2251
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Abstract
1. Postnatal changes in Ca2+ current were studied in voltage clamped atrial myocytes isolated from Sprague-Dawley rats. T- and L-type Ca2+ currents were identified using standard electrophysiological and pharmacological techniques. Cells were studied from seven groups of male and six groups of female rats ranging in age from 3 to 14 weeks. 2. The density of atrial T-type Ca2+ current showed significant variation during postnatal development, with a maximum density reached at 4.5-5 weeks. At this age, T-current density was 1.44 +/- 0.11 pA/pF (n = 23) for cells isolated from male and 1.25 +/- 0.09 pA/pF (n = 25) for cells isolated from female animals in bathing solutions containing 2 mM-Ca2+. T-current density in atrial cells isolated from younger animals (3.5 weeks postnatal) averaged 1.22 +/- 0.06 (n = 18) and 1.00 +/- 0.05 pA/pF (n = 22) or 85 and 80% of the maximum seen at 4.5-5 weeks for male and female rats, respectively. For rats older than 13 weeks, the average T-current density in atrial cells was 0.50 +/- 0.03 (n = 18) and 0.51 +/- 0.02 pA/pF (n = 35) or 35 and 41% of the maximum seen at 4.5-5 weeks for male and female rats, respectively. 3. In contrast to the T-type current, the density of atrial L-type Ca2+ current remained unchanged in rats from 3 to 14 weeks old. L-type current averaged 8.2 +/- 0.2 (n = 134) in male and 7.9 +/- 0.2 pA/pF (n = 102) in female rats. 4. Fluctuation analysis was used to estimate single T-channel current levels in 4.5- and 7.5-week-old male rats. While the T-current density differed by 70% at these two postnatal ages, no significant difference (P > 0.2) in single channel current was found. Single channel current was 0.12 +/- 0.01 pA (n = 9) for cells from 4.5-week-old and 0.13 +/- 0.01 pA (n = 7) for cells from 7.5-week-old rats. Currents were stimulated by test pulses from -80 to -30 mV at 5 mM-Ca2+. 5. No postnatal changes were seen in either the kinetics of activation or inactivation of macroscopic T-current.(ABSTRACT TRUNCATED AT 400 WORDS)
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2252
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Xu X, Kantrowitz E. The importance of aspartate 327 for catalysis and zinc binding in Escherichia coli alkaline phosphatase. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(18)41992-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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2253
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Yagi T, Xu X, Matsuno-Yagi A. The energy-transducing NADH-quinone oxidoreductase (NDH-1) of Paracoccus denitrificans. BIOCHIMICA ET BIOPHYSICA ACTA 1992; 1101:181-3. [PMID: 1633184] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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2254
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Xu X, Matsuno-Yagi A, Yagi T. Structural features of the 66-kDa subunit of the energy-transducing NADH-ubiquinone oxidoreductase (NDH-1) of Paracoccus denitrificans. Arch Biochem Biophys 1992; 296:40-8. [PMID: 1605643 DOI: 10.1016/0003-9861(92)90542-5] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The structural gene of the Paracoccus denitrificans NADH-ubiquinone oxidoreductase encoding a homologue of the 75-kDa subunit of bovine complex I (NQO3) has been located and sequenced. It is located approximately 1 kbp downstream of the gene coding for the NADH-binding subunit (NQO1) [Xu, X., Matsuno-Yagi, A., and Yagi, T. (1991) Biochemistry 30, 6422-6428] and is composed of 2019 base pairs and codes for 673 amino acid residues with a calculated molecular weight of 73,159. The M(r) 66,000 polypeptide of the isolated Paracoccus NADH dehydrogenase complex is assigned the NQO3 designation on the basis of N-terminal protein sequence analysis, amino acid analysis, and immuno-cross-reactivity. The encoded protein contains a putative tetranuclear iron-sulfur cluster (probably cluster N4) and possibly a binuclear iron-sulfur cluster. An unidentified reading frame (URF3) which is composed of 396 base pairs and possibly codes for 132 amino acid residues was found between the NQO1 and NQO3 genes. When partial DNA sequencing of the regions downstream of the NQO3 gene was performed, sequences homologous to the mitochondrial ND-1, ND-5, and ND-2 gene products of bovine complex I were found, suggesting that the gene cluster carrying the Paracoccus NADH dehydrogenase complex contains not only structural genes encoding water-soluble subunits but also structural genes encoding hydrophobic subunits.
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2255
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Wang XY, Weng YL, Xu X, Kong DG, Hu ZK, Wang ZM. [The causes of misdiagnosis of periapical diseases and subsequent management]. SHANGHAI KOU QIANG YI XUE = SHANGHAI JOURNAL OF STOMATOLOGY 1992; 1:15-7. [PMID: 15159916] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Subscribe] [Scholar Register] [Indexed: 04/29/2023]
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2256
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Chu HT, Henriksen PN, Jing J, Wang H, Xu X. Magnetic-field dependence of Hall resistance in thin films of pure bismuth. PHYSICAL REVIEW. B, CONDENSED MATTER 1992; 45:11233-11237. [PMID: 10001047 DOI: 10.1103/physrevb.45.11233] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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2257
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Xu X. [Mechanical principles of L-trapezoid compression plate in the fixation of trochanter fractures]. ZHONGHUA YI XUE ZA ZHI 1992; 72:261-4, 318. [PMID: 1327456] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Three pairs of human cadaver femur were used for simulation electric test with load on both legs and single leg. An Evans III osteotomy was made, and stabilized with L-trapezoid compression plate (L-TCP). L-angled plate (L-AP) 95 degrees and 130 degrees respectively. The results demonstrated that the stability of fixation of L-TCP was significantly greater than L-AP. Since the cancellous screw of L-TCP can hold the proximal fragment and forms a stable triangular truss with the L end, the bony support of the medial posterior part can be reconstructed by holding the lesser trochanter with the lag screw. From June 1980 to August 1990, 68 patients with 71 trochanter fractures and osteotomies were treated with L-CTP. 54 patients with 57 fractures and osteotomies were followed up for 6-52 months. All fractures and osteotomies were healed. No bone cutting off failure was encountered. The hips and knees of 51 patients (54 limbs) (94.8%) showed excellent and good functions. Infection occurred in 3 patients (4.4%). Varus deformity developed in 2 patients with an Evans IV fracture, and plate fracture occurred in one of them.
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2258
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Gupta KC, Xu X. Facile PCR cloning of full-length Sendai virus mRNAs. PCR METHODS AND APPLICATIONS 1992; 1:293-6. [PMID: 1282435 DOI: 10.1101/gr.1.4.293] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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2259
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Berg CM, Vartak NB, Wang G, Xu X, Liu L, MacNeil DJ, Gewain KM, Wiater LA, Berg DE. The m gamma delta-1 element, a small gamma delta (Tn1000) derivative useful for plasmid mutagenesis, allele replacement and DNA sequencing. Gene 1992; 113:9-16. [PMID: 1314210 DOI: 10.1016/0378-1119(92)90664-b] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Transposon gamma delta (Tn1000), a 6-kb member of the Tn3 family, is widely used for plasmid mutagenesis. A 1.8-kb derivative of gamma delta was constructed that contains the kan gene from Tn5 and the resolution (res) site from gamma delta cloned between 40-bp inverted repeats of gamma delta's delta (delta) end. This element, named m gamma delta-1, lacks the genes encoding transposase and resolvase, and therefore depends on its host to supply transposition and resolution functions. Thus, in strains lacking gamma delta, m gamma delta-1 will not transpose. The m gamma delta-1 element is shown to be useful for mutagenesis of plasmids, DNA sequencing, and allele replacement (in Streptomyces avermitilis).
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2260
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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. [PMID: 1534239 DOI: 10.1037//0735-7044.106.2.307] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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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2261
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Xu X, Caulfield JP. Characterization of human low density lipoprotein binding proteins on the surface of schistosomula of Schistosoma mansoni. Eur J Cell Biol 1992; 57:229-35. [PMID: 1324838] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Low density lipoproteins (LDL) bound to the surface of Schistosoma mansoni may protect the parasite from assault by the immune system and provide essential lipids for the parasite in human schistosomiasis. Here we have characterized the LDL binding sites on the surface of schistosomula by comparing the binding of fluorescently labeled LDL to the parasite with LDL binding proteins as seen by ligand blotting before and after enzymatic treatment of viable parasites. Ligand blotting revealed two LDL binding bands, 17.8 +/- 0.8 and 15.7 +/- 0.6 kDa, in intact schistosomula. Trypsinization eliminated all of the specific and approximately two-thirds of the total LDL binding capacity of schistosomula in a time and concentration-dependent manner. LDL did not bind to any bands on blots of trypsinized, viable worms. Specific LDL binding was also eliminated by phosphatidylinositol-specific phospholipase C (PIPLC). PIPLC treatment removed both LDL binding bands from the worms and caused the appearance of an LDL binding band, 16.6 +/- 0.3 kDa, in the culture medium. LDL binding to the parasite recovered within 24 to 48 h after trypsinization but the recovery was inhibited by either monensin or puromycin. Both LDL binding bands reappeared in ligand blots of cultured worms within 24 h; the reappearance was blocked by puromycin but not by monensin. These studies suggest that the specific binding of human LDL to schistosomula is mediated by GPI-linked low molecular weight proteins that are continually synthesized and transported to the parasite surface.
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2262
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2263
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Runde M, Routbort JL, Rothman SJ, Goretta KC, Mundy JN, Xu X, Baker JE. Tracer diffusion of oxygen in Bi2Sr2CaCu2Ox. PHYSICAL REVIEW. B, CONDENSED 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] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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2264
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Xu X, Hagen SJ, Jiang W, Peng JL, Li ZY, Greene RL. Thermoelectric power of Nd2-xCexCuO4 crystals. PHYSICAL REVIEW. B, CONDENSED 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] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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2265
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Xu X, Philipsen HP, Jablonski NG, Pang KM, Zhu J. Age estimation from the structure of adult human teeth: review of the literature. Forensic Sci Int 1992; 54:23-8. [PMID: 1618452 DOI: 10.1016/0379-0738(92)90077-a] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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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2266
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Luo Y, Jiang X, Lai L, Qu C, Xu X, Tang Y. Building protein backbones from C alpha coordinates. PROTEIN ENGINEERING 1992; 5:147-50. [PMID: 1594568 DOI: 10.1093/protein/5.2.147] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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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2267
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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] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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2268
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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] [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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2269
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2270
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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] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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2271
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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. CHINESE MEDICAL SCIENCES JOURNAL = CHUNG-KUO I HSUEH K'O HSUEH TSA CHIH 1991; 6:148-52. [PMID: 1793877] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [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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2272
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Xu X, Kantrowitz ER. A water-mediated salt link in the catalytic site of Escherichia coli alkaline phosphatase may influence activity. Biochemistry 1991; 30:7789-96. [PMID: 1907846 DOI: 10.1021/bi00245a018] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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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2273
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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 = JOURNAL OF WEST CHINA UNIVERSITY OF MEDICAL SCIENCES = HUAXI YIKE DAXUE XUEBAO 1991; 22:213-5. [PMID: 1686259] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [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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2274
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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 = EYE SCIENCE 1991; 7:21-4. [PMID: 1843124] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [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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2275
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