2326
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Zhang C, Lerch ML, Martin AD, Simmonds PE, Eaves L. Plasmon assisted resonant tunneling in a double barrier heterostructure. PHYSICAL REVIEW LETTERS 1994; 72:3397-3400. [PMID: 10056188 DOI: 10.1103/physrevlett.72.3397] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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2327
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Zhang C, Lee CS, Guo P. The proximate 5' and 3' ends of the 120-base viral RNA (pRNA) are crucial for the packaging of bacteriophage phi 29 DNA. Virology 1994; 201:77-85. [PMID: 8178491 DOI: 10.1006/viro.1994.1267] [Citation(s) in RCA: 80] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
In vitro mutagenesis was performed to identify the DNA packaging domain of the 120-base pRNA essential and specific for DNA encapsidation by bacteriophage phi 29 of Bacillus subtilis. All deletions and mutations targeted the 5' and 3' ends of the pRNA. DNA templates of a control or mutant pRNAs used for in vitro transcription with T7 RNA polymerase were generated by PCR. Fourteen mutant pRNA molecules were synthesized from DNA templates either directly after PCR or after cloning the PCR fragments into the pCR II vector. Ten of the mutant pRNA species were inactive in packaging of the phi 29 genome. Mutation of base one at the 5' end did not affect the pRNA packaging activity. Mutation of the first two bases at the 5' end of the pRNA to noncomplementary bases in the predicted RNA secondary structure (U1 C2/A117G116 to G1 G2/A117G116) resulted in a pRNA with no detectable DNA-gp3 packaging activity assayed by either sucrose gradient sedimentation or agarose gel electrophoresis, and 10(5)-fold reduction in activity was found when measured by plaque-forming units with a new highly sensitive assay system. Changing bases 116 and 117 so that they were complementary to the mutated bases, 1 and 2, from the previous mutant (G1 G2/A117G116 to G1 G2/C117C116) generated an RNA molecule with restored DNA packaging ability. Our results show that, although not essential for procapsid binding, both the 5' and 3' ends of the pRNA were proximate and crucial for phi 29 DNA packaging.
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2328
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Zhang X, Kidder GM, Zhang C, Khamsi F, Armstrong DT. Expression of plasminogen activator genes and enzymatic activities in rat preimplantation embryos. JOURNAL OF REPRODUCTION AND FERTILITY 1994; 101:235-40. [PMID: 8064688 DOI: 10.1530/jrf.0.1010235] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Plasminogen activator has been implicated in tissue invasion and remodelling because of its role in the degradation of the extracellular matrix. Its activity can be detected in mouse embryos as early as day 6 of pregnancy, suggesting that plasminogen activator is involved in the process of implantation. The present study determined the time course of expression of the genes encoding tissue-type plasminogen activator (tPA) and urokinase-type plasminogen activator (uPA) during the preimplantation period in rats by the sensitive mRNA phenotyping procedure of reverse transcription-PCR. The tPA mRNA was present in rat oocytes and two-cell embryos, but was not detected between the four-cell and blastocyst stages. The uPA mRNA was first detected in two-cell rat embryos, and was present through to the blastocyst stage. In chromogenic assays, plasminogen activator activity was detected in oocytes and embryos between two-cell and blastocyst stages. Most plasminogen activator activity present in preimplantation embryos appeared to be uPA, as it could be inhibited by anti-uPA antibody and a specific uPA inhibitor, amiloride, but not by anti-tPA antibody. The present data demonstrate the expression of uPA gene and uPA activity in preimplantation rat embryos, suggesting that embryonic uPA may be involved in early embryo development and implantation.
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2329
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Tso MO, Zhang C, Abler AS, Chang CJ, Wong F, Chang GQ, Lam TT. Apoptosis leads to photoreceptor degeneration in inherited retinal dystrophy of RCS rats. Invest Ophthalmol Vis Sci 1994; 35:2693-9. [PMID: 8188463] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
PURPOSE To determine the pathogenetic mechanism of photoreceptor cell degeneration in the inherited retinal dystrophy in Royal College of Surgeons (RCS) rats. METHODS The dystrophic retinas of the pink-eyed RCS (RCS-rdy-p) rats were examined for DNA fragmentation by agarose gel electrophoresis of retinal DNA and by TdT-mediated biotin-dUDP nick-end labeling (TUNEL) in paraffin sections. Rats ranging in age from 3 to 60 days were examined. RESULTS Agarose gel electrophoresis of retinal DNA isolated from animals 25, 30, 35, and 40 days old showed a ladder pattern of degradation with bands corresponding to multiples of 180 to 200 base pair subunits. TUNEL study showed increasing labeling of photoreceptor cells with progression of the retinal dystrophy of the RCS rats. CONCLUSIONS Apoptosis is the dominant mechanism of photoreceptor degeneration in the RCS rat, which has a genetic defect in the phagocytic activity of retinal pigment epithelium. The onset of the degeneration appeared to vary between rod cells in the different regions of the eye.
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2330
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Zhao Q, Zhao M, Zhang C. [The alteration of histidase catalytic activity and the expression of the enzyme protein in rat primary hepatomas]. ZHONGGUO YI XUE KE XUE YUAN XUE BAO. ACTA ACADEMIAE MEDICINAE SINICAE 1994; 16:135-9. [PMID: 7987941] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The catalytic activity of histidase and the expression of the enzyme protein were investigated in rat hepatomas induced by diethylnitrosamine. The results indicated that the activities of histidase in the hepatomas were significantly diminished as compared with normal rat livers (P < 0.01). Western blot analysis revealed that enzyme protein levels in hepatomas were markedly reduced. It is thus inferred that some factors which control expression of histidase protein may be altered during carcinogenesis. These findings lay a foundation for studying the relationship between the regulation and expression of the histidase gene and hepato carcinogenesis.
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2331
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Baumer A, Zhang C, Linnane AW, Nagley P. Age-related human mtDNA deletions: a heterogeneous set of deletions arising at a single pair of directly repeated sequences. Am J Hum Genet 1994; 54:618-30. [PMID: 8128959 PMCID: PMC1918099] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Deletions in mtDNA accumulate during the human aging process, arising from either intramolecular illegitimate recombination or strand slippage during replication, which results in subgenomic mtDNA molecules. We identify here two classes of mtDNA deletions--class A deletions, which are homogeneous at the breakpoints, with all subgenomic molecules therefore being identical in size, and class B deletions, which arise from a less stringent process that gives rise to heterogeneity at the breakpoints, with the subgenomic molecules being of slightly different sizes. A novel approach is described that offers a global overview of the populations of different deletions in individual tissues. It is based on PCR cycle-sequencing reactions that are carried out directly on mtDNA segments, amplified by PCR from total cellular DNA. The results show a clear size homogeneity of the subgenomic mtDNA molecules representative of class A, which carry a commonly detected 4,977-bp deletion occurring at a pair of 13-bp directly repeated sequences. In this case, precisely one copy of the repeat is retained in the subgenomic molecules. We then describe a class B situation comprising a family of at least nine closely related 8.04-kb deletions involving the same pair of 5-bp direct repeats. In this situation, the breakpoints differ at the base-pair level (8,037-8,048-bp deletions); the subgenomic molecules retain > 1 copy, 1 copy, or < 1 copy of the 5-bp repeat. In different tissues from either the same individual or among different individuals, there is a widely variable occurrence of particular deletions in the subgenomic mtDNA population within this class B set. Class B deletions offer a new approach for studying the accumulation of mtDNA deletions, thereby providing insight into the independent somatic origin of mutated mtDNA molecules, both in aging and in mitochondrial diseases. We also report a convenient method for ascertaining whether a given PCR product results from the amplification of a subgenomic mtDNA template, on the basis of the selective degradation of full-length mtDNA molecules prior to PCR.
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2332
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Matsumoto K, Yokogoshi Y, Fujinaka Y, Zhang C, Saito S. Molecular cloning and sequencing of porcine somatostatin receptor 2. Biochem Biophys Res Commun 1994; 199:298-305. [PMID: 8123027 DOI: 10.1006/bbrc.1994.1228] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The porcine somatostatin receptor gene was isolated from a porcine genomic library. Based on the deduced amino acid sequence, this gene encodes a 369 amino acid protein with seven hydrophobic segments, a characteristic of G-protein coupled receptors, and shows only 13 amino acid difference (identity 96.5%, similarity 99.2%) in amino acid sequence from human somatostatin receptor 2. The data indicate that the amino acid sequence is highly conserved in pig, human, rat and mouse somatostatin receptor 2.
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2333
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Zhang C. Electron correlations in a double-quantum-well structure. PHYSICAL REVIEW. B, CONDENSED MATTER 1994; 49:2939-2942. [PMID: 10011136 DOI: 10.1103/physrevb.49.2939] [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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2334
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Zhang C, Evans T. Differential regulation of the two xGATA-1 genes during Xenopus development. J Biol Chem 1994; 269:478-84. [PMID: 8276839] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Xenopus laevis provides an established developmental system to study the regulation of cell lineage establishment and the generation of tissue-specific patterns of gene expression. We have isolated from Xenopus erythroid cell RNA two distinct cDNA clones encoding the xGATA-1 transcription factor. We have identified, in erythroid nuclear extracts, the sequence-specific DNA-binding protein they encode. By characterizing the expression patterns for RNA derived from two distinct homologues, we find that the two xGATA-1 genes are differentially regulated. The xGATA-1a mRNA predominates in embryos prior to terminal differentiation of erythroid cells, while the differentiated cells contain RNA derived predominantly from the xGATA-1b gene. Both proteins activate a target globin promoter in transient transfection assays. During early development, GATA-1 transcripts are localized to ventral regions of the embryo. GATA-1 should therefore provide a useful early marker for studying signalling pathways which result in the generation of ventral mesoderm. The differentially regulated genes may be distinct markers for targets of ventral mesoderm induction.
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2335
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Xiao S, Ren H, You J, Zhao L, Li B, Zhang C. Effect of albendazole on Ancylostoma caninum larvae migrating in the muscles of mice. ZHONGGUO JI SHENG CHONG XUE YU JI SHENG CHONG BING ZA ZHI = CHINESE JOURNAL OF PARASITOLOGY & PARASITIC DISEASES 1994; 12:214-217. [PMID: 7867159] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
When mice inoculated with 1,000 third-stage larvae of Ancylostoma caninum for 1 week were treated intragastrically (ig) with albendazole (Alb) 75, 150 or 300 mg/kg.d for 3 days, the mean larva numbers collected from the muscles of each group were 2.7 +/- 1.7, 2.0 +/- 1.5 and 1.0 +/- 1.0, respectively, being much less than that 205 +/- 68 of the control group. In mice treated ig with Alb 150 mg/kg.d for 3 days, the concentrations of Alb and its effective metabolite, albendazole sulfoxide (AlbSO), were determined in plasma and the muscles at different intervals after the last medication using high performance liquid chromatography. The results showed that only low concentrations of Alb were detected in both plasma and the muscles. However, higher concentrations of AlbSO were found not only in the plasma (5.4-10.5 micrograms/ml), but also in the muscles (2.2-4.6 micrograms/g). The higher contents of AlbSO in the muscles would be helpful for killing the Ancylostoma larvae migrating in the muscles of mice.
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2336
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Shan J, Zhang C, Sun J, Li L. [Synaptonemal complex analysis of 13/17 Robertsonian translocation in the domestic pig]. YI CHUAN XUE BAO = ACTA GENETICA SINICA 1994; 21:96-103. [PMID: 8080664] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
G and C-banding study of the chromosomes of several male pigs, indicate that all of these pigs carry rob(13;17). The karyotype is 2n = 37, XY, rob (13;17). In this paper, silverstained Synaptonemal Complexes (SCs) in surface-spread pachytene nuclei from these pigs are analysed by electron microscope. The result is as follows: Robertsonian translocation metacentrics rob (13;17) paired with homologous acrocentrics (13,17), forming a trivalent. All trivalents are in a cis configuration and there is delayed pairing in the trivalent. We measured every part of trivalent in the different stage of prophase (based on the morphology of XY-bivalent). It is shown that accompanying with rob(13;17) formation there has been a deletion in the proximal part of 13, 17 translocation chromosome. In the process of synapsis, the length adjustment phenomenon in the trivalent occurred: a. There is nonhomologous synapsis between the two short arms of the acrocentrics (13;17). The length of short SC varied. b. The position of the short SC, which is on the long SC(homologous synapsis of rob(13; 17) and 13, 17) moved, from one-fourth of long SC to one-tenth of it, near the end of 17 arm. These phenomenon is the result of a gradual length adjustment of lateral elements of 13,17 to the lateral element of the rob (13;17). We has discussed the mechanism of the trivalent synaptic adjustment, and it's important use to control the chiasmata and disjunction of the chromosomes.
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2337
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Li ZQ, Luo XM, Wei HJ, Feng YM, Zhang C. Inhibition of the transforming ability of cigarette smoking condensate-treated human fetal lung DNA induced by oltipraz. J Environ Pathol Toxicol Oncol 1994; 13:133-5. [PMID: 7884644] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Rat-1 cells transfected by genomic DNA of human fetal lung explants treated with 100 micrograms/ml of oltipraz (5-(2-pyrazimyl)-4-methyl-1, 2-dithiol-3-thione) for 14 hr or 100 micrograms/ml of cigarette smoking condensate for 6 hr formed 0 to 8 transformation foci, respectively. If 100 micrograms/ml of oltipraz was added to culture of human fetal lung explants 8 hr prior to the treatment of cigarette smoking condensate, the Rat-1 cells transfected by genomic DNA of human fetal lung explants formed only two foci. In addition, the growth speed of Rat-1 cells transfected by genomic DNA of human fetal lung treated with both oltipraz and cigarette smoking condensate was lower than that transfected by cigarette smoking condensate-treated human fetal lung DNA. Our results indicate that oltipraz can block the irreversible change of human fetal lung DNA caused by cigarette smoking condensate, and the results suggest the possibility of using oltipraz as control in the experimental initiation of human lung carcinogenesis.
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2338
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Ma L, Zhang C, Liu WJ. [Effects of arsenic on the offspring development in mice]. ZHONGHUA YU FANG YI XUE ZA ZHI [CHINESE JOURNAL OF PREVENTIVE MEDICINE] 1994; 28:20-3. [PMID: 8082454] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Effects of arsenic exposure on offspring development were studied in pregnant mice. The results showed arsenic contents of the body and brain tissue increased and the structure of neural cells in cerebral cortex became abnormal after exposure. The offspring neurobehavioral development appeared retardant and the proportion of their peripheral lymphocytes with alpha-naphthalene acetate enzyme (ANAE) declined in a mice group with exposure to 0.75 mg/kg arsenic, and the offspring body weight gain slowed after weaning, blood cholinesterase activity and serum level of haemolysin declined significantly in a group with 4.50 mg/kg. It indicated arsenic could affect embryonic and offspring development in mice through pregnant exposure.
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2339
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Scholz E, Zhang C, Guo P. Transactivation of the early SV40 promoter by avian infectious laryngotracheitis virus in avian hepatoma cells. J Virol Methods 1993; 45:291-301. [PMID: 8106602 DOI: 10.1016/0166-0934(93)90114-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
An avian hepatoma cell line has been reported to be suitable for the cultivation of avian laryngotracheitis virus (ILTV) (Scholz et al. (1993) J. Virol. Methods, 273-286; Guo et al. (1993) Am. J. Vet. Res., in press). To provide information for the establishment of avian expression systems and for the construction of avian recombinant viruses, five expression plasmids were constructed to test two avian viral and two mammalian viral promotors for their suitability and strength for gene expression in this cell line. Chicken hepatoma cells were transfected with plasmids carrying the bacterial beta-galactosidase (beta-gal) gene as a reporter gene. The beta-gal gene of three plasmid constructs expressed in both E. coli and avian hepatoma cells, while the beta-gal gene of two other constructs expressed only in avian hepatoma cells. The beta-gal gene expressed independently of any viral infection when under the control of the early Rous sarcoma virus (RSV) promoter or the immediate-early cytomegalovirus (CMV) promoter. However, expression of beta-gal gene under the control of the SV40 early promoter/enhancer and the ILTV TK promoter was greatly potentiated when the transfected cells were co-infected with ILTV. This finding provides a system for the enhancement of gene expression in avian cells, especially when ILTV is used as vector.
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2340
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Zhang C. [Experimental study on bone formation induced by porous HA-beta-TCP bioceramics]. ZHONGHUA WAI KE ZA ZHI [CHINESE JOURNAL OF SURGERY] 1993; 31:722-5. [PMID: 8033701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Three types of HA-beta-TCP active bioceramics which have various porosity and porous diameters were implanted into femurs and muscles of dogs. Histological and biomechanical tests proved that the porous HA-beta-TCP could make the active stage of bone formation moved up in bones and induce new bone formation in muscles. The pores were easily filled with new bones in samples which had smaller porous diameter than samples having larger porous diameter. The final strength after accomplishment of repair process was closely related with porosity. In samples with lower porosity, the proportion of organic bone and the strength were also lower, but in samples with higher porosity the proportion of organic bone and the strength were also higher. Up to the fourth month postoperatively, the strength of HA-beta-TCP with proper porous diameter and porosity which had been implanted into bones was as high as that of organic bone.
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2341
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Tian JG, Zhang C, Zhang G, Li J. Position dispersion and optical limiting resulting from thermally induced nonlinearities in Chinese tea liquid. APPLIED OPTICS 1993; 32:6628-6632. [PMID: 20856509 DOI: 10.1364/ao.32.006628] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
We employ the z-scan method to distinguish thermally induced nonlinearities from others by varying the beam waist radius and to determine the thermo-optic coefficient of materials. One can attribute the origin of optical nonlinearities of Chinese tea liquid to laser-heating-induced nonlinear refraction while one irradiates the media with a cw He-Ne laser. We also analyze the influence of position dispersion on optical limiting.
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2342
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Lee CH, Yu G, Moses D, Pakbaz K, Zhang C, Sariciftci NS, Heeger AJ, Wudl F. Sensitization of the photoconductivity of conducting polymers by C60: Photoinduced electron transfer. PHYSICAL REVIEW. B, CONDENSED MATTER 1993; 48:15425-15433. [PMID: 10008082 DOI: 10.1103/physrevb.48.15425] [Citation(s) in RCA: 101] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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2343
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Holas A, March NH, Takahashi Y, Zhang C. Hartree-Fock method posed as a density-functional theory: Application to the Be atom. PHYSICAL REVIEW. A, ATOMIC, MOLECULAR, AND OPTICAL PHYSICS 1993; 48:2708-2715. [PMID: 9909919 DOI: 10.1103/physreva.48.2708] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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2344
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Hardin CD, Zhang C, Kranias EG, Steenaart NA, Raeymaekers L, Paul RJ. Regulation of glycolytically fueled Ca2+ uptake in smooth muscle plasmalemmal vesicles by phosphorylation. THE AMERICAN JOURNAL OF PHYSIOLOGY 1993; 265:H1326-33. [PMID: 8238421 DOI: 10.1152/ajpheart.1993.265.4.h1326] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
A highly purified plasma membrane vesicular preparation from porcine antrum had an endogenous protein kinase activity with substrates of molecular weights of 11, 15, 20.5, 25, 35, 44, 155, and 230 x 10(3). Phosphorylation of the plasma membranes by the endogenous protein kinase activity resulted in a stimulation of initial rates of Ca2+ uptake into inside-out vesicles, which was associated with an increase in the maximum velocity of the Ca2+ pump with no apparent changes in the half-maximal effective concentration for calcium. Because we have previously reported that a membrane-associated glycolytic system may preferentially provide ATP to fuel the Ca2+ pump (9), we examined the effects of phosphorylation on Ca2+ uptake when glycolysis was the sole source of ATP for the pump. We found that the stimulation of Ca2+ uptake by phosphorylation was more pronounced when Ca2+ uptake was supported by glycolysis rather than 2 mM ATP. When ATP was added at a level similar to that produced by endogenous glycolysis, the stimulation of Ca2+ uptake by phosphorylation was comparable to when glycolysis supported the Ca2+ pump. Our observations suggest that the dynamic range (up to threefold) for regulation of the plasmalemmal Ca2+ pump by phosphorylation is considerably larger than previously reported and thus likely to be of physiological significance.
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2345
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Zhang C, Markham GD, LoBrutto R. Coordination of vanadyl(IV) cation in complexes of S-adenosylmethionine synthetase: multifrequency electron spin echo envelope modulation study. Biochemistry 1993; 32:9866-73. [PMID: 8396974 DOI: 10.1021/bi00088a043] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
S-Adenosylmethionine (AdoMet) synthetase requires two freely dissociable divalent cations for activity, and its activity is greatly stimulated by certain monovalent cations (K+, Tl+). Omission of the native Mg2+ cations prevents enzyme-catalyzed reactions, although the substrates and products still bind. Vanadyl (oxovanadium, VO2+) serves as a convenient paramagnetic probe of the substrate-independent, divalent cation binding site in the enzyme. In the present study, multifrequency electron spin echo envelope modulation (ESEEM) is employed to explore the cation's coordination sphere in several functionally relevant complexes. In the substrate complex enzyme.VO2+.ATP.methionine.K+, an equatorially coordinating 14N ligand is found, with Aiso = 4.3 MHz. Selective 15N labeling of the epsilon-amino nitrogens of all lysine residues in the protein reveals that lysine is the source of the ligand. A lysine 14N ligand is also observed in the intermediate complex enzyme.VO2+.AdoMet.PPPi.K+, with Aiso = 4.8 MHz, and in the initial product complex enzyme.VO2+.AdoMet.PPi.K+. In the subsequent product, enzyme.VO2+.AdoMet.K+ (formed upon dissociation of PPi), the methionyl amino nitrogen of AdoMet coordinates VO2+ (Aiso = 5.3 MHz), and the lysine ligand is lost. In each complex, the monovalent cation activator can be changed from K+ to Tl+ or Na+ with no effect on the ESEEM spectra. Combination of the ESEEM data from this study with previous CW data [Markham, G. D. (1984) Biochemistry 23, 470-478] leads to identification of three of the equatorial ligands to VO2+ and places constraints upon the identity of the fourth ligand, in both the substrate and product complexes. A hypothetical outline of changes in the metal coordination scheme during the reaction is presented, based upon these results.
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2346
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Zhang C, Blarre L, Walser RM, Becker MF. Mechanisms for laser-induced functional damage to silicon charge-coupled imaging sensors. APPLIED OPTICS 1993; 32:5201-5210. [PMID: 20856326 DOI: 10.1364/ao.32.005201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
We measured the functional degradation of silicon CCD photodetector arrays when subjected to Nd:YAG laser irradiation at 1.06 µm by 10-ns pulses. Operational tests such as dark leakage, point-spread function, and modulation transfer function were developed for testing individual pixels and applied to the testing of locally laser-damaged CCD arrays. Testing revealed that the primary failure mechanism was the spreading of the point-spread function in the direction of clocked charge motion that resulted from a decreased depth of potential wells within the laser-damaged spot. Lesser degradation was observed at pixels near the damaged spot that were served by clock lines that traversed the damage spot. This damage behavior was correlated with decreased breakdown voltage and increased leakage current between adjacent clock lines. Subsequent morphological and TEM examination of similarly constructed chips indicated that laser heating of the polysilicon clock lines led to degradation of the adjacent isolation oxide between clock lines. Functional damage occurred at locations where two clock lines were very close to each other, and the thin oxide layer separating them was subjected to high temperatures that resulted from melting of the neighboring polysilicon.
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2347
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Zhang C, Bachoo M, Polosa C. The receptors activated by exogenous and endogenous opioids in the superior cervical ganglion of the cat. Brain Res 1993; 622:211-4. [PMID: 8242358 DOI: 10.1016/0006-8993(93)90821-4] [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: 01/29/2023]
Abstract
Nicotinic transmission in the superior cervical ganglion of the cat was studied in vivo and in vitro by recording the postganglionic compound action potential evoked, under partial block with hexamethonium, by supramaximal 0.2 Hz stimulation of the cervical sympathetic trunk. The compound action potential was depressed following a stimulus train (5 Hz, 40 s) applied to the same set of axons. The inhibition was antagonized by naloxone, suggesting mediation by endogenous opioids. Agonists selective for mu-, delta- and kappa-opioid receptors, injected into the arterial supply of the in situ ganglion or added to the perfusion fluid in the in vitro ganglion, also produced a naloxone-sensitive inhibition of the compound action potential. The synaptic inhibition was antagonized by the delta-selective antagonist ICI 174,864 and by the mu-selective antagonist CTAP, but not by the kappa-selective antagonist Nor-BNI. These results suggest that all three main types of opioid receptors are present in the ganglion but only mu- and delta-receptors are involved in the inhibition of ganglionic transmission mediated by the endogenous opioids.
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MESH Headings
- Amino Acid Sequence
- Animals
- Cats
- Endorphins/physiology
- Female
- Male
- Molecular Sequence Data
- Naloxone/pharmacology
- Receptors, Nicotinic/drug effects
- Receptors, Nicotinic/physiology
- Receptors, Opioid, delta/antagonists & inhibitors
- Receptors, Opioid, delta/drug effects
- Receptors, Opioid, delta/physiology
- Receptors, Opioid, kappa/antagonists & inhibitors
- Receptors, Opioid, kappa/drug effects
- Receptors, Opioid, kappa/physiology
- Receptors, Opioid, mu/antagonists & inhibitors
- Receptors, Opioid, mu/drug effects
- Receptors, Opioid, mu/physiology
- Superior Cervical Ganglion/drug effects
- Superior Cervical Ganglion/physiology
- Synaptic Transmission/drug effects
- Synaptic Transmission/physiology
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2348
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Zhang C, Huang M, Holloway BW. Mapping of ben genes of Pseudomonas aeruginosa. FEMS Microbiol Lett 1993; 112:255-9. [PMID: 8224789 DOI: 10.1016/0378-1097(93)90609-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Four ben genes responsible for the conversion of benzoate to catechol in Pseudomonas aeruginosa PAO have been mapped to a 4.6 kb KpnI fragment, ben-1 and ben-4 were known to be separate genes but now ben-1508 has been found to be different from ben-2. The two genes were distinguished by Tn5 mutagenesis of a cosmid clone and deletion mapping. It is likely that the four genes mapped (ben-4, ben-2, ben-1508 and ben-1) correspond to the previously characterized benR (regulatory gene) and benABC (benzoate dioxygenase) respectively.
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2349
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Zhang C, Linnane AW, Nagley P. Occurrence of a particular base substitution (3243 A to G) in mitochondrial DNA of tissues of ageing humans. Biochem Biophys Res Commun 1993; 195:1104-10. [PMID: 8373389 DOI: 10.1006/bbrc.1993.2158] [Citation(s) in RCA: 106] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Allele-specific polymerase chain reaction has been used to demonstrate the occurrence, during the human ageing process, of the mutation A to G at nucleotide position 3243 on mitochondrial DNA. An oligonucleotide with a 3'-end specific to this mutation was designed to selectively amplify DNA bearing this mutation under annealing temperature conditions that efficiently discriminate between normal and mutant mitochondrial DNA templates. Seven out of 38 adult tissues tested were found to contain this mutation, whereas the mutation could not be detected in any of the 16 infant tissues analyzed. The present demonstration of an age-related point mutation adds to the growing list of mutations in human mitochondrial DNA, till now almost exclusively large deletions, that accumulate in human tissues as a function of age. The method described here has general application in the detection of other age-related point mutations in human mitochondrial DNA.
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2350
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Zhang C, Liu Y, Liu Y, Liu H, Jiang J, Chen H, Yang Y. [Capillary blood viscosimeter of the microcomputer]. HUA XI YI KE DA XUE XUE BAO = JOURNAL OF WEST CHINA UNIVERSITY OF MEDICAL SCIENCES = HUAXI YIKE DAXUE XUEBAO 1993; 24:346-8. [PMID: 8288217] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
On the basis of specific property of non-Newtonian fluid (blood) we have worked out the formula of capillary blood viscosimeter:sheat stress tau alpha = alpha rho gh/2L shear rate f (tau alpha) = 1/pi alpha 3 [3q + h(dq/dh)] and designed and produced the prototype. Repetition experiments have indicated that the property of the instrument is stable, and a comparison of the prototype with the cone and plate viscosimeter has demonstrated the reliability of the measurements.
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