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Malencik DA, Zhao Z, Anderson SR. Preparation and functional characterization of a catalytically active fragment of phosphorylase kinase. Mol Cell Biochem 1993; 127-128:31-43. [PMID: 7935360 DOI: 10.1007/bf01076755] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Limited proteolysis of rabbit muscle phosphorylase kinase catalyzed by chymotrypsin generates a 33 kD product whose kinase activity is independent of both calcium and pH over the range of 6.8 to 8.3 (Malencik, D.A. & Fischer, E.H. Calcium and Cell Function III: 161-188, 1982). This active preparation consists of three related species containing residues 1-290, 1-296, and 1-298 of the 44.7 kD gamma-subunit of phosphorylase kinase (Harris, W.R., Malencik, D.A., Johnson, C.M., Carr, S.A., Roberts, G.D., Byles, C.E., Anderson, S.R., Heilmeyer, L.M.G., Fischer, E.H. & Crabb, J.W.J. Biol. Chem. 265:11740-11745, 1991). Good recoveries of catalytic activity--with varying degrees of calcium dependence--result upon the digestion of phosphorylase kinase with assorted proteases. However, especially high yields of the chymotryptic fragment are obtainable, with purification on an Ultrogel-34 column and a DEAE Sepharose CL-6B column giving 23% of the maximum possible protein. Physical characterization shows that the 33 kD chymotryptic fragment is globular, with S20,w = 2.9S, and that it has an isoelectric point of 5.3. Our continuous catalytic assay, based on differences in the binding of the fluorescent dye 1-anilinonaphthalene-8-sulfonate by phosphorylase a and b, shows that, on a molar basis, the activity of the fragment is 2.8 fold greater than that of phosphorylase kinase (Malencik, D.A., Zhao, Z. and Anderson, S.R. Biochem. Biophys. Res. Comm. 174: 344-350, 1991). The active fragment also undergoes autophosphorylation. Incubation with Mg[gamma-P32] ATP results in the reaction of 0.7 mol 32P/mol fragment. When the catalytic subunit of the cAMP-dependent protein kinase is also present, the amount of 32P incorporated increases to 1.1 mol/mol. In the former case, phosphorylation occurs primarily at Ser30 while in the latter an additional reaction takes place at Ser81. The phosphopeptides correspond to sequences occurring in the gamma-subunit of phosphorylase kinase.
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1252
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Eide DJ, Bridgham JT, Zhao Z, Mattoon JR. The vacuolar H(+)-ATPase of Saccharomyces cerevisiae is required for efficient copper detoxification, mitochondrial function, and iron metabolism. MOLECULAR & GENERAL GENETICS : MGG 1993; 241:447-56. [PMID: 8246899 DOI: 10.1007/bf00284699] [Citation(s) in RCA: 82] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Mutations in the GEF2 gene of the yeast Saccharomyces cerevisiae have pleiotropic effects. The gef2 mutants display a petite phenotype. These cells grow slowly on several different carbon sources utilized exclusively or primarily by respiration. This phenotype is suppressed by adding large amounts of iron to the growth medium. A defect in mitochondrial function may be the cause of the petite phenotype: the rate of oxygen consumption by intact gef2 cells and by mitochondrial fractions isolated from gef2 mutants was reduced 60%-75% relative to wild type. Cytochrome levels were unaffected in gef2 mutants, indicating that heme accumulation is not significantly altered in these strains. The gef2 mutants were also more sensitive than wild type to growth inhibition by several divalent cations including Cu. We found that the cup5 mutation, causing Cu sensitivity, is allelic to gef2 mutations. The GEF2 gene was isolated, sequenced, and found to be identical to VMA3, the gene encoding the vacuolar H(+)-ATPase proteolipid subunit. These genetic and biochemical analyses demonstrate that the vacuolar H(+)-ATPase plays a previously unknown role in Cu detoxification, mitochondrial function, and iron metabolism.
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1253
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Fukai J, Zhao Z, Poulikakos D, Megaridis CM, Miyatake O. Modeling of the deformation of a liquid droplet impinging upon a flat surface. ACTA ACUST UNITED AC 1993. [DOI: 10.1063/1.858724] [Citation(s) in RCA: 227] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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1254
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Zhao Z, Malik A, Lee ML. Solute adsorption on polymer-coated fused-silica capillary electrophoresis columns using selected protein and peptide standards. Anal Chem 1993; 65:2747-52. [PMID: 8250261 DOI: 10.1021/ac00068a008] [Citation(s) in RCA: 94] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Three series of basic proteins and peptides were selected for use in studying the adsorption behavior of fused-silica capillary electrophoresis columns. A comparative study of untreated and treated fused-silica columns was done. The polymers used as coating materials ranged from very hydrophobic to very hydrophilic. The average efficiency of weakly hydrophilic Ucon-coated capillaries for basic proteins was over 1 million theoretical plates at a buffer pH of 4.8. For this coating, it was found that the maximum column efficiency was obtained at a film thickness of approximately 100 nm. It was easily seen that both ionic and hydrophobic interaction forces can play important roles in protein adsorption onto the capillary walls. Furthermore, strongly hydrophilic polymer coatings may possibly lead to hydrogen-bonding interactions, which decrease column efficiency. Studies have been conducted using two series of polypeptides with varying chain lengths. One series was used to study the effect of polypeptide chain length on retention behavior. Efficient separations of bioactive peptide drugs on Ucon-coated columns were achieved. The results indicate that high efficiency and resolution of basic peptides tested can be realized on columns modified with weakly hydrophilic polymers at a pH value of about 5.
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1255
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Rugari SL, France RH, Lund BJ, Zhao Z, Gai M, Butler PA, Holliday VA, James AN, Jones GD, Poynter RJ, Tanner RJ, Ying KL, Simpson J. Broken reflection symmetry in 114Xe. PHYSICAL REVIEW. C, NUCLEAR PHYSICS 1993; 48:2078-2081. [PMID: 9969052 DOI: 10.1103/physrevc.48.2078] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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1256
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Pon EW, Ren H, Margolis H, Zhao Z, Schatz GC, Diwan A. Hepatitis B virus infection in Honolulu students. Pediatrics 1993; 92:574-8. [PMID: 8414830] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
OBJECTIVES To determine hepatitis B virus (HBV) carrier and infection rates and HBV epidemiology in Honolulu students. DESIGN Cross-sectional survey. SETTING Honolulu public elementary, intermediate, and high schools. PATIENTS A volunteer sample of 4936 students from 43 Honolulu schools. MAIN OUTCOME MEASURES HBV carrier rate (presence of hepatitis B surface antigen) and infection rate (presence of either hepatitis B surface antigen, antibody to hepatitis B surface antigen, antibody to hepatitis B core antigen, or any combinations of these) by school grade, ethnicity, and place of birth. RESULTS Eighty-three (1.68%) students were identified as HBV carriers, and a total of 353 (7.15%) students had serologic evidence of infection. Infection rates increased from elementary school age to high school age, more so in Asian/Pacific Island-born students. The prevalence of infection was higher in Asian/Pacific Island-born students than in those born in the United States. The majority of infected Hawaiian-born students were first-generation Asian/Pacific Island Americans. CONCLUSIONS Horizontal transmission of HBV occurs in Honolulu school-age children. HBV immunization of all infants in Hawaii, not just those born to carrier mothers, is necessary to reduce HBV transmission in Hawaii.
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1257
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Xu G, Salen G, Shefer S, Batta AK, Ness GC, Nguyen LB, Zhao Z, Chen TS, Niemann W, Tint GS. Different feedback regulation of hepatic cholesterol and bile acid synthesis by glycodeoxycholic acid in rabbits. Gastroenterology 1993; 105:1192-9. [PMID: 8405866 DOI: 10.1016/0016-5085(93)90967-h] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
BACKGROUND To explore the sexual difference in the feedback regulation of hepatic bile acid synthesis, glycodeoxycholic acid (GDCA) was administered to 15 male and 14 female rabbits. METHODS After bile diversion, GDCA equivalent to the hepatic bile acid influx was infused intraduodenally. Biliary cholic acid output represented bile acid synthesis. Hepatic 3-hydroxy-3 methylglutaryl coenzyme A (HMG-CoA) reductase and cholesterol 7 alpha-hydroxylase activities and steady state messenger RNA (mRNA) levels were determined. RESULTS GDCA inhibited bile acid synthesis less in female than in male rabbits. Hepatic HMG-CoA reductase activity decreased 39% in males, but increased 48% in females. Hepatic cholesterol 7 alpha-hydroxylase activity decreased similarly in males and females, and mRNA levels decreased 86% in males but were unchanged in females. CONCLUSIONS (1) Total bile diversion stimulated both hepatic cholesterol and bile acid synthesis by activating the rate-controlling enzymes and increasing mRNA levels. (2) GDCA decreased mRNA levels of HMG-CoA reductase and cholesterol 7 alpha-hydroxylase in males, but mRNA levels did not decrease in females. (3) Bile acid synthesis was sustained in females because continued biosynthesis of cholesterol provided a substrate for cholesterol 7 alpha-hydroxylase and stimulus for enzyme formation.
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1258
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Jia W, Mu J, Hu Q, Zhao Z, Wang D, Zhao B, Liu W. [Study on the induction of active immunity in human by injecting human anti-HBs antibodies]. HUA XI YI KE DA XUE XUE BAO = JOURNAL OF WEST CHINA UNIVERSITY OF MEDICAL SCIENCES = HUAXI YIKE DAXUE XUEBAO 1993; 24:246-9. [PMID: 8288189] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
One hundred and three health volunteers were injected with various doses of human anti-HBs (Ab1). The anti-idotypic antibodies (Ab2) and anti-antiidiotypic antibodies (Ab)3 in sera were tested at intervals of 30 days with ELISA. We found that the dynamic changes between Ab2 and Ab3 of immune sera were cyclical by way of their interaction and the Ag-specific Ab3 were the same as Ab1 in specificity. The results reconfirmed that exogenous human anti-HBs could induce active immunity by activation of idiotypic network and regulation in human body suggesting that injection of Ig into body could bring about not only passive immunity but also active immunity.
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Abstract
As our understanding of the dynamics of the transmission of the HIV virus toward diagnosis of AIDS increases, numerous models are being developed to help explain the underlying mechanism. We show that many of the models established so far in the literature are examples of a general class of multi-stage epidemic models that are themselves right-shift processes as developed in 1969 by Severo. We focus attention on those models that can be described as three-stage, four-stage, five-stage, etc. models.
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1260
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Mester JC, Meyer ES, Reynolds MW, Huber TE, Zhao Z, Freedman B, Kim J, Silvera IF. Cold collisions of ground state 4He: Giant S-wave scattering cross sections. PHYSICAL REVIEW LETTERS 1993; 71:1343-1346. [PMID: 10055516 DOI: 10.1103/physrevlett.71.1343] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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1261
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Ramirez LH, Munck JN, Bognel C, Zhao Z, Ardouin P, Poupon MF, Gouyette A, Rougier P. Pharmacology and antitumour effects of intraportal pirarubicin on experimental liver metastases. Br J Cancer 1993; 68:277-81. [PMID: 8347482 PMCID: PMC1968574 DOI: 10.1038/bjc.1993.328] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Early liver metastases have a predominant portal blood supply. Intraportal (i.port.) vein administration of cytotoxics could theoretically achieve enhanced drug concentrations in tumour cells and be effective as adjuvant therapy after resection of colorectal carcinoma. Pirarubicin (which has a higher hepatic extraction than doxorubicin) was investigated on liver metastases of the VX2 rabbit tumour, which were of less than 2 mm in diameter 7 days after cells injection into the portal vein. To evaluate antitumour activity, 24 rabbits were randomised into three groups 7 days after implantation: (a) control, (b) i.v. pirarubicin, (c) i.port. pirarubicin at doses of 2 mg kg-1 in both groups. Portal infusions led to no hematological or hepatic toxicity. Pharmacokinetic parameters showed a significantly reduced systemic exposure after i.port. administration. Fourteen days after treatment, livers and lungs were analysed. The mean number (+/- s.d.) of tumour foci was (a) 8.62 (+/- 5.4), (b) 4.62 (+/- 3.2), (c) 2.25 (+/- 1.4) (P < 0.05 a vs c). The mean tumour area was (a) 6.31 (+/- 6.1), (b) 1.31 (+/- 2.2), (c) 0.43 (+/- 0.4 cm2) (P < 0.05 a vs c) and the percentage (95% C.I.) of rabbits with lung metastasis was: (a) 87.5% (47-99%), (b) 75% (35-97%), (c) 12.5% (3-52%) (P < 0.02 b vs c). Intraportal pirarubicin seems to be well tolerated and more efficient than i.v. administration, particularly in preventing extrahepatic dissemination.
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1262
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Zhao Z, France RH, Lai KS, Gai M, Wilds EL, Kryger RA, Winger JA, Beard KB. Study of the beta-delayed alpha-particle emission of 16N. PHYSICAL REVIEW. C, NUCLEAR PHYSICS 1993; 48:429-432. [PMID: 9968837 DOI: 10.1103/physrevc.48.429] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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1263
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Zhao Z, Tepperman K, Dorsey JG, Elder RC. Determination of cisplatin and some possible metabolites by ion-pairing chromatography with inductively coupled plasma mass spectrometric detection. JOURNAL OF CHROMATOGRAPHY 1993; 615:83-9. [PMID: 8340466 DOI: 10.1016/0378-4347(93)80293-d] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
A sensitive method is described for measuring cisplatin and some possible metabolites. The method combines reversed-phase ion-pairing liquid chromatography (LC) with inductively coupled plasma mass spectrometry (ICP-MS) for platinum-specific detection. Separation conditions for cisplatin hydrolysis products and the reaction products of cisplatin with methionine, cysteine, and glutathione have been investigated with sodium dodecylsulfate or heptanesulfonate as the ion-pairing agent. The detection limit for cisplatin was found to be 0.1 ng, corresponding to a concentration detection limit of 1 ng/ml when using an injection volume of 100 microliters. This study has demonstrated the usefulness of LC-ICP-MS for cisplatin metabolism studies.
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1264
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Daum G, Solca F, Diltz CD, Zhao Z, Cool DE, Fischer EH. A general peptide substrate for protein tyrosine phosphatases. Anal Biochem 1993; 211:50-4. [PMID: 8323038 DOI: 10.1006/abio.1993.1231] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The determination of protein tyrosine phosphatase (PTP) activity using different protein substrates such as modified lysozyme or myelin basic protein is greatly affected by the type of enzyme involved, the condition of the assay, and the presence of effectors. The purpose of this study was to develop a general substrate of wide applicability with which variations in enzymatic activity would be minimized. A nonapeptide ENDYINASL derived from a highly conserved region of the T-cell phosphatase TC.PTP (Cool et al. (1989) Proc. Natl. Acad. Sci. USA 86, 5257-5261) was phosphorylated with a recombinant tyrosine kinase domain of the EGF receptor and purified on a C18 cartridge. Phosphatase activities of intracellular and receptor-linked PTPs were as high as the highest values obtained with the protein substrates. The intracellular, low-molecular-weight PTPs exhibited Km values between 0.5 and 1.3 microM, whereas the receptor forms CD45 and RPTP alpha gave values of 14 and 35 microM, respectively. All PTPs displayed similar properties toward the peptide including a low pH optimum and inhibition by vanadate, divalent cations, and heparin. Following immunoprecipitation, 1 ng of TC.PTP could be detected with ENDY(P)INASL compared to 10 ng in presence of protein substrates.
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1265
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Fukamachi T, Negishi R, Yoshizawa M, Ehara K, Kawamura T, Nakajima T, Zhao Z. X-ray dynamical diffraction in Ge with a zero-real-part scattering factor. Acta Crystallogr A 1993. [DOI: 10.1107/s010876739201242x] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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1266
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Zhao Z, Shen SH, Fischer EH. Stimulation by phospholipids of a protein-tyrosine-phosphatase containing two src homology 2 domains. Proc Natl Acad Sci U S A 1993; 90:4251-5. [PMID: 7683430 PMCID: PMC46484 DOI: 10.1073/pnas.90.9.4251] [Citation(s) in RCA: 86] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
PTP1C, a protein-tyrosine-phosphatase (protein-tyrosine-phosphate phosphohydrolase, EC 3.1.3.48) containing two src homology 2 domains, is poorly active when assayed with various protein substrates in vitro. Its activity is stimulated > 1000-fold by anionic phospholipids when myelin basic protein or mitogen-activated protein kinase is used as substrate but reduced in the presence of several other substrates. Data are presented to indicate a direct interaction of the enzyme with phospholipids. Enzyme stimulation directed only toward certain specific substrates is interpreted by assuming that these compounds also bind to the phospholipid vesicles where they will be subjected to rapid enzymatic attack. A possible regulation of PTP1C by its translocation to the cell membrane is hypothesized.
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1267
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Zhao Z, France RH, Lai KS, Rugari SL, Gai M, Wilds EL. Astrophysical S factor of 12C( alpha, gamma )16O from the beta-delayed alpha-particle emission of 16N. PHYSICAL REVIEW LETTERS 1993; 70:2066-2069. [PMID: 10053462 DOI: 10.1103/physrevlett.70.2066] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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1268
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Munck JN, Riggi M, Rougier P, Chabot GG, Ramirez LH, Zhao Z, Bognel C, Ardouin P, Herait P, Gouyette A. Pharmacokinetic and pharmacodynamic advantages of pirarubicin over adriamycin after intraarterial hepatic administration in the rabbit VX2 tumor model. Cancer Res 1993; 53:1550-4. [PMID: 8453622] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Intraarterial chemotherapy with Adriamycin (ADM) has shown limited advantages over i.v. administration, with no reduction in systemic toxicities and modest decrease in peripheral plasma levels. In an effort to improve the selectivity of i.a. anthracycline chemotherapy, we compared pirarubicin (4'-O-tetrahydropyranyladriamycin, THP) and ADM in the surgically implanted VX2 rabbit tumor model. Both drugs were administered at the same dose (0.5 mg/kg) either by the intraarterial hepatic route (i.a.h.) or by the i.v. route. Anthracycline plasma and tissue levels were determined by high-performance liquid chromatography with fluorescence detection. ADM peak plasma concentration and area under the curve were not significantly reduced after i.a.h. administration compared to the i.v. route; however, ADM tumor concentration was 1.9-fold higher following i.a.h. administration compared to the i.v. infusion. After THP administration by the i.a.h. route, systemic exposure (area under the curve) was markedly reduced (8-fold) compared to the same dose administered i.v. These findings correlated well with the very low concentration of the drug in heart tissue following i.a.h. infusion. After i.a.h. administration, tumor THP concentrations were 10.5 times higher compared to the i.v. route. The pharmacokinetic advantage of i.a.h. administration of THP also led to a better antitumoral effect, as shown by a significantly lower tumor growth rate [3 +/- 2% (SD)] in the i.a.h.-treated animals compared to the i.v.-treated groups (58 +/- 9%). Administration of ADM by the i.a.h. route was also inferior to i.a.h. THP. Taken together, our results suggest a clear-cut advantage of THP over ADM for i.a.h. locoregional chemotherapy, because of higher local tumor concentrations, greater antitumoral effect, and lower systemic exposure following the i.a.h. administration of THP. This anthracycline analogue could also be of therapeutic advantage in tumors partially resistant to anthracyclines that would become vulnerable to the high local concentrations achieved with i.a.h. administration. Based on these encouraging results, clinical trials using THP administered by the i.a.h. route were initiated.
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1269
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Zhao Z, Peng L. Glutamate effects on calcium homeostasis in cerebellar granule cells in primary cultures grown under depolarizing and nondepolarizing conditions. Synapse 1993; 13:315-21. [PMID: 8097597 DOI: 10.1002/syn.890130404] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Cerebellar granule cell cultures are normally grown under partly depolarizing conditions (in a medium with approximately 25 mM K+), but these cultures can also be grown at a normal potassium concentration (5.4 mM K+), although some of their characteristics are altered. In this study, intracellular free calcium concentration and 45Ca uptake were measured in cerebellar granule cell cultures grown at either 25 or 5.4 mM extracellular potassium in the presence of glutamate, and/or some of its subtype-specific agonists and antagonists. Granule cells in cultures grown at 25 mM K+ responded to glutamate, but not to quisqualate, with an increase in free cytosolic calcium concentration and in 45Ca uptake. This increase in free cytosolic calcium concentration was dependent on extracellular calcium and it was antagonized by AP5 and ketamine, NMDA receptor antagonists. In contrast, granule cells in cultures grown at 5.4 mM K+ responded to both glutamate and quisqualate, and these responses were independent of extracellular calcium and not sensitive to AP5 and ketamine. In agreement with this, 45Ca uptake was not affected by glutamate. Neither of the two culture types responded to kainate with an increase in calcium concentration or uptake. These observations indicate that calcium uptake in granule cells in cultures grown at 25 mM K+ reflect NMDA activation of calcium influx, whereas the cells in cultures grown at 5 mM K+ increase cytosolic calcium concentration on account of intracellular release of bound calcium, caused by activation of the metabotropic receptor.(ABSTRACT TRUNCATED AT 250 WORDS)
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1270
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Keller RK, Cannons A, Vilsaint F, Zhao Z, Ness GC. Identification and regulation of rat squalene synthetase mRNA. Arch Biochem Biophys 1993; 302:304-6. [PMID: 8470905 DOI: 10.1006/abbi.1993.1215] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
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1271
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Ahmad S, Banville D, Zhao Z, Fischer EH, Shen SH. A widely expressed human protein-tyrosine phosphatase containing src homology 2 domains. Proc Natl Acad Sci U S A 1993; 90:2197-201. [PMID: 7681589 PMCID: PMC46053 DOI: 10.1073/pnas.90.6.2197] [Citation(s) in RCA: 159] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
A cDNA encoding a nontransmembrane protein-tyrosine phosphatase (PTP; EC 3.1.3.48), termed PTP2C, was isolated from a human umbilical cord cDNA library. The enzyme contains a single phosphatase domain and two adjacent copies of the src homology 2 (SH2) domain at its amino terminus. A variant of PTP2C (PTP2Ci) which has four extra amino acid residues within the catalytic domain has been identified also. PTP2C is widely expressed in human tissues and is particularly abundant in heart, brain, and skeletal muscle. The catalytic domain of PTP2C was expressed as a recombinant enzyme in Escherichia coli and purified to near homogeneity by two chromatographic steps. The recombinant enzyme was totally specific toward phosphotyrosine residues. The structural similarity between PTP2C and the previously described PTP1C suggests the existence of a subfamily of SH2-containing PTPs; these may play an important role in signal transduction through interaction of their SH2 domains with phosphotyrosine-containing proteins.
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1272
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Zhao Z, Bouchard P, Diltz CD, Shen SH, Fischer EH. Purification and characterization of a protein tyrosine phosphatase containing SH2 domains. J Biol Chem 1993; 268:2816-20. [PMID: 8428956] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
A protein tyrosine phosphatase (PTP) containing two SH2 domains (PTP1C) was purified to near homogeneity from an adenovirus expression system by a two-step chromatographic procedure with a yield of 67%. The purified enzyme behaves as a monomer of 68 kDa on gel filtration and is totally specific for phosphotyrosyl residues. Its optimal pH is around neutrality for protein substrates such as reduced, carboxyamidomethylated, maleylated (RCM)-lysozyme and myelin basic protein but below 5 for low molecular weight compounds such as para-nitrophenyl phosphate (p-NPP) and phosphotyrosine. Furthermore, with the protein substrates, it displays an activity less than 1% of that obtained with other known PTPs but comparable activities toward p-NPP and phosphotyrosine. Its responsiveness toward the usual PTP activators (e.g. spermine) or inhibitors (e.g. vanadate, molybdate, heparin, or Zn2+) varied considerably with the nature of the substrates involved. Limited digestion with trypsin caused the cleavage of a C-terminal segment of the enzyme, giving rise to a 63-kDa fragment; this cleavage resulted in an approximately 20- and 10-fold activation of the enzyme toward RCM-lysozyme and myelin basic protein, respectively.
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1273
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Wu J, Wang Y, Guo P, Shen H, Yan Y, Zhao Z. Elastic constants and observation of significant elastic softening in superconducting Bi2Sr2CaCu2O8 single crystals. PHYSICAL REVIEW. B, CONDENSED MATTER 1993; 47:2806-2811. [PMID: 10006339 DOI: 10.1103/physrevb.47.2806] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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1274
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Zhao Z, Bouchard P, Diltz C, Shen S, Fischer E. Purification and characterization of a protein tyrosine phosphatase containing SH2 domains. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(18)53846-1] [Citation(s) in RCA: 80] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
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1275
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Toyama FM, Nogami Y, Zhao Z. Relativistic extension of the Kay-Moses method for constructing transparent potentials in quantum mechanics. PHYSICAL REVIEW. A, ATOMIC, MOLECULAR, AND OPTICAL PHYSICS 1993; 47:897-902. [PMID: 9909008 DOI: 10.1103/physreva.47.897] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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