3001
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Affiliation(s)
- K S Pang
- Faculty of Pharmacy, University of Toronto, Ontario, Canada
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3002
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Runde M, Routbort JL, Rothman SJ, Goretta KC, Mundy JN, Xu X, Baker JE. Tracer diffusion of oxygen in Bi2Sr2CaCu2Ox. Phys Rev B Condens Matter 1992; 45:7375-7382. [PMID: 10000513 DOI: 10.1103/physrevb.45.7375] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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3003
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Xu X, Hagen SJ, Jiang W, Peng JL, Li ZY, Greene RL. Thermoelectric power of Nd2-xCexCuO4 crystals. Phys Rev B Condens Matter 1992; 45:7356-7359. [PMID: 10000510 DOI: 10.1103/physrevb.45.7356] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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3004
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Abstract
The literature on age estimation from the structure of adult human teeth is reviewed. Several anatomic changes of teeth have been shown to be valuable in age determination, but there is still controversy concerning the accuracy of cemental annulation. It is believed that improvements in age estimation can be made using direct measurement rather than scoring systems.
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Affiliation(s)
- X Xu
- Faculty of Forensic Medicine, Sun Yat-sen University of Medical Sciences, Guangzhou, P.R., China
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3005
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Abstract
An automatic procedure for building polyalanine backbones from guiding alpha-carbon positions is presented. Polyalanine backbones are built based on the geometric restraints of angle N-C alpha-C and the knowledge of main-chain dihedral angle distributions. A building module constructs a list of polyalanine backbones that follow exactly the C alpha trace. Then a selection module selects one backbone with the largest portion of phi-psi pairs in favoured regions. Several test cases on C alpha coordinates from X-ray refined structures give acceptable results. Less than 10% of the peptide planes are incorrectly built, and the result is not sensitive to random shift up to 0.5 A of C alpha coordinates.
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Affiliation(s)
- Y Luo
- Institute of Physical Chemistry, Peking University, Beijing, P.R. China
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3006
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Guha S, Yang J, Banerjee A, Glatfelter T, Xu X. Advances in amorphous silicon alloy-based multijunction cells and modules. ACTA ACUST UNITED AC 1992. [DOI: 10.1063/1.42943] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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3007
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Xu X, Davis RE. N-methyl-D-aspartate receptor antagonist MK-801 impairs learning but not memory fixation or expression of classical fear conditioning in goldfish (Carassius auratus). Behav Neurosci 1992; 106:307-14. [PMID: 1534239 DOI: 10.1037/0735-7044.106.2.307] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The amnestic effects of the noncompetitive antagonist MK-801 on visually mediated, classic fear conditioning in goldfish (Carassius auratus) was examined in 5 experiments. MK-801 was administered 30 min before the training session on Day 1 to look for anterograde amnestic effects, immediately after training to look for retrograde amnestic effects, and before the training or test session, or both, to look for state-dependence effects. The results showed that MK-801 produced anterograde amnesia at doses that did not produce retrograde amnesia or state dependency and did not impair the expression of conditioned or unconditioned branchial suppression responses (BSRs) to the conditioned stimulus. The results indicate that MK-801 disrupts the mechanism of learning of the conditioned stimulus-unconditioned stimulus relation. Evidence is also presented that the learning processes that are disrupted by MK-801 occur during the initial stage of BSR conditioning.
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Affiliation(s)
- X Xu
- Mental Health Research Institute, University of Michigan, Ann Arbor 48104-1687
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3008
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3009
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Bruin G, Stegeman G, Van Asten A, Xu X, Kraak J, Poppe H. Optimization and evaluation of the performance of arrangements for UV detection in high-resolution separations using fused-silica capillaries. J Chromatogr A 1991. [DOI: 10.1016/0021-9673(91)80068-r] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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3010
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Wu Y, Cai R, Zhou B, Xu X. Effects of genetic factors and dietary electrolytes on blood pressure of rural secondary school students in Hanzhong. Chin Med Sci J 1991; 6:148-52. [PMID: 1793877] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
In this study, 24-h urine specimens were collected on 3 consecutive days from 181 adolescents (94 boys and 87 girls), aged 12-16 years, in a rural district--Hanzhong, Shaanxi Province, and sodium, potassium, calcium and magnesium levels were determined. Dietary intake of the four electrolytes and blood pressure were measured in children and their parents on the same consecutive days. The results were as follows: urinary output of calcium and magnesium might not be an appropriate index to reflect intake; after adjusting for age, sex, BMI, heart rate, and parental blood pressure, the ratio of dietary calcium to total calories was negatively related to diastolic blood pressure in the whole group, and the ratio of urinary calcium to creatinine was positively related to systolic blood pressure in girls; not only blood pressure but also its relation to electrolytes are affected by parental blood pressure after adjusting for age, sex, BMI and heart rate.
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Affiliation(s)
- Y Wu
- Cardiovascular Institute, CAMS, Beijing
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3011
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Abstract
Escherichia coli alkaline phosphatase catalyzes the hydrolysis of a wide variety of phosphomonoesters at similar rates, and the reaction proceeds through a phosphoenzyme intermediate. The active site region is highly conserved between the E. coli and mammalian alkaline phosphatases. The three-dimensional structure of the E. coli enzyme indicates that Lys-328, which is replaced by histidine in all mammalian alkaline phosphatases, is bridged to the phosphate through a water molecule. This water molecule is also hydrogen bonded to Asp-327, a bidendate ligand of the one of the two zinc atoms. Here we report the use of site-specific mutagenesis to convert Lys-328 to both histidine and alanine. Steady-state kinetic studies above pH 7.0 indicate that both mutant enzymes have altered pH versus activity profiles compared to the profile for the wild-type enzyme. At pH 10.3, in the presence of Tris, the Lys-328----Ala enzyme is approximately 14-fold more active than the wild-type enzyme. At the same pH in the absence of Tris the Lys-328----Ala enzyme is still 6-fold more active than the wild-type enzyme. Both mutant enzymes have lower phosphate affinities than the wild-type enzyme at all pH values investigated. Pre-steady-state kinetics at pH 5.5 reveal that the Lys-328----Ala enzyme behaves very similar to the phosphate-free wild-type enzyme.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- X Xu
- Department of Chemistry, Boston College, Chestnut Hill, Massachusetts 02167
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3012
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Xu X, Guo P, Song Y, Li Z. [The contents of gamma-aminobutyric acid and glutamic acid in brain affected by coriaria lactone]. Hua Xi Yi Ke Da Xue Xue Bao 1991; 22:213-5. [PMID: 1686259] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Capillary chromatography was applied to studying the contents of gamma-aminobutyric acid (GABA) and glutamic acid (Glu) in brain affected by coriaria lactone. The results showed that there was a significant increase in the content of Glu whereas no significant change in the content of GABA was noted. The precisions for GABA and Glu were 3.3% and 4.98% and the recoveries of them were 80.5% and 85.2%, respectively. Capillary chromatography is a good method for determining the contents of GABA and Glu in brain, which has the characteristics of rapid and high sensitivity.
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3013
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Wu DZ, Wu L, Xu X, Chen H, Luo T. The significance of testing preoperative visual function in cataract using laser interferometric visual acuity and ERG. Yan Ke Xue Bao 1991; 7:21-4. [PMID: 1843124] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Tests of preoperative visual function and prediction of postoperative E chart visual acuity (ECVA) using laser interferometric visual acuity (LIVA) and electroretinogram (ERG) were performed in 16 cases (19 eyes) of cataract. The results showed that the coincident rate between preoperative LIVA and postoperative ECVA was 63.2%, and there was a parallel correlation between preoperative amplitude of photopic ERG b-wave and postoperative ECVA in 79.0% of the eyes. Comparing these two methods, the test of LIVA is very simple, fast, and is easily accepted by the patients with cataract. ERG is an objective method, which is slightly influenced by dense lens, but the test is more complex. Therefore, the combined use of these two methods will provide a more comprehensive and correct evaluation of preoperative visual function and a more reliable prediction for postoperative visual acuity in patients with cataract.
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Affiliation(s)
- D Z Wu
- Zhongshan Ophthalmic Center, Sun Yat-sen University of Medical Sciences, Guangzhou, China
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3014
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3015
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Wei S, Si X, Xu X. [Chemical constituents in the stem of Premna crassa Hand. -Mazz]. Zhongguo Zhong Yao Za Zhi 1990; 15:487-8, 512. [PMID: 2093323] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
In this paper four compounds isolated from the stem of Premna crassa are described. Their structures have been identified as friedelin, epifriedelanol, stearic acid and beta-sitosterol respectively by comparing their chemical and spectroscopic data with those of the authentic samples.
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Affiliation(s)
- S Wei
- Department of Pharmacy, Guangxi College of Traditional Chinese Medicine, Nanning
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3016
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Wu D, Xu X, Wu L, Luo T. ERG characteristics of congenital stationary night blindness. Yan Ke Xue Bao 1990; 6:32-5. [PMID: 2101357] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The ERGs of 9 cases (18 eyes) of congenital stationary night blindness with normal fundi or myopia were tested. All eyes showed nonrecordable rod ERG and cone ERG with normal a-wave. Scotopic mixed ERGs were of the negative type in 7 eyes and of the subnormal type in 11 eyes. The b/a ratio was reduced in all eyes. The ERG characteristics are useful for the classification, estimation of the probable location of the lesion, and differential diagnosis of the disease.
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Affiliation(s)
- D Wu
- Zhongshan Ophthalmic Center, Sun Yat--sen University of Medied Sciences, Guangzhou, China
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3017
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Xu X, Tang BK, Pang KS. Sequential metabolism of salicylamide exclusively to gentisamide 5-glucuronide and not gentisamide sulfate conjugates in single-pass in situ perfused rat liver. J Pharmacol Exp Ther 1990; 253:965-73. [PMID: 2359032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Gentisamide (GAM), the hydroxylated metabolite of salicylamide (SAM), underwent sequential metabolism, and GAM-5-glucuronide was the only metabolite detected in the single-pass in situ rat liver preparation (10 ml/min/liver) perfused at varying SAM steady-state input concentrations (CIn). The exclusive formation of GAM-5-glucuronide was unexpected, because GAM, when administered to the rat liver, formed predominantly monosulfate conjugates at the 5- and 2-positions (Morris et al., J. Pharmacol. Exp. Ther. 245: 614-624, 1988). Kinetic parameters obtained from single-pass studies for SAM sulfation (CIn increasing from 31 to 347 microM) and glucuronidation and hydroxylation (CIn decreasing from 1383 to 130 microM, with 0.85 mM SO4(2-), and CIn increasing from 32 to 800 microM in an absence of SO4(2-), with 2,6-dichloro-4-nitrophenol, a sulfation inhibitor) revealed sulfation as a high-affinity, high-capacity pathway, glucuronidation as a lower-affinity, high-capacity pathway and hydroxylation as a low-affinity, low-capacity pathway. However, these parameters would not explain the exclusive glucuronidation of GAM when generated from SAM. Rather the zonal localization of metabolizing activities [a periportal sulfation, evenly distributed glucuronidation, and perivenous hydroxylation system (Xu and Pang, J. Pharmacokinet. Biopharm. 17: 645-671, 1989; Morris et al., J. Pharmacokinet. Biopharm. 16: 633-656, 1988)] could explain the complete lack of sulfation in SAM sequential metabolism. The different metabolite patterns arising from the administrations of a metabolite precursor (SAM) versus a preformed metabolite (GAM), due to the proximity of enzymes for formation and sequential metabolism, may serve to explain the differential toxic or pharmacologic effects observed in other precursor-metabolite pairs.
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Affiliation(s)
- X Xu
- Faculty of Pharmacy, University of Toronto, Ontario, Canada
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3018
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Xu X, Sasaki H, Morimoto A, Kumeda M, Shimizu T. Thermal-equilibrium defects in undoped hydrogenated amorphous silicon, silicon-carbon, and silicon-nitrogen. Phys Rev B Condens Matter 1990; 41:10049-10057. [PMID: 9993389 DOI: 10.1103/physrevb.41.10049] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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3019
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Cai Z, Li X, Xu X. [Determination of eucalyptole in eucalyptus oil by gas chromatography]. Zhongguo Zhong Yao Za Zhi 1990; 15:298-9, 319. [PMID: 2275783] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
This paper reports the determination of eucalyptole in eucalyptus oil by gas chromatography. The results were similar to the specifications in the Chinese Pharmacopoeia. The method is simple, rapid, accurate and sensitive and requires only small amount of samples. The coefficient of variation is less than or equal to 0.52%.
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Affiliation(s)
- Z Cai
- Guangdong Provincial Institute for Drug Control, Guangzhou
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3020
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Xu X. [Stress analysis following femoral shaft osteotomy fixed using various plates with different rigidities in a simulation test]. Zhonghua Yi Xue Za Zhi 1990; 70:186-90, 14. [PMID: 2167754] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
A pair of human cadaver femora were used for electric measurement under simulation-bearing test, which was performed on intact bone and osteotomy bone fixed by 3 types of plate with different rigidities respectively. The results indicated that the plates with uniform thickness did not adhere to the principle of identical strength. The stress was significantly greater between the two central screw holes. However, the device of trapezoidal plate conformed to the principle of identical strength, and the safety factors of it are proposed. The osteotomy site was subjected to compression stress in standing phase with load on both femora, but subjected to bending stress with load on single femur. The total compression stress at the osteotomy site was significantly greater than that on intact bone when the load was added to twice of the body weight with load on both legs. We believe that stress shielding can be overcome by using optimized plate and normal bearing.
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3021
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Abstract
Sequence comparisons of the three homologous polypeptide chains that compose vertebrate fibrinogens imply that the molecule evolved before the divergence of vertebrates and invertebrates, but, to our knowledge, no protein resembling vertebrate fibrinogen has even been reported from an invertebrate. We used primers based on sequences conserved between lamprey and human fibrinogens and applied the polymerase chain reaction (PCR) to cDNA preparations from various invertebrates. A fibrinogen-like sequence was identified in cDNA prepared from the soft tissues of a sea cucumber, parastichopus parvimensis. The PCR-prepared material was then used to clone two closely related mRNA sequences from a sea cucumber soft tissue cDNA library. The putative fibrinogen-related proteins, FReP-A and FReP-B, correspond to the carboxyl-terminal two-thirds of vertebrate fibrinogen beta and gamma chains. Computer comparisons of various fibrinogen-related sequences indicate that the sea cucumber proteins diverged before the beta-gamma gene duplication.
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Affiliation(s)
- X Xu
- Center for Molecular Genetics M-034, University of California, San Diego, La Jolla 92093
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3022
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Tang YW, Ruo SL, Xu X, Sanchez A, Fisher-Hoch SP, McCormick JB, Xu ZY. Hantavirus strains isolated from rodentia and insectivora in rural China differentiated by polymerase chain reaction assay. Arch Virol 1990; 115:37-46. [PMID: 2123383 DOI: 10.1007/bf01310621] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Polymerase chain reaction (PCR) assay and other techniques were applied to differentiate Hantavirus strains isolated from different animal hosts and geographic regions in China. Two groups of related strains, Hantaan and Seoul, have been classified by cross-neutralization, radioimmunoprecipitation (RIP), and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) assays. The molecular weights of glycoprotein 1 (G1) of Hantaan and Seoul viruses were 72k and 80k, whereas those of the nucleocapsid (N) and glycoprotein 2 (G2) remained the same, respectively. The PCR assay was used to differentiate these isolates using synthetic oligonucleotide primers selected from various regions of the M genome of 76118 and R22 strains. 76118-specific primers amplified only the RNAs extracted from Hantaan strains while R22-specific primers, the RNAs from Seoul strains. The PCR results for classification are consistent with those obtained by cross-neutralization, RIP and SDS-PAGE assays.
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Affiliation(s)
- Y W Tang
- Department of Epidemiology, School of Public Health, Shanghai Medical University, People's Republic of China
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3023
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Abstract
Adipose precursor cells from male rats were exposed in primary culture to testosterone (T) or dihydrotestosterone (DHT), and their effects on the regulation of lipolysis were studied. T, but not DHT, stimulated catecholamine-induced lipolysis in a dose-dependent manner, including physiological concentrations. The effect was equally pronounced with isoproterenol (a pure beta-adrenergic agonist) and norepinephrine (a mixed alpha 2- and beta-adrenergic agonist). The higher lipolytic capacity of catecholamines on T-treated cells was paralleled by a similar increase in the number of beta-adrenoceptors in the cells, without a change in the receptor affinity, suggesting that T induced new synthesis or externalization of beta-adrenoceptors. Both T and DHT stimulated forskolin-induced lipolysis, suggesting an androgen effect at the level of the catalytic subunit of adenylate cyclase. The pertussis toxin-stimulated lipolysis was not influenced by the presence of androgens in the culture medium, and no effect was seen on the antilipolytic effect of insulin. These effects did not disappear in the presence of an aromatase inhibitor, suggesting that the T effects were not mediated by conversion to estrogens. These cells showed specific saturable binding for androgens, with a Kd in the range of androgen concentrations shown to be active. In conclusion, androgens enhance the lipolytic capacity of these cells by increasing the apparent number of beta-adrenoceptors (T only) and the activity of adenylate cyclase (both T and DHT). These changes are not mediated by conversion to estrogens. These effects probably occur via binding to specific androgen receptors.
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Affiliation(s)
- X Xu
- Wallenberg Laboratory, Sahlgren's Hospital, University of Goteborg, Sweden
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3024
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Xu X, Wang C, Li Q, D'Alfonso S, Pozzi C, Richiardi P. Characterization of four murine monoclonal antibodies recognizing respectively HLA-A2 plus Aw69, HLA-B13, HLA-Bw4 and HLA-A28. Tissue Antigens 1990; 35:101-2. [PMID: 2343451 DOI: 10.1111/j.1399-0039.1990.tb01764.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- X Xu
- Wuhan Institute of Biological Products Ministry of Public Health, China
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3025
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Abstract
This paper investigates a neural network model-interpattern association (IPA) model-in which the basic logical operations are used to determine the interpattern association (i.e., association between the reference patterns), and simple logical rules are applied to construct tristate interconnections in the network. Computer simulations for the reconstruction of similar English letters embedded in the random noise by the IPA model have shown improved performance compared with the Hopfield model. A 2-D hybrid optical neural network is used to demonstrate the usefulness of the IPA model. Since there are only three gray levels used in the interconnection weight matrix for the IPA model, the dynamic range imposed on a spatial light modulator is rather relaxed, and the interconnections are much simpler than the Hopfield model.
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3026
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Xu X, Pang KS. Hepatic modeling of metabolite kinetics in sequential and parallel pathways: salicylamide and gentisamide metabolism in perfused rat liver. J Pharmacokinet Biopharm 1989; 17:645-71. [PMID: 2635738 DOI: 10.1007/bf01062123] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Previous data on salicylamide (SAM) metabolism in the perfused rat liver had indicated that SAM was metabolized by three parallel (competing) pathways: sulfation, glucuronidation, and hydroxylation, whereas sequential metabolism of the hydroxylated metabolite, gentisamide (GAM), was solely via 5-glucuronidation to form GAM-5G. However, under comparable conditions, preformed GAM formed mainly two monosulfate conjugates at the 2- and 5-positions (GAM-2S and GAM-5S); 5-glucuronidation was a minor pathway. In the present study, the techniques of normal (N) and retrograde (R) rat liver perfusion with SAM and mathematic modeling on SAM and GAM metabolism were used to explore the role of enzymic distributions in determining the dissimilar fates of GAM, as a generated metabolite of SAM or as preformed GAM. Changes in the steady-state extraction ratio of SAM (E) and metabolite formation ratios between N and R perfusions were used as indices of the uneven distribution of enzyme activities. Two SAM concentrations (134 and 295 microM) were used for single-pass perfusion: the lower SAM concentration exceeded the apparent Km for SAM sulfation but was less than those for SAM glucuronidation and hydroxylation; the higher concentration exceeded the apparent Km's for SAM sulfation and glucuronidation but was less than the Km for hydroxylations. Simulation of SAM metabolism data was carried out with various enzyme distribution patterns and extended to include GAM metabolism. At both input concentrations, E was high (0.94 at 134 microM and 0.7 at 295 microM) and unchanged during N and R, with SAM-sulfate (SAM-S) as the major metabolite and GAM-5G as the only detectable metabolite of GAM. Saturation of SAM sulfation occurred at the higher input SAM concentration as shown by a decrease in E and a proportionally less increase in sulfation rates and proportionally more than expected increases in SAM hydroxylation and glucuronidation rates. At both SAM concentrations, the steady-state ratio of metabolite formation rates for SAM-S/SAM-G decreased when flow direction changed from N to R. An insignificant decrease in SAM-S/SAM-OH was observed at the low input SAM concentration, due to the small amount of SAM-OH formed and hence large variation in the ratio among the preparations, whereas at the high input SAM concentration, the decrease in SAM-S/SAM-OH with a change in flow direction from N to R was evident. The metabolite formation ratio, SAM-G/SAM-OH, however, was unchanged at both input concentrations and flow directions.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- X Xu
- Faculty of Pharmacy, University of Toronto, Ontario, Canada
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3027
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3028
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Abstract
A 2-D hybrid optical neural network using a high resolution video monitor as a programmable associative memory is proposed. Experiments and computer simulations of the system have been conducted. The high resolution and large dynamic range of the video monitor enable us to implement a hybrid neural network with more neurons and more accurate operation. The system operates in a high speed asynchronous mode due to the parallel feedback loop. The programmability of the system permits the use of orthogonal projection and multilevel recognition algorithms to increase the robustness and storage capacity of the network.
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3029
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Xu X, Hirayama H, Pang KS. First-pass metabolism of salicylamide. Studies in the once-through vascularly perfused rat intestine-liver preparation. Drug Metab Dispos 1989; 17:556-63. [PMID: 2573500] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Salicylamide (SAM) metabolism was studied in a once-through in situ perfused rat intestine-liver preparation in a manner which mimicked the first-pass effect. SAM (40 or 200 microM) was delivered into the intestine via the superior mesenteric artery at a flow rate of 7.5 ml/min. The intestine venous outflow into the portal vein and the hepatic arterial flow (2.5 ml/min; without drug) served as dual inflows into the liver. The steady state intestinal and hepatic extraction ratios were 0.262 +/- 0.055 and 0.992 +/- 0.014, respectively, at 40 microM, and 0.206 +/- 0.035 and 0.638 +/- 0.117, respectively, at 200 microM. SAM glucuronide was found to be the only metabolite formed by the intestine at both doses. Less than 3% of the dose was secreted into the intestinal lumen, with SAM glucuronide and SAM as the major and minor components, respectively. Hepatic metabolism of SAM, however, revealed SAM sulfation as the predominant pathway, while glucuronidation and hydroxylation were minor metabolic pathways. About 6% of the dose was excreted into bile, mostly as SAM and gentisamide glucuronides. The interrelationship between the intestine and liver clearances was also examined by mass balance considerations and simulation of data. The total rate of elimination of substrate across the two organs is the sum of the rates of metabolism by each organ. However, the overall effective extraction ratio and, hence, the clearance, are less than the sum of the individual extraction ratios and organ clearances, respectively. Our results showed that intestinal metabolism regulated the available substrate for hepatic elimination, and hence modified the contribution of hepatic metabolism in the overall first-pass effect.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- X Xu
- Faculty of Pharmacy, University of Toronto, Ontario, Canada
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3030
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Abstract
Function and stability of vascularly perfused, recirculating in situ rat intestine (I) and intestine-liver (IL) preparations were evaluated in fasted and nonfasted rats because these techniques may be readily applied in drug metabolism studies. The rat intestine was perfused with blood medium (7.5 ml/min) via the superior mesenteric artery, with the venous outflow draining into the portal vein, which, together with hepatic arterial flow (2.5 ml/min), constituted the total blood flow (10 ml/min) to the liver. Maintenance of intestinal membrane integrity was observed. Rapid [14C]glucose absorption against a concentration gradient and a lack of [3H]-polyethylene glycol 4000 (PEG 4000, less than 4%) and Evans blue absorption by the recirculating I and IL preparations resulted after bolus injections of these markers into the pyloric end of the duodenum. Other indexes that revealed stable intestinal and liver functions were the following: preservation of reservoir perfusate volume, constancy in perfusion pressure, bile flow, and hemoglobin concentrations, evidence of intestinal glucose utilization and liver glucose production, and a lack of significant leakage of serum glutamic oxalic transaminase. The intestine and liver consumed oxygen at relatively constant rates, but the consumption rates for the fasted tissues (I or L) were significantly higher than those for nonfasted tissues. These results indicate that the vascularly perfused I and IL preparations were maintained in a viable and stable state for a 2-h perfusion period.
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Affiliation(s)
- H Hirayama
- Faculty of Pharmacy, University of Toronto, Ontario, Canada
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3031
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Huang RH, Xu X. [The fluorometric method for analysis of some acid drugs]. Yao Xue Xue Bao 1989; 24:37-42. [PMID: 2801122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
By using salicylate as a working drug, pyronine was chosen from 31 dyes to form drug-dye complex. In Na2HPO4 solution, salicylate reacts with pyronine to form a complex which is soluble in chloroform. Pyronine fluoresces strongly at lambda ex 542 nm and lambda cm 566 nm and the intensity of pyronine in complex is proportional to the amount of salicylate in the complex with detection limit of 5 ng/ml. By using this method, suberogorgin, flufenamic acid, mechlofenamic acid, mefenamic acid, sodium tauroglycocholate and trichloroacetic acid may be determined with the sensitivity of 10 approximately 50 ng/ml. Salicylate in blood was determined by this method with the sensitivity of 10 ng/ml blood. Good recovery and precision were obtained.
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3032
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Xu X, Okumura A, Morimoto A, Kumeda M, Shimizu T. Thermally induced metastable defects in hydrogenated amorphous silicon and silicon-carbon alloy films. Phys Rev B Condens Matter 1988; 38:8371-8376. [PMID: 9945594 DOI: 10.1103/physrevb.38.8371] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/11/2023]
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3033
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Abstract
Because of the propensity of nascently formed metabolites towards sequential metabolism within formation organs, theoretical and experimental treatments that achieve mass conservation must recognize the various sources contributing to primary, secondary, and tertiary metabolite formation. A simple one-compartment open model, with first-order conditions and the liver as the only organ of drug disappearance and metabolite formation, was used to illustrate the metabolism of a drug to its primary, secondary, and tertiary metabolites, encompassing the cascading effects of sequential metabolism. The concentration-time profiles of the drug and metabolites were examined for two routes of drug administration, oral and intravenous. Formation of the primary metabolite from drug in the gut lumen, with or without further absorption, and metabolite formation arising from first-pass metabolism of the drug and the primary metabolite during oral absorption were considered. Mass balance equations, incorporating modifications of the various absorption and conversion rate constants, were integrated to provide the explicit solutions. Simulations, with and without consideration of the sources of metabolite formation other than from its immediate precursor, were used to illustrate the expected differences in circulating metabolite concentrations. However, a simple relationship between the area under the curve of any metabolite, M, or [AUC (m)], its clearance [CL(m)], and route of drug administration was found. The drug dose, route, fraction absorbed into the portal circulation, Fabs, fraction available of drug from the liver, F, availabilities of the metabolites F(m) from formation organs, and CL(m) are determinants of the AUC(m)'s. After iv drug dosing, the area of any intermediary metabolites is determined by the iv drug dose divided by the (CL(m)/F(m] of that metabolite. When a terminal metabolite is not metabolized, its area under the curve becomes the iv dose of drug divided by the clearance of the terminal metabolite since the available fraction for this metabolite is unity. Similarly, after oral drug administration, when loss of drug in the gut lumen does not contribute to the appearance of metabolites systematically, the general solution for AUC(m) is the product of Fabs and oral drug dose divided by [CL(m)/F(m)]. A comparison of the area ratios of any metabolite after po and iv drug dosing, therefore, furnishes Fabs. When this fraction is divided into the overall systemic availability or Fsys, the drug availability from the first-pass organs, F, may be found.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- M V St-Pierre
- Faculty of Pharmacy, University of Toronto, Ontario, Canada
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3034
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Wang YZ, Xu YZ, Luo D, Xu X. [Purification and characterization of depressor component of Agkistrodon acutus venom]. Zhongguo Yao Li Xue Bao 1988; 9:334-7. [PMID: 3195344] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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3035
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Yin QZ, Ye MJ, Xu X, Liu HC, Liu J, Liu XM. [The use of avidin-biotin peroxidase complex-ELISA for the examination of HBsAg]. Hua Xi Yi Ke Da Xue Xue Bao 1988; 19:174-6. [PMID: 3198100] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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3036
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Huang RH, Xu X. [Phosphorimetric method for the determination of dihydroetorphine and its application]. Yao Xue Xue Bao 1988; 23:298-303. [PMID: 3176985] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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3037
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Anholt R, Xu X, Stoller C, Molitoris JD, Meyerhof WE, Rude BS, McDonald RJ. Intermediate-velocity atomic collisions: Electron capture and loss in 10-42-MeV C ions. Phys Rev A Gen Phys 1988; 37:1105-1114. [PMID: 9899771 DOI: 10.1103/physreva.37.1105] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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3038
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Xu X, Chen S, Tsai W, Huang N. A case study of solving optimization problems using neural networks. Neural Netw 1988. [DOI: 10.1016/0893-6080(88)90190-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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3039
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Kung HF, Guo YZ, Billings J, Xu X, Mach RH, Blau M, Ackerhalt RE. Preparation and biodistribution of [125I]IBZM: a potential CNS D-2 dopamine receptor imaging agent. Int J Rad Appl Instrum B 1988; 15:195-201. [PMID: 2966782 DOI: 10.1016/0883-2897(88)90088-8] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
A new CNS D-2 dopamine receptor imaging agent [125I]IBZM, (S)-3-[125I]-iodo-N-[(1-ethyl-2-pyrrolidinyl)] methyl-2-hydroxy-6-methoxybenzamide, was prepared by either an exchange reaction or by the chloramine-T method. After an i.v. injection, the agent easily passed through the blood-brain barrier and localized in the rat brain. At 2, 15, 30 and 60 min after the injection, the brain uptake was 2.9, 2.3, 1.8 and 0.7% dose/organ, respectively. Regional uptake ratio of striatum/cerebellum (target to nontarget ratio) increased from 1.4 at 30 s to 10.3 at 2 h after the i.v. injection. Digital autoradiography of rat brain sections showed high regional uptake in the caudate putamen and accumbens nucleus, areas known to have a high concentration of the D-2 dopamine receptor. The specific uptake at the D-2 dopamine receptor site was blocked by pretreatment with spiperone, a selective D-2 antagonist. When labeled with 123I (t1/2 = 13 h, 159 keV), [123I]IBZM may be useful for imaging the CNS D-2 dopamine receptor.
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Affiliation(s)
- H F Kung
- Department of Nuclear Medicine, SUNY, Buffalo
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3040
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3041
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Cannizzaro LA, Bollum FJ, Huebner K, Croce CM, Cheung LC, Xu X, Hecht BK, Hecht F, Chang LM. Chromosome sublocalization of a cDNA for human DNA polymerase-beta to 8p11----p12. Cytogenet Cell Genet 1988; 47:121-4. [PMID: 3378450 DOI: 10.1159/000132527] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
We have localized a cDNA fragment that codes for human DNA polymerase-beta. Using somatic cell and in situ hybridization techniques, this cDNA was cloned by screening a human KM-3 cell cDNA library in lambda gt 11 for expression of fused beta-galactosidase-human DNA polymerase-beta proteins. We have mapped this human polymerase-beta gene to the short arm of chromosome 8 in the subregion 8p11----p12.
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Affiliation(s)
- L A Cannizzaro
- Genetics and Cancer Center, Southwest Biomedical Research Institute, Scottsdale, AZ 85251
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3042
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Xu X, Pang KS. High-performance liquid chromatographic method for the quantitation of salicylamide and its metabolites in biological fluids. J Chromatogr 1987; 420:313-27. [PMID: 3693503 DOI: 10.1016/0378-4347(87)80187-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
A high-performance liquid chromatographic (HPLC) assay is described for the determination of salicylamide (SAM) and its metabolites in biological fluids obtained from an in situ rat liver preparation and rat in vivo. SAM and its six metabolites, salicylamide sulphate, salicylamide glucuronide, gentisamide (GAM), gentisamide 2-sulphate, gentisamide 5-sulphate and gentisamide 5-glucuronide, were separated on a mu Bondapak C18 column with 0.085 M potassium dihydrogenphosphate pH 3.35, as mobile phase and by using a flow gradient. Enriched recovery of SAM and GAM from blood was achieved by extraction followed by a second HPLC procedure with a mobile phase consisting of acetic acid and methanol. Furthermore, the reproducibility and the stability of the samples under assay conditions were investigated.
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Affiliation(s)
- X Xu
- Faculty of Pharmacy, University of Toronto, Ontario, Canada
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3043
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Anholt R, Meyerhof WE, Xu X, Gould H, Feinberg B, McDonald RJ, Wegner HE, Thieberger P. Atomic collisions with relativistic heavy ions. VIII. Charge-state studies of relativistic uranium ions. Phys Rev A Gen Phys 1987; 36:1586-1600. [PMID: 9899039 DOI: 10.1103/physreva.36.1586] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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3044
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Xu X, Guan Y, Tang Y, Wang S. Study of structure–activity relationship for some isomers of cinnamamides. Acta Crystallogr A 1987. [DOI: 10.1107/s0108767387084253] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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3045
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Huang RH, Xu X. [Phosphorimetric analysis of amines]. Yao Xue Xue Bao 1987; 22:284-8. [PMID: 3687449] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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3046
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Abstract
The messages for two small but abundant apolipoproteins found in lamprey blood plasma were cloned with the aid of oligonucleotide probes based on amino-terminal sequences. In both cases, numerous clones were identified in a lamprey liver cDNA library, consistent with the great abundance of these proteins in lamprey blood. One of the cDNAs (LAL1) has a coding region of 105 amino acids that corresponds to a 21-residue signal peptide, a putative 8-residue propeptide, and the 76-residue mature protein found in blood. The other cDNA (LAL2) codes for a total of 191 residues, the first 23 of which constitute a signal peptide. The two proteins, which occur in the "high-density lipoprotein fraction" of ultracentrifuged plasma, have amino acid compositions similar to those of apolipoproteins found in mammalian blood; computer analysis indicates that the sequences are largely helix-permissive. When the sequences were searched against an amino acid sequence data base, rat apolipoprotein IV was the best matching candidate in both cases. Although a reasonable alignment can be made with that sequence and LAL1, definitive assignment of the two lamprey proteins to typical mammalian classes cannot be made at this point.
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3047
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Spooner DW, Stoller C, Chemin J, Meyerhof WE, Scheurer J, Xu X. Large resonance effect in K-shell ionization probability in elastic proton backscattering on 138Ba. Phys Rev Lett 1987; 58:341-344. [PMID: 10034909 DOI: 10.1103/physrevlett.58.341] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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3048
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Hotchkis MA, Reiff JE, Vieira DJ, Blönnigen F, Lang TF, Moltz DM, Xu X, Cerny J. Beta-delayed proton decay of 61Ge. Phys Rev C Nucl Phys 1987; 35:315-319. [PMID: 9953763 DOI: 10.1103/physrevc.35.315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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3049
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Xu X. [A tentative discussion on family planning problems in Xinjiang's minorities]. Renkou Yanjiu 1987:36-40. [PMID: 12341828] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/26/2023]
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3050
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Gu FL, Xu X, Wu JP. [The problem of tumor cell wound seeding in the open excision and partial cystectomy in bladder cancer]. Zhonghua Wai Ke Za Zhi 1986; 24:533-5, 573. [PMID: 3582039] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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