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  • 1
    Electronic Resource
    Electronic Resource
    Ammonia assimilation and oxygen evolution by a reconstituted chloroplast system in the presence of 2-oxoglutarate and glutamate (1983)
    Springer
    Planta 159 (1983), S. 247-253 
    Details
    ISSN: 1432-2048
    Keywords: Ammonia assimilation ; Chloroplast ; Glutamate synthase ; Glutamine synthesis ; Glutamine synthetase ; Spinacia (ammonia assimilation)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract (Ammonia plus 2-oxoglutarate)-dependent O2 evolution by intact chloroplasts was enhanced three- to five fold by 2 mM L- and D-malate, attaining rates of 9–15 μmol mg-1 Chl h-1. Succinate and fumarate also promoted activity but D-aspartate and, in the presence of aminooxyacetate, L-aspartate inhibited the malate-promoted rate. A reconstituted chloroplast system supported (ammonia plus 2-oxoglutarate)-dependent O2 evolution at rates of 6-11 μmol mg-1 Chl h-1 in the presence of MgCl2, NADP(H), ADP plus Pi (or ATP), ferredoxin and L-glutamate. The concentrations of L-glutamate and ATP required to support 0.5 V max were 5 mM and 0.25 mM, respectively. When the reaction was initiated with NH4Cl, O2 evolution was preceded by a lag phase before attaining a constant rate. The lag phase was shortened by addition of low concentrations of L-glutamine or by preincubating in the dark in the presence of glutamate, ATP and NH4Cl. Oxygen evolution was inhibited by 2 mM azaserine and, provided it was added initially, 2 mM methionine sulphoximine. The (ammonia plus 2-oxoglutarate)-dependent O2 evolution was attributed to the synthesis of glutamine from NH4Cl and glutamate which reacted with 2-oxoglutarate in a reaction catalysed by ferredoxin-specific glutamate synthase using H2O as the ultimate electron donor. The lag phase was attributed to the establishment of a steady-state pool of glutamine. L-Malate did not affect the activity of the reconstituted system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00397532
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  • 2
    Electronic Resource
    Electronic Resource
    Light-dependent reduction of dehydroascorbate and uptake of exogenous ascorbate by spinach chloroplasts (1983)
    Springer
    Planta 158 (1983), S. 442-450 
    Details
    ISSN: 1432-2048
    Keywords: Ascorbate uptake ; Chloroplast ; Dehydroascorbate reduction ; Glutathione dehydrogenase ; Glutathione metabolism ; Spinacia (ascorbate metabolism)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A reconstituted spinach chloroplast system containing thylakoids, stroma and 0.1 mM NADPH supported O2 evolution in the presence of oxidised glutathione (GSSG). The properties of the reaction were consistent with light-coupled GSSG-reductase activity involving H2O as eventual electron donor. The reconstituted system also supported dehydroascorbate-dependent O2 evolution in the presence of 0.6 mM reduced glutathione (GSH) and 0.1 mM NADPH with the concomitant production of ascorbate. The GSSG could replace GSH in which case the production of GSH preceded the accumulation of ascorbate. The data are consistent with the light-dependent reduction of dehydroascorbate using H2O as eventual electron donor via the sequence H2O→NADP→GSSG→dehydroascorbate. Approximately 30% of the GSH-dehydrogenase activity of spinach leaf protoplasts is localised in chloroplasts: this could not be attributed to contamination of chloroplasts by activity from the extrachloroplast compartment. Washed intact chloroplasts supported the uptake of ascorbate but the uptake mechanism had a very low affinity for ascorbate (Km approximately 20 mM). The rate of uptake of ascorbate was less than the rate of light-dependent reduction of dehydroascorbate and too slow to account for the rate of H2O2 reduction by washed intact chloroplasts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00397738
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  • 3
    Electronic Resource
    Electronic Resource
    Electron microscopic and autoradiographic characterization of hindlimb muscle regeneration in the mdx mouse (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 219 (1987), S. 243-257 
    Details
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The pattern of postnatal growth and development of skeletal muscle in mdx mice was studied by light and transmission electron microscopy and by autoradiography and was compared with that in their normal age-matched controls at 4 and 32 weeks of age. The muscle weights of both the extensor digitorum longus (EDL) and soleus muscles of mdx mice were significantly greater than those in control mice at both ages. Body weights of male and female mdx mice were also increased over controls up to 12 weeks of age. At 4 weeks, both the EDL and soleus muscles exhibited focal areas of degeneration, necrosis; and regeneration of centrally nucleated extrafusal fibers resulting in a wide range of fiber sizes. By 32 weeks, the majority of fibers in both muscles were centrally nucleated, and focal areas of recent regeneration were observed. By electron microscopy, the course of macrophage infiltration into areas of degenerating fibers and the ongoing regeneration of myofibers within redundant cylinders of external lamina were noted. This pattern was frequent in 4-week-old mdx muscles and was present to a lesser degree at 32 weeks. A notable lack of both adipose tissue infiltration and fibrotic change in the endomysium were observed in muscles at both ages. Autoradiograms of muscles from 4-week-old mdx mice injected with tritiated thymidine showed an increased proportion of labeled sublaminal nuclei at 24 and 48 hours after injection compared to controls. At 32 weeks of age, labeling of nuclei in muscles of mdx mice was also greater than in controls, but was reduced compared to muscle labeling in 4-week-old mdx mice. The observed features of mdx muscle tissue suggest that this animal model is more applicable to the study of regeneration dynamics than to Duchenne-type human muscular dystrophy.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ar.1092190305
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  • 4
    Electronic Resource
    Electronic Resource
    Morphometry and cytochemistry of leydig cells in experimental diabetes (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    American Journal of Anatomy 180 (1987), S. 41-48 
    Details
    ISSN: 0002-9106
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Leydig cell ultrastructure and function in diabetic rats were studied by concurrent cytochemisty, morphometry, and testosterone assay. The streptozotocin (Stz) model was modified to include nondiabetic Stz-injected rats, an insulin-treated diabetic group, and semistarved animals in addition to controls and untreated diabetic rats. The separation of the effects of diabetes, Stz, semistarvation, and insulin treatments was achieved by application of orthogonal contrast statistics.After 3 months of treatments, testes were perfusion fixed, incubated Δ5,3β-hydroxysteroid dehydrogenase (HSD) activity, and processed for electron microscopy.Diabetes increased Leydig cell smooth endoplasmic reticulum (SER), increased mitochondrial and lipid content, decreased HSD staining, and decreased serum testosterone levels. Insulin treatment reduced SER and increased testosterone concentrations. Semistarvation also increased SER and reduced testosterone levels but did not alter HSD staining. Stz had no significant effect on these variables. The results suggested that the hypoandrogen state was due to a primary Leydig cell compromise and not solely to malnutrition and that it was correctable by insulin treatment.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aja.1001800104
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  • 5
    Electronic Resource
    Electronic Resource
    Measurement of the size distribution of human erythrocytes by a sedimentation methodThis investigation was supported by grant MA-2586 from the Medical Research Council of Canada. (1972)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 79 (1972), S. 127-137 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The distribution of sedimentation velocities was determined, by a photoelectric method, for human erythrocytes at low concentrations in Ringer solution. The light absorption at 414 nm was measured, as a function of time, 10 mm below the top of the column. From the frequency distribution of cell velocities that of Rs √ρ-σ was found; Rs being the Stokes' radius, ρ the cell density and σ the density of the solution. Cell density was measured by the phthalate method and the mean Stokes' radius was found to be 2.58 μm. The size distributions showed some skewness but were in good general agreement with those measured by Celloscope counter, and with reported measurements from photomicrographs of cells in hanging drop suspensions. The skewness was much less than that encountered with electric sensing zone instruments (e.g. Celloscope) and the sedimentation method, being based on entirely different premises, provides an important check on such data. The skewness is due to a bias in the orientation of human erythrocytes during sedimentation. This bias may be a characteristic of biconcave cells; it could be absent in many species and reliable measurements of size distribution would then be obtained.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1040790115
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  • 6
    Electronic Resource
    Electronic Resource
    Baculoviruses on the bench. Baculovirus expression vectors: A laboratory manual (1992). By DAVID R. O'REILLY, LOIS K. MILLER AND VERNE A. LUCKNOW W. H. Freeman and Co., New York. 347 pp. ISBN 0-7167-7017-2. $49.95 £39.95 (1993)
    New York, NY : Wiley-Blackwell
    BioEssays 15 (1993), S. 217-217 
    Details
    ISSN: 0265-9247
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bies.950150312
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  • 7
    Electronic Resource
    Electronic Resource
    Problems and paradigms: Fine tuning of DNA repair in transcribed genes: Mechanisms, prevalence and consequences (1993)
    New York, NY : Wiley-Blackwell
    BioEssays 15 (1993), S. 209-216 
    Details
    ISSN: 0265-9247
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Cells fine-tune their DNA repair, selecting some regions of the genome in preference to others. In the paradigm case, excision of UV-induced pyrimidine dimers in mammalian cells, repair is concentrated in transcribed genes, especially in the transcribed strand. This is due both to chromatin structure being looser in transcribing domains, allowing more rapid repair, and to repair enzymes being coupled to RNA polymerases stalled at damage sites; possibly other factors are also involved. Some repair-defective diseases may involve repair-transcription coupling: three candidate genes have been suggested.However, preferential excision of pyrimidine dimers is not uniformly linked to transcription. In mammals it varies with species, and with cell differentiation. In Drosophila embryo cells it is absent, and in yeast, the determining factor is nucleosome stability rather than transcription.Repair of other damage departs further from the paradigm, even in some UV-mimetic lesions. No selectivity is known for repair of the very frequent minor forms of base damage. And the most interesting consequence of selective repair, selective mutagenesis, normally occurs for UV-induced, but not for spontaneous mutations. The temptation to extrapolate from mammalian UV repair should be resisted.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bies.950150311
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