Cross-sectional study on their reproductive health status of 604 female floating residents in Beijing.
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Asia↗
Biomedical subjects
S X Wang
Publications and source records attributed to S X Wang.
The insertion of human apolipoprotein H into phospholipid membranes: a monolayer study.
Apolipoprotein H (ApoH) is a plasma glycoprotein isolated from human serum. The interactions of ApoH with lipid membrane were reported to be essential for its physiological and pathogenic roles. In this paper we studied the ability of ApoH to insert into phospholipid membranes using the monolayer approach. The results show that ApoH is surface active and can insert into the lipid monolayers. The insertion ability of ApoH is stronger when a higher content of negatively charged lipids is present in the membrane. The acidic-pH and low-ionic-strength conditions will also enhance ApoH insertion, but these factors may not have much influence on the final insertion ability of ApoH, suggesting that, in the mechanism of ApoH insertion, not only electrostatic forces, but also hydrophobic interactions, are evidently involved. Modification by heat inactivation and reduction/alkylation does not change the critical insertion pressure (pic) of ApoH, suggesting a stable domain, maybe a linear sequence motif, but not the native three-dimensional structure of ApoH, is responsible for its insertion. The extent to which insertion of ApoH into phospholipid membranes may facilitate the 'immune cleaning' of plasma liposomes is discussed.
1,2-Dipalmitoylphosphatidylcholine↗
The Xenopus Chk1 protein kinase mediates a caffeine-sensitive pathway of checkpoint control in cell-free extracts.
We have analyzed the role of the protein kinase Chk1 in checkpoint control by using cell-free extracts from Xenopus eggs. Recombinant Xenopus Chk1 (Xchk1) phosphorylates the mitotic inducer Cdc25 in vitro on multiple sites including Ser-287. The Xchk1-catalyzed phosphorylation of Cdc25 on Ser-287 is sufficient to confer the binding of 14-3-3 proteins. Egg extracts from which Xchk1 has been removed by immunodepletion are strongly but not totally compromised in their ability to undergo a cell cycle delay in response to the presence of unreplicated DNA. Cdc25 in Xchk1-depleted extracts remains bound to 14-3-3 due to the action of a distinct Ser-287-specific kinase in addition to Xchk1. Xchk1 is highly phosphorylated in the presence of unreplicated or damaged DNA, and this phosphorylation is abolished by caffeine, an agent which attenuates checkpoint control. The checkpoint response to unreplicated DNA in this system involves both caffeine-sensitive and caffeine-insensitive steps. Our results indicate that caffeine disrupts the checkpoint pathway containing Xchk1.
14-3-3 Proteins↗
A novel extracellular domain variant of the human integrin alpha 7 subunit generated by alternative intron splicing.
The integrin alpha 7 beta 1 laminin receptor, which is expressed on replicating myoblasts, and upregulated during myogenic differentiation, is involved in cell adhesion and communication between muscle cells and the extracellular matrix. It is a major cell-surface substrate in skeletal muscle cells for the cell-surface, argininespecific, ADP-ribosyltransferase. Both the extracellular and cytoplasmic domains of the mouse alpha 7 subunit undergo alternative splicing during development, generating differentially expressed variants with presumably unique ligand-binding and signalling properties. Here human cDNA clones isolated from a fetal heart lambda gt10 cDNA library encoded the complete sequence of the alpha 7 subunit and hybridised to a single major 4.4 kb alpha 7 subunit transcript abundantly expressed in human skeletal muscle, moderately expressed in heart, and weakly expressed in most other tissues. One clone out of four contained a novel 225-nucleotide in-frame deletion corresponding to 75 amino acids in the C-terminal region of the extracellular domain. The variant, whose expression appears to be tissue-specific, is created by alternative splicing at sites flanking an intron in the alpha 7 gene. A related mouse form was identified in P19 embryonal carcinoma cells. Deletion of the spliced region, which either contains or is in very close proximity to the major ADP-ribosylation site of the alpha 7 subunit, may serve to modulate the effects of ADP-ribosylation, or alternatively molecular associations, and receptor-ligand affinity.
Alternative Splicing↗
Characterization of the native lysine tyrosylquinone cofactor in lysyl oxidase by Raman spectroscopy.
Lysine tyrosylquinone (LTQ) recently has been identified as the active site cofactor in lysyl oxidase by isolation and characterization of a derivatized active site peptide. Reported in this study is the first characterization of the underivatized cofactor in native lysyl oxidase by resonance Raman (RR) spectrometry. The spectrum is characterized by a unique set of vibrational modes in the 1200 to 1700 cm-1 region. We show that the RR spectrum of lysyl oxidase closely matches that of a synthetic LTQ model compound, 4-n-butylamino-5-ethyl-1,2-benzoquinone, in aqueous solutions but differs significantly from those of other topa quinone-containing amine oxidases under similar conditions. Furthermore, we have observed the same 18O shift of the C=O stretch in both the lysyl oxidase enzyme and the LTQ cofactor model compound. The RR spectra of different model compounds and their D shifts give additional evidence for the protonation state of LTQ cofactor in the enzyme. The overall similarity of these spectra and their shifts shows that the lysyl oxidase cofactor and the model LTQ compound have the same structure and properties. These data provide strong and independent support for the new cofactor structure, unambiguously ruling out the possibility that the structure originally reported had been derived from a spurious side reaction during the derivatization of the protein and isolation of the active site peptide.
Animals↗
A crosslinked cofactor in lysyl oxidase: redox function for amino acid side chains.
A previously unknown redox cofactor has been identified in the active site of lysyl oxidase from the bovine aorta. Edman sequencing, mass spectrometry, ultraviolet-visible spectra, and resonance Raman studies showed that this cofactor is a quinone. Its structure is derived from the crosslinking of the epsilon-amino group of a peptidyl lysine with the modified side chain of a tyrosyl residue, and it has been designated lysine tyrosylquinone. This quinone appears to be the only example of a mammalian cofactor formed from the crosslinking of two amino acid side chains. This discovery expands the range of known quino-cofactor structures and has implications for the mechanism of their biogenesis.
Amino Acid Sequence↗
Glycine 699 is pivotal for the motor activity of skeletal muscle myosin.
Myosin couples ATP hydrolysis to the translocation of actin filaments to power many forms of cellular motility. A striking feature of the structure of the muscle myosin head domain is a 9-nm long "lever arm" that has been postulated to produce a 5-10-nm power stroke. This motion must be coupled to conformational changes around the actin and nucleotide binding sites. The linkage of these sites to the lever arm has been analyzed by site-directed mutagenesis of a conserved glycine residue (G699) found in a bend joining two helices containing the highly reactive and mobile cysteine residues, SH1 and SH2. Alanine mutagenesis of this glycine (G699A) dramatically alters the motor activity of skeletal muscle myosin, inhibiting the velocity of actin filament movement by > 100-fold. Analysis of the defect in the G699A mutant myosin is consistent with a marked slowing of the transition within the motor domain from a strong binding to a weak binding interaction with actin. This result is interpreted in terms of the role of this residue (G699) as a pivot point for motion of the lever arm. The recombinant myosin used in these experiments has been produced in a unique expression system. A shuttle vector containing a regulated muscle-specific promoter has been developed for the stable expression of recombinant myosin in C2C12 cells. The vector uses the promoter/enhancer region, the first two and the last five exons of an embryonic rat myosin gene, to regulate the expression of an embryonic chicken muscle myosin cDNA. Stable cell lines transfected with this vector express the unique genetically engineered myosin after differentiation into myotubes. The myosin assembles into myofibrils, copurifies with the endogenous myosin, and contains a complement of muscle-specific myosin light chains. The functional activity of the recombinant myosin is readily analyzed with an in vitro motility assay using a species-specific anti-S2 mAb to selectively assay the recombinant protein. This expression system has facilitated manipulation and analysis of the skeletal muscle myosin motor domain and is also amenable to a wide range of structure-function experiments addressing questions unique to the muscle-specific cytoarchitecture and myosin isoforms.
Animals↗
[Effects of subtotal nephrectomy and high salt intake on atrial natriuretic peptide in the brains of rats].
In order to explore the role of brain atrial natriuretic peptide (ANP) in regulating water and electrolytes, the changes of the ANP content of various brain areas in the status of high salt intake and in 3/4 nephrectomy rats. In control group, a wide distribution of ANP was observed in different areas of the brain. The amount of daily water intake and urine were larger, and urine sodium concentration was lower in the 3/4 nephrectomy group than those in the control group (P < 0.05). In the ten nuclei we have studied, ANP content was not significantly different from that of the control (P > 0.05). In the high salt group, water intake, urine volume and urine sodium concentration were significantly higher than those in the control. In this group, brain ANP increased in the periventricular nuclues (PVN) and arcute nucleus (Arc) (P < 0.05). The results indicate that ANP in anteroventral region of the third ventricle (AV3V) might play important role in the regulation of water and electolytes.
Animals↗
A new non-LTR retrotransposon provides evidence for multiple distinct site-specific elements in Crithidia fasciculata miniexon arrays.
We have identified a new member of the family of trypanosome site-specific retrotransposons, using a degenerate oligonucleotide PCR strategy. The 9595 bp element, termed Crithidia retrotransposable element 2 (CRE2), was cloned and found to be inserted in the tandemly arrayed miniexon genes of Crithidia fasciculata. The element is flanked by 29 bp target site duplications but lacks the 3' poly dA tract characteristic of most other non-long terminal repeat retrotransposons. The amino terminal region of the single 2518-codon open reading frame contains a putative metal-binding motif and a proline-rich region similar to gag-like domains of other retrotransposons. The carboxy terminal region of this open reading frame shares sequence homology with the reverse transcriptase and putative endonuclease regions of three previously described trypanosomatid site-specific retrotransposons. All four of these retrotransposons are specifically inserted between nucleotides 11 and 12 of the highly conserved 39mer sequence of the miniexon gene. Most copies of CRE2 and the previously characterized CRE1 are located on different sized chromosomes. Additional CRE-related sequences were identified by screening Crithidia libraries. These results suggest that a particular sequence in the C. fasciculata miniexon repeat is the target for multiple distinct site-specific retrotransposon insertions.
Amino Acid Sequence↗
[Care of malignant tumors treated with ultraviolet irradiation and oxygenation of autotransfusion].
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Blood Transfusion, Autologous↗
13C-NMR off-resonance rotating frame spin-lattice relaxation studies of bovine lens gamma-crystallin self association: effect of 'macromolecular crowding'.
The NMR technique of 13C off-resonance rotating frame spin-lattice relaxation, which provides an accurate assessment of the effective rotational correlation time (tau 0, eff) for macromolecular rotational diffusion, was applied to the study of gamma-crystallin association as a function of protein concentration and temperature. Values of the effective rotational correlation time for gamma-crystallin rotational diffusion were obtained at moderate to high protein concentrations (80-350 mg/ml) and at temperatures above, and below, the cold cataract phase transition temperature. With increasing concentration gamma-crystallin was observed to increasingly associate as reflected by larger values of tau 0, eff Decreasing temperature in the range of 35 to 22 degrees C was found to result in no change in the temperature corrected value of tau 0, eff at a gamma-crystallin concentration of 80 mg/ml, whereas at temperatures of 18 degrees C or below, this parameter was approx. twofold larger, suggesting the occurrence of a well defined phase transition, which correlated well with the cold cataract phase transition temperature. At higher protein concentrations, by contrast, tau 0, eff (temperature corrected) was found to increase by approx. 1.6- to 2-times in the temperature interval 35 degrees C to 22 degrees C, a result consistent with the dependence of the cold cataract phase transition temperature on gamma-crystallin concentration. Analysis of intensity ratio dispersion curves, using an assumed model of isodesmic association, permitted the estimation of the association constant characterizing the aggregation under particular conditions of concentration and temperature. The significant increase in the value of the association constant with moderate increases in protein concentration was rationalized by invoking the effect of 'macromolecular crowding'. The results obtained in this study suggest that in the intact lens, where high protein concentrations prevail, gamma-crystallin is unlikely to be found in the monomeric state, but more likely, as a significantly aggregated species, representing a broad molecular weight distribution.
Animals↗
A natural vaccine candidate strain against cholera.
E1 Tor Vibrio cholerae (EVC) strains may be classified into two kinds-epidemigenic (EEVC) strains and non-epidemigenic (NEEVC) strains-based on a phage-biotyping system. A large number of EEVC strains have been screened for toxigenic and putative colonization attributes. One such naturally occurring strains (designated IEM101) has been found which is devoid of genes encoding cholera toxin (CT), accessory cholera enterotoxin (ACE), zonula occludens toxin (ZOT), but possesses RS1 sequences and toxin-coregulated pilus A gene (icpA) although icpA is poorly expressed. It expresses type B pili but does not possess type C pili. It is an E1 Tor Ogawa strain and does not cause fluid accumulation in rabbit ilcal loop tests. Active immunization of rabbits with strain IEM101 elicited good protection against challenge with virulent strains of V. cholerae O1. Oral administration caused no side effects in 15 human volunteers, colonized the gut for four to ten days and elicited good immune responses.
Animals↗
[Preoperative diet instruction to patients with esophageal diseases].
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Diet↗
[Self-made fibrin sealant administered in thoracic surgery].
From April 1990 to May 1993, 15 patients with thoracic complication or thoracic diseases have been treated with self-made fibrin sealant. All patients have been cured successfully in a short time without thoracotomy. The methods of its make-up, administer and assessment were discussed. It is economical and effective. The major advantage is simple method and easily administered. It could be used in other surgery.
Adult↗
Assessment of protein rotational diffusion by 13C off-resonance rotating frame spin-lattice relaxation: effect of backbone and side-chain internal motion.
The 13C off-resonance rotating frame spin-lattice relaxation technique is applicable to the study of protein rotational diffusion behavior in a variety of experimental situations. The original formalism of James and co-workers (1978) (J. Am. Chem. Soc. Vol. 100, pp. 3590-3594) incorporated random isotropic reorientational motion of a rigid spherical rotor with no provision for backbone or side-chain carbonyl group internal motion. Here we demonstrate that the failure to include such internal motion may lead to erroneous rotational correlation time determinations for overall reorientational motion. The effect becomes severe for protein molecular masses in excess of 100 kD. Inclusion of both backbone and side-chain carbonyl carbon internal motion, using reasonable parameters derived from the literature [R. Levy and M. Karplus (1979), Chemical Physics Letters, Vol. 65, pp. 4-11; G. Careri, P. Fasella, and E. Gratton (1975), Critical Reviews in Biochemistry, Vol. 3, pp. 141-164; G. Lipari, A. Szabo, and R. LEvy (1982), Nature, Vol. 300, pp. 197-198], plus corrections for anisotropic tumbling [C. F. Morgan, T. Schleich, G. H. Caines, and D. Michael (1990), Biopolymers, Vol. 29, pp. 469-480] and microscopic viscosity [S. H. Koenig (1980), ACS Symposium Series, Vol. 127, pp. 157-176], leads to reliable values for the correlation time describing overall protein reorientation up to molecular masses of approximately 1000 kD.
Carbon Isotopes↗
13C NMR studies of protein motional dynamics in bovine, human, rat, and chicken ocular lenses.
The motional dynamics of lens proteins were studied by two 13C nuclear magnetic resonance (NMR) techniques sensitive to molecular motion to define the effect of lens water content on the presence of solid-like protein domains in ocular lenses from bovine (juvenile and adult), human, rat, and chicken eyes. The solid state 13C NMR technique of proton dipolar decoupling was used to study slow (solid-like) motions (correlation time, tau o > or = 10 microseconds), whereas for intermediate (mobile) protein, rotational reorientational motion (tau o range of 1-500 nsec) the 13C off-resonance rotating frame spin-lattice relaxation technique was employed. 13C NMR studies of calf lens cortical and nuclear homogenates indicated a reversible loss of lens protein motional freedom with decreasing water content. Values of 6% and 63% solid-like protein contents were obtained for native cortical and nuclear calf lens homogenates, respectively. At equivalent total protein concentrations cortical and nuclear calf lens homogenates exhibited essentially the same solid-like (motionally restricted) protein content. Lens protein rotational correlation times determined by off-resonance rotating frame spin-lattice relaxation measurements were consistent with lens protein aggregation. The solid-like protein content of the bovine nuclear lens region was observed to increase with age, whereas no significant change was detected for the cortex. Across lens species an inverse correlation between the percentage of solid-like protein content and water content was observed. Very broad 13C NMR resonances, even in the presence of proton dipolar decoupling, were observed for the lens proteins present in the cataractous human lens, indicating the presence of highly aggregated protein species. The occurrence of solid-like protein domains in lens tissue has implications for the interpretation of proton nuclear magnetic resonance dispersion (NMRD) measurements of lens homogenates and for proton magnetization transfer contrast enhanced magnetic resonance imaging of lens. Solid-like protein domains may play a protective role in the maintenance of lens transparency by minimizing enhanced refractive index fluctuations created by protein packing defects resulting from post-translational modification.
Adult↗
[The isolation and identification of qianhucoumarin B and qianhucoumarin C from Peucedanum praeruptorum].
Five compounds were isolated from the traditional Chinese medicine Qianhu, roots of Peucedanum praeruptorum. Their structures were identified as 3'-angeloyloxykhellactone (IX), qianhucoumarin B (X), qianhucoumarin C (XI), Pd-III (XIII) and peucedanocoumarin III (XV). Among them, X and XI are new compounds, their absolute configurations were elucidated by chemical correlation with khellactones, as 3'(S)-acetoxy-4'(S)-hydroxy-3',4'-dihydroseselin(X) and 3'(S)-hydroxy-4'(S)-acetoxy-3',4'-dihydroseselin (XI). Compound IX was isolated from plants for the first time.
Coumarins↗
[Effect of cholecystokinin and its antagonists lorglumide, devazepide, and L-365,260 on gastrointestinal motility in rats].
Cholecystokinin (CCK) plays an important role in gallbladder contraction and gut motility. Sincalide (CCK-8) evoked guinea pig isolated ileum contraction at 10(-5)-10(-1) mumol.L-1 in a concentration-dependent manner, EC50 being 207 pmol.L-1. It delayed the gastric emptying as well. The rate of inhibition of gastric emptying was 71 +/- 12% at 100 micrograms.kg-1 by ip. Sincalide antagonists: lorglumide, devazepide, and L-365,260 antagonized the ileal smooth muscle response to sincalide in a concentration-dependent manner. Their pA2 were 7.30, 10.02, and 7.77, respectively. Lorglumide, devazepide, and L-365,260 inhibited the delaying of gastric emptying evoked by sincalide. The IC50 were 0.11, 0.0064, and 0.66 mg.kg-1, respectively.
Animals↗