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  • 1
    Electronic Resource
    Electronic Resource
    The primary processes of photosystem II in purified guard-cell protoplasts and mesophyll-cell protoplasts from Commelina communis L. (1983)
    Springer
    Planta 159 (1983), S. 554-560 
    Details
    ISSN: 1432-2048
    Keywords: Chlorophyll fluorescence ; Commelina ; Guard cell ; Oxygen evolution (guard cell) ; Photosystem II ; Protoplast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Guard-cell protoplasts were isolated by enzymic digestion of the epidermis peeled from the abaxial surface of leaves from Commelina communis L. The protoplasts were separated from mesophyll-cell protoplasts and other contaminants by density-gradient centrifugation, and the purity of the preparations carefully and quantitatively assessed by light microscopy. The preparations of guard-cell protoplasts were then compared with mesophyll-cell protoplasts in terms of the activity of photosystem II as assessed by a) the light-induced evolution of oxygen under both steady-state and flashing light and b) the characteristics of photosystem-II chlorophyll fluorescence. In all experiments, clear photosystem-II activity was found in guard-cell protoplasts, although some subtle distinctions between guard-cell and mesophyll-cell protoplasts were found. The contribution of any contaimination by mesophyll-cell chlorophyll to guard-cell-protoplast signals was estimated to be less than 3% in all cases. The results indicate that photosystem II is present and active in guard cells of Commelina.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00409145
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  • 2
    Electronic Resource
    Electronic Resource
    CO2 and O2 dependence of PS II activity in C4 plants having genetically produced deficiencies in the C3 or C4 cycle (1998)
    Springer
    Photosynthesis research 58 (1998), S. 91-101 
    Details
    ISSN: 1573-5079
    Keywords: C4 photosynthesis ; PEP carboxylase mutants ; Photosystem II ; Rubisco transgenic plants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The CO2 dependence of rates of CO2 fixation (A) and photochemistry of PS II at 5, 15 and 30% O2 were analyzed in the C4 plant Amaranthus edulis having a C4 cycle deficiency [phosphoenolpyruvate carboxylase (PEPC) mutants], and in the C4 plant Flaveria bidentis having a C3 cycle deficiency [Rubisco small subunit antisense (αSSU)]. In the wild type (WT) A. edulis and its heterozygous mutant having less than 50% WT PEPC activity there was a similar dependence of A and PS II photochemistry on varying CO2, although the CO2 saturated rates were 25% lower in heterozygous plants. The homozygous plants having less than 2% PEPC of the WT had significant levels of photorespiration at ambient levels of CO2 and required about 30 times ambient levels for maximum rates of A. Despite variation in the capacity of the C4 cycle, more than 91% of PS II activity was linearly associated with A under varying CO2 at 5, 15 and 30% O2. However, the WT plant had a higher PS II activity per CO2 fixed under saturating CO2 than the homozygous mutant, which is suggested to be due to elimination of the C4 cycle and its associated requirement for ATP from a Mehler reaction. In the αSSU F. bidentis plants, a decreased rate of A (35%) and PS II activity (33%) accompanied a decrease in Rubisco capacity. There was some increase in alternative electron sinks at high CO2 when the C3 cycle was constrained, which may be due to increased flux through the C4 cycle via an ATP generating Mehler reaction. Nevertheless, even with constraints on the function of the C4 or C3 cycle by genetic modifications, analyses of CO2 response curves under varying levels of O2 indicate that CO2 assimilation is the main determinant of PS II activity in C4 plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006176713574
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  • 3
    Electronic Resource
    Electronic Resource
    Flash-induced redox changes in oxygen-evolving spinach Photosystem II core particles (1993)
    Springer
    Photosynthesis research 38 (1993), S. 169-176 
    Details
    ISSN: 1573-5079
    Keywords: Photosystem II ; PS II core ; oxygen-evolving complex ; UV asorbance changes ; EPR signal II
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Flash-induced redox reactions in spinach PS II core particles were investigated with absorbance difference spectroscopy in the UV-region and EPR spectroscopy. In the absence of artificial electron acceptors, electron transport was limited to a single turnover. Addition of the electron acceptors DCBQ and ferricyanide restored the characteristic period-four oscillation in the UV absorbance associated with the S-state cycle, but not the period-two oscillation indicative of the alternating appearance and disappearance of a semiquinone at the QB-site. In contrast to PS II membranes, all active centers were in state S1 after dark adaptation. The absorbance increase associated with the S-state transitions on the first two flashes, attributed to the Z+S1→ZS2 and Z+S2→ZS3 transitions, respectively, had half-times of 95 and 380 μs, similar to those reported for PS II membrane fragments. The decrease due to the Z+S3→ZS0 transition on the third flash had a half-time of 4.5 ms, as in salt-washed PS II membrane fragments. On the fourth flash a small, unresolved, increase of less than 3 μs was observed, which might be due to the Z+S0→ZS1 transition. The deactivation of the higher S-states was unusually fast and occurred within a few seconds and so was the oxidation of S0 to S1 in the dark, which had a half-time of 2–3 min. The same lifetime was found for tyrosine D+, which appeared to be formed within milliseconds after the first flash in about 10% inactive centers and after the third and later flashes by active centers in Z+S3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00146416
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  • 4
    Electronic Resource
    Electronic Resource
    Absorbance difference spectra of the S-state transitions in Photosystem II core particles (1993)
    Springer
    Photosynthesis research 38 (1993), S. 323-330 
    Details
    ISSN: 1573-5079
    Keywords: Photosystem II ; PS II core ; oxygen evolving complex ; UV absorbance changes ; S-state spectra
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Redox changes of the oxygen evolving complex in PS II core particles were investigated by absorbance difference spectroscopy in the UV-region. The oscillation of the absorbance changes induced by a series of saturating flashes could not be explained by the minimal Kok model (Kok et al. 1970) consisting of a 4-step redox cycle, S0 → S1 → S2 → S3 → S0, although the values of most of the relevant parameters had been determined experimentally. Additional assumptions which allow a consistent fit of all data are a slow equilibration of the S3 state with an inactive state, perhaps related to Ca2+-release, and a low quantum efficiency for the first turnover after dark-adaptation. Difference spectra of the successive S-state transitions were determined. At wavelengths above 370 nm, they were very different due to the different contribution of a Chl bandshift in each spectrum. At shorter wavelengths, the S1 → S2 transition showed a difference spectrum similar to that reported by Dekker et al. 1984b and attributed to an Mn(III) to Mn(IV) oxidation. The spectrum of absorbance changes associated with the S2 → S3 transition was similar to that reported by Lavergne 1991 for PS II membranes. The S0 → S1 transition was associated with a smaller but still substantial absorbance increase in the UV. Differences with the spectra reported by Lavergne 1991 are attributed to electrostatic effects on electron transfer at the acceptor side associated with the S-state dependence of proton release in PS II membranes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00046757
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  • 5
    Electronic Resource
    Electronic Resource
    Degradation of the Photosystem II D1 and D2 proteins in different strains of the cyanobacterium Synechocystis PCC 6803 varying with respect to the type and level of psbA transcript (2000)
    Springer
    Plant molecular biology 42 (2000), S. 635-645 
    Details
    ISSN: 1573-5028
    Keywords: cyanobacteria ; D1 ; D2 ; Photosystem II ; psbA ; Synechocystis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The turnover of the D1 and D2 proteins of Photosystem II (PSII) has been investigated by pulse-chase radiolabeling in several strains of the cyanobacterium Synechocystis PCC 6803 containing different types and levels of the psbA transcript. Strains lacking psbA1 and psbA3 gene and containing high levels of the psbA2 transcript showed the selective synthesis of D1 whose degradation could be slowed down by the protein synthesis inhibitor lincomycin. In contrast, in strains containing just the psbA3 gene, the intensity of the D1 protein labeling was lower and labeling of the D2 and CP43 proteins was stimulated in comparison to the psbA2-containing strains. In addition, the rate and selectivity of the D1 degradation and its dependence on the presence of lincomycin was proportional to the level of the psbA3 transcript in the particular strain. Consequently, there was parallel, lincomycin-independent and slowed-down breakdown of the D1 and D2 proteins in strains with the lowest level of psbA3 transcript. These results are discussed in terms of a model in which the rate of D1 and D2 degradation in cyanobacteria is affected not only by the rate of PSII photodamage, but also by the availability of newly synthesized D1 protein. Moreover, the comparison of the non-oxygen-evolving D1 mutants D170A** and Y161F*** differing by the presence of tyrosine Z has indicated a minor role of the oxidized form of this secondary PSII electron donor in the donor side mechanism of D1 and D2 protein breakdown.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006305308196
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  • 6
    Electronic Resource
    Electronic Resource
    Localization of 3H-dihydrotestosterone in the pituitary gland of the rhesus monkey (1981)
    Springer
    Cell & tissue research 215 (1981), S. 499-504 
    Details
    ISSN: 1432-0878
    Keywords: Androgen receptors ; Pituitary gland ; Rhesus monkey ; Autoradiography ; Immunocytochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The uptake and retention of radiolabelled dihydrotestosterone by the pituitary gland was examined in the rhesus monkey. Two animals were given an intravenous injection of 1.0μg/kg 3H-dihydrotestosterone (DHT) alone while one monkey received both the labelled androgen and 100μg/kg of unlabelled steroid. One and a half hours later, they were sacrificed. The pituitary glands were removed and processed for autoradiography and immunocytochemistry. Autoradiographic localization of DHT was discernible in the partes nervosa, intermedia and distalis, albeit the highest concentration of radiolabelled cells was noted in the pars distalis. Immunocytochemical staining with antibodies to rat PRL, human TSHβ and ovine LHβ revealed a population of steroid-concentrating cells that contained TSH and a second group that contained LH. None of the cells that reacted with the anti-PRL serum were radiolabelled.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00233526
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  • 7
    Electronic Resource
    Electronic Resource
    Autoradiographic localization of sex steroid hormones in the lymphatic organs of baboons (1983)
    Springer
    Cell & tissue research 231 (1983), S. 593-601 
    Details
    ISSN: 1432-0878
    Keywords: Lymphatic organs ; Sex steroids ; Baboon ; Autoradiography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The localization of radiolabeled estradiol and dihydrotestosterone was examined in the lymphatic organs of both male and female baboons. A total of 12 baboons were divided into two groups, each containing three males and three females. Each animal in one group, both males and females, was injected intravenously with 1 μg/kg body weight of 3H-estradiol while those in the second group were each injected with 1 μg/kg body weight of 3H-dihydrotestosterone. As controls, one male and one female from each group also received a dose of 100 μg/kg body weight of the corresponding unlabeled steroid. One and a half hours after the injections, the animals were sacrificed and the spleen, thymus, and inguinal lymph nodes removed and processed for autoradiography. The localization of 3H-estradiol was similar in both males and females. In the thymus fibroblasts and epithelio-reticular cells, but not thymocytes, localized 3H-estradiol. In lymph node and spleen, nonlymphoid tissue concentrated the labeled estrogen. Additionally, in the paracortical region of the lymph node, an unknown cell type was labeled with estrogen. Only one male baboon demonstrated nuclear localization of 3H-dihydrotestosterone. This was observed in the reticular cells in the spleen and lymph nodes. The same cell type in the organs of the remaining animals was unlabeled.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00218117
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  • 8
    Electronic Resource
    Electronic Resource
    Cellular and subcellular localization of 3H-diethylstilboestrol in the central nervous system (1977)
    Springer
    Cell & tissue research 183 (1977), S. 379-384 
    Details
    ISSN: 1432-0878
    Keywords: Brain ; Rat ; Diethylstilboestrol ; Autoradiography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The cellular and subcellular localization of radioactivity in the brain of immature female rats was determined by dry-mount autoradiography 2 h after iv injection of 1.0 μg of (monethyl-3H) diethylstilboestrol per 100 g body weight. A specific topographic pattern of nuclear concentration of the synthetic oestrogen was obtained similar to that for 3H-oestradiol-17β in specific neurons of the basal hypothalamus, preoptic region and amygdala. In competition experiments, the nuclear concentration of radioactivity in all areas studied was inhibited by unlabeled oestradiol, while unlabeled testosterone had no effect. These data suggest that although oestradiol can bind to androgen receptors, the oestrogen receptor itself can account for the localization seen after the injection of 3H-oestradiol.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00220644
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  • 9
    Electronic Resource
    Electronic Resource
    Estrogen receptors in the islets of Langerhans of baboons (1983)
    Springer
    Cell & tissue research 230 (1983), S. 219-223 
    Details
    ISSN: 1432-0878
    Keywords: Steroid receptors ; Estradiol ; Diabetes mellitus ; Autoradiography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Previous clinical studies have indicated that during pregnancy and following administration of contraceptives women show altered carbohydrate metabolism. We performed autoradiographic studies using 3H-estradiol-17β and 3H-dihydrotestosterone on male and female baboons. Discrete sites of localization of exposed photographic emulsion were observed over nuclei of cells of the islets of Langerhans of the pancreases of baboons injected with estrogen but not over those of baboons injected with androgen. These observations that islet cells contain specific receptors for estrogen when combined with the clinical observations, suggest that estrogens have a direct effect on the islet cells that may modulate the release of insulin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00216041
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  • 10
    Electronic Resource
    Electronic Resource
    Uptake and retention of3H-estradiol by gonadotrophs and lactotrophs in the pituitary glands of the guinea pig, hamster and gerbil (1987)
    Springer
    Cell & tissue research 248 (1987), S. 75-78 
    Details
    ISSN: 1432-0878
    Keywords: LH-cells ; Prolactin cells ; Immunocytochemistry ; Estrogen ; Autoradiography ; Guinea pig ; Hamster ; Gerbil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Nuclear uptake and retention of3H-estradiol by luteinizing hormone (LH) and prolactin (PRL) cells was examined in three species of rodents (guinea pigs, hamsters and gerbils) using the combined techniques of immunocyto-chemistry and autoradiography. Castrated animals were injected with3H-estradiol and decapitated 1.5 h later. The pituitary glands were processed for thaw-mount autoradiography followed by conventional immunocytochemical staining for LH and PRL.3H-estradiol accumulated in more than 80% of the anterior pituitary cells in the gerbils, while only 33 and 22% of the cells accumulated3H-estradiol in the hamsters and guinea pigs, respectively. A varying percentage of immunoreactive LH and PRL cells in all three species were found also to contain binding sites for estradiol. Some LH and PRL cells in hamsters and guinea pigs and only some in PRL cells of gerbils were found to be devoid of grains. Quantitative analysis revealed that the number of grains per nucleus differed considerably from cell to cell. LH cells of guinea pigs accumulated much larger amounts of3H-estradiol than did the PRL cells, while the LH cells in the hamsters and gerbils accumulated only slightly more3H-estradiol than the PRL cells. These results confirm the previous observations in rats and baboons that demonstrated tremendous species differences in percentage of cells in the anterior pituitary gland that accumulated3H-estradiol. Also, these data suggest that there are functionally heterogeneous cell types among the LH and PRL cells in hamsters, guinea pigs and gerbils as has been previously demonstrated in rats and baboons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01239965
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