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  • 1
    Digitale Medien
    Digitale Medien
    Effects of N addition rates on the productivity ofPicea Sitchensis,Thuja plicata, andTsuga heterophylla seedlings (1996)
    Springer
    Trees 10 (1996), S. 198-205 
    Details
    ISSN: 1432-2285
    Schlagwort(e): Nitrogen ; Photosynthesis ; Picea sitchensis ; Thuja plicata ; Tsuga heterophylla
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract The effects of differing, exponentially increasing rates of N addition (0.025, 0.05, 0.07 and 0.09 gN gN-1day-1) on photosynthesis, discrimination against13C and partitioning of foliar N to chlorophyll and major photosynthetic proteins were compared in seedlings of the evergreen conifersPicea sitchensis, Thuja plicata andTsuga heterophylla. T. heterophylla had the lowest range of foliar N concentrations (Nlm). Across species, photosynthetic rates (A) increased linearly with Nlm to a maximum at 21 mg g-1 and declined at higher Nlms. Species differences inA resulted from differences in Nlm, not from differences in photosynthetic N use efficiency. Self-shading may have causedA to decline at a high Nlm inP. sitchensis andT. plicata. Measurements of gas exchange and δ13C suggested that carboxylation capacity increased more than did stomatal conductance as Nlm increased. The responses were small and confined to Nlms associated with the lesser rates of N addition. Concentrations of total protein, ribulose 1,5-bisphosphate carboxylase (RUBISCO) and the light harvesting chlorophyll a/b protein complex (LHC) increased with Nlm, but the fraction of foliar N allocated to RUBISCO and LHC increased with Nlm only inP. sitchensis and only between the 0.025 and 0.05N regimes. The responsiveness ofA and concentrations of RUBISCO to Nlm were less than reported for deciduous C3 species.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02340772
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  • 2
    Digitale Medien
    Digitale Medien
    Effects of N addition rates on the productivity of Picea Sitchensis, Thuja plicata, and Tsuga heterophylla seedlings (1996)
    Springer
    Trees 10 (1996), S. 198-205 
    Details
    ISSN: 0931-1890
    Schlagwort(e): Key words Nitrogen ; Photosynthesis ; Picea sitchensis ; Thuja plicata ; Tsuga heterophylla
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract  The effects of differing, exponentially increasing rates of N addition (0.025, 0.05, 0.07 and 0.09 gN gN–1day–1) on photosynthesis, discrimination against 13C and partitioning of foliar N to chlorophyll and major photosynthetic proteins were compared in seedlings of the evergreen conifers Picea sitchensis, Thuja plicata and Tsuga heterophylla. T. heterophylla had the lowest range of foliar N concentrations (Nlm). Across species, photosynthetic rates (A) increased linearly with Nlm to a maximum at 21 mg g–1 and declined at higher Nlms. Species differences in A resulted from differences in Nlm, not from differences in photosynthetic N use efficiency. Self-shading may have caused A to decline at a high Nlm in P. sitchensis and T. plicata. Measurements of gas exchange and δ13C suggested that carboxylation capacity increased more than did stomatal conductance as Nlm increased. The responses were small and confined to Nlms associated with the lesser rates of N addition. Concentrations of total protein, ribulose 1,5-bisphosphate carboxylase (RUBISCO) and the light harvesting chlorophyll a/b protein complex (LHC) increased with Nlm, but the fraction of foliar N allocated to RUBISCO and LHC increased with Nlm only in P. sitchensis and only between the 0.025 and 0.05N regimes. The responsiveness of A and concentrations of RUBISCO to Nlm were less than reported for deciduous C3 species.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/PL00009648
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  • 3
    Digitale Medien
    Digitale Medien
    Cyclic AMP does not modulate hexose uptake of serum-deprived BHK-21 fibroblasts (1982)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 112 (1982), S. 373-375 
    Details
    ISSN: 0021-9541
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: We have studied the uptakes of the glucose analogs, 2-deoxyglucose (2DG), and 3-O-methylglucose (3OMG) in serum-deprived BHK-21 fibroblasts. Incubation for 4 hours with 0.25 mM 1-methyl-3-isobutylxanthine (MIX) increased cellular cyclic AMP 3 to 15 fold, without affecting the initial rates of uptake of these sugars. Incubation with 100 nM insulin, doubled hexose uptake without affecting cyclic AMP. Insulin did not modify the cyclic AMP response to MIX; nor did MIX alter the hexose uptake response to insulin. There was no effect of 0.1 mM L-isoproterenol (ISO) or 0.1 mM prostaglandin E1 (PGE1) on cyclic AMP. PGE1 slightly stimulated uptake of 2DG but not 3OMG; ISO did not affect hexose uptake. We conclude that cyclic AMP does not directly regulate hexose uptake in these cells.
    Zusätzliches Material: 3 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcp.1041120310
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  • 4
    Digitale Medien
    Digitale Medien
    Cytochalasin inhibition of isolated rat gastric parietal cell function (1981)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 109 (1981), S. 53-57 
    Details
    ISSN: 0021-9541
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: Submicrogram concentrations (0.04--0.29 μM) of the microfilament disrupting agents cytochalasins D, E, and B (CD, CE, CB) were shown to inhibit secretagogue-stimulated 14C-aminopyrine accumulation (AP) in isolated rat gastric mucosal parietal cells. The microtubule disrupting agent colchicine had little influence on AP accumulation. Histamine- and dibutyryl cyclic AMP (DbcAMP)-stimulated AP accumulation was inhibited with an order of potency CD 〉 CE ≍ CB. CB inhibition of these secretagogue actions was, however only approximately 65--70% of the maximal stimulated response, whereas CD and CE caused 100% inhibition. On the other hand, carbamylcholine-stimulated AP accumulation was inhibited 100% by all cytochalasins tested with an order of potency CD ≍ CE 〉 CB. These data are discussed in relation to acid secretagogue-induced morphological changes involving actin filament organization in parietal cells.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcp.1041090107
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  • 5
    Digitale Medien
    Digitale Medien
    Effects of insulin on glycogen metabolism of serum-deprived BHK-21 fibroblasts (1980)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 103 (1980), S. 55-62 
    Details
    ISSN: 0021-9541
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: We have studied the effects of insulin on glycogen metabolism of cultured BHK-21 fibroblasts. Addition of insulin to cells cultured in 0.5% serum stimulated incorporation of 5mM 14C-glucose into glycogen and increased cellular glycogen content, without inducing proliferation. With serum-deprived cells incubated for 2 hr, maximal stimulation of incorporation of glucose into glycogen was 3.5-fold and the half-maximal dose of insulin was 5nM. After culture for 24 hr with 100nM insulin, incorporation was increased 13-fold and glycogen content was increased by 44%. Incorporation of glucose into glycogen was reduced by agents which elevate cellular adenosine 3,5-cyclic monophosphate (cyclic AMP): 10μM prostaglandin E1 (PGE1), 0.25 mM 1-methyl-3-isobutylxanthine (MIX), 10μM L-epinephrine (L-EPI), and 10μM L-isoproterenol (L-ISO). Culture with 100nM insulin for 2 hr stimulated incorporation three-fold in the presence of any of these compounds, but insulin did not affect cellular cyclic AMP.At all times from 1 hr to 24 hr after addition of insulin to serum-deprived cultures, the 1-min uptake of 10μM 3H-2-deoxyglucose (3H-2DG) was increased. There were small (30 to 40%) increases in glycogen synthase I activity at 15 and 30 min but not 4 hr after addition of insulin. After 24 hr with insulin, total glycogen synthase and phosphorylase activities were increased approximately two-fold, without changes in their activation states.We conclude that insulin promotes glycogenesis in serum-deprived BHK-21 cells. This response is mediated principally by increased entry of glucose into cells, and is not mediated by a change in cellular cyclic AMP concentration.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcp.1041030109
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  • 6
    Digitale Medien
    Digitale Medien
    Regulation of cyclic nucleotide phosphodiesterase forms by serum and insulin in cultured fibroblasts (1979)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 100 (1979), S. 497-507 
    Details
    ISSN: 0021-9541
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: A rapid reduction of cyclic nucleotide phosphodiesterase activity occurs after the replating of confluent cultures of BHK 21 c/13 fibroblasts into fresh medium. This reduction in activity depends on the density to which the cultures are reseeded and the concentration of serum in the medium. Enzyme activity in BHK cells is restored after 24 to 48 hours if cells are diluted into medium containing 10% fetal calf serum or 0.5% fetal calf serum supplemented with insulin (10-6 M), but not into 0.5% serum alone. The restoration in enzyme activity is blocked by cycloheximide or Actinomycin D.When BHK cells become quiescent by maintenance in 0.5% serum conditions for 48 hours, a rapid (15-60 minutes) increase in cyclic AMP phosphodiesterase activity occurs when 10% serum is added to the cultures. Enzyme activity is increased even further after 24 to 48 hours in the 10% serum. Cycloheximide or Actinomycin D do not affect the rapid increase in enzyme activity in response to serum, but completely inhibit the long term increase. In contrast to serum, insulin (10-8 to 10-6 M) has no short term effect, but does increase enzyme activity after 24 to 48 hours to levels comparable to those seen with addition of 10% serum. As is the case with serum, this long term effect of insulin on enzyme activity is prevented by inhibitors of protein and RNA synthesis.Kinetic analyses of cyclic AMP phosphodiesterase activity in homogenates of quiescent BHK cells indicate the presence of only high Km (≃ 20 μM) enzyme activity. Addition of serum or insulin to quiescent cells results in the appearance of apparent low Km enzyme activity in homogenates. Sucrose gradient analysis of BHK cells displays two forms of cyclic AMP phosphodiesterase enzyme activity: a 3-4 S form and 5-6 S form. In quiescent cells, the 5-6 form greatly predominates relative to the 3-4 form. Addition of serum to quiescent cells results in a rapid appearance of increased 3-4 S form enzyme activity. Insulin also increases the activity of this higher affinity 3-4 S enzyme form after 24 to 48 hours in culture. The functional significance of short and long term regulation of cyclic nucleotide phosphodiesterase(s) in cells is discussed.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcp.1041000312
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  • 7
    Digitale Medien
    Digitale Medien
    Fura 2 analysis of cytosolic calcium regulation in elutriated rat gastric parietal cells (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 139 (1989), S. 632-640 
    Details
    ISSN: 0021-9541
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: The calcium probe, Fura 2, is used to establish and partially characterize histamine-, carbachol- and forskolin-induced calcium transients in enriched parietal cell populations prepared by centrifugal elutriation of dispersed rat fundic mucosa cell isolates. The magnitude of the maximal carbachol response, which is blocked by atropine but not cimetidine, is nearly five times that of histamine or forskolin. Time to peak responses for carbachol, forskolin, and histamine are approximately 7, 17, and 28 sec, respectively. Carbachol-, histamine-, and forskolin-induced increases in Fura 2 fluorescence appear dependent upon extracellular calcium, since these responses are attentuated in low calcium media and blocked by EGTA in low-calcium media or by lanthanum in high- or low-calcium medium. Trifluoperazine and fenoctimine, at concentrations that inhibit secretion, have no effect on either carbachol- or histamine-induced increases in cytosolic calcium. Seven major calcium/EGTA-sensitive phosphopro-teins are identified by SDS-PAGE electrophoresis of ATP 32P-labeled cell sonicates. We conclude that cytosolic calcium in enriched rat gastric parietal cell populations is regulated by secretagogue receptor-controlled calcium channels. We postulate that these channels may be controlled by cyclic AMP-dependent phosphorylation, since neither changes in cyclic AMP nor calcium alone mediate the effects of secretagogues entirely, but the interplay between these two second-messenger systems potentiates the actions of these agents. The role of cytosolic calcium as a second messenger in secretagogue action appears similar to that of cyclic AMP in that a specific cellular concentration must be reached to initiate acid secretion.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcp.1041390325
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