

[Electronic speckle pattern interferometric analysis on force distribution of different mandibular unilateral free-end dentures].

OBJECTIVE: To study the force distribution of three kinds of mandibular unilateral free-end partial denture under vertical loading on the artificial tooth. METHODS: A fresh mandible with right 2nd and 3rd molars missing was restored with cantilever fixed partial denture (CFD), casting three arm clasp removable partial denture (CCD) and RPI removable partial denture (RPID) respectively. The force distribution on the surface of supporting bone was studied by using electronic speckle pattern interferometry (ESPI). The ESIP was displayed real-time and recorded. The fringes determining was prossed by microcomputer image processing. The corresponding out of plane displacement of the supporting bone was measured and analyzed. RESULTS: Showed all of the three kinds of dentures contribute to transmit stress to supporting bone. The corresponding out of plane displacement of supporting bone decreased, the degree of decrease was CFD < CCD < RPID in order. CONCLUSION: This finding provides a useful reference for design of denture construction.

Adult↗
PubMed1998

[Morphometrical study on inhibitory effect of vitamin B6 and banana-stem extract on calcium crystallization].

OBJECTIVE: To search for the anticrystallization mechanism by vitamin B(6) and banana stem extract. METHOD: Thirty-six male China-1 mice were divided into 4 groups: normal, crystallization, vitamin B(6) and banana-stem extract groups. Calcium oxalate crystallization was induced by 1% glycol and 1% ammonium chloride in the last 3 groups. Vitamin B(6) was then given to the 3rd group and banana stem extract to the 4th group for 3 weeks. At the end of 3 weeks, all the mice were sacrificed and the kidneys were taken for morphometrical studies using image analysis system and assayed for calcium oxalate. RESULT: Morphometrical area density and numerical density of crystallization was significantly less in the vitamin B(6) group and the banana-stem extract group as compared with the crystallization group, being the least in the banana-stem extract group. Oxalate in renal tissue was also significantly reduced. Both vitamin B(6) and banana stem extract had no effect on renal tissue calcium. CONCLUSION: Vitamin B(6) and banana-stem extract may be useful agents in the treatment of patients with hyperocaluric urolithiasis.

Animals↗