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Y Sheng

Publications and source records attributed to Y Sheng.

At least 37 records · Page 2Linked to original sources
PubMed2000

The classical progesterone receptor mediates Xenopus oocyte maturation through a nongenomic mechanism.

Xenopus laevis oocytes are physiologically arrested at G(2) of meiosis I. Resumption of meiosis, or oocyte maturation, is triggered by progesterone. Progesterone-induced Xenopus oocyte maturation is mediated via an extranuclear receptor and is independent of gene transcription. The identity of this extranuclear oocyte progesterone receptor (PR), however, has remained a longstanding problem. We have isolated the amphibian homologue of human PR from a Xenopus oocyte cDNA library. The cloned Xenopus progesterone receptor (xPR) functioned in heterologous cells as a progesterone-regulated transcription activator. However, endogenous xPR was excluded from the oocyte nucleus and instead appeared to be a cytosolic protein not associated with any membrane structures. Injection of xPR mRNA into Xenopus oocytes accelerated the progesterone-induced oocyte maturation and reduced the required concentrations of progesterone. In enucleated oocytes, xPR accelerated the progesterone-induced mitogen-activated protein kinase activation. These data suggest that xPR is the long sought after Xenopus oocyte receptor responsible for progesterone-induced oocyte maturation.

Animals↗
PubMed2000

Down-regulation of X-linked inhibitor of apoptosis protein induces apoptosis in chemoresistant human ovarian cancer cells.

Cisplatin-centered chemotherapy is a key treatment for ovarian cancer, but resistance to chemotherapeutic agents remains a major cause of treatment failure. Multiple factors are known to contribute to the development of this chemoresistance. Although it has been demonstrated that X-linked inhibitor of apoptosis protein (Xiap) prevents apoptosis by inhibiting effector caspases, if and how it is important in chemoresistance in ovarian cancer has not been studied. The effects of Xiap down-regulation and/or restoration of wild type p53 by recombinant adenovirus infection were examined on four ovarian epithelial cancer cell lines [C13*, A2780-s (wild type p53), A2780-cp (mutant p53), and SKOV3 (null p53)]. Apoptosis and protein expression (e.g., Xiap, caspase-3, p53, MDM2, and p21waf1) were assessed by Hoechst 33258 stain and Western blot, respectively. We demonstrated that Xiap down-regulation following adenoviral antisense expression induces apoptosis in the wild-type p53 cells, but not in the mutated or null cells. Xiap down-regulation resulted in caspase-3 activation, caspase-mediated MDM2 processing, and p53 accumulation. Restoration of wild type p53 in the p53-mutated or -null cells significantly enhanced the proapoptotic effect of Xiap antisense expression. Down-regulation of Xiap induced apoptosis in chemoresistant ovarian cancer cells, a process dependent on p53 status.

Adenocarcinoma↗
PubMed2000

Structural and functional similarities in the ADP-forming amide bond ligase superfamily: implications for a substrate-induced conformational change in folylpolyglutamate synthetase.

Comparison of the three-dimensional structures of folylpolyglutamate synthetase (FPGS) and the bacterial cell wall ligase UDP-N-acetylmuramoyl-l-alanine:d-glutamate ligase (MurD) reveals that these two enzymes have a remarkable structural similarity despite a low level of sequence identity. Both enzymes have a modular, multi-domain structure and catalyse a similar ATP-dependent reaction involving the addition of a glutamate residue to a carboxylate-containing substrate, tetrahydrofolate in the case of FPGS, and UDP-N-acetylmuramoyl-l-alanine in the case of MurD. Site-directed mutations of selected residues in the active site of Lactobacillus casei FPGS (P74A, E143A, E143D, E143Q, K185A, D313A, H316A, G411A and S412A) showed that most of these changes resulted in an almost complete loss of activity. Several of these amino acid residues in FPGS are found in structurally equivalent positions to active-site residues in MurD. Some insights into the function of these residues in FPGS activity are proposed, based on the roles surmised from the structures of two MurD. UDP-N-acetylmuramoyl-l-alanine.ADP complexes and a MurD. UDP-N-acetylmuramoyl-l-alanine-d-glutamate complex. Furthermore, the comparison has led us to propose that conformational changes induced by substrate binding in the reaction mechanism of FPGS result in a movement of the domains towards each other to more closely resemble the orientation of the corresponding domains in MurD. This relative domain movement may be a key feature of this new family of ADP-forming amide bond ligases.

Adenosine Diphosphate↗
PubMed2000

Coronavirus-induced membrane fusion requires the cysteine-rich domain in the spike protein.

The spike glycoprotein of mouse hepatitis virus strain A59 mediates the early events leading to infection of cells, including fusion of the viral and cellular membranes. The spike is a type I membrane glycoprotein that possesses a conserved transmembrane anchor and an unusual cysteine-rich (cys) domain that bridges the putative junction of the anchor and the cytoplasmic tail. In this study, we examined the role of these carboxyl-terminal domains in spike-mediated membrane fusion. We show that the cytoplasmic tail is not required for fusion but has the capacity to enhance membrane fusion activity. Chimeric spike protein mutants containing substitutions of the entire transmembrane anchor and cys domain with the herpes simplex virus type 1 glycoprotein D (gD-1) anchor demonstrated that fusion activity requires the presence of the A59 membrane-spanning domain and the portion of the cys domain that lies upstream of the cytoplasmic tail. The cys domain is a required element since its deletion from the wild-type spike protein abrogates fusion activity. However, addition of the cys domain to fusion-defective chimeric proteins was unable to restore fusion activity. Thus, the cys domain is necessary but is not sufficient to complement the gD-1 anchor and allow for membrane fusion. Site-specific mutations of conserved cysteine residues in the cys domain markedly reduce membrane fusion, which further supports the conclusion that this region is crucial for spike function. The results indicate that the carboxyl-terminus of the spike transmembrane anchor contains at least two distinct domains, both of which are necessary for full membrane fusion.

Amino Acid Sequence↗
PubMed2000

Cell cycle-dependent regulation of N-acetylglucosaminyltransferase-III in a human colon cancer cell line, Colo201.

The mechanism for cell-cycle-dependent regulation of N-acetylglucosaminyltransferase III (GnT-III) activity was investigated using synchronized culture of Colo201, a human colon cancer cell line. In the synchronized culture, it was found that GnT-III activity rapidly increased in the M phase and the maximal activity was five times higher than the basal level found in the G1 phase. Northern blot and Western blot analyses revealed that the increase in the activity is due not to an increase in expression level of its mRNA but, rather, to the level of protein. Furthermore, it was shown by a pulse-chase experiment that the increased protein level of GnT-III is the result of its prolonged turnover rate. Lectin blotting with erythroagglutinating phytohemagglutinin showed that the content of bisecting N-acetylglucosamine structure in glycoproteins was transiently increased during the M phase in conjunction with the increased activity of GnT-III. These results suggest that GnT-III activity undergoes a cell-cycle-dependent regulation and thereby oligosaccharide structures of N-glycans vary specifically during the M phase of the cell cycle. Thus, it is possible that the cell-cycle-dependent alteration of N-glycans by GnT-III might play a role in biological events, such as the progression of cell cycle and cell division.

Aphidicolin↗
PubMed2000

Enhanced DNA repair, immune function and reduced toxicity of C-MED-100, a novel aqueous extract from Uncaria tomentosa.

Female W/Fu rats were gavaged daily with a water-soluble extract (C-MED-100) of Uncaria tomentosa supplied commercially by CampaMed at the doses of 0, 5, 10, 20, 40 and 80 mg/kg for 8 consecutive weeks. Phytohemagglutinin (PHA) stimulated lymphocyte proliferation was significantly increased in splenocytes of rats treated at the doses of 40 and 80 mg/kg. White blood cells (WBC) from the C-MED-100 treatment groups of 40 and 80 mg/kg for 8 weeks or 160 mg/kg for 4 weeks were significantly elevated compared with controls (P < 0.05). In a human volunteer study, C-MED-100 was given daily at 5 mg/kg for 6 consecutive weeks to four healthy adult males. No toxicity was observed and again, WBC were significantly elevated (P < 0.05) after supplement. Repair of DNA single strand breaks (SSB) and double strand breaks (DSB) 3 h after 12 Gy whole body irradiation of rats were also significantly improved in C-MED-100 treated animals (P < 0.05). The LD50 and MTD of a single oral dose of C-MED-100 in the rat were observed to be greater than 8 g/kg. Although the rats were treated daily with U. tomentosa extracts at the doses of 10-80 mg/kg for 8 weeks or 160 mg/kg for 4 weeks, no acute or chronic toxicity signs were observed symptomatically. In addition, no body weight, food consumption, organ weight and kidney, liver, spleen, and heart pathological changes were found to be associated with C-MED-100 treatment.

Adult↗
PubMed2000

Treatment of chemotherapy-induced leukopenia in a rat model with aqueous extract from Uncaria tomentosa.

The Uncaria tomentosa water extracts (C-Med-100) depleted of indole alkaloids (< 0.05%, w/w) have been shown to induce apoptosis and inhibit proliferation in tumor cells in vitro and to enhance DNA repair, mitogenic response and white blood cells in vivo. In this study, the effect of C-Med-100 in the treatment of chemically induced leukopenia was evaluated in a rat model. W/Fu rats were treated first with doxorubicin (DXR) 2 mg/kg x 3 (i.p. injection at 24 hour-intervals) to induce leukopenia. Twenty-four hours after the last DXR treatment, the rats were daily gavaged with C-Med-100 for 16 consecutive days. As a positive control, Neupogen, a granulocyte colony stimulator was also administered by subcutaneous injection at a dose of 5 and 10 microg/ml for 10 consecutive days. The results showed that both C-Med-100 and Neupogen treatment groups recovered significantly sooner (p < 0.05 by Duncan test) than DXR group. However, the recovery by C-Med-100 treatment was a more natural process than Neupogen because all fractions of white blood cells were proportionally increased while Neupogen mainly elevated the neutrophil cells. These results were also confirmed by microscopic examination of the blood smears. The mechanism of the C-Med-100 effect on WBC is not known but other data showing enhanced effects on DNA repair and immune cell proliferative response support a general immune enhancement.

Administration, Oral↗
PubMed2000

[Preclinical study of preimplantation genetic diagnosis in animal].

OBJECTIVE: To perform preimplantation genetic diagnosis (PGD) in transgenic mice. METHODS: Single blastomere from murine heterozygous pre-embryo at 4 or 8-cell stage was sampled by microbiopsy for detection of the human gene delta F508 mutation of cystic fibrosis and biopsied pre-embryo was transferred to Swiss mice foster mothers. delta F508 mutation detection on the single blastomere was performed with nested polymerase chain reaction(PCR). RESULTS: (1) Significant difference was not observed statistically for the in vitro hatching rate (n = 102), the birth rate (n = 79), birth weight and organ weight (n = 133) at 3 weeks after births between mice born from biopsied embryos and controls. (2) Thirty-two nested PCR were performed for the diagnosis of the cystic fibrosis delta F508 mutation, with 100.0% specificity and 100.0% sensitivity. CONCLUSIONS: Microbiopsy of pre-embryos with 4 or 8-cells did not alter their viability and further development. The technique of nested PCR on a single blastomere for the detection of cystic fibrosis delta F508 mutation is reliable.

Animals↗
PubMed2000

[A comparison between latanoprost and timolol in treatment of patients with primary open-angle glaucoma and ocular hypertension].

OBJECTIVE: To evaluate the therapeutic value of latanoprost on glaucoma. METHODS: In an open-label fashion, multicenter, randomized control clinical trial, the efficacy and adverse drug reactions of topical application of 0.005% latanoprost once daily were compared with that of 0.5% timolol twice daily for 12 weeks in patients with open-angle glaucoma or ocular hypertension. RESULTS: The study included 128 patients (63 patients in latanoprost group and 65 patients in timolol group) and 117 patients remained at the end of the study (60 cases in latanoprost group and 57 cases in timolol group). Comparing 12 weeks with baseline diurnal intraocular pressure (IOP), the IOP reduction (mean +/- standard deviation) in latanoprost group was (7.5 +/- 0.3) mm Hg (1 mm Hg = 0.133 kPa) (32%, t = 22.73, P < 0.0001) greater than the reduction in timolol group (6.1 +/- 0.3) mm Hg (26%, t = 17.94, P < 0.0001), the difference between the two groups being significant (F = 9.54, P = 0.0026). Two patients treated with timolol and none treated with latanoprost were withdrawn from the study because of inadequate IOP control; 3 patients with latanoprost had foreign body sensation. In latanoprost group, there was one patient whose eyelashes became darker and longer at the last visit (the 12th week). No ocular and systemic adverse events related to the two drugs were found. CONCLUSION: It is demonstrated that 0.005% latanoprost topically applied once daily is well tolerated and more effective in reducing IOP than 0.5% timolol topically applied twice daily. Thus, latanoprost has the potential to be a new first-line antiglaucoma drug.

Adrenergic beta-Antagonists↗
PubMed2000

[Analysis of postoperative astigmatism after phacoemulsification with intraocular lens implantation].

OBJECTIVE: To study the corneal astigmatism and the changes of surgically induced astigmatism after phacoemulsification with intraocular lens (IOL) implantation. METHODS: Thirty-eight eyes of 38 patients treated with phacoemulsification through a superior inversed frown shaped scleral incision were examined by corneal topography and auto-ref-keratometer preoperatively, one day, one month and three months postoperatively. RESULTS: The postoperative corneal astigmatism at one day, one month and three months were (1.10 +/- 0.71), (1.08 +/- 0.66) and (0.87 +/- 0.55) D respectively. There was no statistic significance between the postoperative astigmatism at three months and at preoperative one day (P > 0.05). The mean surgically-induced astigmatism at postoperative one day, one month and three months were (1.37 +/- 1.03), (1.24 +/- 0.93) and (1.04 +/- 0.75) D respectively. There was significant difference between the astigmatism at three months and at one day postoperatively (P < 0.05). CONCLUSIONS: The superior inversed frown shaped scleral small incision with no suture has little effect on corneal astigmatism. Vector analysis can systemically evaluate surgically induced astigmatism. The results of corneal topography are more reliable to reflect changes in corneal curvature than that of auto-ref-keratometer, and corneal topography has more important clinical value in evaluating surgically induced astigmatism.

Astigmatism↗
PubMed1998

Anti-beta 2-glycoprotein I autoantibodies from patients with the "antiphospholipid" syndrome bind to beta 2-glycoprotein I with low affinity: dimerization of beta 2-glycoprotein I induces a significant increase in anti-beta 2-glycoprotein I antibody affinity.

"Antiphospholipid" autoantibodies are associated with arterial and venous thrombosis, recurrent fetal loss, and thrombocytopenia. At present, the best-characterized antigenic target for these autoantibodies (or Abs) is the phospholipid-binding protein beta2-glycoprotein I (beta2GPI). These Abs bind beta2GPI only in the presence of negatively charged phospholipids or microtiter polystyrene plates that have been specially treated to give the surface a negative charge. To determine whether the binding of these Abs to beta2GPI on negatively charged surfaces is dependent on increased density or neo-epitopes formed as a consequence of a conformational change on beta2GPI, we generated mutants of beta2GPI by site-directed mutagenesis and assessed the binding characteristics of anti-beta2GPI Abs to these mutants. Our results demonstrate that mutant F307*, which spontaneously forms significant dimerization, is bound best by all the anti-beta2GPI Abs in an anti-beta2GPI ELISA using irradiated polystyrene microtiter plates. In addition, these Abs bound mutant F307* coated onto standard polystyrene microtiter wells in the absence of phospholipid, whereas there was minimal binding with wild-type and mutant F307*/C288A, which formed minimal dimerization. Affinity-purified anti-beta2GPI Abs from patients with the antiphospholipid syndrome demonstrated significantly higher binding affinity for mutant F307* in fluid phase than for wild-type or mutant F307*/C288A of beta2GPI. These results demonstrate that autoantibody binding to beta2GPI is intrinsically of low affinity and that the binding is dependent on the density of the Ag and not on neo-epitope formation.

Amino Acid Sequence↗
PubMed1998

Current insights into the "antiphospholipid" syndrome: clinical, immunological, and molecular aspects.

Advances in defining the target antigen(s) for the autoantibodies in the APS highlight the inadequacies of the current classification of these autoantibodies into anticardiolipin and LA antibodies. The discovery that beta 2GPI is the target antigen for the autoantibodies detected in solid-phase immunoassays has opened a number of areas of research linking these autoantibodies to atherogenesis and thrombus formation. Although the role of beta 2GPI in the regulation of blood coagulation in unclear, current evidence suggests that anti-beta 2GPI antibodies interfere with its "normal" role and appear to promote a procoagulant tendency. The expansion of research in this area and the diversity of the clinical manifestations of patients with APS have resulted in the inclusion of molecular biologists and pharmaceutical companies joining immunologists, hematologists, rheumatologists, obstetricians, neurologists, vascular surgeons, and protein and lipid biochemists in attempting to understand the pathophysiology of this condition. Although the published literature may result in conflicting results and introduce new controversies, developing standardized laboratory methods and extrapolation of in vitro experimental results to the vivo situation will advance our understanding of the regulation of the immune system and its interaction with normal hemostatic mechanisms. Since the authors' last review in 1991, the study and understanding of the pathophysiology of APS have evolved from lipid biochemistry to molecular techniques that may eventually provide specific therapies for the clinical manifestations of this condition. Although current treatment has improved the morbidity associated with this condition, especially in improving pregnancy outcomes, future therapies, as outlined in this review, may specifically address the biological abnormalities and have fewer side effects. Better diagnostic tools, such as magnetic resonance imaging with perfusion studies, will allow the study of the true incidence and prevalence of vascular flow changes/tissue ischemia and infarction associated with aPL antibodies and help determine treatment and prophylaxis for APS patients. APS is still the only hypercoagulable condition where both arterial and venous beds can be affected independently or in the same individual.

Antibodies, Antiphospholipid↗
PubMed1998

DNA repair enhancement by a combined supplement of carotenoids, nicotinamide, and zinc.

Four volunteers were involved for 5 weeks of a baseline period, followed by 7 weeks of a combined supplementation of nicotinamide, zinc, and carotenoids (Nicoplex). Blood sampling and bioassays were carried out every week during the evaluation period. The supplementation of Nicoplex resulted in statistically significant increased resistance to DNA single-strand breaks induced by H2O2 (DNA retained on filter % from 46.7 +/- 1.9 to 59.4 +/- 4.3; p < 0.01), increased DNA repair 60 min after induction of damage (DNA retained on filter % from 74.6 +/- 4.8 to 88.3 +/- 4.2; p < 0.01), elevated poly (ADP-ribose) polymerase (PARP) activity (p < 0.05), and an increased proliferative response to phytohemagglutinin (PHA) (p < 0.05) when compared with the levels before supplementation. However, when the same subjects were supplemented with nicotinamide, zinc, and carotenoids together with another 17 nutrients or minerals, there were no changes in DNA damage, DNA repair, or proliferative response to PHA. Through the use of a rat model, DNA repair of splenocytes 3 h after 12 Gy whole-body irradiation was significantly enhanced in rats supplemented with Nicoplex for 6 weeks (p < 0.05) and 8 weeks (p < 0.01). Comparison of Nicoplex and its components administered separately revealed that there was an additive effect on DNA repair for both single- and double-strand breaks (both p < 0.05). On the basis of the results, it is hypothesized that the enhanced effect of combined supplement of nicotinamide, zinc, and carotenoids on DNA repair depends on their diversified mechanisms of action while multinutrient supplementation may compromise the effects by inhibitory interactions including uptake and absorption.

Adult↗
PubMed1998

Beta2-glycoprotein I: target antigen for 'antiphospholipid' antibodies. Immunological and molecular aspects.

It has become clear that beta2-glycoprotein I (beta2GPI) is the most common and best-characterised antigenic target for 'antiphospholipid' (aPL) autoantibodies. These antibodies preferentially bind beta2GPI that has been immobilised on anionic phospholipid membranes or certain synthetic surfaces. These surfaces appear to act by increasing antigen density to allow binding of intrinsically low-affinity anti-beta2GPI autoantibodies. Binding of beta2GPI in fluid phase is weak and requires high concentrations of beta2GPI. Our understanding of the pathophysiology of the 'Antiphospholipid' Syndrome (APS) has increased exponentially with the number of studies into the interactions of aPL antibodies and beta2GPI.

Antibodies, Anticardiolipin↗
PubMed1997

Remodeling of glycoconjugates on CD44 enhances cell adhesion to hyaluronate, tumor growth and metastasis in B16 melanoma cells expressing beta1,4-N-acetylglucosaminyltransferase III.

Beta1-4 N-acetylglucosaminyltransferase III (GnT-III) synthesizes bisecting N-acetylglucosamine structures on asparagine-linked oligosaccharides. Using B16-hm mouse melanoma cells stably expressing GnT-III activity as positive transfectants, the effect of bisecting N-acetylglucosamine on the function of CD44 was analyzed in association with adhesion to hyaluronate and tumor spread in mice. Transfection of GnT-III caused increased affinity of immunoprecipitated CD44 to erythro-agglutinating phytohemagglutinin, that preferentially recognizes bisecting N-acetylglucosamine, without affecting the surface CD44 amount, indicating an increase in bisecting N-acetylglucosamine residues on CD44 in positive transfectants. CD44-mediated adhesion to immobilized hyaluronate and the binding of fluorescence-labeled hyaluronate to the cell surface were increased in positive transfectants. The enhanced adhesion in positive transfectants was suppressed by the treatment with beta-N-acetylhexosaminidase, indicating that N-acetylglucosamine residues were responsible for the enhanced adhesion. Positive transfectants showed promoted CD44-mediated tumor growth and metastatic development in the spleen after subcutaneous inoculation into mice. These results indicate that glycosylation of CD44 due to GnT-III causes enhanced adhesion to hyaluronate, local tumor growth and metastatic growth in spleen, suggesting that the CD44-mediated adhesion and tumor spread can be modified through introduction of a glycosyltransferase gene.

Acetylglucosamine↗
PubMed1997

Cloning and characterization of the gene encoding the mouse beta 2-glycoprotein I.

beta 2-Glycoprotein I, a serum protein with in vitro anticoagulant properties, plays a vital role in the binding of "anticardiolipin" antibodies purified from patients with autoimmune disease in a cardiolipin ELISA. The gene (ApoH) encoding the mouse beta 2-glycoprotein I, including 5' and 3' flanking sequences, has been isolated and characterized. The gene covers approximately 18 kb and consists of eight exons. We demonstrate that the gene is present in a single copy in the mouse genome. The exon/intron structure was elucidated by nucleotide sequencing and restriction enzyme mapping. The exon/intron splice junction sites follow the gt/ag consensus sequence rule. The transcription start site was identified by primer extension 44 nucleotides upstream of the initiator AUG codon. beta 2-Glycoprotein I consists of repeated domains that correspond well to the exon/intron structure of the gene.

Animals↗
PubMed1997

Transplantation of RPE in age-related macular degeneration: observations in disciform lesions and dry RPE atrophy.

UNLABELLED: A study was carried out to investigate whether human RPE allografts are tolerated or rejected in the subretinal space and to determine the feasibility of RPE transplantation in subjects with age-related macular degeneration (AMD). METHODS: Patches of human fetal RPE (13-20 weeks of gestational age) were transplanted into the subretinal space of five patients after surgical removal of subfoveal fibrovascular membranes, and to four subjects with dry geographic atrophy. Suspensions of RPE cells were transplanted to four other patients with nonexudative AMD. Results were evaluated with clinical ophthalmological examination, SLO microperimetry and fluorescein angiography over 8-20 months. RESULTS: In disciform lesions, RPE transplants developed macular edema and fluorescein leakage concomitant with gradual reduction of visual acuity, implying host-graft rejection, over 1-6 months. In geographic atrophy, three of four transplants showed little change in shape and size after 12 months (one transplant was slowly rejected). In non-exudative AMD, RPE suspension transplants showed no evidence of rejection and were associated with the disappearance of drusen; visual acuity remained stable and SLO microperimetry confirmed retinal function over the transplanted area. CONCLUSION: Human RPE allografts are not invariably rejected in the subretinal space without immunosuppression. The rejection rate is lower in nonexudative than in neovascular AMD. An intact blood-retinal barrier is likely to protect against rejection. It is technically feasible to transplant human RPE into the submacular space without adversely affecting visual function in nonexudative AMD over relatively long periods of time.

Aging↗