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  • 1
    Digitale Medien
    Digitale Medien
    Coordination of the cell-specific distribution of the four subunits of glycine decarboxylase and of serine hydroxymethyltransferase in leaves of C3-C4 intermediate species from different genera (1993)
    Springer
    Planta 190 (1993), S. 468-473 
    Details
    ISSN: 1432-2048
    Schlagwort(e): C3-C4 intermediate species (Flaveria, Moricandia, Panicum) ; C4 evolution ; Glycine decarboxylase (localization) ; Photorespiration ; Serine hydroxymethyltransferase (localization)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The cell-specific distribution of the four subunit proteins (P, L, T and H) of glycine decarboxylase (GDC) and of serine hydroxymethyltransferase (SHMT) has been studied in the leaves of C3-C4 intermediate and C4 species of three genera (Flaveria, Moricandia and Panicum) using immunogold localization. Antibodies raised against these proteins from pea leaf mitochondria were used to probe Western blots of total leaf proteins of F. linearis Lag., M. arvensis (L.) DC and P. milioides Nees ex Trin. (C3-C4), and F. trinervia (Spring.) Mohr and P. miliaceum (L.) (C4). For all species, each antibody recognised specifically a protein of similar molecular weight to that in pea leaves. In leaves of M. arvensis the P protein was present in the mitochondria of the bundle-sheath cells but was undetectable in those of the mesophyll, whereas the L, T and H proteins and SHMT were present in both cell types. The density of immunogold labelling of SHMT on the mitochondria of mesophyll cells was less than that on those of the bundle-sheath cells, which correlates with the relative activities of SHMT in these cell types. These data reveal that the lack of functional GDC in the mesophyll cells of M. arvensis, which is the principal biochemical reason for reduced photorespiration in this species, is due to the loss of a single subunit protein. This lack of coordinate expression of the subunit proteins of GDC within a photosynthetic cell represents a clear difference between M. arvensis and other C3 and C3-C4 species. None of the GDC proteins was detectable in the mesophyll cells of the C3-C4 and C4 Flaveria and Panicum species but all were present in the bundle-sheath cells. The differences in the distribution of the GDC proteins in leaves of the C3-C4 species studied are discussed in relation to the evolution of photosynthetic mechanisms.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00224785
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  • 2
    Digitale Medien
    Digitale Medien
    Yohimbine — facilitated acoustic startle reflex in humans (1993)
    Springer
    Psychopharmacology 110 (1993), S. 342-346 
    Details
    ISSN: 1432-2072
    Schlagwort(e): Yohimbine ; Noradrenergic ; Anxiety
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Preclinical studies have suggested the acoustic startle reflex (ASR) may be a useful animal model to investigate the neurochemical basis of anxiety and fear states. This work has revealed that the anxiogenic alpha-2 receptor antagonist, yohimbine, increases the amplitude of the ASR in laboratory animals. The present investigation evaluated the effects of yohimbine on the ASR in healthy subjects. Seven healthy subjects received IV yohimbine (0.4 mg/kg) or saline placebo on two separate days in a randomized double blind placebo control design. A trial of 2 tone frequencies with varied intensity (90, 96, 102, 108, 114 dB) white noise, instantaneous rise time, was delivered binaurally through headphones. Tones were delivered every 25–60 sec, for a 30 ms duration. Startle testing was done 80 minutes post infusion and lasted 15–20 minutes. Sign rank testing indicated yohimbine caused an overall increase in startle amplitude, as well as significant augmentation of startle amplitude at 96, 102, 108, 114 decibels but not at the 90 dB intensity. Sign rank tests indicated a significant reduction of startle latency by yohimbine at only the 96 dB intensity. Significant correlations were observed between startle and peak anxiety, startle and plasma MHPG, peak anxiety and plasma MHPG. This study demonstrates in healthy human subjects an excitatory effect of yohimbine on the mangnitude of the ASR and a decrease in its latency. In the context of the key role of this reflex in the alarm response, this finding adds to the array of documented behavioral, biochemical and cardiovascular effects of yohimbine in humans which support the relationship between increased noradrenergic function and anxiety states.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02251291
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  • 3
    Digitale Medien
    Digitale Medien
    Yohimbine facilitated acoustic startle in combat veterans with post-traumatic stress disorder (1995)
    Springer
    Psychopharmacology 117 (1995), S. 466-471 
    Details
    ISSN: 1432-2072
    Schlagwort(e): Yohimbine ; Noradrenergic ; Anxiety PTSD
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Preclinical and clinical studies have suggested that the acoustic startle reflex (ASR) is a useful model to investigate the neurochemical basis of anxiety and fear states. This work has revealed that the anxiogenic alpha-2 receptor antagonist, yohimbine, increases the amplitude of the ASR in laboratory animals and in healthy human controls. Because of the growing body of data that support the hypothesis that severe stress results in substantial alterations in noradrenergic neuronal reactivity, the present investigation evaluated the effects of yohimbine on the ASR of 18 patients with PTSD and 11 healthy combat controls. Subjects received IV yohimbine (0.4 mg/kg) or saline placebo on 2 separate days in a randomized double blind placebo control design. A trial of two tone frequencies with varied intensity (90, 96, 102, 108, 114 dB) white noise and instantaneous rise time, was delivered binaurally through headphones. Tones were delivered every 25–60 s, for a 40-ms duration. Startle testing was performed 80 min post-infusion and lasted 15–20 min. Yohimbine significantly increased the amplitude, magnitude and probability of the ASR in combat veterans with PTSD, but did not do so in combat controls. Overall startle was significantly larger in the PTSD subjects; however, this did not account for the differential effect of yohimbine, since yohimbine had no significant effect in the control group. This study demonstrates an excitatory effect of yohimbine on the amplitude, magnitude and probability of the ASR in PTSD patients that is not seen in combat controls. In the context of the key role of this reflex in the alarm response, this finding adds to the array of documented behavioral, biochemical and cardiovascular effects of yohimbine in humans which support the relationship between increased noradrenergic function and exaggerated startle symptomatology of PTSD.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02246220
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  • 4
    Digitale Medien
    Digitale Medien
    Expression of the C3-C4 intermediate character in somatic hybrids between Brassica napus and the C3-C4 species Moricandia arvensis (1996)
    Springer
    Theoretical and applied genetics 93 (1996), S. 1234-1241 
    Details
    ISSN: 1432-2242
    Schlagwort(e): Brassica napus ; Moricandia arvensis ; Somatic hybridisation ; C3-C4 intermediate ; Photorespiration
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The wild crucifer Moricandia arvensis is a potential source of alien genes for the genetic improvement of related Brassica crops. In particular M. arvensis has a C3-C4 intermediate photosynthetic mechanism which results in enhanced recapture of photorespired CO2 and may increase plant water-use efficiency. In order to transfer this trait into Brassica napus, somatic hybridisations were made between leaf mesophyll protoplasts from cultured M. arvensis shoot tips and hypocotyl protoplasts from three Brassica napus cultivars, ‘Ariana’, ‘Cobra’ and ‘Westar’. A total of 23 plants were recovered from fusion experiments and established in the greenhouse. A wide range of chromosome numbers were observed among the regenerated plants, including some apparent mixoploids. Thirteen of the regenerated plants were identified as nuclear hybrids between B. napus and M. arvensis on the basis of isozyme analysis. The phenotypes of these hybrids were typically rather B. napus-like, but much variability was observed, including variation in flower colour, leaf shape and colour, leaf waxiness, fertility and plant vigour. CO2 compensation point measurements on the regenerated plants demonstrated that 3 of the hybrids express the M. arvensis C3-C4 intermediate character at the physiological level. Semi-thin sections through leaf tissues of these 3 plants revealed the presence of a Kranz-like leaf anatomy characteristic of M. arvensis but not found in B. napus. This is the first report of the expression of this potentially important agronomic trait, transferred from Moricandia, in M. arvensis x B. napus hybrids.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00223455
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  • 5
    Digitale Medien
    Digitale Medien
    Analysis of fluorescence transients of DCMU-treated leaves of Triticum species to provide estimates of the densities of photosystem II reaction centres (1986)
    Springer
    Photosynthesis research 7 (1986), S. 203-219 
    Details
    ISSN: 1573-5079
    Schlagwort(e): fluorescence induction ; photosynthesis ; photosystem II ; Triticum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The fluorescence of the chlorophyll associated with photosystem II was studied in seedling and flag leaves of Triticum species. Seedling leaves of the diploid species T. urartu had higher values of t (the normalised area over the fluorescence induction curve of DCMU treated leaves) than those of the other species studied which included hexaploid T. aestivum. However this difference was not evident when leaves were grown in a low light intensity (40 µmol quanta of photosynthetically active radiation m−2 s−1). The smaller total number of chlorophyll molecules per photosystem II reaction centre (chl/RCII) in T. urartu (177) as compared with the other species (mean 234) was deduced from the observed differences in t. As a consequence of its lower chl/RCII, despite slightly lower chlorophyll content (mg m−2), T. urartu had a greater density of reaction centres than the other species (2880 cf 2230 nmol m−2 of leaf). Consistent with the lower chl/RCII of T. urartu, it had a higher chlorophyll a/b ratio than the other genotypes. Seedling leaves of T. urartu had higher light saturated rates of photosynthesis than those of the other species, when grown at high light, a difference associated with reaction centre density. In flag leaves, when the complications due to variable development and senescence patterns were eliminated, t of the diploid species including T. urartu was lower than that of T. aestivum. The lower apparent chl/RCII of T. urartu arose partly because the molar extinction coefficient of the chlorophyll in the leaves of T. urartu was greater than in T. aestivum. However, the density of PS II reaction centres was slightly lower for the diploid species studied because their chlorophyll contents were lower than the hexaploids. The validity of the method for estimating chl/RCII from fluorescence transients is discussed. The possibility is considered that the difference in apparent chl/RCII of flag and seedling leaves of R. urartu as compared to the other five genotypes is a consequence of its different adaptive response to the spectral quality of the light.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00014675
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  • 6
    Digitale Medien
    Digitale Medien
    Estimation of the light distribution between photosystems I and II in intact wheat leaves by fluorescence and photoacoustic measurements (1986)
    Springer
    Photosynthesis research 7 (1986), S. 257-267 
    Details
    ISSN: 1573-5079
    Schlagwort(e): Chlorophyll a fluorescence ; photoacoustic spectroscopy ; photosystem I ; photosystem II ; wheat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Usisng intact leaves, the extent of the decrease in chlorophyll a fluorescenece caused by the addition of continuous 710 nm light superimposed on modulated (20 Hz) 550 nm light was used to determine the distribution of this absorbed light between photosystems I (α) and II (β). The Fo and Fm levels, which defined the total variable fluorescenece, were taken as equal to those obtained with excess 710 nm light and with saturating blue-green light, respectively. An analogous procedure was used with a photoacoustic detector, saturating white light defining a base line for oxygen yield, the levels with an without 710 nm light being used to define β and α respectively. The two methods gave similar values for the distribution of light between the two photosystems for the experimental conditions used, β averaging 0.55 for a range of Triticum genotypes and Brachypodium sylvaticum grown in high or low light.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00014679
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