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S Wang

Publications and source records attributed to S Wang.

At least 415 records · Page 23Linked to original sources
PubMed2000

FISH analysis of an AML-M5a with segmental rearrangements involving 11q23-MLL region.

A 66-year-old man was diagnosed 10 years ago with thrombocytosis and treated with hydroxyurea. Recently, his condition deteriorated and he was found to have 68% blasts in the blood and AML-M5a. Conventional cytogenetic analysis and fluorescence in situ hybridization studies using 11-painting and MLL probes showed that chromosome 11 had duplications or triplications; the markers were also derived from the chromosome 11-MLL region. Therefore, we have demonstrated segmental rearrangement of chromosome 11 involving the MLL region resulting in multiple copies of the MLL gene.

Aged↗
PubMed2000

[Protection of metallothionein on the peroxidative injury in testis induced by cadmium].

In order to study the protection effect of metallothionein (MT) on peroxidative injury in testis induced by cadmium and to detect the mechanism of reproduction toxicity of cadmium, the SD rats were injected intraperitoneally with different doses of cadmium (0.2, 0.4 and 0.8 mg/kg BW) for 7 days. The content of MT, the activities of antioxidases and the content of malondialdehyde(MDA) in testis were detected. The results showed that the increase of MT content in the low dose group was not obvious. MT content increased significantly in the 0.4 mg/kg BW group, while decreased in the 0.8 mg/kg BW group. There was a significant reduction of the activities of superoxide dismutase(SOD) and glutathione peroxidase (GSH-Px) in the high dose group. The content of MDA did not change obviously in the low and middle dose groups, but increased significantly in the high dose group. It was concluded that MT might play an important role in protecting testis from oxidative damage. The toxicity of cadmium on male reproduction might be related to the unbalance of anti-oxidation system including MT.

Animals↗
PubMed2000

[Kinetics of plasma membrane and mitochondrial alterations in HL-60 cells undergoing apoptosis].

In the present study, VP16, an inhibitor of topoisomerase II, and NaN3, a chemical toxic substance, were used to induce apoptosis and necrosis of HL-60 cells, respectively. Cells were examined by transmission electron microscopy and by fluorescence microscopy after staining with Hoechst 33258 at 0, 2, 4, 8, 16 and 24 h of culture. Alterations of fluorescent intensity produced by FDA, Rh 123 and PI were measured by flow cytometry, which reflects sequential changes on plasma membrane permeability and the potential of mitochondrial membrane. The results indicated that the nuclear morphologic alteration of cells treated with VP-16 began at 4 hour of culture and the cells with condensed nucleus culminated at 8 h of culture and then reduced with no drop in cell counts, while the percentage of cells with fragmented nuclei reached its maximum at 24 h of culture accounting for some 80%. The potential of mitochondrial membrane of of apoptotic cells decreased gradually from 8 h of culture and showed obvious decline at 16 h of culture. In necrotic cells, the potential decreased by 50% at 4 h of culture which indicates an earlier and more rapid decline than that in apoptotic cells. Alteration of plasma membrane permeability appeared at 8 h of culture and showed a steady increase over time. It was concluded that plasma membrane permeability and mitochondrial membrane potential could reflect the development and degree of apoptosis, and the combination of these two criteria with nuclear morphology revealed by staining with Hoechst 33258 would be a simple and reliable assay for apoptosis and its progression.

Apoptosis↗
PubMed2000

[Study on plasma lipids, apolipoprotein A1, apolipoprotein B100 in simple obese children].

To investigate the disorder of lipid metabolism and explore the possible mechanism of increasing risk of atherosclerosis(AS) in simple childhood obesity, serum lipids and apolipoprotein were examined. 49 obese children were selected and another 49 non-obese children were selected as control. Their serum lipids (TG, TC, VLDL-ch, HDL-ch and LDL-ch) and apolipoprotein(apoA1 and apoB100) were measured. The results showed TG, VLDL-ch, apoB100, artherosclerosis index (AI) and LDL-ch/HDL-ch ratio in childhood obesity were significantly higher than that in normal children (P < 0.05), while HDL-ch, apoA1, HDL-ch/TC, apoA1/apoB100 ratio in obese children were obviously lower than that in normal ones(P < 0.05). The results suggested that metabolic disorder of lipid and apolipoprotein took place in obese children. The disorder which may increase the risk of AS should be paid great attention.

Adolescent↗
PubMed2000

Determination of harmane and harmine in human blood using reversed-phased high-performance liquid chromatography and fluorescence detection.

A number of tremorogenic beta-carboline alkaloids have been found in common plant-derived foodstuffs, beverages, and inhaled substances. Because of their natural presence in the food chain, there is a growing concern regarding the potential risks of certain essential tremors associated with the long-term, low-level dietary exposure to these alkaloids. The purpose of this study was to develop an effective analytical method to determine blood levels of two major beta-carboline derivatives, harmane and harmine. Human blood was extracted with ethyl acetate and methyl-t-butyl ether (2:98) under an alkaline condition. After evaporation of organic solvent, the samples were reconstructed in methanol. The samples were fractionated on a 250 x 4.6-mm C18 reversed-phase column with an isocratic mobile system consisting of 17.5 mM potassium phosphate buffer (ph 6.5) and methanol (30:70), followed by an on-line fluorescence detection. The method had the detection limit to determine 206 and 81 pg/ml of harmane and harmine, respectively, in 10 ml of human blood. The intraday precision (C.V.) at 25 ng/ml was less than 6.7 and 3.4% for harmane and harmine, respectively. The interday precision was 7.3% for harmane and 5.4% for harmine. The method has proven sensitive, reproducible, and thus useful for both laboratory and clinical studies of beta-carboline toxicities.

Animals↗
PubMed2000

Production and purification of protease from a Bacillus subtilis that can deproteinize crustacean wastes*

A protease-producing microorganism was isolated in northern Taiwan and identified as a strain of Bacillus subtilis. B. subtilis Y-108 thus isolated can be used for deproteinization of crustacean wastes in the preparation of chitin. For deproteinization tests, liquid phase fermentation of untreated shrimp shell, crab shell, and lobster shell wastes with this microbe showed protein removal of 88, 67, and 83%, respectively. In contrast, the protein removal of the acid treated wastes was 76, 62, 56%, respectively. The optimized conditions for protease production was found when the culture was shaken at 30 degrees C for 3 days in 100 ml of medium (phosphate buffer adjusted to pH 6.0) containing 7% shrimp and crab shell powder (SCSP), 0.1% K(2)HPO(4), 0.05% MgSO(4), 1.0% arabinose, 1.5% NaNO(3), and 1.5% CaCl(2). Under such conditions, the protease of B. subtilis Y-108 attained the highest activity. It was as high as 20.2 U/ml. The protease was purified in a three-step procedure involving ammonium sulfate precipitation, DEAE-Sepharose CL-6B ionic exchange chromatography, and Sephacryl S-200 gel permeation chromatography. The enzyme was shown to have a relative molecular weight of 44 kDa by SDS polyacrylamide gel electrophoresis. The protease was most active at pH 8.0 and 50 degrees C with casein as substrate. The protease was activated by Mn(+2), Fe(+2), Zn(+2), Mg(+2), Co(+2), but inhibited completely by Hg(+2). The protease was also inhibited by metal-chelating agent such as EDTA, sulfhydryl reagents as beta-mercaptoethanol, and by cysteine hydrochloride, histidine, glycerol. The EDTA was the most effective inhibitor that caused complete inhibition of protease. It was concluded that this enzyme is a metal-chelator-sensitive neutral protease.

Journal Article↗
PubMed2000

Crystal structures of a low-molecular weight protein tyrosine phosphatase from Saccharomyces cerevisiae and its complex with the substrate p-nitrophenyl phosphate.

Low-molecular weight protein tyrosine phosphatases are virtually ubiquitous, which implies that they have important cellular functions. We present here the 2.2 A resolution X-ray crystallographic structure of wild-type LTP1, a low-molecular weight protein tyrosine phosphatase from Saccharomyces cerevisiae. We also present the structure of an inactive mutant substrate complex of LTP1 with p-nitrophenyl phosphate (pNPP) at a resolution of 1.7 A. The crystal structures of the wild-type protein and of the inactive mutant both have two molecules per asymmetric unit. The wild-type protein crystal was grown in HEPES buffer, a sulfonate anion that resembles the phosphate substrate, and a HEPES molecule was found with nearly full occupancy in the active site. Although the fold of LTP1 resembles that of its bovine counterpart BPTP, there are significant changes around the active site that explain differences in their kinetic behavior. In the crystal of the inactive mutant of LTP1, one molecule has a pNPP in the active site, while the other has a phosphate ion. The aromatic residues lining the walls of the active site cavity exhibit large relative movements between the two molecules. The phosphate groups present in the structures of the mutant protein bind more deeply in the active site (that is, closer to the position of nucleophilic cysteine side chain) than does the sulfonate group of the HEPES molecule in the wild-type structure. This further confirms the important role of the phosphate-binding loop in stabilizing the deep binding position of the phosphate group, thus helping to bring the phosphate close to the thiolate anion of nucleophilic cysteine, and facilitating the formation of the phosphoenzyme intermediate.

Amino Acid Sequence↗
PubMed2000

Ammonia concentration in bovine follicular fluid and its effect during in vitro maturation on subsequent embryo development.

10 mm) to determine ammonia concentration. Ammonia concentration was greater (P<0.001) in the bFF from smaller follicles compared with bFF from larger follicles, and ammonia concentration decreased (P10 mm follicles, respectively. In Experiment 2, abattoir oocytes (n=2885) were matured in vitro in media containing ammonia at the concentrations of 0 microM (Control), 29 microM (A1), 88 microM (A2), 132 microM (A3), 176 microM (A4) and 356 microM (A5), followed by in vitro fertilization and culture. There was no difference (P0.05) in cleavage rates and morula or blastocyst development between treatments, indicating that in vitro exposure of bovine oocytes to ammonia does not adversely influence subsequent embryonic development.

Ammonia↗
PubMed2000

Proteinase inhibitor 9, an inhibitor of granzyme B-mediated apoptosis, is a primary estrogen-inducible gene in human liver cells.

Although liver is an estrogen target tissue, the number of hepatic genes known to be directly induced by estrogen is very small. We identified proteinase inhibitor 9, or PI-9, as being rapidly and strongly induced by estrogen in an estrogen receptor-positive human liver cell line (HepG2-ER7). Since PI-9 mRNA was also induced by estrogen in a human liver biopsy sample, PI-9 is a genuine estrogen-regulated human gene. PI-9 is a potent inhibitor of granzyme B and of granzyme B-mediated apoptosis. Estrogens induced PI-9 mRNA within 2 h, PI-9 mRNA levels reached a plateau of 30-40-fold induction in 4 h, and induction was not blocked by cycloheximide, indicating that induction of PI-9 mRNA is a primary response. The antiestrogen trans-hydroxytamoxifen was a partial agonist for PI-9 mRNA induction, whereas the antiestrogen ICI 182, 780 was a pure antagonist. Western blot analysis showed that estrogen strongly increases PI-9 protein levels. Inhibition of transcription with actinomycin D resulted in identical rates of PI-9 mRNA decay in the presence and absence of estrogen. We isolated genomic clones containing the PI-9 promoter region, identified a putative transcription start site, and carried out transient transfections of PI-9-luciferase reporter gene constructs. The estrogen, moxestrol, elicited a robust induction from the PI-9-luciferase reporter. Mutational inactivation of three potential imperfect estrogen response elements in the PI-9 5'-flanking region had no effect on moxestrol estrogen receptor induction.

Apoptosis↗
PubMed2000

Structural and mechanistic basis for the activation of a low-molecular weight protein tyrosine phosphatase by adenine.

Although the activation of low-molecular weight protein tyrosine phosphatases by certain purines and purine derivatives was first described three decades ago, the mechanism of this rate enhancement was unknown. As an example, adenine activates the yeast low-molecular weight protein tyrosine phosphatase LTP1 more than 30-fold. To examine the structural and mechanistic basis of this phenomenon, we have determined the crystal structure of yeast LTP1 complexed with adenine. In the crystal structure, an adenine molecule is found bound in the active site cavity, sandwiched between the side chains of two large hydrophobic residues at the active site. Hydrogen bonding to the side chains of other active site residues, as well as some water-mediated hydrogen bonds, also helps to fix the position of the bound adenine molecule. An ordered water was found in proximity to the bound phosphate ion present in the active site, held by hydrogen bonding to N3 of adenine and Odelta1 of Asp-132. On the basis of the crystal structure, we propose that this water molecule is the nucleophile that participates in the dephosphorylation of the phosphoenzyme intermediate. Solvent isotope effect studies show that there is no rate-determining transfer of a solvent-derived proton in the transition state for the dephosphorylation of the phosphoenzyme intermediate. Such an absence of general base catalysis of water attack is consistent with the stability of the leaving group, namely, the thiolate anion of Cys-13. Consequently, adenine activates the enzyme by binding and orienting a water nucleophile in proximity to the phosphoryl group of the phosphoenzyme intermediate, thus increasing the rate of the dephosphorylation step, a step that is normally the rate-limiting step of this enzymatic reaction.

Adenine↗
PubMed2000

The catalytic subunit of DNA-dependent protein kinase selectively regulates p53-dependent apoptosis but not cell-cycle arrest.

DNA damage induced by ionizing radiation (IR) activates p53, leading to the regulation of downstream pathways that control cell-cycle progression and apoptosis. However, the mechanisms for the IR-induced p53 activation and the differential activation of pathways downstream of p53 are unclear. Here we provide evidence that the catalytic subunit of DNA-dependent protein kinase (DNA-PKcs) serves as an upstream effector for p53 activation in response to IR, linking DNA damage to apoptosis. DNA-PKcs knockout (DNA-PKcs-/-) mice were exposed to whole-body IR, and the cell-cycle and apoptotic responses were examined in their thymuses. Our data show that IR induction of apoptosis and Bax expression, both mediated via p53, was significantly suppressed in the thymocytes of DNA-PKcs-/- mice. In contrast, IR-induced cell-cycle arrest and p21 expression were normal. Thus, DNA-PKcs deficiency selectively disrupts p53-dependent apoptosis but not cell-cycle arrest. We also confirmed previous findings that p21 induction was attenuated and cell-cycle arrest was defective in the thymoctyes of whole body-irradiated Atm-/- mice, but the apoptotic response was unperturbed. Taken together, our results support a model in which the upstream effectors DNA-PKcs and Atm selectively activate p53 to differentially regulate cell-cycle and apoptotic responses. Whereas Atm selects for cell-cycle arrest but not apoptosis, DNA-PKcs selects for apoptosis but not cell-cycle arrest.

Animals↗
PubMed2000

Discovery of a novel dopamine transporter inhibitor, 4-hydroxy-1-methyl-4-(4-methylphenyl)-3-piperidyl 4-methylphenyl ketone, as a potential cocaine antagonist through 3D-database pharmacophore searching. Molecular modeling, structure-activity relationships, and behavioral pharmacological studies.

A novel, fairly potent dopamine transporter (DAT) inhibitor, 4-hydroxy-1-methyl-4-(4-methylphenyl)-3-piperidyl 4-methylphenyl ketone (3, K(i) values of 492 and 360 nM in binding affinity and inhibition of dopamine reuptake, respectively), with significant functional antagonism against cocaine and a different in vitro pharmacological profile from cocaine at the three transporter sites (dopamine, serotonin, and norepinephrine) was discovered through 3D-database pharmacophore searching. Through structure-activity relationships and molecular modeling studies, we found that hydrophobicity and conformational preference are two additional important parameters that determine affinity at the DAT site. Chemical modifications of the lead compound (3) led to a high affinity analogue (6, K(i) values of 11 and 55 nM in binding affinity and inhibition of dopamine reuptake, respectively). In behavioral pharmacological testing, 6 mimics partially the effect of cocaine in increasing locomotor activity in mice but lacks cocaine-like discriminative stimulus effect in rats. Taken together, these data suggest that 6 represents a promising lead for further evaluations as potential therapy for the treatment of cocaine abuse.

Animals↗
PubMed2000

Isolation of a ribonucleoprotein complex involved in mRNA localization in Drosophila oocytes.

Localization of bicoid (bcd) mRNA to the anterior and oskar (osk) mRNA to the posterior of the Drosophila oocyte is critical for embryonic patterning. Previous genetic studies implicated exuperantia (exu) in bcd mRNA localization, but its role in this process is not understood. We have biochemically isolated Exu and show that it is part of a large RNase-sensitive complex that contains at least seven other proteins. One of these proteins was identified as the cold shock domain RNA-binding protein Ypsilon Schachtel (Yps), which we show binds directly to Exu and colocalizes with Exu in both the oocyte and nurse cells of the Drosophila egg chamber. Surprisingly, the Exu-Yps complex contains osk mRNA. This biochemical result led us to reexamine the role of Exu in the localization of osk mRNA. We discovered that exu-null mutants are defective in osk mRNA localization in both nurse cells and the oocyte. Furthermore, both Exu/Yps particles and osk mRNA follow a similar temporal pattern of localization in which they transiently accumulate at the oocyte anterior and subsequently localize to the posterior pole. We propose that Exu is a core component of a large protein complex involved in localizing mRNAs both within nurse cells and the developing oocyte.

Amino Acid Sequence↗
PubMed2000

Heterogenous properties of dentate granule neurons in the adult rat.

Postnatal neurogenesis contributes substantially to the neuronal population of the adult dentate gyrus. We report here that the neurons located in the deep aspects of the granule cell layer, near the proliferative zone, have different properties from those located in the superficial layers. The former group of neurons, tentatively designated as young, can be readily identified in a standard hippocampal slice preparation by morphological, immunohistochemical, and electrophysiological criteria. Electrophysiological recordings and imaging with Lucifer yellow from these neurons in the standard hippocampal slice preparation showed one or two main dendrites and conically shaped branches possessing varicose protrusions. These features are in agreement with the appearance of the same population of young neurons immunopositive for TOAD-64, a marker for immature neurons. In disinhibited slices, these putative young neurons are distinguished from the mature neurons, located in the superficial granule cell layer, by showing paired pulse facilitation and having a lower threshold for induction of long-term potentiation. The putative young neurons are completely unaffected by GABA(A) inhibition and always display robust long-term potentiation. In contrast, the mature neurons never produce long-term potentiation when the GABA(A) inhibition is intact. We propose that the heterogeneity of the functional properties of the granule neurons is related to the ongoing neurogenesis in the adult animals.

Animals↗
PubMed2000

Promoter-targeted selection and isolation of neural progenitor cells from the adult human ventricular zone.

Adult humans, like their nonhuman mammalian counterparts, harbor persistent neural progenitor cells in the forebrain ventricular lining. In the absence of adequate surface markers, however, these cells have proven difficult to isolate for study. We have previously identified and selected neural progenitor cells from both the fetal and adult rodent ventricular zone (VZ), by sorting forebrain cells transfected with plasmid DNA encoding the gene for green fluorescent protein driven by the early neuronal promoter for Talpha1 tubulin (P/Talpha1:hGFP). We have now extended this approach by purifying both P/Talpha1:hGFP tubulin-defined neuronal progenitors, as well as potentially less committed E/nestin:hGFP-defined neural progenitor cells, from the adult human VZ. The ventricular wall of the temporal horn of the lateral ventricle was dissected from temporal lobes obtained from four adult patients undergoing therapeutic lobectomy. These samples were dissociated, and the cultured cells transduced with either P/Talpha1:hGFP or E/nestin:EGFP plasmid DNA. A week later, the cells were redissociated, selected via fluorescence-activated cell sorting (FACS) on the basis of neural promoter-driven GFP expression, and replated. The majority of these cells expressed the early neuronal protein betaIII-tubulin upon FACS; within the week thereafter, most matured as morphologically evident neurons that coexpressed betaIII-tubulin and microtubule-associated protein (MAP)-2. Many of these neurons had incorporated bromodeoxyuridine in vitro in the days before FACS, indicating their mitogenesis in vitro. Thus, the use of fluorescent transgenes under the control of early neural promoters permits the enrichment of neuronal progenitor cells from the adult human ventricular zone. The specific acquisition, in both purity and number, of residual neural progenitor cells from the adult human brain may now permit hitherto unfeasible studies of both their biology and practical application.

Adult↗
PubMed2000

[Effects of phoxim on sperm production and motility of rats].

The effects of phoxim at various dosage levels on sperm production and motility in rats were studied. Sperm motility was measured by computer assisted sperm analysis (CASA). The results showed that rats exposed to phoxim at higher doses(24.5 and 73.5 mg/kgBW) for 60 successive days showed significant reduction of daily sperm production as compared with the control (P < 0.05, P < 0.01). Sperm motion parameters such as currilinear velocity (VCL), straight line velocity(VSL), beat cross frequency(BCF), linearity(LIN) and straightness(STR) were significantly decreased than those of the control(P < 0.05, P < 0.01) which indicated a dose-dependent relationship to some extent. However, there was no obvious change in body weight, testis weight and the rate of motile sperm in epididymis. It suggests that the male reproductive toxicilIty of phoxim at higher doses (24.5 and 73.5 mg/kgBW) mainly induces a reduction of sperm production and motility.

Animals↗
PubMed2000

[Ethanol-induced apoptosis in human HL-60 cells].

The purpose of this study was to examine the effect of ethanol on apoptosis of human promyelocytic leukemia cell line HL-60 cells and search for a possible reason for reduced PMNs, monocytes, lymphocytes in the blood of alcoholics. Human promyelocytic leukemia cell line HL-60 cells was used as a model of apoptosis, with ethanol being the interfering factor. Qualitative and quantitative detection was done by both electron microscopy and flow cytometry. Compared with the control treatment of HL-60 cells with ethanol at 50, 100, 150, 200, 250 mmol/L for 3 days increased apoptotic cells significantly (P < 0.01), and apoptosis was dose-dependent for ethanol. It suggest that ethanol can induce apoptosis of HL-60 cells. So as far as reduced PMNs, monocytes, phagocytes and lymphocytes of alcoholics are concerned, ethanol-induced apoptosis may well be an important reason.

Apoptosis↗