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  • Spektralphotometrie  (167)
  • bioavailability  (65)
  • pheromone  (60)
  • Phytochrome  (56)
  • Springer  (348)
  • American Association for the Advancement of Science
  • Cambridge University Press
  • 1975-1979  (348)
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  • Springer  (348)
  • American Association for the Advancement of Science
  • Cambridge University Press
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  • 1
    ISSN: 1432-2048
    Keywords: Bryophyllum ; Circadian rhythm ; CO2 output ; Phytochrome ; Red light ; Rhythm (circadian)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The rhythm of carbon dioxide output in Bryophyllum leaves was entrained on exposure to 0.25 h of white light every 24 h. Entrainment also occurred on similar exposure to monochromatic radiation in spectral bands centred at 660 nm and, to a lesser extent, at 730 nm, but a band centred at 450 nm was without effect. A “skeleton” irradiation programme comprising two 0.25-h exposures to white light per 24 h also entrained the rhythm when the intervening dark periods were either 7.5 h and 16 h, or 10.5 h and 13 h. The rhythm disappeared when the two exposures were separated by 11.5-h and 12-h dark periods. Regular 0.25-h exposures to red light separated by 11.75-h periods of darkness also resulted in loss of the rhythm. Red/far-red reversibility was observed in irradiation schedules having either one or two exposures to red light daily. In the latter case, far-red reversal of the effects of one of the exposures to red light resulted in entrainment of the rhythm by the other, instead of abolition of the rhythm. The occurrence of distinct red/far-red reversibility suggests strongly that phytochrome is the pigment involved in entrainment of this rhythm by cycles of light and darkness.
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  • 2
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    Planta 133 (1977), S. 169-177 
    ISSN: 1432-2048
    Keywords: Cell fractionation ; Cucurbita ; Histochemical staining ; Phosphotungstate-chromate staining ; Phytochrome ; Plasma membrane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The phosphotungstic acid-chromic acid (PTA-CrO3) stain, putatively specific for the plasma membrane of plants, has been used in an attempt to monitor the distribution of this membrane in a 20,000 x g particulate fraction from Cucurbita hypocotyl hooks. On discontinuous sucrose gradients, the relative distributions of the phytochrome and PTA-CrO3-positive vesicles present in this fraction appear to be correlated. When intact tissue is stained, however, other components, in addition to the plasma membrane, react positively to the stain. These components include prolamellar-body membranes, lipid droplets, and ribosomes. This lack of specificity calls into question the reliability of the technique for the unequivocal identification and accurate quantitation of plasma-membrane fragments in isolated particulate fractions. The present data do not, therefore, provide unambiguous evidence that phytochrome is associated with plasma membrane in tissue homogenates from Cucurbita.
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  • 3
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    Planta 134 (1977), S. 11-16 
    ISSN: 1432-2048
    Keywords: Brassica ; Chlorophyll ; Cotyledons ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phytochrome determinations at 730/800 nm were performed on de-etiolated turnip (Brassica rapa L.) cotyledons in which chlorophyll (Chl) content had been reduced experimentally to varying degrees by pre-treatment with high temperature (HT), or transfer to 3% ethanol. The magnitude of detectable phytochrome depended on Chl content, showing a linear relationshop in vivo. The results were confirmed by an in vitro experiment where, however, the correlation was exponential. An attempt is made to illustrate phytochrome decay in continuous blue or red light after corretion for Chl interference. To overcome the possible objection that the higher Δ(ΔA) measured in continuous light after HT pre-treatment could be caused by a reduced rate of destruction, apparent re-synthesis following red light was measured after several hours of darkness during which time the HT effect was lost. Under these conditions HT pre-treated samples display a more realistic magnitude of apparent new synthesis and make correlation with a physiological response possible.
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  • 4
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    Planta 134 (1977), S. 57-59 
    ISSN: 1432-2048
    Keywords: Cell culture ; Clycine ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract No phytochrome can be detected spectrophotometrically in soybean (Glycine max (L.) Merr. cv. Mandarin) cell suspensions grown in darkness. White light from a tungsten filament lamp and a band of far-red light have been found to induce the appearance of phytochrome in them. Red light failed to bring about phytochrome increase and destroyed the phytochrome induced by far-red light.
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  • 5
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    Planta 135 (1977), S. 119-123 
    ISSN: 1432-2048
    Keywords: Chlorophyll ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Measurements of phytochrome by Δ (ΔA725–815 nm) were completely suppressed at chlorophyll concentrations of the order of 20–40 μg g-1 f.wt. in vivo and 37 μg cm-3 in vitro, and the readings were reduced by 50% at only 12 μg cm-3 in vitro. At these concentrations of chlorophyll in aqueous methanol, the loss of phytochrome signal in vitro appeared to be due to failure of phytochrome photoconversion rather than to interference with ΔA measuremebt by chlorophyll fluorescence in the 125/815 nm measuring beam.
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  • 6
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    Planta 136 (1977), S. 125-129 
    ISSN: 1432-2048
    Keywords: Blue-light-response ; Elongation ; High-irradiance-response ; Photomorphogenesis ; Phytochrome ; Raphanus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In etiolated hypocotyls of Raphanus sativus L. the growth responses to continuous red, far-red and blue light have been distinguished on the bases of photoreceptive sites and regions of physiological response. Blue light appeared to retard a fairly mature stage of elongation, acting immediately and directly on the cells irradiated. Far-red light caused a marked inhibition of all stages of elongation after a lag period, and the stimulus could be transmitted from the hook region. The effect of red light was complex and consisted of one promotive and two inhibitory responses.
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  • 7
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    Planta 136 (1977), S. 131-134 
    ISSN: 1432-2048
    Keywords: Action-spectrum ; Blue-light photoreceptor ; High-irradiance-response ; Photomor-phogenesis ; Phytochrome ; Raphanus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In etiolated seedlings of Raphanus sativus L. the inhibition of hypocotyl elongation by continuous light showed a major bimodal peak of action in the red and far-red, and two minor peaks in the blue regions of the spectrum. It is argued that, under conditions of prolonged irradiation, phytochrome is the pigment controlling the inhibition of hypocotyl elongation by red and far-red light, but that its mode of action in far-red is different from that in red. A distinct pigment is postulated for blue light.
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  • 8
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    Planta 136 (1977), S. 181-186 
    ISSN: 1432-2048
    Keywords: Enzyme Regulation ; Sinapis alba ; Phytochrome ; Phenylalanine ammonia-lyase ; Ribulosebisphosphate carboxylase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phytochrome controls the appearance of many enzymes in the mustard (Sinapis alba L.) cotyledons. The problem has been whether the effect of phytochrome on the appearance of enzymes in this organ is due to a common initial action of Pfr, e.g. due to the liberation of a “second messenger”. We have compared the modulation by light (phytochrome) of the appearance of phenylalanine ammonia lyase (PAL)+ and ribulosebisphosphate carboxylase (Carboxylase)+. PAL becomes detectable in the mustard cotyledons at 27 h after sowing while Carboxylase starts to appear only at 42 h after sowing (starting points, 25° C). The starting points cannot be shifted by light. As a major result, in the case of PAL the inductive effect of continuous red light (given from the time of sowing) remains fully reversible by 756 nm-light up to the starting point (27 h after sowing) while with Carboxylase full reversibility in continuous red light is lost at approximately 15 h after sowing. While the induction of Carboxylase is already saturated at a very low level of Pfr (e.g. continuous 756 nm-light saturates the response) and does not depend on irradiance (e.g. continuous 675 mW m-2 red light and 67.5 mW m-2 red light lead to the same time course), PAL induction is a graded response over a wide range of Pfr doses and depends strongly on the fluence rate (high irradiance response, HIR). It is concluded that PAL induction and Carboxylase induction are not only separated in time but differ in every regard except that both responses are mediated by phytochrome. The present data support the previous conclusion that the specification of the temporal and spatial pattern of development is independent of phytochrome even though the realization of the pattern of development can only occur in the presence of phytochrome (Pfr). It seems that there is no feedback from pattern realization to pattern specification.
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  • 9
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    Planta 137 (1977), S. 61-64 
    ISSN: 1432-2048
    Keywords: Phaseolus ; Phytochrome ; Potassium uptake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Uptake of potassium (K) and 86rubidiumlabelled potassium (86Rb) by sub-hypocotyl hook sections of Phaseolus aureus L. was inhibited by red light. The effect was reversible with far red light. Using short exposures of high irradiance the effect on 86Rb-labelled K uptake was observed after 5 min. The response showed no specificity for a particular anion. Uptake of 86Rb-labelled K by sections cut immediately below the cotyledons was enhanced by red light after 10 min incubation and was also far red reversible. These results are interpreted as a rapid phytochrome-induced change in membrane properties resulting in modified K uptake.
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  • 10
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    Planta 137 (1977), S. 225-229 
    ISSN: 1432-2048
    Keywords: Calcium Ions ; Membrane potential ; Nitella ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Isolated internodes of Nitella (N. opaca, N. flexilis) and Nitellopsis spec. were punctured with single microelectrodes and their membrane potentials were recorded continuously during various light treatments. In red light the initial response was always a depolarization. This depolarization began with a lag-time of 0.4-3.5s and reached a steady state within 1–2 min of continuous illumination. Repolarization began within several seconds after turning off the light. The magnitude of the red-light-induced depolarization increased with the Ca2+-concentration of the medium. The largest depolarizations were recorded in 5 m mol l-1 Ca2+. Ca2+ could not be replaced in this function by Na+, Mg2+, La3+ or mannitol. Far-red light alone had no effect on the resting membrane potential. Far-red light applied immediately after red light accelerated the repolarization of the membrane potential. Far-red light applied simultaneously with red light reduced the amount of depolarization and increased the rate of repolarization. The results indicate that phytochrome and Ca2+ are involved in the light-induced depolarization of the membrane. They are consistent with the hypothesis that phytochrome may act by triggering a Ca2+-influx at the plasma membrane.
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  • 11
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    Planta 138 (1978), S. 25-28 
    ISSN: 1432-2048
    Keywords: Action spectrum ; Chlorophyll ; Phaseolus ; Photomorphogenesis ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Red light absorption by photosynthetic pigments screens stem tissue of Phaseolus vulgaris L. seedlings to such an extent that the most effective wavelength for the phytochrome induction control of stem growth is approximately 628 nm. Screening is greater in the first internode than in the hypocotyl. The consequences are that, compared with etiolated seedlings, much higher irradiances are required for phytochrome control in green plants, and the efficiency of 660 nm light is markedly reduced. Even very high exposures at 660 nm may not achieve appreciable photoconversion of P r to P fr.
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  • 12
    ISSN: 1432-2048
    Keywords: Adiantum ; Blue-light effect ; Cell division ; Light, microbeam ; Photomorphogenesis ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Protonemata of the fern Adiantum capillusveneris L., grown as single-cell filaments under continuous red light, were irradiated with a narrow beam of blue light. Only irradiation of the region containing the nucleus induced cell division. Beams of 30 μm in width, which corresponds to the diameter of the nucleus, or wider, were equally effective; beams 10 μm wide or less were less effective. The results indicate that the nuclear region is the site of the blue- and near ultraviolet-light-absorbing pigment (PB-NUV) which mediates the timing effect of cell division. In contrast, the effect of a narrow beam of far-red (FR) light, which delays the onset of the blue-light-induced cell division, was found to be present along the entire length of the protonema cell, including the largely vacuolated basal region of the latter. Polarized FR light having the electrical vector parallel to the protonema axis was less effective than that vibrating in other directions. These observations support the hypothesis that the phytochrome controlling the timing effect is localized in the plasma membrane.
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  • 13
    ISSN: 1432-2048
    Keywords: Lemna ; Membrane potential ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Light-stimulated transmembrane potential changes have been measured continuously after implantation of microelectrodes into subepidermal cells of the short-day plant Lemna paucicostata 6746. Irradiation for 5 min with white or red light caused a transient hyperpolarization. These potential changes could be suppressed with 10-6 M DCMU. Irradiation of DCMU-inhibited plants with far-red light for 5 min hyperpolarized the membrane potential, which thereafter was not changed by further far-red application. Consecutive red light irradiation for 5 min depolarized the membrane potential. The red/far-red reversibility of the potential changes (which could be repeated several times with a single plant) suggests the participation of phytochrome.
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  • 14
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    Planta 141 (1978), S. 1-7 
    ISSN: 1432-2048
    Keywords: Flowering ; Pharbitis ; Photomorphogenesis ; Photoperiodic induction ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract For dark-grown seedlings of Pharbitis nil capacity to flower in response to a single inductive dark period was established by 24 h white, far-red (FR) or ruby-red (BCJ) light and by a skeleton photoperiod of 10 min red (R)-24 h dark-10 min R. FR alone was ineffective without a brief terminal (R) irradiation, confirming that the form of phytochrome immediately prior to darkness is a crucial factor for flowering in Pharbitis. The magnitude of the flowering response was significantly greater after 24 h FR or white light (WL) (at 18° C and 27° C) than after two brief skeleton R irradiations, but the increased flowering response was not attributable to photosynthetic CO2 uptake because this could not be detected in seedlings exposed to 24 h WL at 18° C. Photophosphorylation could have contributed to the increased flowering response as photosystem I fluorescence was detectable in plants exposed to FR, BCJ, or WL, but there were large differences between flowering response and photosystem I capacity as indicated by fluorescence. We conclude that phytochrome plays a major role in photoresponses regulating flowering. There was no simple correlation between developmental changes, such as cotyledon expansion and chlorophyll formation during the 24-h irradiation period, and the capacity to flower in response to a following inductive dark period. Changes in plastid ultrastructure were considerable in light from fluorescent lamps and there was complete breakdown of the prolamellar body with or without lamellar stacking at 27 or 18° C, respectively, but plastid reorganization was minimal in FR-irradiated seedlings.
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  • 15
    ISSN: 1432-2048
    Keywords: Hordeum ; Membranes ; Organelles ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Red light treatment in vitro increases the pelletability of phytochrome in homogenates of etiolated barley (Hordeum vulgare L. cv. ‘Julia’) leaves. When mixtures of soluble phytochrome (100,000 x g supernatant) and partially-purified organelles (Sephadex G-50 eluate) are irradiated the amount of pelletable phytochrome increases by a factor of two. Pre-irradiation treatments show that phytochrome in both components of the mixture must be in the Pfr form for increased pelletability to be observed. Once associated, photoreversion of Pfr to Pr does not result in decreased pelletability. The results are consistent with a non-artifactual in vitro association of soluble phytochrome to organelle membranes. One possible explanation is that Pfr molecules associate to form dimers.
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  • 16
    ISSN: 1432-2048
    Keywords: Avena ; Immunocytochemistry ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phytochrome of oat (Avena sativa L., cv. Garry) coleoptile cells in the red-light-absorbing form, Pr, is diffusely distributed while after conversion to the far-red-light-absorbing form, Pfr, it is observed only in very small areas within the cell. Comparison of phytochrome photoversibility measurements to the distribution of the pigment within the cell indicates that the spectral assay is not influenced by the observed compartmentalization of the chromoprotein. However, the observed compartmentalization of phytochrome is correlated with a loss in spectrophotometrically detectable Pr.
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  • 17
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    Planta 141 (1978), S. 211-216 
    ISSN: 1432-2048
    Keywords: Hypocotyl growth ; Photomorphogenesis ; Phytochrome ; Sinapis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract After sowing, mustard (Sinapis alba L.) seedlings were grown for 48 h in white light (25°C). These fully de-etiolated, green seedlings were used as experimental material between 48 and 72 (84) h after sowing. The question researched was to what extent control by light of hypocotyl elongation is due to phytochrome in these seedlings. It was found that the light effect on hypocotyl growth is very probably exerted through phytochrome only. In particular, we found no indication for the involvement of a specific blue light photoreceptor pigment.
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  • 18
    ISSN: 1432-2048
    Keywords: Avena ; Etioplasts ; Mitochondria ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phytochrome was determined in etiolated laminae of Avena sativaL. either without pretreatment or after 5 min of red irradiation followed by different periods of darkness (0–24 h). At given intervals laminae were homogenized and phytochrome was determined spectrophotometrically in the total homogenate and in purified etioplasts and mitochondria. Enhanced specific activity of phytochrome was found in all fractions after the irradiation in comparison to dark controls. Phytochrome destruction was observed in all fractions at the beginning of the subsequent dark period. Whereas the homogenate and the mitochondrial fraction showed a continuous destruction so that phytochrome reached a level far below that in etiolated plants, the phytochrome level in the plastid fraction reacheda minimum at 2 h with a subsequent increase beyond the dark level. This increase was most pronounced between 4 and 8 h after the red irradiation. The results are discussed in terms of the destruction and possible de novo synthesis of phytochrome that may be different in mitochondria and plastids.
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  • 19
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    Planta 144 (1978), S. 1-5 
    ISSN: 1432-2048
    Keywords: Germination (seeds) ; Lactuca ; Phytochrome ; Seed germination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Germination of certain dry “seeds” (achenes) of Lactuca sativa L. cv. Grand Rapids was increased to ca. 75% after irradiation with 665 nm red light (R; 1x103 J m-2); this response was eliminated by far-red light (FR) following the R. The response of dry seeds required an order of magnitude more light than that of wetted seeds, and was not maximal until 48 h after irradiation. Other seeds, which could not be stimulated by R in dry state, showed a partial response after 10 min hydration. Irradiation of dry seeds (or seeds wetted 1 h) with FR (1x103 J m-2) reduced dark germination from 26% to 2%. Seeds dehydrated in an oven (60°C, 90 min) showed a decrease in germination if irradiated with R (1x105 J m-2) before wetting. The results show that phytochrome is present in dry lettuce seeds (and functional in some seed lots) prior to wetting; and that in other seed lots the molecule becomes functional within minutes after wetting the seeds. Transformation of the FR absorbing from of phytochrome (PFR) to the inactive from (PR) occurs at lower seed moisture content than the reverse reaction. It appears that dormancy in seeds ripened in sunlight might be assured during seed drying and maturation by the more effective transformation of PFR to PR than vice versa as phytochrome is dehydrated.
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  • 20
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    Planta 143 (1978), S. 309-313 
    ISSN: 1432-2048
    Keywords: Avena ; Light-grown tissue ; Phytochrome ; San 9789
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phytochrome was studied spectrophotometrically in Avena sativa L. seedlings that had been grown for 6 d in continous white fluorescent light from lamps. Greening was prevented through the use of the herbicide San 9789. When placed in the light, phytochrome (Ptot) decreased with first order kinetics (τ1/2 ≈ 2 h) but reached a stable low level (≈2.5% of the dark level) after 36 h. This concentration of phytochrome remained constant in the light and during the initial hours of a subsequent dark period, but increased significantly after a prolonged dark period. Evidence suggests that the constant pool of phytochrome in the light is achieved through an equilibrium between synthesis of the red absorbing (Pr) and destruction of the far-red absorbing form (Pfr) of phytochrome. It is concluded that the phytochrome system in light-grown oat seedlings is qualitatively the same as that known from etiolated monocotyledonous seedlings, but different than that described for cauliflower florets.
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  • 21
    ISSN: 1432-2048
    Keywords: Citrate synthase ; Fat degradation ; Isocitrate lyase ; Malate synthase ; Phytochrome ; Sinapis ; Starch (transitory)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The degradation of storage fat in the cotyledons of mustard seedlings is unaffected by phytochrome and photosynthesis (irradiation with continuous red or far-red light from sowing of the seeds) although light imposes a strong constraint on the translocation of organic matter from the cotyledons into the seedling axis. Likewise, the development and disappearance of glyoxysomal enzyme activities (isocitrate lyase, malate synthase, citrate synthase) takes place independently of light. It is concluded that the mobilization of storage fat (fat→carbohydrate transformation) is independent of photomorphogenesis. The surplus of carbohydrate produced from fat in the light seems to be converted to starch grains in the plastids, which function as a secondary storage pool in the cotyledons.
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  • 22
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    Planta 146 (1979), S. 31-39 
    ISSN: 1432-2048
    Keywords: Autoradiography ; Calcium ; Mougeotia ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Ca2+ is proposed to function as a messenger in such phytochrome-mediated responses as localized cell growth, intracellular movements, and control of plasma membrane properties. To test this hypothesis, the uptake of Ca2+ in irradiated and non-irradiated regions of individual threads of the green alga Mougeotia was studied with the aid of 45Ca2+ and low temperature autoradiography: 10–20 cells within 40–60 cell-long threads were irradiated for up to 1 min, transferred to darkness for 3 to 10 min, submersed in a radioactive medium for 1 min, washed in an unlabelled medium for 30 min, and then autoradiographed at-80° C for several days. The autoradiographs show that those cells which had been pre-irradiated with red light did take up 2–10 times more Ca2+ than the adjacent non-irradiated cells of the same thread. Cells pre-irradiated with farred light or red light followed by far-red light showed no enhanced uptake of Ca2+. These results might be interpreted to indicate, firstly, that phytochrome-Pfr is involved in the enhanced uptake of Ca2+ and secondly, that the accumulation of radioactive Ca2+ in red light irradiated cells is an expression of an increased intracellular concentration of Ca2+. This interpretation is based on the data that (i) the dark interval between irradiation and labelling precluded the involvement of photosynthesis, (ii) the effect of red light was reversible with far-red light, and (iii) the accumulation of Ca2+ persisted during the long wash-out period. We speculate, that the red light-enhanced accumulation of Ca2+ in Mougeotia cells is caused by a Pfr-mediated increase of the Ca-permeability of the plasma membrane, and perhaps by a Pfr-impeding of an active Ca2+-extrusion.
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  • 23
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    Planta 143 (1978), S. 323-328 
    ISSN: 1432-2048
    Keywords: Bryophyllum ; Circadian rhythm ; Photocontrol ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A 4-h exposure to white light from fluorescent lamps can shift the phase of the rhythm of CO2 output in leaves of Bryophyllum fedtschenkoi Hamet & Perr. otherwise kept in continuous darkness. The position in the cycle at which irradiation occurs determines the magnitude and direction of the phase shift. Red and white light induce similar advances or delays in the phase, but blue and far-red irradiation have no effect. Far-red irradiation given simultaneously with, or immediately after, exposure to red light, modifies the phase-shift induced by red light alone. Radiation in the red and far-red regions of the spectrum interacted in several experimental régimes, but complete red/far-red reversibility was not observed. The evidence suggests that phytochrome is the receptor molecule involved in the induction of phase-shifts by light.
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  • 24
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    Planta 147 (1979), S. 229-235 
    ISSN: 1432-2048
    Keywords: Avena ; Greening ; Mitochondria ; Oxidative Phosphorylation ; Phytochrome ; Respiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Mitochondria isolated from 7-day old darkgrown Avena sativa L. (var. Arnold) laminae given 5 min illumination of red light, followed by varying lengths of darkness up to 3 h, showed at least a twofold increase in the rates of both NADH-dependent oxygen consumption and respiratory chain phosphorylation over those of mitochondria isolated from unilluminated tissue. Similar organelles, isolated from tissue given either far-red or red followed by far-red pretreatment, exhibited rates of both functions of between 25% and 75% below those of the mitochondria from unilluminated tissue. The induction-reversion criteria for phytochrome control of respiration and oxidative phosphorylation were satisfied under all experimental conditions during the greening process. Treatment with continuous far-red light, acting presumably through the ‘high irradiance’ reaction of phytochrome, served to disengage phytochrome activity from photosynthesis. The stimulation of oxidative phosphorylation still occurred under these conditions, slightly slower but much more prolonged in the absence of ATP from photophosphorylation.
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  • 25
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    Planta 143 (1978), S. 233-239 
    ISSN: 1432-2048
    Keywords: Adaptation (chromatic) ; Chromatic adaptation ; Cyanophyta (cyanobacteria) ; Phycobiliproteins ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Action spectra for chromatic adaptation in Fremyella diplosiphon Drouet have been determined using techniques previously described. Action maxima are at 540 nm, with a half-band width of 80 nm, for induction of phycoerythrin synthesis (green action) and at 650 nm, with a half-band width of 90 nm, for reversal of induction of phycoerythrin synthesis (red action). The red-action spectrum includes a secondary action band centered at ca. 360 nm. Red and green action overlap from 570 to 590 nm with an isosbestic point in the vicinity of 580 nm. Shoulders are present at 520 and 630 nm. Red light is more active than green light. The 540:650-nm quantum effectiveness ratio is 1:7. There is relatively little action of either kind in the blue. The 387:540 nm and 460:650-nm quantum effectiveness ratios are zero. These results contrast strongly with previous determinations in the same organism, with major activity indicated in the blue; they are consistent with the control of photomorphogenesis in the Cyanophyta by a master pigment, analogous to phytochrome.
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  • 26
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    Planta 137 (1977), S. 203-206 
    ISSN: 1432-2048
    Keywords: ATPase ; Membrane ; Phaseolus ; Photomorphogenesis ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Membrane-bound phytochrome and ATPase (ATP phosphohydrolase EC 3.6.1.3.) activity extracted from hypocotyl hooks of etiolated Phaseolus aureus Roxb. were both separated from solute proteins by gel filtration on Sepharose C1-2B. The amount of phytochrome detected in the membrane fraction was very small and was not significantly increased by red irradiation (in vivo or in vitro). Membrane-bound ATPase activity was modulated in vitro by the phytochrome in the membrane fraction, being lower after red light than after far-red light. This effect was potentiated by a preliminary light reaction which occurred only in vivo and, in continuous red light, required 60 to 90 s at 25°C. Thus a two minute, in vivo, red irradiation reduced membrane-bound ATPase activity to about half that of the etiolated state. Subsequently bound-ATPase activity was determined by the form of phytochrome (Pr or Pfr) irrespective of whether established in vivo or in vitro. These results indicate that binding or release (of enzyme, cofactors or inhibitors) is not involved in phytochrome modulation of enzyme activity in the membrane fraction.
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  • 27
    ISSN: 1432-2048
    Keywords: Flowering ; Pharbitis ; Photoperiodic induction ; Phytochrome ; Spectrophotometry (phytochrome)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The low chlorophyll content of cotyledons of Pharbitis nil grown for 24 h in far-red light (FR) or at 18° C in white light from fluorescent lamps (WL) allows spectrophotometric measurement of phytochrome in these tissues. The Δ(ΔA) measurements utilize measuring beams at 730/802 nm and an actinic irradiation in excess of 90 s. The constancy of the relationship between phytochrome content and sample thickness confirms that, under these conditions of measurement, a true maximum phytochrome signal was obtained. These techniques have been used to follow changes in the form and amount of phytochrome during an inductive dark period for flowering. Following exposure to 24h WL at 18° C with a terminal 10 min red (R), Pfr was lost rapidly in darkness and approached zero in less than 1 h; during this period there was no change in the total phytochrome signal. Following exposure to 24 h FR with a terminal 10 min R, Pfr approached zero in 3 h, and the total phytochrome signal decreased by about half. The relevance of these changes to photoperiodic time measurement is discussed.
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  • 28
    ISSN: 1432-2048
    Keywords: Flowering ; Pharbitis ; Photoperiodic induction ; Phytochrome ; Spectrophotometry (phytochrome)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract During an inductive dark period for flowering, changes in phytochrome have been followed in cotyledons of Pharbitis nil seedlings using a spectrophotometric and a physiological technique. There was agreement between the two techniques, both indicating a rapid lowering of the levels of the far-red-absorbing form of the pigment (Pfr) during the first 30–90 min of darkness. Thus, Pfr could provide the cue which signals the beginning of darkness and the length of the critical dark period was, in some instances, correlated with the time of Pfr disappearance. However, there was no correlation with another indicator of photoperiodic time measurement, the time in darkness at which a brief night interruption becomes inhibitory to flowering. These results imply that the transition from light to darkness is not signalled by the disappearance of Pfr. However, the involvement of other photoreceptors seems unlikely. Thus, some mode of phytochrome action other than a simple Pfr-mediated response may be involved in the light/dark-sensing reactions of photoperiodism
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  • 29
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    Planta 145 (1979), S. 405-409 
    ISSN: 1432-2048
    Keywords: Chenopodium ; Internode elongation ; Photoreception sites ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The elongation of the fourth internode of ‘fully green’ Chenopodium polyspermum L. is modulated by far-red light (FR) given in addition to the main light period. Two different types of organs are responsible for the photoreception of FR producing the end-of-day effect; the stem and the leaves situated just above and below the reacting internode. Photoreversibility can be obtained within certain limits in the two organs. Evidence is presented which shows that in the ‘fully green’ plant there is an interorgan reaction whose primary reaction is the photoconversion of phytochrome.
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  • 30
    ISSN: 1432-2048
    Keywords: Carotenoids ; Chlorophylls ; Herbicides ; Phytochrome ; Plastid development ; Ribulosebisphosphate carboxylase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Treatment of the mustard (Sinapis alba L.) seedling with the herbicide SAN 9789 inhibits synthesis of colored carotenoids and interferes with the formation of plastid membrane lipids without affecting growth and morphogenesis significantly. In farred light, which is hardly absorbed by chlorophyll, development of plastid ultrastructure, synthesis of ribulosebisphosphate carboxylase and synthesis of chlorophyll are not affected by SAN 9789. It is concluded that normal phytochrome actions on plastid structural development, protein and chlorophyll syntheses are not affected by the absence of carotenoids provided that there is no significant light absorption in chlorophyll. The findings show that the inhibition of synthesis of one set of plastid membrane components (the carotenoids) does not stop synthesis of other components such as chlorophyll and does not halt membrane assembly. Supplementary experiments with the closely related compound SAN 9785, which affects the amount and composition of plastid lipids but not carotenoid and chlorophyll syntheses, suggest that the effect of the herbicide SAN 9789 is due exclusively to its inhibition of synthesis of colored carotenoids. In the presence of SAN 9789 white or red light at high fluence rate causes photodestruction of chlorophyll and ribulosebisphosphate carboxylase and photodecomposition of thylakoids. These effects are interpreted as resulting exclusively from the self-photooxidation and photosensitizing action of chlorophyll once the protection by carotenoids of chlorophyll against self- and sensitized photooxidation is lost.
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  • 31
    ISSN: 1432-2048
    Keywords: Chlorophyll ; Chloroplasts ; Grana ; Phytochrome ; Sinapis ; Thylakoids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The etioplast»chloroplast transition in the cotyledons of mustard seedlings (Sinapis alba L.) has been studied by electron microscopy. It was found that the active form of phytochrome, established by a red light pulse pretreatment, increases the initial rate and eliminates the lag of grana and stroma thylakoid formation after the onset of white light 60 h after sowing. The effect of a pretreatment with 15 s red light pulses is fully reversible by 756 nm light pulses. This reversibility is lost within 5 min. Evidence is presented which suggests that the time course of grana and stroma thylakoid formation is not correlated with the time course of the dispersal of the prolamellar body. The different functions of phytochrome and chlorophyll in controlling thylakoid formation are discussed.
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  • 32
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    Planta 142 (1978), S. 119-122 
    ISSN: 1432-2048
    Keywords: Chlorophyll ; Ethylene ; Phenylalanine ammonia-lyase ; Phytochrome ; Sinapis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The concept (Burg, 1973) that ethylene mediates the action of phytochrome in seedling photomorphogenesis was tested in the intact mustard (Sinapis alba L.) seedling. The effect of exogenous ethylene (100 μl l−1) on five distinct, phytochrome-mediated photoresponses of the cotyledons was investigated. It was found that anthocyanin contents (see Bühler et al., 1978) and phenylalanine ammonia-lyase levels (EC 4.3.1.5) are strongly reduced by ethylene while the capacity of chlorophyll synthesis is considerably enhanced. Levels of glutathione reductase (EC 1.6.4.2) and pools of photoconvertible protochlorophyll(ide) are unaffected by ethylene. It is concluded that these findings are incompatible with the idea that ethylene plays the role of a mediator in phytochrome-induced photomorphogenesis.
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  • 33
    ISSN: 1432-2048
    Keywords: Chenopodium ; Far-red ; Photoequilibrium ; Phytochrome ; Stem extension
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Chenopodium album seedlings were grown in light environments in which supplementary far-red light was mixed with white fluorescent light during various parts of the photoperiod. Both the logarithmic rate constant of stem extension and the leaf dry weight: stem dry weight ratio were linearly related to estimated phytochrome photoequilibrium (ϕ) in each treatment regime. These data are taken to be indicative of a functional link between phytochrome and development in the green plant. A layer of chlorophyllous tissue only affected the linearity between calculated ϕ and the logarithmic stem extension rate at high chlorophyll concentrations, whilst even low concentrations-equivalent to the levels found in stem tissue-caused a significant shift in measured ϕ. End-of-day supplementary far-red (FR) light induced between 0–35 per cent of the response elicited by all-day supplementary FR, whilst daytime supplementary FR (with a white fluorescent light end-of-day treatment) induced approximately 90 per cent. The ecological significance of this difference is discussed with respect to shade detection.
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  • 34
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    Planta 143 (1978), S. 109-111 
    ISSN: 1432-2048
    Keywords: Boron ; Fluorescein ; Gravity ; Phytochrome ; Vigna
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Hypocotyl sections from dark-grown mung bean (Vigna radiata (L.) Wilczek) seedlings grown without boron exhibit little or no increase in the translocation of fluorescein in phloem cells following gravitational stimulation or red irradiation. In contrast, pretreatment of the hypocotyl sections with low concentrations of boric acid before red irradiation or gravitational stimulation results in a rapid increase in fluorescein movement. Mung bean root tips without boron fail to remain attached to a negativelycharged glass surface after several minutes of red irradiation. A low boron concentration in the solution induces tip attachment. The suggestion is made that boron is required to stabilize a positive electrostatic charge in the plasma membrane that is generated by the actions of phytochrome and gravity.
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  • 35
    ISSN: 1432-2048
    Keywords: Phytochrome ; Development habitat ; Natural radiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A survey of the responsiveness of plant species, typical of open and shade habitats, to simulated natural shade-light quality (i.e. white light plus supplementary far-red) has demonstrated a systematic relationship between habitat and certain developmental responses. Supplementary far-red light has a much greater effect on stem extension rate, petiole length, and leaf dry weight: stem dry weight ratio of the open habitat, shade-intolerant species. Far-red effects on leaf chlorophyll content show no such systematic grading. These results are discussed in relation to habitat adaptation. In most cases, the relationship between developmental response and the estimated phytochrome photoequilibrium, which is established by the radiation treatment, is linear. This is taken as an indication of phytochrome involvement in shade perception.
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  • 36
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    Planta 145 (1979), S. 269-272 
    ISSN: 1432-2048
    Keywords: Flowering ; Gibberellin ; Photoperiodism ; Phytochrome ; Sorghum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Combinations of far-red light (FR) (4 min) and gibberellic acid (GA3), given at the beginning of a daily 12-h dark period in a growth room, were used to study floral induction in four maturity genotypes of the milo group of sorghum (Sorghum bicolor (L.) Moench). The 12-h dark period without GA3 application or FR induced flowering in only the early genotype; FR hastened initiation in the early genotype, while GA3 hastened floral initiation in the two intermidiate-flowering genotypes. GA3 and FR together had a strong synergistic effect, hastening floral initiation by 30 to more than 80 d in the early and intermediate genotypes. Red light (R) did not hasten flowering; FR preceded by R gave the same effect as FR alone. GA3 promoted stem elongation equally whether floral initiation occurred or not; thus, its effect on stem elongation was independent of floral initiation. The capacity of GA3 to induce flowering in sorghum, a short-day plant, seems to be enhanced by phytochrome being in the PR form at the beginning of the night when GA3 was applied.
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  • 37
    ISSN: 1432-2048
    Keywords: Action spectrum ; Dormancy (seeds) ; Germination (seeds) ; Lactuca ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Light of wavelengths in the range 400–500 nm induces germination of seeds of Lactuca sativa L. (cv. Noran and May Queen) when made light requiring by high temperature (thermodormancy) or prolonged exposure to far red light (far red dormancy). TD seeds proved more sensitive to blue light than FRD seeds by several orders of magnitude. Blue induced germination could be reversed by far red. Fluence response curves for this reversion are less steep for TD than for FRD seeds. The degree of germination of TD seeds after moderate doses of blue light is decreased by dark storage at 22° C or by exposure to far red and this is accompanied by a marked change in the shape of the fluence response curves. In these respects, germination induction by blue resembles that by red light. Continuous exposure to blue light inhibits germination of TD seeds but hardly that of FRD seeds. An action spectrum is given for blue induced germination of TD seeds.
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  • 38
    ISSN: 1432-2048
    Keywords: Action spectra ; Dormancy (seeds) ; Germination (seeds) ; Lactuca ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Fluence response curves for red light-induced germination of thermodormant (TD) seeds of Lactuca sativa L. show two regions that differ in their light sensitivity. In the region of high sensitivity, the germination responses differ between seed batches and can be altered by dark storage or far red irradiation. Induction of germination in far red dormant (FRD) seeds requires far higher fluences. Action spectra for induction to 60% germination were determined for these various response types. Spectra for the regions of low sensitivity response are similar for TD and FRD seeds. In comparison, the action spectrum for the highly sensitive response in TD seeds is significantly shifted to longer wavelengths. Analogous differences exist in the action spectra for far red reversal of the red induced germination responses. Germination induction in the low sensitivity region shows repeated red-far red reversibility. Far red reversal of red induction in the high sensitivity region does not saturate even at the highest far red fluences available and requires increased red fluences for subsequent reinduction. A model quantitatively accounting for these observations is presented. It is pointed out that action spectra of processes involving photoreversible pigments with partly overlapping absorption spectra in general are not identical with the absorption spectra of the partners. They should depend upon the degree of phototransformation required to elicit a given physiological response. In the case of induction of lettuce seed germination the observed action spectra can be interpreted as reflecting different requirements for P fr of the various response types. Our results do not necessitate the assumption of spectroscopically different forms of phytochrome in these seeds.
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  • 39
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    Planta 146 (1979), S. 75-81 
    ISSN: 1432-2048
    Keywords: Adenosine-5′-triphosphate ; Membrane ; Phaseolus ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In a membrane fraction isolated from hypocotyls of Phaseolus aureus Roxb. the activity of a number of enzymes was regulated by red and far-red irradiation in vitro, provided that the tissue received a brief red light treatment before extraction. Other enzymes showed no photoregulation. There were two types of photocontrol, neither of which could be detected in the solute fraction, nor in extracts from completely etiolated material. One (Type I) was a red/far-red reversible regulation of the rate of enzyme activity, depending on the light given (in vivo or in vitro) before the assay was begun. The second (Type II) was a promotion of enzyme activity by red or far-red light given during the assay. The action spectra for type II responses do not coincide with either the phytochrome absorption or difference spectra. However, the effectiveness of red and far-red was correlated with the Pfr/P ratio present at the beginning of the assay, such that far-red was more efficient at high Pfr/P and red at low Pfr/P ratios. All enzymes that were regulated involved ATP. In samples that showed enzyme regulation, small changes in fluorescence yield of tryptophan and the covalent probe “Fluram” (Roche) accompanied the photoconversion of phytochrome, but no fluorescence changes could be measured after briefly incubating the membrane fraction with ATP. The results indicate that light may affect the interaction of ATP with the membrane fraction.
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  • 40
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    Planta 141 (1978), S. 311-314 
    ISSN: 1432-2048
    Keywords: Abscission resistance ; Malformin ; Phaseolus ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The active portion of the visible spectrum which is required for malformin to produce leaves which are resistant to dark abscission from cuttings of Phaseolus aureus is red light. Abscission resistance was partially to almost completely lost by far irradiation prior to dark incubation. Although Ethrel, an ethylene releasing compound, stimulated dark abscission of resistant and control leaves, resistance was not lost because control leaves always abscised at a greater rate. The participation of phytochrome in the induction of abscission resistance by malformin is indicated.
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  • 41
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    Planta 142 (1978), S. 109-117 
    ISSN: 1432-2048
    Keywords: Anthocyanin synthesis ; Ethylene ; Phytochrome ; Sinapis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The etiolating, intact mustard (Sinapis alba L.) seedling exhibits a distinct temporal pattern of ethylene production. Light, operating through phytochrome, increases the rate of ethylene production without changing the pattern. Ethylene production of the isolated plant parts (segments), added together, exceed the production of the intact system even if the wound effect is taken into account. There is no significant light effect on ethylene production of the segments. Phytochrome-mediated anthocyanin synthesis in the cotyledons is inhibited by ethylene. The responsiveness towards ethylene of the anthocyanin producing metabolic chain is decreased by phytochrome. As anthocyanin synthesis is only partly inhibited under saturating ethylene concentrations in the atmosphere around the seedlings (100 μl l−1), a twofactor analysis becomes feasible. This analysis leads to the result that phytochrome and ethylene show multiplicative behavior, meaning that phytochrome and ethylene act on the same metabolic sequence (leading to anthocyanin) but independently of each other, and at different sites. Therefore, the hypothesis that ethylene mediates the action of phytochrome in anthocyanin synthesis and photomorphogenesis in general appears to be inapplicable.
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  • 42
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    Planta 147 (1979), S. 1-5 
    ISSN: 1432-2048
    Keywords: Polyribosomes ; Phytochrome ; Raphanus ; Ribonucleases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The total ribosome content of radish cotyledons increases during the first 2–3 days of germination both in darkness and under far-red light irradiation; ribonuclease activity is not under phytochrome control during this period. Changes in ribonuclease activity interfere with the analysis of the polyribosomal population. A maximal ratio of polysomes to monosomes is observed 12 h after the onset of far-red light and then it decreases. A 12 h far-red irradiation stimulates the in vivo incorporation of amino acids into proteins. This stimulation persists when seedlings are transferred for 4 h to the dark.
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  • 43
    ISSN: 1432-2048
    Keywords: Cell wall ; Cytoplasm ; β-Fructosidase (transfer) ; Phytochrome ; Raphanus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The far-red absorbing form of phytochrome, Pfr, rapidly increases the rate of transfer of β-fructosidase (E.C.3.2.1.26) from the cytoplasm to the cell wall in radish hypocotyls. Far-red light increases the level of enzyme in a particulate fraction: after two hours of light treatment, the particulate enzyme is associated almost exclusively with the endoplasmic reticulum. Transfer from the endoplasmic reticulum to the cell wall involves an incorporation into Golgi bodies and the plasmalemma: these membrane fractions were separated by centrifugation on a discontinuous sucrose density gradient and their degree of purity was determined by the use of known biochemical markers. With respect to β-fructosidase, light controls, via Pfr: (1) the total amount, (2) the incorporation into the endoplasmic reticulum and (3) the transfer to the cell-wall. These three processes have different sensitivities to cycloheximide.
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  • 44
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    Planta 142 (1978), S. 225-228 
    ISSN: 1432-2048
    Keywords: Hordeum ; Phytochrome ; Receptor site
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The absorption maximum of the far-red absorbing form of phytochrome in the difference spectrum for phototransformation (Pfr λmax) was investigated in vivo and in in vitro pellets from dark grown Hordeum vulgare L. primary leaves. Exposure of pellets in Honda medium from tissue pre-irradiated with red light to far red light gave a Pfr λmax of 734 nm, a slightly longer wavelength than was seen in vivo (730 nm). After incubation as the red absorbing form of phytochrome (Pr) for 2 h at 0° C irradiation with red light showed that Pfr λmax had shifted to shorter wavelength (716 nm) in Honda medium. Further incubation as Pfr for 2 h at 0° C and irradiation with far red light showed that Pfr λmax had shifted to longer wavelength (726 nm). Similar shifts were also seen in other media, although the peak positions were different. Phytochrome remained pelletable throughout these experiments and Pfr λmax is compared to that of soluble phytochrome in similar media. The results are interpreted as indicating changes in molecular environment of the putative phytochrome membrane receptor site and that Pfr λmax can be used to probe the nature of this binding.
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  • 45
    ISSN: 1432-2048
    Keywords: Anthocyanin ; Mode of action of phytochrome ; Phenylalanine ammonia-lyase ; Phytochrome ; Sinapis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Induction by light of phenylalanine ammonia-lyase (PAL; EC 4.3.1.5) and of anthocyanin in cotyledons of the mustard (Sinapis alba L.) seedling is strongly affected by a light pretreatment which operates through phytochrome. If PAL or anthocyanin is induced by a light pulse, the effectiveness of phytochrome (Pfr) is strongly increased by a light pretreatment; however, if the increase of the PAL level or synthesis of anthocyanin is elicited by continuous far-red light (operating via phytochrome in the ‘High Irradiance Response’), effectiveness of light is strongly reduced by the same light pretreatment. This reduction of effectiveness is correlated with a decrease of total phytochrome (Ptot) caused by the light pretreatment. It is argued that the observations are compatible only with the ‘open phytochrome-receptor model’ as suggested by Schäfer (J. Mathem. Biol. 2, 41–56, 1975). The peaks of the time courses of the PAL levels under continous far-red light are located at 48 h after sowing and do not depend on the original level of phytochrome. The decrease of the PAL levels beyond 48 h after sowing takes place independently of phytochrome and of the actual level of PAL.
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  • 46
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    Planta 146 (1979), S. 415-417 
    ISSN: 1432-2048
    Keywords: Germination (seeds) ; Osmotic stress ; Phytochrome ; Seed germination ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Maize caryopses sown in water germinate equally well either in darkness or under any light regime. However, when they are imbibed in mannitol solutions, continuous far-red light proves to be strongly inhibitory on the final germination as compared to darkness. Similar but less pronounced inhibition is also exhibited by continuous red or blue light. Intermittent far-red light can partially substitute for continuous far-red light in inhibiting maize caryopsis germination, and its effect is reversed to the intermittent red light level when red light is given immediately after each far-red illumination. These results are interpreted as a proof of existence and involvement of phytochrome in the germination control of maize caryopses, though its manifestation is realized only under osmotic stress.
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  • 47
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    Planta 146 (1979), S. 545-550 
    ISSN: 1432-2048
    Keywords: Blue light ; Cucumis ; Hypocotyl growth ; Lactuca ; Lycopersicon ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of blue light on hypocotyl extension in de-etiolated seedlings of lettuce, cucumber and tomato was investigated under conditions which precluded the involvement of phytochrome. Small but highly inhibitory amounts of blue light were added to a high intensity background illumination from low pressure sodium lamps. A log-linear response for inhibition of hypocotyl extension against the blue light fluence rate was obtained for lettuce and cucumber, and inhibition in tomato was also related to the blue light fluence rate. The added blue light did not alter phytochrome photostationary state and its effect was independent of the total fluence rate. Growth inhibition by Pfr could be demonstrated in tomato and cucumber but not in lettuce. The results indicate that two photoreceptors may normally be involved in the control of seedling growth but their relative importance varies greatly between species.
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  • 48
    ISSN: 1432-2048
    Keywords: Chenopodium ; Day light fluence rate ; End-of-day effect ; Internode elongation ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The elongation of the fourth internode of fully green Chenopodium polyspermum L. is strongly stimulated by far-red light (FR) given at the end of the day. The end-of-day effect is more important when the plants had been cultivated for several days with a main light period of 140 Wm-2 than with a main light period of 85 Wm-2. There exists a quantitative relationship between the FR end-of-day effect mediated by phytochrome and the value of the light fluence during the day.
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  • 49
    ISSN: 1432-2048
    Keywords: Organelle transformation ; Glyoxysomes ; Peroxisomes ; Phytochrome ; Sinapis alba
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The specific changes in the temporal pattern of glyoxysomal and peroxisomal enzymes in dark-grown and continuously far-red irradiated mustard seedlings are accompanied by specific changes in the spatial associations of microbodies with other cell organelles which can be quantitatively estimated from electron micrographs. The association (surface contact) with oleosomes (lipid bodies) and with plastids have been used as operational criteria for the glyoxysomal and peroxisomal engagement, respectively, of individual microbodies. The time course of these specific associations during the phytochrome-mediated changeover from glyoxysomal to peroxisomal character reveals the transient formation of functionally intermediary microbodies (“glyoxyperoxisomes”) which are associated to oleosomes as well as to plastids. In continuous far-red light, up to 50% of the microbody profiles detectable on electron micrographs fall into this category, compared to about 10% in darkness. It is concluded that peroxisomes of cotyledons neither originate de novo as an independent population nor are formed from pre-existing glyoxysomes by repackaging of enzymes. We suggest rather that a transition from glyoxysomal to peroxisomal enzyme formation in the presence of continuous turnover of microbody particles leads to a gradual replacement of microbodies of glyoxysomal character by microbodies of intermediary character and ultimately by microbodies of peroxisomal character.
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  • 50
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    Planta 133 (1977), S. 103-106 
    ISSN: 1432-2048
    Keywords: Chenopodium rubrum ; Flowering ; High Energy Reaction ; Photosynthesis ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Seedlings of C. rubrum were irradiated with different light qualities and intensities following a single inductive dark period. Our results show that relatively low intensity white light (35–100 ft. c.) does not support flower development while high intensity white light (650–800 ft. c.) permits 100% flowering. We have shown that the low intensity light inhibiton of flower development is not due to suboptimal photosynthesis. Relatively low intensities of light rich in far-red or blue wavebands sustains optimum flower development, whereas red light is totally ineffective in this respect. Considering that the intensity dependent High Energy Reaction (HER) has its action maxima in the blue and far-red we propose that HER may be positively involved in the flower development of C. rubrum. Our study further suggests that there may be some flower inhibitory component at play in relatively low intensity white light conditions and HER may be required to counteract this flower inhibitory effect.
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  • 51
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    Planta 133 (1977), S. 149-156 
    ISSN: 1432-2048
    Keywords: Fuchsia ; Internode development ; Photoperiodism ; Phytochrome
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    Topics: Biology
    Notes: Abstract Stems of the caulescent long-day plant, Fuchsia hybrida cv Lord Byron, showed 2 types of response to light. In one, internode length was increased by far-red irradiation given at the end of an 8 h photoperiod: the response was no greater with prolonged exposure and was less when the start of far-red was delayed. The effect of far-red was reversible by a subsequent exposure to red light. Internode length was inversely proportional to the Pfr/P ratio established before entry to darkness and there was no evidence for loss of Pfr during a 16 h dark period. The inhibitory effect of Pfr acted at a relatively late stage of internode growth. With the development of successive internodes a second response appeared in which stems lengthened following prolonged daily exposures to red or far-red light, or mixtures of the two, or to brief breaks with red or white light. In these later internodes, a short exposure to far-red near the middle of the night was not reversible by red because red alone promoted elongation at this time. Internode length increased with increase in the daily duration of light and, when light was given throughout an otherwise dark period of 16 h, with increase in illuminance to a saturation value of 200 lx from tungsten lamps. Elongation increased as a linear function of decrease in photostationary state of phytochrome down to Pfr/P≃0.3; however, internodes were shorter in far-red light than in 25% red/red+far-red. It was concluded that stem length is a net response to two modes of phytochrome action. An inductive effect of Pfr inhibits a late stage in internode expansion, and a phytochrome reaction which operates only in light (and may involve pigment cycling) promotes an early stage of internode development. Stem elongation is thus a function both of the daily duration of light and its red/red+far-red content. The outgrowth of axillary buds was controlled by the first type of phytochrome action only.
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  • 52
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    Planta 133 (1977), S. 97-102 
    ISSN: 1432-2048
    Keywords: Chenopodium rubrum ; Flowering ; High Energy Reaction ; Photosynthesis ; Phytochrome
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    Topics: Biology
    Notes: Abstract Seedlings of the short-day plant, Chenopodium rubrum L. (Ecotype 60° 47′ N) were irradiated with different intensities and qualities of light for 24 h preceding a single inductive dark period (12 h). Our data shows that a relatively low intensity incandescent light (35–100 ft. c.) is not effective as the photoperiod for flowering. The above effect is not due to a requirement for a relatively high level of photosynthesis. Our results suggest a definite promotory role of a blue High Energy Reaction (HER). We could not demonstrate the involvement of a far-red HER. We suggest that ineffectiveness of far-red may have been due to establishment of rather low Phytochrome, P FR , levels, suboptimal for flowering. A certain critical level of P FR (30–40%, that presumably established by blue light) seems to be necessary for photoreactions involved in flowering of C. rubrum. There are indications in our experiments of the operation of a red radiation mediated flower inhibitory photoreaction.
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  • 53
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    European journal of clinical pharmacology 8 (1975), S. 293-299 
    ISSN: 1432-1041
    Keywords: Rifampicin ; p-aminosalicylic acid ; bentonite ; drug interaction ; bioavailability ; drug adsorption
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The bioavailability (plasma concentrations, AUC and urinary excretion) of an oral solution of rifampicin was investigated in six healthy volunteers. Simultaneous administration of PAS granules produced a significant decrease in the absorption of RMP, whereas Na-PAS tablets had no effect. This indicated that the dosage form of the granules and not PAS itself was responsible for the interaction, and that the dissolution of RMP was not involved. The interaction could be reproduced by giving dummy granules that contained the same excipients but no PAS. The disintegration and dissolution of PAS granulesin vitro correlated well with the disappearance of RMP from the solution. The major excipient of the granules, bentonite (a mineral closely related to kaolin), was found to adsorb rifampicin rapidly and strongly.
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  • 54
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    European journal of clinical pharmacology 8 (1975), S. 365-370 
    ISSN: 1432-1041
    Keywords: Particle size ; bioavailability ; digoxin
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The bioavailability of digoxin in three tablets prepared from materials with different particle sizes was measured in healthy volunteers in a cross-over study using an alcoholic solution of digoxin as a reference standard. Its bioavailability in tablets with particle sizes of 7 µ or 13 µ was 78–97% of that of digoxin in solution. The tablet with largest particle size (102 µ) showed markedly lower bioavailability than the reference solution, namely 39%. It is obvious that particle size is an important determinant of the dissolution rate and bioavailability of digoxin.
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  • 55
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    European journal of clinical pharmacology 9 (1975), S. 209-212 
    ISSN: 1432-1041
    Keywords: Anticonvulsants ; phenytoin ; diphenylhydantoin ; bioavailability
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Plasma phenytoin levels were measured in 60 patients under steady-state conditions for a period of six weeks. During the trial, the preparation of phenytoin was changed from Phenytoin BP (Regent) to Epanutin Infatabs. A significant increase in plasma phenytoin levels following the change of tablet was matched by a decrease in the number of seizures.
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  • 56
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    European journal of clinical pharmacology 9 (1975), S. 213-218 
    ISSN: 1432-1041
    Keywords: Phenytoin ; diphenylhydantoin ; anticonvulsants ; bioavailability ; drug absorption ; generic inequivalence
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary In order to evaluate the bioavailability of four different brands of phenytoin (diphenylhydantoin, DPH) tablets single doses of 600 mg DPH in acid form were given to six volunteers in a cross-over study. A micronized DPH-acid suspension was used as the reference standard. Significant differences between various products were found. The areas under the serum DPH concentration-time curves (AUC) were 26, 59, 68 and 90 per cent of the AUC of the DPH suspension. The peak serum DPH concentrations using the different tablets were 24, 54, 55 and 80 per cent of the peak value of the DPH suspension. It is likely that the differences in bio-availability of the DPH tablets are of clinical significance.
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  • 57
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    European journal of clinical pharmacology 9 (1976), S. 315-317 
    ISSN: 1432-1041
    Keywords: Tolamolol ; bioavailability ; maximum exercise tachycardia
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Bioavailability of capsule and tablet formulations of tolamolol were compared by measuring plasma concentration of tolamolol and reduction in maximum exercise heart rate over a period of twelve hours in eight healthy subjects in a two-way cross-over study. Tolamol was absorbed more rapidly from capsules than from tablets; this did not result in any significant difference in the reduction in maximum exercise heart rate between the two formulations. There was no significant difference between area under curve of reduction in exercise tachycardia and area under curve of plasma concentration of tolamolol for the two formulations. Reduction in maximum exercise heart rate was related to logarithm of plasma concentration of tolamolol between two and twelve hours after both formulations.
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  • 58
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    European journal of clinical pharmacology 9 (1976), S. 373-379 
    ISSN: 1432-1041
    Keywords: Methyldigoxin ; repetitive doses ; bioavailability ; deep compartments ; oral and i.v. dose ; volunteers
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary To obtain true half lives, glycoside elimination from six healthy subjects was studied for 14 days after multiple intravenous doses or oral administration of a daily maintenance dose of β-methyldigoxin 0.3 mg. After oral or intravenous administration of β-methyldigoxin ceased, the plasma concentrations declined from the 14th to the 16th days with a half life of 1.7 days. From the 16th to the 20th day a change from a shorter to a longer half life of 2.8 and 2.9 days was observed. Similar half lives were found in urine: after the last dose the initial slope from the 14th to the 16th day had a half life of 1.8 days, and the terminal slope had one of 3.2 days. The results indicate release of the glycoside from slowly equilibrating tissues.
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  • 59
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    European journal of clinical pharmacology 8 (1975), S. 371-376 
    ISSN: 1432-1041
    Keywords: Digoxin ; bioavailability ; plasma levels ; cumulative urinary excretion ; particle size ; man
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Various brands of digoxin tablets, and even different batches of one brand, may differ greatly in bioavailability. Digoxin-Sandoz® tablets have been compared with Lanoxin® manufactured between 1969 and 1972 and after May 1972. Comparisons were also made between and within batches of Digoxin-Sandoz tablets. Three separate cross-over studies were conducted involving a total of 20 volunteers. Digoxin-Sandoz tablets were shown to have a constant bioavailability and to produce plasma concentrations very similar to “new” Lanoxin. Storage for 2 years of one batch of Digoxin-Sandoz did not alter the bioavailability. Particle size was shown to influence bioavailability. Care should be exercised when plasma data alone are interpreted as an index of bioavailability. Measures of bioavailability based on plasma data obtained up to 6 h after administration differed from those based on cumulative urinary excretion data (in this study by a factor of about 2), which can lead to the belief that a difference in bioavailability is much greater than is actually the case. Data from cumulative urinary excretion, collected over a sufficiently long period of time, are likely to be the most reliable method for determining the bioavailability of a substance such as digoxin.
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  • 60
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    European journal of clinical pharmacology 16 (1979), S. 211-215 
    ISSN: 1432-1041
    Keywords: fluoride ; bioavailability ; calcium
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The effect of milk products on the gastrointestinal absorption of fluoride from sodium fluoride tablets was studied in five healthy subjects. Two different diets were tested: (1) 250 ml standardized milk (3% fat) and (2) 500 ml of milk, 3 pieces of white bread with cheese and 150 ml of yoghurt. The 100% bioavailability of sodium fluoride tablets during fasting was greatly decreased by coadministration of milk products: with Diet 1 the absolute bioavailability calculated from combined plasma and urine data was in the range 50–79% and with Diet 2 it ranged from 50–71%. It is suggested that the decreased bioavailability produced by dairy products should be taken into account when establishing fluoride dosage regimens for prophylaxis of caries.
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  • 61
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    European journal of clinical pharmacology 10 (1976), S. 231-236 
    ISSN: 1432-1041
    Keywords: Digoxin ; beta-methyl-digoxin ; capsules ; bioavailability
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The intestinal absorption and urinary elimination rate of total cardioactive material was compared following digoxin and beta-methyldigoxin (BMD) administration to twelve healthy volunteers. Significantly more injected digoxin was recovered in urine. Urinary clearance was more rapid for digoxin, mean half-lives of elimination being 35 hours for digoxin and 40 hours for BMD. Calculated percentage intestinal absorption was lowest for digoxin tablets with a dissolution rate of 77% in one hour, intermediate for BMD tablets, and maximal for an experimental soft gelatin formulation of digoxin in solution. Respective mean values were 75%, 87% and 97%. Similar steady state plasma concentrations followed twice daily ingestion of the 0.25 mg digoxin tablets and 0.20 mg BMD tablets. Mean peak plasma concentration and percentage urinary recovery of ingested dose were higher during continued BMD administration. Between-subject variation in absorption was higher for the digoxin tablets. The comparative intestinal absorption of BMD and digoxin depends upon the formulation. Digoxin is virtually completely absorbed from a solution encapsulated in soft gelatin. Relatively more BMD is eliminated by nonrenal routes.
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  • 62
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    European journal of clinical pharmacology 10 (1976), S. 251-256 
    ISSN: 1432-1041
    Keywords: Sisomicin ; pharmacokinetics ; bioavailability ; two-compartment analysis ; man
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of sisomicin, a new single component aminoglycoside antibiotic related to gentamicin c1a, were determined in four healthy volunteers after intravenous and intramuscular administration of a 1 mg/kg dose. The elimination profile of this antibiotic follows two-compartment model kinetics after I.V. administration. The fast (α) and slow (β) disposition rate constants averaged 0.072 and 0.004 min−1, respectively. The volume of distribution at the steady-state averaged 0.185 liters/kg which approximately corresponds to the volume of extracellular space. The physiological availability of an intramuscular dose appeared to be complete. A method of administration adapted to the kinetic properties of the drug is proposed.
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  • 63
    ISSN: 1432-1041
    Keywords: Cefoxitin ; lidocaine ; intramuscular ; bioavailability ; pain
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The use of lidocaine HCl solution at concentrations of 0.5 and 1.0% to reconstitute sodium cefoxitin relieves the pain associated with intramuscular injections of the antibiotic. Cefoxitin absorption by the intramuscular route is initially rapid and is virtually complete. Peak serum concentrations, corresponding to about one-half those of a comparable intravenous infusion, are achieved in 30 min. Continuing absorption tends to maintain higher serum concentrations for longer times. Renal clearance and serum half-life of cefoxitin do not appear to be affected by lidocaine at its effective anaesthetic concentrations.
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  • 64
    ISSN: 1432-1041
    Keywords: p-Chlorophenoxyisobutyric acid ; clofibrate ; steady-state plasma concentrations ; bioavailability ; pharmacokinetics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Plasma concentrations and bioavailability of clofibrinic acid have been estimated under conditions approaching the steady-state during a ten-day period of administration as clofibrate or as a calcium clofibrinate-carbonate combination (1:1 w/w) at a dosage interval of 12 h. Formulation — related differences in bioavailability were not significant, and the 95% confidence limits of these differences were within −2% to +8% of the mean for the reference formulation of clofibrate. The mean steadystate plasma concentrations of clofibrinic acid measured on the tenth day of dosing were 116 µg/ml±22 S.D. and 119 µg/ml±23 S.D. after administration of 885 mg as clofibrate and the calcium clofibrinate-carbonate combination respectively. The peaks of mean plasma concentrations were 70 µg/ml±15 S.D., 119 µg/ml±32 S.D. and 131 µg/ml±26 S.D. on the first, fifth and tenth day of dosing with clofibrate, and 62 µg/ml±13 S.D., 127 µg/ml±S.D. and 143 µg/ml±25 S.D. on the corresponding days of dosing with the calcium clofibrinate-carbonate combination. After the last dose on the tenth day of dosing, the mean apparent half-lives of elimination of clofibrinic acid from plasma were 24.2 h±4.4 S.D. and 25.5 h±3.2 S.D. after administration of clofibrate and the calcium clofibrinate-carbonate combination respectively.
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  • 65
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    European journal of clinical pharmacology 13 (1978), S. 125-128 
    ISSN: 1432-1041
    Keywords: bioavailability ; diuretics ; gastrointestinal absorption ; hydrochlorothiazide ; thiazides ; food effect
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Hydrochlorothiazide (hct) 75 mg was administered orally to eight healthy volunteers without (Study I) or together with a standardized meal (Study II), and plasma and urine concentrations of hct were analyzed by GLC. The plasma levels of hct were higher initially when the tablets were taken on an empty stomach, but after 5 h they were higher in Study II. There was no difference between the two studies in the area under plasma concentration time curves. The urinary recovery of hct totalled 55.6±4.9 mg when the drug was given with food and 47.4±6.0 when it was taken on an empty stomach. The difference is significant (p〈0.01). As the urinary recovery represents the uptake of hct, it appears that the gastrointestinal absorption of hct is enhanced when the drug is given with food.
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  • 66
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    European journal of clinical pharmacology 10 (1976), S. 257-262 
    ISSN: 1432-1041
    Keywords: Anti-inflammatory and analgesic drug ; indoprofen ; pharmacokinetics ; bioavailability ; man
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary In a pharmacokinetic study of the new analgesic and anti-inflammatory drug indoprofen, plasma levels and urinary excretion were determined in four healthy volunteers after 100 mg and 200 mg iv, and after 100 mg (capsules) and 200 mg (tablets) oral doses. After iv administration, the mean biological half-life (t1/2 β) was about 2 h (range 1.4 to 3.2 h). The apparent volume of distribution Vdβ ranged between 11 to 17 % of body weight, indicating its limited extravascular distribution. Most of the drug was excreted in urine as glucuronide and a smaller proportion as unchanged indoprofen: the 24 h urinary excretion of these compounds accounted for 67 to 95 % of an iv dose. Peak plasma levels occurred between 30 and 120 minutes after oral administration of 100 mg as capsules or 200 mg as tablets. The mean biological half-life was about 2 h, as after iv administration. The bioavailability of oral doses was assessed using both plasma levels and urinary excretion data. The absorption of capsules and tablets was practically complete, that of the former being faster.
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  • 67
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    European journal of clinical pharmacology 10 (1976), S. 101-108 
    ISSN: 1432-1041
    Keywords: Cardiac glycosides ; methyl proscillaridin ; plasma concentrations ; electrocardiogram ; bioavailability ; 86Rb-erythrocyte assay
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The aim of this study was to obtain data about the pharmacological properties of a new glycoside derivative in man. Plasma concentrations and ECG parameters were measured after oral and intravenous administration of a single dose of 1.2 mg methyl proscillaridin in 16 healthy volunteers, using a strictly randomized, two-period change-over design. Glycoside concentrations were measured using a modified86Rb-erythrocyte-assay. QT-duration, corrected for frequency (QTc), was the principal variable measured in the ECG. By either route, there was a maximum plasma level after 1 hour, which had decreased to a minimum at 3 hours, followed by a second peak at 4 to 10 hours (orally〉iv). From 10 to 72 hours the concentrations decreased with a median t 1/2 of 23.3 hours (iv) and 33.0 hours (orally). Comparison of the ratio of plasma concentrations following oral and iv administration resulted in a bioavailability of 69 % using the 48 hour plasma levels, and 59 % using the areas under the concentration-time curves. The mean QTc was maximally shortened to 28 msec at 1 hour after iv and to 19 msec at 10 hours after the oral dose. A distinct similarity between time-concentration and time-QTc curves was seen after the initial distribution phase, both after oral and intravenous administration. The new derivative shows a rapid elimination. Its bioavailability is reasonably high.
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  • 68
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    European journal of clinical pharmacology 16 (1979), S. 417-421 
    ISSN: 1432-1041
    Keywords: theophylline ; aminophylline ; bioavailability ; rapidly dissolving tablet
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The bioavailability of a rapidly dissolving tablet of theophylline and three brands of standard aminophylline tablets was estimated in a four way cross-over study involving 8 healthy adult volunteers. The relative extent of bioavailability as assessed by the measurement of the total area under the plasma concentration time curves showed no difference between the products (P〉0.05). Computed estimates of the rate of drug absorption were similar for all 4 products tested. The results indicate that the rapidly dissolving tablet offers no advantage in respect to rate and extent of absorption over conventional aminophylline tablets.
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  • 69
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    European journal of clinical pharmacology 12 (1977), S. 69-72 
    ISSN: 1432-1041
    Keywords: Metronidazole ; serum concentration ; bioavailability ; food intake ; healthy subjects ; Crohn's disease
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The possible influence of food intake on the bioavailability of metronidazole was examined in ten healthy volunteers by administration of a single dose of metronidazole on an empty stomach, and with a standardized breakfast. Food intake did not significantly alter the bioavailability of metronidazole. The interindividual variation in bioavailability appeared to be slight. In nine patients with Crohn's disease, the absorption of metronidazole appeared to be reduced and to be more variable than in healthy subjects. In both groups there was a clear relationship between the amount absorbed and dose/kg body weight. Thus, from the pharmacokinetic point of view, metronidazole can safely be given either with or between meals. The dose should be related to body weight.
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  • 70
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    European journal of clinical pharmacology 12 (1977), S. 285-290 
    ISSN: 1432-1041
    Keywords: Phenytoin acid ; phenytoin calcium ; bioavailability ; inequivalence of generics ; normal subjects ; volunteers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Serum phenytoin concentrations have been studied in epileptic patients and healthy subjects taking tablets of phenytoin calcium (Desitin), A, phenytoin acid (Desitin), B, and phenytoin acid (Nordmark), C. Retrospective data and prospective investigation of hospitalized patients on long-term phenytoin treatment showed that significantly higher serum concentrations of phenytoin were produced by the phenytoin acid preparations B and C than by the phenytoin calcium preparation A. In a cross over study six volunteers received 200 mg/day of preparations A, B, and C for three weeks. In this study, too, higher phenytoin serum concentrations were produced by B and C than by A, although the differences were not statistically significant. The reasons for the discrepancies between the studies in healthy and epileptic subjects are discussed.
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  • 71
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    European journal of clinical pharmacology 12 (1977), S. 383-386 
    ISSN: 1432-1041
    Keywords: Benzodiazepine ; temazepam ; pharmacokinetics ; bioavailability ; hard and soft gelatine capsules
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Plasma levels of temazepam were determined in healthy subjects after single oral administration of soft and hard gelatin capsules, and after 7 consecutive night-time doses in soft capsules. Absorption from soft gelatin capsules was significantly faster and produced earlier and higher peak plasma levels. The two pharmaceutical forms did not show any significant difference in relative availability. The apparent half-life of temazepam after night-time administration was significantly shorter than after morning administration, but no change in half-life was observed between the first and seventh night-time doses.
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  • 72
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    European journal of clinical pharmacology 14 (1978), S. 253-259 
    ISSN: 1432-1041
    Keywords: Pseudoephedrine ; side effects ; bioavailability ; multiple oral dosing
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Dose tolerance and pharmacokinetic studies of pseudoephedrine sustained action capsules were performed in thirty-three adult male subjects who received either 120 mg or 150 mg capsules every twelve hours for seven consecutive days in a double-blind parallel design study. Although only one subject in the 150 mg group was discontinued prematurely from this study, a large number of side effects typical of CNS stimulation were seen. A placebo effect might account for a portion of these complaints, however symtoms evaluated as being due to drug were significantly more severe and persistent in the 150 mg group. Pulse rates showed a persistent and significant increase while systolic and diastolic blood pressure fell from the baseline values in both groups. A pharmacokinetic analysis of the pseudoephedrine plasma concentration-time data provided estimates of half-life and the volume of distribution/availability ratio. The values obtained were in good agreement with values reported by others. Half-life was not influenced by urine pH probably as a result of the narrow range of urine pHs observed in the subjects. Calculations of relative bioavailability suggest that the 120 mg capsule formulation has a 30% greater bioavailability compared to the 150 mg capsule.
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  • 73
    ISSN: 1432-1041
    Keywords: chlorthalidone ; pharmacokinetics ; oral and i.v. doses ; bioavailability
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Seven normal human volunteers each received a constant-rate infusion of chlorthalidone for 2 h, and the same (commonly 50 mg) single oral dose on separate occasions. The concentration of unchanged chlorthalidone was analyzed over a 100 to 220 h period in plasma, red blood cells, urine and faeces after both dosage forms. A three compartment model was required to describe the intravenous plasma concentrations in five of the subjects. A two compartment model sufficed to account for the decay of the oral plasma concentrations in all seven subjects. The mean plasma t1/2 after i.v. dosing was 36.5 h (±10.5 SD), and the mean plasma t1/2 after oral doses was 44.1 h (±9.6 SD). The mean red blood cell concentration t1/2 after i.v. doses was 46.4 h (±9.9 SD), and the mean red blood cell t1/2 after the oral doses was 52.7 h (±9.0 SD). The shorter i.v. half-live was not equally manifest in all subjects, being mainly apparent in three of them. In all cases the urinary excretion rate plots were parallel to the plasma concentration curves. As the faster decay after i.v. administration was not accompanied by increased renal clearance, the difference must have been due to non-renal mechanism. The mean total of 65.4 (±8.6 SD) % of the intravenous dose was excreted in urine over infinite time, whereas the mean total excretion after the oral dose was 43.8 (±8.5 SD) %. Faecal excretion ranged from 1.3–8.5% of dose in the i.v. study to 17.5–31.2% of dose in the oral study. The sum of the amounts present in urine plus faeces pointed strongly to an important metabolic route of elimination of chlorthalidone. Bioavailability estimates (F) from three sets of data were — a mean F of 0.61 from plasma concentrations, 0.67 from urinary excretion measurements and 0.72 from the erythrocyte concentrations. Simulations with a non-linear model indicated lesser validity of the estimate from erythrocyte concentrations. It was concluded that the average of plasma and urine data, F=0.64, yielded the best estimate of the oral availability of chlorthalidone 50 mg in man.
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  • 74
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    European journal of clinical pharmacology 16 (1979), S. 31-38 
    ISSN: 1432-1041
    Keywords: bezafibrate ; hyperlipoproteinemia ; bioavailability ; pharmacokinetics ; GC-MS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The disposition kinetics of bezafibrate, a newly developed drug of great lipid-lowering potency, were investigated in normal male subjects. Five male volunteers received14C-labelled bezafibrate orally in solution, and a further 10 were given the same dose (300 mg) of un-labelled drug as tablets. The concentration of bezafibrate in serum and urine from the latter was determined by GC, and in the former total radioactivity in serum, urine and feces was followed for 48 h, and urinary excretion products were analysed by TLC and GC-MS. Rapid absorption from the gastrointestinal tract led to peak serum levels 30 min and 2 h after administration of solution and tablets, respectively. Since approximately 95% of the administered14C-bezafibrate was excreted in urine within 48 h, and almost all the remainder was detected in feces, absorption can be regarded as complete after administration in solution. The relative optimal bioavailability from the tablets was also complete, since in both cases approximately 50% of the administered dose was detected as unchanged bezafibrate in urine within 24 h by GC in the tablet study, and by TLC in the solution study. Of the decomposition products, more than 20% of the dose was present as glucuronides and the remainder consisted of several more polar compounds, one of which was identified as a hydroxyderivative of bezafibrate. Since the apparent halflife of bezafibrate in serum was 2.1 h, this new drug possesses favourable pharmacokinetic features: rapid and complete absorption, even from tablets, combined with a conveniently short half-life, and clearance which is half renal (56 ml/min) and half metabolic (43 ml/min), giving a total clearance of 99 ml/min.
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  • 75
    ISSN: 1432-1041
    Keywords: indobufen ; platelet aggregation ; single dose ; bioavailability ; pharmacodynamics ; pharmacokinetics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Six healthy volunteers received single iv and oral doses of 2-[p-(1-oxo-2-isoindolinyl)phenyl] butyric acid 100 mg (indobufen; K 3920), an inhibitor of platelet aggregation. Plasma levels and urinary excretion of the drug were determined by GLC. Collagen-induced platelet aggregation was assessed turbidimetrically at various intervals after administration. The plasma half-life of the drug was 7–8 h and more than 70% of the administered dose was recovered within 48 h in urine, as unchanged drug and as the glucuronide of indobufen. After oral administration of tablets of two different formulations, the drug was completely absorbed, but one formulation showed faster absorption. The maximal inhibitory effect on platelet aggregation was observed 1 to 4 h after iv administration, and it had decreased by 8 h. After tablets, peak effect and the time of the peak were similar, but activity was significantly prolonged, in accordance with the higher plasma levels found at 8 h. The data suggest that the effect of indobufen on platelets is reversible, and that for this drug platelets behave as a compartment that slowly equilibrates with plasma.
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  • 76
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    European journal of clinical pharmacology 16 (1979), S. 45-48 
    ISSN: 1432-1041
    Keywords: quinidine ; slow release formulation ; pharmacokinetics ; bioavailability
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The bioavailability of quinidine in two sustained release preparations A and B has been compared in three females and three males with i.v. administration of quinidine. The initial rate of oral absorption did not differ between the two drug preparations; the peak concentration was observed after 4 h both for A and B, but was significantly higher after B. A slower decrease in plasma concentration was observed after preparation A than B. Absolute bioavailability did not differ significantly between A (median value 78.4%) and B (median 87.1%). Drug absorption in vivo was in good agreement with the results of in vitro dissolution tests on both preparations. The slower decrease in plasma concentration found for the new sustained release form of quinidine should be of clinical advantage.
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  • 77
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    European journal of clinical pharmacology 10 (1976), S. 183-187 
    ISSN: 1432-1041
    Keywords: Hydralazine ; bioavailability ; pharmacogenetics ; first pass effect ; pharmacokinetics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary After oral administration of a single 50 mg dose of hydralazine (Apresoline®), the serum half-life (T1/2) and bioavailability (AUC0−∞) were assessed in 16 healthy volunteers. The half-life was 2.57±0.14 h (S.E.) in 10 slow acetylators of sulphadimidine, and 2.18±0.15 h in 6 fast acetylators (difference not statistically significant). AUC0−∞ was significantly higher in slow acetylators, at 1.04±0.10 µg·hour·ml−1, compared to 0.66±0.12 µg·hour·ml−1 in the fast acetylators (p〈0.025). Treatment with Apresoline® 25 mg tid produced minimum serum concentrations at steady-state of 57.3±7.3 ng·ml−1 and 33.4±4.2 ng·ml−1 in 8 slow and 5 fast acetylators, respectively (p〈0.05). The corresponding maximum concentrations were 228.8±20.3 ng·ml−1 and 147.6±15.0 ng·ml−1 in slow and fast acetylators, respectively (p〈0.025). First-pass metabolism of hydralazine could explain the difference in bioavailability of the drug between fast and slow acetylators, without any corresponding difference in the elimination rate of the drug in the post-distributive phase.
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  • 78
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    European journal of clinical pharmacology 10 (1976), S. 395-401 
    ISSN: 1432-1041
    Keywords: Hydralazine ; bioavailability ; polymorphic acetylation ; first-pass metabolism ; oral and intravenous dosing
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The bioavailability of orally administered hydralazine was assessed in 4 healthy subjects after separate administration of a single oral or intravenous dose (0.3 mg·kg−1). Comparison of the areas under the serum concentration-time curves showed that 26 – 55 % of the oral dose was available to the systemic circulation as unchanged drug. The O - 24 h excretion of the drug in urine was rapid: 11.4 – 14.1 % of the dose after intravenous administration, and 2.0 – 3.6 % after an oral dose. Acetylation of hydralazine leads to formation of 3-methyl-s-triazolo-3,4,a-phthalazine (MTP) and a gas-liquid-chromatographic method for its measurement in urine was developed. After oral and intravenous administration, 0.8 – 1.2 % and 1.4 – 2.3 % of the dose, respectively, were recovered within 24 hours from urine as MTP. After oral administration there was a relative increase in the amount of MTP in every subject, which indicates route-dependent metabolism. The lower bioavailability of oral hydralazine could be explained in terms of first-pass metabolism.
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  • 79
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    European journal of clinical pharmacology 16 (1979), S. 335-340 
    ISSN: 1432-1041
    Keywords: cimetidine ; enterohepatic circulation ; irregular absorption ; bioavailability ; pharmacokinetics ; volunteers
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The bioavailability and pharmacokinetics of cimetidine have been studied in healthy volunteers after administration of single intravenous (100 mg) and oral doses (100, 400 and 800 mg). After i.v. administration, the kinetics of cimetidine could be described by a linear, two compartment open model. Substantial variation in half-life was observed between subjects, with a mean value of 2.1 h (range 0.9–4.7). Cimetidine had a low hepatic extraction ratio and a high total plasma clearance, due to extensive urinary excretion of unchanged drug. After oral administration, the plasma concentration vs time curves in most subjects exhibited two marked peaks, an observation that seemed to be constant within individuals and was independent of dose. Bioavailability, estimated as the area under the plasma concentration vs time curves (AUC), after oral doses as compared to the intravenous dose, in most cases exceeded 100%. There was no correlation between bioavailability estimated as AUC and as urinary excretion of unchanged drug. These observations may indicate an enterohepatic circulatory mechanism, predominantly after oral administration. Both unchanged drug and its sulphoxide metabolite appear to be excreted in bile. The latter was shown in vitro to be reduced to cimetidine by fecal bacteria.
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  • 80
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    European journal of clinical pharmacology 13 (1978), S. 267-274 
    ISSN: 1432-1041
    Keywords: Chlordiazepoxide ; benzodiazepines ; pharmacokinetics ; bioavailability ; intramuscular injection ; alcohol withdrawal
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The absorption of oral and intramuscular (i. m.) chlordiazepoxide hydrochloride (CDX · HCl) was compared in two pharmacokinetic studies. In Study One, single 50-mg doses of CDX · HCl were administered orally and by i. m. injection to 14 healthy volunteers using a crossover design. Whole-blood concentrations of chlordiazepoxide (CDX) and its first active metabolite, desmethylchlordiazepoxide (DMCDX), were determined in multiple samples drawn after the dose. Mean pharmacokinetic variables for CDX following oral and i. m. administration, respectively, were: highest measured blood concentration, 1.65 vs 0.87 µg/ml (p〈0.001); time of highest concentration, 2.3 vs 7.6 h after dosing (p〈0.001); apparent absorption half-life, 0.71 vs 3.39 h (p〈0.001). Biphasic absorption after i. m. injection, consistent with precipitation at the injection site, was observed in 9 of 14 subjects. Based upon comparison with previous intravenous data, the completeness of absorption was 100% for oral vs 86% for i. m. CDX · HCl (p〈0.1). In Study Two, 28 male chronic alcoholics with clinical manifestations of the acute alcohol withdrawal syndrome were randomly assigned to one of four treatment conditions: 50 or 100 mg doses of CDX · HCl, by mouth or by i. m. injection. Concentrations of CDX and DMCDX, determined in plasma samples drawn every 20 min for 5 h following the dose, were significantly higher after oral administration of a given dose than at corresponding points in time after i.m. injection after the same dose. Thus absorption of oral CDX is reasonably rapid and complete, whereas the absorption rate of i. m. CDX is slow.
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  • 81
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    European journal of clinical pharmacology 15 (1979), S. 269-274 
    ISSN: 1432-1041
    Keywords: phenytoin ; food-intake ; bioavailability ; pharmacokinetics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The influence of food intake on the absorption of phenytoin was examined in eight healthy volunteers, by study of single-dose kinetics following ingestion of phenytoin 300 mg either with a standardized breakfast or on an empty stomach. Blood samples were collected at regular intervals from 0 to 48 h, and serum concentrations of unmetabolized phenytoin were determined by gas chromatography. Serum concentrations of the major metabolite of phenytoin, 4-hydroxyphenytoin, were measured by mass fragmentography. Concurrent intake of food and phenytoin appeared to accelerate absorption of the drug from the formulation used, and the peak concentrations were significantly higher (mean increase 40%) in the postprandial than in the preprandial state. As reflected by the AUC (area under the curve), the amount of drug absorbed was increased during postprandial conditions, although the difference only reached borderline significance. It is suggested that phenytoin should always be taken in a defined relation to meals.
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  • 82
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    European journal of clinical pharmacology 16 (1979), S. 107-112 
    ISSN: 1432-1041
    Keywords: quinidine ; enteric-coated tablets ; bioavailability ; gastric emptying ; pH
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The absorption of quinidine from single and multiple doses of an enteric-coated preparation (Systodin®) was studied in seven healthy subjects, and was compared with the pharmacokinetics of intravenously administered quinidine and the results of in vitro dissolution tests of the tablets. Absorption of quinidine began after a variable delay, 2–8 h (mean 4.8) after fasting and 3–10 h (mean 6.1) after food. The rate of absorption varied both in and between individuals. It appeared to be lower when the drug was administered after food. Multiple doses after food gave a pattern of plasma concentration-time curves similar to that found on administration of single doses after food. The delay prior to absorption was prolonged at night. The ratio between the maximum and minimum concentration of quinidine during a dose interval varied from 1.3 to 3.2 (mean 2.0). Bioavailability of quinidine in fasting subjects ranged from 69 to 95% (mean 83); variation was greater when doses were administered after food. The release of quinidine from the enteric-coated preparation was pH dependent and was sustained at low pHs as may be found in the intestines. The results indicate that the absorption of quinidine from the enteric-coated formulation was dependent on the highly variable rate of gastric emptying and the pH of intestinal fluid, and it varied greatly both within and between individuals.
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  • 83
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    European journal of clinical pharmacology 16 (1979), S. 141-147 
    ISSN: 1432-1041
    Keywords: prazepam ; N-desmethyldiazepam ; bioavailability ; pharmokinetics ; electron-capture gasliquid chromatography
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary An original electron-capture gas chromatographic assay was developed for simultaneous measurement of plasma levels of the benzodiazepine derivative prazepam and of its principal unconjugated metabolite, N-desmethyldiazepam. The assay was used to study the pharmacokinetics of the drug and its comparative bioavailability from tablets and from a specially prepared solution. Nine healthy adult volunteers were studied. Each volunteer on one occasion took 30 mg of the drug in tablet form, and on another occasion 30 mg of the drug in solution. In all subjects, N-desmethyldiazepam appeared in plasma shortly after prazepam appeared and reached a peak within four hours of prazepam ingestion. Thereafter plasma N-desmethyldiazepam levels were much higher than plasma prazepam levels throughout. Prazepam became undetectable within six hours of intake, whereas its metabolite could still be measured in plasma fourteen days after dosage. Thus much of the pharmacological action of prazepam may be mediated through its metabolite, N-desmethyldiazepam. In five of the nine subjects, areas under the plasma level curves for the metabolite were not markedly different for the tablet and solution formulations studied. In the other four subjects the area under the curve for the tablets was 50% to 80% of the area under the curve for the solution. The time to reach peak plasma level for the metabolite was shorter after the solution formulation (mean 2.0±SD 1.2 h) than after the tablet formulation (mean 4.2±SD 1.7 h).
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  • 84
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    European journal of clinical pharmacology 10 (1976), S. 55-58 
    ISSN: 1432-1041
    Keywords: Penicillin V ; bioavailability ; pharmacokinetics ; dose ranging
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary An absorption study was performed in ten healthy volunteers to test the bioavailability of various doses of two penicillin V-K preparations: Isocillin® (Hoechst AG, Federal Republic of Germany), — tablets of 600 000 and 1.2 Mega U; V-Cillin® (Eli Lilly, USA), — tablets of 200 000, 400 000 and 800 000 U. The serum concentrations and elimination of the active substance in urine were measured for six hours after administration. Independently of the source of the preparation, a strict linear relation between the dose and the area under the serum curve (AUC), or between the dose and the urinary elimination, was demonstrated by regression analysis. The dose-dependent increase in the AUC was highly significant (p〈0.01) in the range tested, i.e. between 200 000 and 1.2 Mega U. The relative elimination of active substance in urine lay within narrow limits for all doses (35.7–41.3%). Thus, both compounds proved to have the same bioavailability.
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  • 85
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    Keywords: Ampicillin ; bioavailability ; pharmacokinetics ; branded products ; proprietary preparations ; capsule formulation ; tablet formulation
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics and bioavailability of three different brands of ampicillin were studied in 10 volunteers. After intravenous administration ampicillin can be described adequately by a two-compartment open pharmacokinetic model. The half-life during the α-phase was 9 min and the β-half-life was in the range 50–60 min, independent of the mode of administration. Absolute bioavailability was determined from the ratio of the areas under the serum concentration curves obtained after oral and intravenous administration of equal doses. Bioavailability was also estimated by analysis of variance. The results indicated absolute availability of the three products of 39–54%. One of the products, a capsule formulation, showed a significantly lower bioavailability than the others, which were tablet formulations.
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  • 86
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    European journal of clinical pharmacology 11 (1977), S. 277-281 
    ISSN: 1432-1041
    Keywords: Proscillaridin ; oral administration ; portal venous sample ; porto-peripheral concentration difference ; bioavailability ; 86Rb-uptake inhibition assay
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The absorption of proscillaridin A was studied in four patients undergoing catheterization of the portal vein for diagnostic purposes. Proscillaridin 1.5 mg was given as a single oral dose and plasma glycoside activity was analyzed by the86Rb-uptake inhibition technique. Proscillaridin appeared rapidly in the portal blood, peak activity being found after 15 min in three and after 30 min in one patient. In peripheral blood the peak activity occurred after approximately 35 min. Despite rapid passage across the gut wall, porto-peripheral differences in glycoside activity were small; they were zero after 4 h. The mean amount absorbed as active proscillaridin during the first 4 h after the dose was calculated to be only 7.1% of the given amount. Late porto-peripheral differences, probably due to enterohepatic recycling, appeared after 6 h in three patients. The results suggest that proscillaridin undergoes first pass inactivation in the gut wall. Enterohepatic recirculation may contribute to the amounts of active glycoside that reach the systemic circulation.
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  • 87
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    European journal of clinical pharmacology 10 (1976), S. 49-54 
    ISSN: 1432-1041
    Keywords: Three-compartment open model ; intravenous infusion ; apparent volume of distribution ; renal insufficiency ; miconazole ; bioavailability
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetic profile of miconazole has been studied in normal subjects and in patients suffering from severe renal insufficiency; one group of patients was undergoing intermittent haemodialysis. A three-compartment open model was fitted to the observed plasma concentrations obtained after intravenous infusion of miconazole 522 mg over fifteen minutes. The rate constants of elimination and exchange between compartments computed for the three groups were not significantly different. The apparent volumes of distribution in the cases of renal failure not undergoing haemodialysis were significantly smaller than the corresponding control values. A computational procedure is described which reduces observations obtained after infusion to the case of a single rapid intravenous administration.
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  • 88
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    European journal of clinical pharmacology 11 (1977), S. 207-212 
    ISSN: 1432-1041
    Keywords: Chlorpropamide ; hypoglycaemic agent ; bioavailability ; plasma concentrations ; bioequivalence ; dissolution tests
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The bioavailability of chlorpropamide from two new formulations (Melitase® tablets) has been compared to that from a reference formulation which is currently in clinical use as a hypoglycaemic agent. In both rate and extent of bioavailability, all three formulations may be considered equivalent, providing allowances are made for differences in drug content. With 95% confidence, the mean bioavailability of chlorpropamide from the new formulations was within about 16% of the mean from the reference formulation, and formulation-related differences were not statistically significant. Although all three formulations were shown to have similar dissolution profiles, dissolution of chlorpropamide was pH-dependent in vitro. Dissolution was almost complete during 30 min at pH 7.2, but only 40%–60% had dissolved during 90 min at pH 2.0. A peak mean concentration of 22.7 µg/ml was reached 3 h after administration of 2×100 mg tablets of the new formulation and peak mean concentrations of 26.8 µg/ml and 27.4 µg/ml were reached 3 h and 4 hours after administration of one 250 mg tablet of the new formulation and one 250 mg tablet of the reference formulation respectively. Formulation-related differences of mean plasma concentrations (after scaling for equal doses of 250 mg) were not significant and each formulation provided similar plasma concentrations at corresponding times after administration. Statistically significant subject-related differences in all the parameters of bioavailability were shown by analyses of variance.
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  • 89
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    Keywords: ergotamine ; migraine ; bioavailability ; radioimmunoassay ; plasma level ; CSF level ; continuous dosing
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Plasma ergotamine concentrations were determined by radioimmunoassay in 10 healthy subjects after a 2 mg oral dose of ergotamine, administered at 24 h intervals on three consecutive days. After the first dose the mean peak plasma level of 0.35±0.05 (SEM) ng/ml was found 1–2 h after administration. In the samples obtained 2 h after the second and third doses, plasma ergotamine levels did not exceed the first peak value. On the other hand, after the third and last dose the plasma ergotamine began to rise slowly, reaching maximum of 0.70± 0.10 ng/ml on the 6th day after administration. This supports the concept of accumulation of the drug or of immunoreactive metabolites. CSF ergotamine was determined in 4 patients, who underwent lumbar puncture for other diagnostic purposes, 1 to 2 h after the 2 mg oral dose. A concentration of 0.40± 0.03 ng/ml was observed. In seven out of 18 migraine patients who were taking ergotamine preparations daily (mean 11.7 mg/week), ergotamine could not be detected in plasma 1 h after administration of the dose. In the remaining migraine patients, the pattern of plasma ergotamine after both the daily and the test doses was similar to that of the 10 healthy subjects. The results in volunteers and migraine patients suggest notable variation in bioavailability of the drug. It seems that in most subjects there is accumulation or tissue redistribution of ergotamine or its immunoreactive metabolites, although in a significant number of migraine patients who use the drug daily, ergotamine does not appear to be biologically available.
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  • 90
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    European journal of clinical pharmacology 16 (1979), S. 405-410 
    ISSN: 1432-1041
    Keywords: diclofenac ; plasma levels ; intravenous bolus administration ; oral administration ; enteric coating ; bioavailability
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of diclofenac were examined following single rapid intravenous injection and also following single oral doses to healthy female volunteers. After intravenous injection plasma levels of diclofenac fell rapidly and were below the limits of detection at 5.5 h postdosing. Individual drug profiles were described by a triexponential function and mean half-lives of the three exponential phases were 0.05, 0.26 and 1.1 h. After oral doses of enteric-coated tablets, the lag time between dosing and the appearance of drug in plasma varied between 1.0 and 4.5 h. However once drug absorption had commenced similar plasma drug profiles were obtained in different individuals. Peak plasma diclofenac levels ranged from 1.4 to 3.0 µg · ml−1. The mean terminal drug half-life in plasma was 1.8 h after oral doses. This value was not significantly greater than the value of 1.1 h following intravenous doses. Fifty percent of orally dosed diclofenac did not reach the systemic circulation due, predominantly, to first-pass metabolism.
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  • 91
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    European journal of clinical pharmacology 11 (1977), S. 219-224 
    ISSN: 1432-1041
    Keywords: Nortriptyline ; 10-OH-nortriptyline ; bioavailability ; plasma metabolites ; first pass metabolism ; oral dose ; intramuscular dose
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Nortriptyline was given orally and intramuscularly to six depressed patients. Plasma concentrations of parent drug and the unconjugated and conjugated principal metabolite, 10-hydroxynortriptyline, were determined by mass fragmentography. There was a significant decrease in the area under the nortriptyline plasma concentration — time curve after the oral route of administration, whilst the elimination rate was unchanged. With the oral dose, plasma concentrations of the metabolites were higher and peaked earlier than after intramuscular administration, whilst the opposite was true for the parent compound. This proves that the difference in bioavailability between the two routes of administration was due to first pass metabolism. As determined from the ratio between corresponding areas, the relative bioavailability of the oral dose was 66±21 S.D. per cent. This fraction is higher than that reported previously when intravenous nortriptyline was used as the reference dosage form.
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  • 92
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    European journal of clinical pharmacology 12 (1977), S. 281-284 
    ISSN: 1432-1041
    Keywords: Tetracycline ; bioavailability ; plasma levels ; nutritional state ; man
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Relative bioavailability after oral administration of a single dose and Cmin levels of tetracycline in plasma after multiple doses were determined in groups of well-nourished and undernourished subjects. The relative bioavailability of tetracycline, assessed by the area under serum concentration time-curves, did not differ in undernourished and well-nourished patients. The plasma levels were not different in the two groups after the conventional dose of tetracycline HCl 250 mg at 6 hour intervals. However, in these studies undernourished subjects received a higher dose per kg body weight, which could have compensated for any effect of a shortened half life of the drug. When the dose per kg body weight was reduced, the Cmin levels were lower. On the other hand, with the same dose per kg body weight at more frequent intervals, the plasma concentrations were similar to those in well-nourished subjects. These studies indicate that the dosage regimen should be based both on body weight and on the nutritional status of the individual.
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  • 93
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    European journal of clinical pharmacology 12 (1977), S. 65-68 
    ISSN: 1432-1041
    Keywords: Indomethacin ; antacids ; drug-drug interactions ; bioavailability ; drug combinations
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The biovailability of indomethacin from two indomethacin-antacid (aluminum hydroxide magnesium carbonate and magnesium hydroxide) combinations was compared with the bioavailability of oral indomethacin. Relative bioavailability was estimated by three methods: comparison of plasma concentrations at various times, comparison of areas under plasma concentration time curves, and comparison of the amount of drug excreted unchanged in the urine. A double blind three-way crossover study was conducted in twelve healthy volunteers. The combination with the slightly smaller amount of antacid (preparation A) showed significantly decreased bioavailability by all three methods in comparison with indomethacin alone (preparation C). The combination with the larger amount of antacid (preparation B) was also less bioavailable than preparation C. This effect was significant only for the comparison of areas under curves and not for plasma levels, although the mean plasma levels produced by preparation B at all times were lower than those for preparation C. These findings suggest that aluminum hydroxide magnesium carbonate and magnesium hydroxide decrease the bioavailability of indomethacin.
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  • 94
    ISSN: 1432-1041
    Keywords: Tolmetin ; pharmacokinetics ; bioavailability ; antacid ; oral dose
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The purpose of this study was to determine whether a concomitant single dose of antacid or multiple doses of antacid administered prior to, and with tolmetin, alter the pharmacokinetics of tolmetin when the drug was administered as a commercially available tablet containing tolmetin sodium. The possible effects of the antacid on plasma concentrations and urinary excretion of tolmetin and its major metabolite were evaluated following administration of: (a) tolmetin sodium alone; (b) antacid four time a day for three days prior to a single dose of tolmetin sodium, with continuation of the antacid during the day tolmetin was given; and (c) co-administration of single doses of tolmetin sodium and antacid. The twenty-four subject study was of the crossover type. There were no significant differences among treatment means for: (i) peak plasma concentrations of both tolmetin and metabolite, (ii) AUC 0–8 h and AUC 0-∞ for both tolmetin and metabolite, (iii) time to peak plasma concentration for both tolmetin and metabolite, (iv) plasma concentrations of both tolmetin and the metabolite at all sampling times (except for tolmetin at 2 h), (v) renal clearance of both tolmetin and its metabolite, and (vi) the amount of metabolite excreted in the 0–24 h urine. There were small, but significant, differences among amounts of tolmetin excreted in the 0–24 h urine. Semilogarithmic plots of both tolmetin and metabolite plasma concentrations past the peak concentrations were curved over the entire 8-h observation period; although the elimination half-life of tolmetin has been reported to be about one hour, the half-life most probably exceeds 2.6 h in most subjects. The results of this study indicate a lack of a significant drug-drug interaction between the non-steroidal anti-inflammatory agent, tolmetin sodium, and a commonly used antacid, which is a mixture of magnesium and aluminium hydroxides.
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  • 95
    ISSN: 1432-1041
    Keywords: Coumarin ; 7-Hydroxycoumarin ; drug disposition ; first-pass effect ; bioavailability
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of coumarin (C) upon i.v. and p.o. administration and its metabolites 7-hydroxy-coumarin (7-HC) and 7-hydroxy-coumarin glucuronide (7-HCG) have been studied. Six healthy volunteers were involved in this investigation. Four of the volunteers participated in a crossover study. Coumarin was administered i.v. and p.o. in dose sizes of 0.25 mg/kg and 0.857 mg/kg, respectively. Coumarin is rapidly absorbed p.o., however the availability to systemic circulation is less than 4%. The rest of the dose appears quantitatively as 7-HC and 7-HCG in systemic circulation suggesting an extensive firstpass effect. Coumarin and 7-HCG are best fitted to an open two-compartment model, whereas 7-HC is best fitted to an open one-compartment model. The biological half-life of both C (0.80 vs. 1.02 h) and 7-HCG (1.47 vs. 1.15 h) was not significantly different for the two routes of administration. The large total clearance of C again suggests a first-pass effect; while that of 7-HCG, which is nearly exclusively eliminated into urine, indicates active tubular secretion of the glucuronide.
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  • 96
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    European journal of clinical pharmacology 13 (1978), S. 35-39 
    ISSN: 1432-1041
    Keywords: Norethindrone ; bioavailability ; man ; competitive protein binding ; sex differences ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary A competitive protein binding assay for norethindrone was developed to measure plasma levels in human subjects. The plasma levels were considerably higher in women than in men, especially at low dose levels. The plasma levels were directly related to the dose in men; but greater variations in the plasma levels were observed in women. The plasma half-life was about 5 h in both sexes with single oral doses of 5 to 20 mg. A comparative bioavailability study with norethindrone from 2 different manufacturers, formulated in the same manner, showed no significant differences in absorption characteristics and provided sufficient data for pharmacokinetic analysis.
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  • 97
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    European journal of clinical pharmacology 14 (1978), S. 261-265 
    ISSN: 1432-1041
    Keywords: Procainamide ; slow release formulations ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Procainamide was given to 20 patients with normal renal function as an i.v. bolus of 500 mg followed by 1.0 or 1.5 g eight-hourly by mouth in the form of a slow release preparation (Durules). 97.6±27.1 (SD)% of the oral procainamide was absorbed, the absorption half life being 1.54 h. The elimination half life following the oral formulation was 6.0±0.8 h, compared to a mean of 3.4±0.4 h following i.v. administration. Elimination half life following i.v. administration was slightly related to acetylator status, being 2.75±0.9 h in fast acetylators, and 4.4±2.4 h in slow acetylators. This dependence on acetylator status was not seen in half life following oral administration. Total body clearance, steady state plasma procainamide and N-acetylprocainamide were not significantly dependent on acetylator status, although a few patients who are slow acetylators had unexpectedly low clearance and high steady state procainamide concentrations when given the higher dose.
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  • 98
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 14 (1978), S. 357-360 
    ISSN: 1432-1041
    Keywords: Lanoxin tablets ; Lanoxicaps ; sorbitol ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary (1) The mean cumulative urinary digoxin excretion over 8 days was compared in 8 healthy volunteers after single doses of digoxin administered as 3 Lanoxin tablets of 0.25 mg, 3 digoxin tablets of 0.2 mg, 12 Lanoxicaps without sorbitol of 0.05 mg, 6 Lanoxicaps without sorbitol of 0.1 mg digoxin, 3 Lanoxicaps without sorbitol of 0.2 mg and 3 Lanoxicaps with sorbitol of 0.2 mg. (2) There was no significant difference between the 8 day cumulative urinary excretion for any of the Lanoxicaps treatments. (3) Cumulative urinary excretion after 3 digoxin tablets of 0.2 mg was significantly (P〈0.05) lower than after all other treatments. (4) Cumulative urinary excretion after 3 Lanoxin tablets of 0.25 mg was not significantly different from that after any of the Lanoxicaps treatments except 0.1 mg Lanoxicaps without sorbitol, it was significantly (P〈0.05) lower after the latter. (5) Mean urinary excretion of digoxin was 60% of ingested dose for all Lanoxicaps treatments and was significantly (P〈0.05) higher than the mean value of 50% for both tablet treatments. (6) Enhanced absorption of digoxin from Lanoxicaps was confirmed and shown to be unrelated to the sorbitol content of the capsule shell.
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  • 99
    Electronic Resource
    Electronic Resource
    Springer
    Journal of chemical ecology 1 (1975), S. 101-113 
    ISSN: 1573-1561
    Keywords: pheromone ; inhibition ; Scolytidae ; Ips ; pini ; paraconfusus ; ipsenol ; linalool
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The bark beetles,Ips pini andI. paraconfusus, are not cross-attractive in the field although they attack the same host material at the same time. Logs containing the pheromone-producing sex (males) of both species side by side attract significantly fewer beetles of each species than do males of either species alone. Ipsenol, a component of the maleI. paraconfusus pheromone, duplicates the activity of maleI. paraconfusus in inhibiting the response ofI. pini to maleI. pini. Linalool from maleI. pini also reduces the catch ofI. paraconfusus in response to maleI. paraconfusus. Simultaneous production of a specific attractant pheromone and an interspecific chemical inhibitor favors exclusive use of the host substrate by the first arriving species.
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  • 100
    ISSN: 1573-1561
    Keywords: Archips argyrospilus ; Archips mortuanus ; pheromone ; attractant ; Tortricidae ; (Z)-11-tetradecenyl acetate ; (E)-11-tetradecenyl acetate ; (Z)-9-tetradecenyl acetate ; dodecyl acetate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract MaleArchips argyrospilus (Walker) were maximally attracted to a 60∶40∶4∶200 admixture of (Z)-11-tetradecenyl, (E)-11-tetradecenyl, (Z)-9-tetradecenyl and dodecyl acetates. The identification of (Z)-9-tetradecenyl acetate, in addition to the other 3 components reported previously, is the first report of a 4-component pheromone system in moths.Archips mortuanus Kearfoot, a sibling species, was maximally attracted to a blend of the same components, but in a 90∶10∶1 mix of the tetradecenyl acetates. Among a number of tortricine moths that co-occur on apples and other hosts in New York, British Columbia, and elsewhere, differences in diel rhythms of attraction and seasonal distribution are insufficient to maintain reproductive isolation. Although the attractant systems of these species often possess components in common, males are maximally attracted to a speciesspecific blend. In tortricine moths attraction specificity appears to be a paramount mechanism for species partitioning.
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