10826
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Zhang Y, Ladjimi MM, Kantrowitz ER. Site-directed mutagenesis of a residue located in the regulatory site of Escherichia coli aspartate transcarbamoylase. Involvement of lysine 94 in effector binding and the allosteric mechanism. J Biol Chem 1988; 263:1320-4. [PMID: 3121627] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Lysine 94 in the regulatory chain of aspartate transcarbamoylase has been changed to a glutamine residue by site-directed mutagenesis. The resulting enzyme is almost insensitive to the activator ATP and shows a substantially reduced response to the feedback inhibitor CTP. Competition experiments indicate that ATP is still able to bind at low concentrations to the regulatory site of the mutant enzyme, even though no stimulation could be detected. When the nucleosides adenosine or cytidine were used, the saturation curves of the mutant and the wild-type enzyme became indistinguishable. Together these results indicate that lysine 94 is strongly involved in the binding of ATP and CTP by interacting specifically with the triphosphate moiety of these nucleotide effectors. Furthermore, unlike the wild-type enzyme, the inhibitory and stimulatory effects in the mutant enzyme are insensitive to changes in aspartate concentrations, implying that the lysine 94 side chain is also involved in the allosteric mechanism of the enzyme.
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10827
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Morosin B, Graham RA, Zhang Y, Stewart JM, Hubbard CR. X-ray Line Broadening Study on Shock-modified Zirconia. ACTA ACUST UNITED AC 1988. [DOI: 10.1071/ph880251] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Zirconia (Zr02) powder compacts have been subjected to controlled, quantitative high pressure shock loading at peak pressures from 5-27 GPa and preserved for post-shock analysis. The overlapping broadened X-ray diffraction peak profiles have been separated by least-squares fitting procedures. The separate lines have been analysed in the usual manner to determine the residual lattice strain and the coherent crystallite sizes. Maximum modification effects are observed near 20 GPa with strain values near 3 x 10-3 and size values near 200 A.
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10828
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Zhang Y, Saison M, Spaepen M, De Strooper B, Van Leuven F, David G, Van den Berghe H, Cassiman JJ. Mapping of human fibronectin receptor beta subunit gene to chromosome 10. SOMATIC CELL AND MOLECULAR GENETICS 1988; 14:99-104. [PMID: 2963381 DOI: 10.1007/bf01535053] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Human-mouse hybrid cells were examined by indirect immunofluorescence with Mab DH12, a monoclonal antibody that recognizes the beta subunit of the human fibronectin receptor. Cells that expressed the antigen at their surface were sorted by FACS and karyotyped. Immunoaffinity chromatography on Mab DH12 was used to confirm the presence of the human antigen. The chromosome assignment was strengthened by isozyme analysis of markers for chromosomes 9 and 10. The results are suggestive for a 10p mapping of this beta subunit of the fibronectin receptor. Since the gene coding for the beta subunit of the VLA proteins was previously assigned to the same chromosome, our result could provide further evidence for the relationship between the beta subunit of the human fibronectin receptor and the VLA protein family.
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10829
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Luo G, Shen C, Yang X, Zhang Y. Effects of ligustrazine and anisodamine on rabbit whole blood viscosity and erythrocyte deformability. Chin Med J (Engl) 1988; 101:48-51. [PMID: 3142732] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
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10830
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Zhang Y. Inhibition of hemoglobin degradation in Plasmodium falciparum by chloroquine and ammonium chloride. Exp Parasitol 1987; 64:322-7. [PMID: 3315731 DOI: 10.1016/0014-4894(87)90042-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The effect of chloroquine (CQ) and NH4Cl on hemoglobin degradation within Plasmodium falciparum was studied by SDS gel electrophoresis. CQ inhibited hemoglobin digestion such that accumulation of hemoglobin in the parasites occurred. Quantitative analysis indicated that the content of hemoglobin in isolated CQ-treated parasites was increased from 2.39 +/- 0.47 micrograms hemoglobin (Hb)/mg protein to 8.34 +/- 0.77 micrograms Hb/mg protein (P less than 0.001) within 45 min and further to 18.7 +/- 1.23 micrograms Hb/mg protein for 2 hr compared with the untreated parasites. These results suggest that the inhibition of hemoglobin degradation in malarial parasites might be the primary target of CQ antimalarial action. The CQ-like effect on the hemoglobin digestion in P. falciparum was observed with another lysosomotropic weak base, NH4Cl, suggesting that the CQ effect on hemoglobin degradation and its antimalarial action, as well as the effect of NH4Cl, are related to their properties of lysosomotropic weak base.
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10831
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Stephenson JL, Zhang Y, Eftekhari A, Tewarson R. Electrolyte transport in a central core model of the renal medulla. THE AMERICAN JOURNAL OF PHYSIOLOGY 1987; 253:F982-97. [PMID: 3688243 DOI: 10.1152/ajprenal.1987.253.5.f982] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Transport of Na+, K+, Cl-, urea, and water is described in a central core model of the renal medulla. Equations for mass balance, Poiseuille flow, and the Nernst-Planck equation describe the continuous behavior of the system along the medullary axis and along the distal nephron; the Kedem and Katchalsky phenomenology describes passive transmural transport; active transmural transport obeys Michaelis-Menten kinetics. Numerical solution of the differential equations shows that to a close approximation any combination of active Na+ and active Cl- transport can generate the same concentration profiles but will generate very different potential profiles, and consequently, very different K+ absorption in thick ascending limb of Henle's loop. If a net transport stoichiometry of 2 Cl- ions to 1 Na+ ion is selected for the pumps, an active Cl- transport rate of approximately 10,000 peq.s-1.cm-2 gives K+ and Na+ concentrations in early distal nephron and a medullary osmolality profile in reasonable agreement with experimental data.
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10832
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Zhang Y. [Transmission of epidemic hemorrhagic fever virus between mice and mites in EHF endemic areas]. ZHONGHUA YU FANG YI XUE ZA ZHI [CHINESE JOURNAL OF PREVENTIVE MEDICINE] 1987; 21:325-7. [PMID: 2898326] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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10833
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Guo YJ, Zhang Y, Liu YX, Lin ZH. Effects of some alcohols on the conformation of mitochondrial H+-ATPase complex and F1-ATPase from pig heart. BIOCHIMICA ET BIOPHYSICA ACTA 1987; 894:11-5. [PMID: 2889469 DOI: 10.1016/0005-2728(87)90207-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The conformations of the H+-ATPase complex and F1-ATPase in low concentrations of methanol, ethanol, n-propanol, iso-propanol and t-butanol were studied by circular dichroism. For F1-ATPase, all but methanol first increased and then decreased the circular dichroism magnitude of helical bands as the alcohol concentration was increased. With ethanol, n-propanol, iso-propanol and t-butanol, the alpha-helix content reached a maximum at about 5% alcohol and began to decrease at 10%. The content of beta-sheet showed the opposite effect, reaching a minimum at 5% and increasing slightly at higher concentrations. None of the alcohols studied had a significant effect on the conformation of the H+-ATPase complex. This difference implies that the alcohols had a greater effect on free F1-ATPase than on the membrane-bound F1-ATPase. The hydrophobic protein F0 and the membrane lipids in the H+-ATPase complex may stabilize and protect F1 from the effects of the alcohols.
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10834
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Wu DF, Zheng ZH, Zhang Y, Fang C, Liu HL. DNA repair capability in human gastric mucosal epithelial cells and high gastric cancer incidence in Fujian Province. Chin Med J (Engl) 1987; 100:778-80. [PMID: 3127129] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
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10835
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Tang M, Zhang GI, Zeng XR, Zhong JY, Zhang Y, Li SR. Relationship between action potential duration of ventricular cells and heart rate in dog under natural breathing. JOURNAL OF TONGJI MEDICAL UNIVERSITY = TONG JI YI KE DA XUE XUE BAO 1987; 7:148-52. [PMID: 3448239 DOI: 10.1007/bf02888208] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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10836
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Wu DF, Zheng ZH, Zhang Y, Fang C. A preliminary study of mixed function oxidase activity in gastric mucosa and stomach cancer mortality in Fujian Province. Chin Med J (Engl) 1987; 100:735-9. [PMID: 3127149] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
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10837
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Pan K, Lin Y, Fu Z, Zhou K, Cai Z, Chen Z, Zhang Y, Dong Y, Wu S, Ma X, Wang Y, Chen S, Wang J, Zhang X, Ni C, Zhang Z, Xia Z, Fan Z, Tian G. The three-dimensional structure of trichosanthin. Acta Crystallogr A 1987. [DOI: 10.1107/s0108767387084915] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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10838
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Zhang Y, Ihlen H, Myhre E, Levorstad K, Nitter-Hauge S. Quantification of mitral regurgitation by Doppler echocardiography. Eur Heart J 1987; 8 Suppl C:59-62. [PMID: 3678248 DOI: 10.1093/eurheartj/8.suppl_c.59] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The present study was undertaken to evaluate a new non-invasive approach to the quantification of mitral regurgitation. Doppler echocardiography and left ventriculography were performed in 20 patients without valvular heart disease (group A), and in 30 patients with pure mitral regurgitation (group B). Volumetric flows through the aortic and mitral valve orifices were determined by Doppler technique. The aortic flow (AF) was calculated as the product of the aortic orifice area by the systolic velocity integral. The mitral flow (MF) was computed as the product of the corrected mitral orifice area by the diastolic velocity integral. The mitral regurgitant fraction (RF) was calculated as: RF = 1 - AF/MF. In group A, there was a close agreement between aortic and mitral flows (r = 0.94, P less than 0.001), and there was no significant difference between the two measurements. In group B, the mitral flow was significantly higher than the aortic flow. The regurgitant fraction assessed by Doppler echocardiography correlated well with the grades of severity of regurgitation obtained at left ventriculography. We conclude that combined measurement of both aortic and mitral flows by Doppler echocardiography provides a new and promising approach to the noninvasive quantification of mitral regurgitation.
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10839
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Zhang Y, Sher JH, Leung B, Shafiq SA. An immunocytochemical study of type I muscle fibres in developing human skeletal muscles. J Neurol Sci 1987; 80:1-12. [PMID: 2440999 DOI: 10.1016/0022-510x(87)90216-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
An immunocytochemical study was done on the skeletal muscles of human fetuses (19-36 weeks gestation), infants and adults using a new monoclonal antibody (McAb) ALD-47. The antibody was generated against slow myosin of chicken and is specific for myosin heavy chain (MHC). In human infants and adults the type I muscle fibres are strongly reactive with this McAb and the type II fibres uniformly non-reactive. In the fetuses from 19-20 weeks gestation (in whom the fibre types are not distinguishable by the histochemical myosin ATPase test) a proportion of muscle fibres react specifically with ALD-47. Other muscle fibres at this stage react positively with a fast specific MHC McAb HM-1.2 or are negative to both ALD-47 and HM-1.2 antibodies. These McAbs, thus, identify three distinct fibre populations in the early fetal muscle which by histochemical staining appears homogeneous. The percentage of ALD-47 positive fibres increases in fetuses at later gestational periods; at all stages these fibres lack reactivity with the HM-1.2 antibody. Because of its selective fibre type reactivity in differentiating muscles, the McAb ALD-47 in conjunction with HM-1.2 should be useful in immunoaffinity fractionation and biochemical studies of myosin isoforms in developing human muscles.
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10840
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Callaway J, Chen DP, Zhang Y. Hubbard model for a cubic cluster. PHYSICAL REVIEW. B, CONDENSED MATTER 1987; 36:2084-2091. [PMID: 9943052 DOI: 10.1103/physrevb.36.2084] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/11/2023]
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10841
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Zhang Y, Tzartos S, Schalke BC, Melms A, Wekerle H. Interaction between AChR-specific T- and B-line lymphocytes: antigen presentation by B hybridoma cells and the enhancing effect of monoclonal antibodies on T-cell activation. Ann N Y Acad Sci 1987; 505:71-81. [PMID: 3500671 DOI: 10.1111/j.1749-6632.1987.tb51283.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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10842
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Goksøyr A, Andersson T, Hansson T, Klungsøyr J, Zhang Y, Förlin L. Species characteristics of the hepatic xenobiotic and steroid biotransformation systems of two teleost fish, Atlantic cod (Gadus morhua) and rainbow trout (Salmo gairdneri). Toxicol Appl Pharmacol 1987; 89:347-60. [PMID: 3496689 DOI: 10.1016/0041-008x(87)90154-2] [Citation(s) in RCA: 89] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Groups of Atlantic cod and rainbow trout were treated (ip) with beta-naphthoflavone (BNF), phenobarbital, or peanut oil (controls), and properties of the hepatic xenobiotic and steroid metabolizing enzyme systems were evaluated. In both species, BNF treatment resulted in significant induction of microsomal 7-ethoxycoumarin O-deethylase, 7-ethoxyresorufin O-deethylase, biphenyl 4-hydroxylase, and phenanthrene oxidation, especially at the 1,2-position. Immunochemical studies with rabbit IgG prepared against the major BNF-inducible cytochrome P-450 in cod, P-450c, revealed increased amounts of immunoreactive protein in liver slices from both species after BNF treatment. The molecular weight of the induced protein was approximately 58,000 Da, as shown by Western blotting. When titrating biphenyl 4-hydroxylation, however, the antibodies distinguished between the two species, inhibiting the activity of BNF-induced cod 90% and that of rainbow trout 40% at 10 mg IgG/nmol P-450. Furthermore, cytochrome b5 content and UDP-glucuronyltransferase activity were significantly induced only in rainbow trout, whereas the specific content of cytochrome P-450 was significantly increased only in cod. Differences between the two species were observed in the levels of constitutive activities, the amount of induction, and in the regioselectivity of phenanthrene oxidation and androstenedione metabolism. Treatment with phenobarbital showed no effect on any of the parameters investigated in either species. The results show that although there are many common features of the hepatic xenobiotic and steroid biotransformation systems of the two teleosts, certain species characteristics exist in constitutive properties and induction responses.
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10843
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Abstract
Drug resistance is a serious problem in malaria, and prospects for new drugs are not optimistic. In 1963, the US Army began a huge programme to develop new antimalarials; they screened over 235 000 compounds, but very few were sufficiently active and safe for use in humans. Part of the problem is that not enough is known about the biochemical properties of malaria parasites, especially the metabolic differences between them and their host cells which could offer targets for specific chemotherapy. An important characteristic of malaria infection is the rapid growth of the parasite population, and changes in host metabolism that result from this. A similar effect occurs in many cancers. In this article, Ya Zhang argues that malaria parasites also have metabolic similarities with tumour cells, and suggests that careful comparison of these two could provide insight for new drug development.
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10844
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Abstract
A simple and rapid solid-phase RNA sequencing method has been developed based on Peattie's direct chemical method. 3'-Terminally labeled RNA was immobilized on DEAE-cellulose sheets and followed by specific modification with dimethyl sulfate, diethylpyrocarbonate, hydroxylamine (at pH 10 for the uridine and pH 5.5 for the cytidine reaction), and cleavage reaction with aniline. RNA fragments were washed from the DEAE-cellulose sheets using salt solutions, precipitated with ethanol, and separated by 15% polyacrylamide gel electrophoresis. Due to the complete removal of the impurities normally present in the solution method, the higher resolution of the sequencing bands and lower background on the autoradiograph make this solid-phase technique more efficient. This solid-phase technique is much faster and more convenient than the original method.
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10845
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Irie H, Matsumoto K, Kitagawa T, Zhang Y, Ueno T, Nakashima T, Fukami H. Total synthesis of esters of AK-toxin II and AF-toxin IIc starting from vitamin C as a chiral material. Chem Pharm Bull (Tokyo) 1987; 35:2598-601. [PMID: 3664857 DOI: 10.1248/cpb.35.2598] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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10846
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Li SG, Zhang Y, Lin ZH. On the mechanism of the reconstitution of F1-depleted ATPase complex with purified F1: possible conformational effects. J Bioenerg Biomembr 1987; 19:273-83. [PMID: 2887556 DOI: 10.1007/bf00762417] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The membrane sector (F0) of H+-ATPase was prepared by trypsin and urea treatment of F1-F0 and reconstituted with purified F1. The oligomycin sensitivity of the reconstituted F1-F0 complex obtained by treating F1 or F0 with Mg2+ before binding is much higher than that obtained without Mg2+ treatment. The greater change in the intrinsic fluorescence of the reconstituted F1-F0 complex obtained by Mg2+ treatment suggests that conformational changes may occur during the reconstitution. We deduce that Mg2+ binds to membrane lipids, thus decreasing membrane fluidity and changing the physical state of the lipids to provide a suitable microenvironment for conformational changes in F0. The data also suggest that the conformational change in the F0 portion of the F1-F0 complex can be transmitted to the F1 portion, the conformation of which is in turn altered, resulting in the formation of an F1-F0 complex with high oligomycin sensitivity. On the other hand, Mg2+ may act on F1 directly to induce a suitable conformational change which is then transmitted to F0, resulting in the formation of an H+-ATPase with greater sensitivity to oligomycin.
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10847
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Zhang Y, Hempelmann E. Lysis of malarial parasites and erythrocytes by ferriprotoporphyrin IX-chloroquine and the inhibition of this effect by proteins. Biochem Pharmacol 1987; 36:1267-73. [PMID: 3297071 DOI: 10.1016/0006-2952(87)90080-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Ferriprotoporphyrin IX(FP) lysed both erythrocytes and isolated Plasmodium falciparum as judged by decrease in turbidity of erythrocyte and parasite suspensions. The lytic effect of FP on erythrocytes was enhanced by chloroquine (CQ). In the presence of 2.5-20 microM CQ, 5 microM FP led to complete hemolysis within 45 min. However, the lytic effect of FP or FP-CQ on both erythrocytes and parasites was inhibited completely by proteins. The protein inhibition was non-specific. This finding, the failure of FP and FP--CQ to cause hemolysis and lysis of malarial parasites in a protein-containing medium, does not support the "FP--CQ complex hypothesis" for the antimalarial action of chloroquine.
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10848
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Zhang Y. [Advances in Doppler echocardiography]. ZHONGHUA NEI KE ZA ZHI 1987; 26:242-5. [PMID: 3308357] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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10849
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Dams R, Zhang Y. Elemental composition of dust in an iron foundry as determined by instrumental neutron activation analysis. J Radioanal Nucl Chem 1987. [DOI: 10.1007/bf02035523] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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10850
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Zhang Y, Fink M. Magnetic susceptibility for Ne derived from small-angle electron scattering data. PHYSICAL REVIEW. A, GENERAL PHYSICS 1987; 35:1943-1944. [PMID: 9898363 DOI: 10.1103/physreva.35.1943] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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