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  • Artikel: DFG Deutsche Nationallizenzen  (46)
  • 1990-1994  (32)
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  • 1955-1959
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  • 1990  (32)
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  • Calcium
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  • Artikel: DFG Deutsche Nationallizenzen  (46)
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  • 1990-1994  (32)
  • 1965-1969  (14)
  • 1955-1959
  • 1930-1934
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Jahr
  • 1
    ISSN: 1432-2285
    Schlagwort(e): Calcium ; Fagus sylvatica ; Magnesium ; Manganese ; Mineral content ; Potassium ; Seasonalvariation ; Xylem sap
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary In a 35-year-old calcareous beech forest stand five beech trees (Fagus sylvatica L.) were felled every 2 weeks, and xylem sap was obtained by means of water displacement from the lowest trunk sections, each 100 cm in length. From mid-October 1988 to mid-October 1989 a total of 130 trees were investigated. The seasonal variations of the Ca, Mg, K and Mn contents, as well as those of pH, show four characteristic phases. Additionally, distribution of the mineral contents along the trunk was studied in four trees. The seasonal increase and decrease of xylem sap mineral contents along the trunk is shown for the characteristic phenophases. The Ca, Mg, K, and Mn contents of xylem saps were determined by means of atomicabsorptionspectrophotometry.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Urological research 18 (1990), S. 213-217 
    ISSN: 1434-0879
    Schlagwort(e): Urinary tract infection ; Calcium ; Adherence
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Since ions are known to influence the interaction between cells, we undertook an examination of the effect of various ions on bacterial adherence to uroepithelial cells. While most of the ions examined had no effect or decreased bacterial adherence, calcium ions significantly increased bacterial adherence. It was demonstrated, in vitro that as the concentration of calcium was increased to levels higher than normally found in the urine, there was a significant increase in bacterial adherence. It was also found that if the diet was supplemented with calcium there was an increase in the excretion of calcium in the urine and a corresponding increase in bacterial adherence when bacteria and uroepithelial cells were incubated in this urine. It is suggested that an excretion of excess calcium in the urine may lead to increased bacterial adherence in vivo and an increased potential for urinary tract infections.
    Materialart: Digitale Medien
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  • 3
    ISSN: 1432-0533
    Schlagwort(e): Muscle necrosis ; Membrance permeabilisation ; Phospholipases ; Free radicals ; Calcium
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Treatment of partially depolarised mouse diaphragm muscle in vitro with the Ca2+-channel agonist Bay K 8644 (1 μM) induces permeabilisation of the sarcolemma (visualised by penetration of procion yellow). Procion yellow staining was widespread (74% of fibres) after 2 h of treatment, but was negligible after 60 min, a time at which myofibre breakdown is well advanced and elevation of [Ca2+]i is minimal (Howl and Publicover 1989). Permeabilisation was inhibited in Ca2+-free saline, and was much less pronounced in polarised fibres. Inhibitors of free radical generation (particularly OH⊙) afforded considerable protection to the muscle membrane against Bay K 8644-induced membrane permeabilisation. Inhibition of phospholipase A2 and lipoxygenase were also effective, but inhibition of xanthine oxidase (by allopurinol) had little effect. It is concluded that the initial effect of Bay K 8644 treatment is to increase Ca2+ influx through Ca2+ channels at the sarcolemma, and that this action subsequently induces membrane permeabilisation. Membrane damage probably occurs due to free radical generation and activation of phospholipase A2, both resulting from elevation of [Ca+]i.
    Materialart: Digitale Medien
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  • 4
    ISSN: 1432-041X
    Schlagwort(e): Ca2+/Mg2+ ATPase ; Molluscan eggs ; Ionic currents ; Polarity ; Calcium
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary During extrusion of the first polar body in eggs ofLymnaea stagnalis andBithynia tentaculata a localized Ca2+ /Mg2+ ATPase activity was detected, using Ando's enzyme-cytochemical method for electron microscopy [Ando et al. (1981) Acta Histochem Cytochem 14:705–726]. The enzyme activity was distributed in a polar fashion, along the cytoplasmic face of the plasma membrane. In the eggs ofLymnaea it was found only in the vegetal hemisphere, whereas inBithynia eggs it was localized both in the vegetal hemisphere and at the animal pole. This pattern of enzyme activity corresponds to the polar pattern of transcellular ionic currents measured with the vibrating probe, which we showed to be partially carried or regulated by calcium [Zivkovic and Dohmen (1989) Biol Bull (Woods Hole) 176 (Suppl):103–109]. The characteristics of the ATPase were studied using a variety of approaches such as ion and substrate depletions and substitutions, addition of specific inhibitors of ATPase activity, treatment with EDTA/EGTA and electron energy-loss spectrometry. The results indicate that, inLymnaea, there are at least two enzymatic entities. The first one is a Ca2+ /Mg2+ ATPase localized along the membrane and in the cortex of the vegetal hemisphere. The second one is a Ca2+-stimulated ATPase (calcium pump of the plasma membrane) localized in a small region of the membrane at the vegetal pole. We speculate that in the eggs ofLymnaea andBithynia a functional relationship exists between the plasma-membrane-associated ATPase activity and the transcellular ionic currents measured in the same region.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Intensive care medicine 16 (1990), S. 463-465 
    ISSN: 1432-1238
    Schlagwort(e): Calcium ; Adrenergic agents ; Arterial hypotension ; Electrolyte abnormalities
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Two patients admitted for decompensated chronic obstructive pulmonary disease developed arterial hypotension requiring the prolonged infusion of dopamine. They had no sign of acute circulatory failure and their blood lactate levels were normal. In the two patients, the correction of unsuspected hypocalcemia allowed the rapid discontinuation of the dopamine infusion.
    Materialart: Digitale Medien
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  • 6
    ISSN: 1432-1912
    Schlagwort(e): Brain microdialysis ; Acetylcholine ; Dopamine ; Calcium ; Perfusion solution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Brain microdialysis experiments were performed to assess the effects of calcium (1.2 mmol/l and 3.4 mmol/l) in the perfusio solution on a variety of pharmacological treatments known to affect the release of dopamine (DA) and/or acetylcholine (ACh). Intrastriatal infusion of the muscarinic receptor agonist oxotremorine (100 μM), the selective dopamine D-2 receptor agonist (−)-N-0437 (1 μM), and the indirect DA agonists (+)amphetamine (10 μM) and nomifensine (1 μM) via the dialysis probe did not affect the overflow of ACh when the perfusion fluid contained 3.4 mmol/l calcium. In contrast, these compounds produced pronounced decreases in the overflow of ACh at 1.2 mmol/l calcium. Intrastriatal infusion of the muscarinic receptor antagonist atropine (1 μM) increased the output of ACh both at 1.2 mmol/l and 3.4 mmol/1 calcium. The selective DA D-2 receptor antagonist (−)-sulpiride (1 μM) did not affect the overflow of ACh at either calcium concentration. Infusion of oxotremorine and atropine had no effect on the overflow of DA at either 1.2 mmol/l or 3.4 mmol/l calcium. (−)-N-0437 decreased and (−)-sulpirde increased DA overflow, both effects being independent of the calcium concentration in the perfusion fluid. Nomifensine and (−)amphetamine caused relatively (but not absolutely) larger increases in the overflow of DA at 1.2 mmol/1 calcium. These findings emphasize the critical importance of the calcium concentration of the perfusion fluid in determining the nature of pharmacological responses in microdialysis experiments, and demonstrate that locally applied dopaminergic drugs can modulate striatal cholinergic function.
    Materialart: Digitale Medien
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  • 7
    ISSN: 1432-2048
    Schlagwort(e): Setcreasea ; Calcium ; Cell-to-cell communication ; Plasmodesma ; Transport, intercellular
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The effect of microinjected calcium-loaded 1,2-bis(2-aminophenoxy) ethane-N,N,N′,N′-tetraacetic acid (CaBAPTA) on cell-to-cell diffusion of carboxyfluorescein (CF) was examined in staminal hairs of S. purpurea Boom. The CaBAPTA was microinjected into the cytoplasm of the staminal hairs either with CF or prior to a subsequent microinjection of CF. The cell-to-cell diffusion of CF along the hair was monitored using enhanced-fluorescence video microscopy. Cytoplasmic streaming stopped in cells treated with CaBAPTA, indicating that intracellular Ca2+ had increased. Cell-to-cell diffusion of CF was blocked in cells treated with Ca-BAPTA. An inhibition of cytoplasmic streaming and cell-to-cell diffusion was observed in the cells adjoining the CaBAPTA-microinjected cell, indicating that the Ca-BAPTA appeared to pass through plasmodesmata. While cytoplasmic streaming resumed 5–10 min after CaBAPTA treatment, cell-to-cell diffusion did not resume until 30–120 min later. These data support an involvement of calcium in the regulation of cell-to-cell communication in plants.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Planta 182 (1990), S. 236-243 
    ISSN: 1432-2048
    Schlagwort(e): Calcium ; Partitioning ; Photosynthesis ; Sucrose synthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract We have investigated whether changes of the cytosolic free-calcium concentration could regulate photosynthetic sucrose synthesis. Partially purified enzymes from spinach (Spinacea oleracea L.) leaves were assayed using calcium-EGTA buffers to obtain defined free-calcium concentrations in the low micromolar and submicromolar ranges. These concentrations of calcium did not directly affect sucrose-phosphate synthase activity. They inhibited the cytosolic fructose-1,6-bisphosphatase, acting competitively to magnesium. The Ki for calcium (1.2 μM) was 400-fold lower than the Km for magnesium. To investigate the in-vivo significance of these observations, the Ca2+ antagonists lanthanum (La3+), trifluoperazine, and ruthenium red were supplied to barley leaves via the transpiration stream. All three antagonists selectively inhibited sucrose synthesis: they inhibited 14C incorporation into sucrose at concentrations which did not affect starch synthesis; in low light, partitioning was changed towards starch without altering the rate of photosynthesis; there was a characteristic change in the induction kinetics of photosynthesis; and there was an accumulation of phosphorylated metabolites in the leaf. The detailed changes in metabolite levels indicate that La3+ was acting via inhibition of the fructose-1,6-bisphosphatase, trifluoperazine via blockage of the turnover of inorganic pyrophosphate, and ruthenium red via changes in the activation state (phosphorylation) of sucrose-phosphate synthase. The results are discussed in terms of a possible contribution of calcium to the regulation of carbon metabolism.
    Materialart: Digitale Medien
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  • 9
    ISSN: 1432-203X
    Schlagwort(e): Calcium ; Daucus carota ; Somatic embryogenesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract An upward shift in the concentration of calcium present in the medium during somatic embryogenesis increased the number of embryos produced approximately two-fold. This was observed when embryogenic suspension cells grown in 2,4-D medium with the normal calcium concentration of 10−3 M were transferred to hormone-free medium containing 10−2 M calcium and when embryogenic suspension cells grown in 2,4-D medium containing 10−4 M calcium were transferred to hormone-free medium with 10−3 M calcium. At calcium concentrations between 6·10−3 and 10−2 M globular stage somatic embryos were found in cultures supplemented with 2·10−6 M of 2,4-D indicating that elevated calcium counteracts the inhibitory effect of 2,4-D on somatic embryogenesis. No qualitative changes were found in the pattern of extracellular polypeptides as a result of growth and embryogenesis in media with different calcium concentrations.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    Sexual plant reproduction 3 (1990), S. 98-102 
    ISSN: 1432-2145
    Schlagwort(e): Synergids ; Calcium ; Chemotropism ; Fertilization ; Energy-dispersive X-ray microanalysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Using energy-dispersive X-ray microanalysis of mature, unpollinated wheat ovaries fixed by freeze-substitution, we show here that the synergid cells store a relatively high concentration of calcium. Based on our results and other indirect evidence, we suggest that supraoptimal levels of calcium in synergids may regulate: (1) correct orientation of the pollen tube, by forming a calcium gradient in the vicinity of the synergids, and (2) arrest and rupture of the pollen tube to release the sperm near the egg.
    Materialart: Digitale Medien
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  • 11
    Digitale Medien
    Digitale Medien
    Springer
    Pflügers Archiv 415 (1990), S. 444-448 
    ISSN: 1432-2013
    Schlagwort(e): Sodium absorption ; Potential difference oscillations ; Calcium ; BAY K 8644 ; Barium ; Ca2+-activated K+ channels ; Rabbit gall-bladder
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract In the present study, we characterized the effects of the calcium (Ca2+) channel activator BAY K 8644 on sodium (Na+) absorption and transepithelial potential difference (Pd) in the rabbit gall-bladder. In gall-bladders mounted in an Ussing chamber it was observed that serosal BAY K 8644 (10±5 M) inhibited Na+ absorption in the presence, but not in the absence of serosal Ca2+. Serosal nifedipine (a Ca2+ channel antagonist) at 10±5 M did not reverse the Na5+ transport inhibition caused by BAY K 8644. Another effect of serosal BAY K 8644 (10±5 M) was to induce oscillations in Pd. These Pd-oscillations had a frequency of about one per minute and an amplitude of 20–40 μV. The appearance of Pd-oscillations was dependent on the presence of Ca2+ in the serosal medium. The oscillations were abolished by 1–3×10±5 M serosal nifedipine and by bilateral application of 3 mM barium (Ba2+) (a K+ channel blocker). In a sac preparation of the rabbit gall-bladder, spontaneous cyclic contractions of smooth muscle cells in the gall-bladder wall were observed as oscillations in the transmural pressure. These spontaneous contractions were not accompanied by oscillations in Pd. Serosal BAY K 8644 (10±5 M) evoked oscillations in Pd in half of the sac preparations, but in each gall-bladder the frequencies of Pdoscillations and pressure oscillations were different. Serosal nifedipine (2×10±5 M) abolished both types of oscillation. The results show that the BAY K 8644-induced Na+ transport inhibition and initiation of Pd-oscillations can be ascribed to specific epithelial Ca2+-dependent effects of BAY K 8644. We postulate that the Pd-oscillations involve Ca2+-activated, Ba2+-sensitive K+ channels in both the luminal and the basolateral cell membrane.
    Materialart: Digitale Medien
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  • 12
    Digitale Medien
    Digitale Medien
    Springer
    Pflügers Archiv 416 (1990), S. 360-367 
    ISSN: 1432-2013
    Schlagwort(e): Ion channels ; Sodium channels ; Voltage-dependent gating ; Calcium ; Barium ; Planar bilayers ; Surface charge ; Divalent cations
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The effects of external divalent cations on the steady-state open probability (P o), opening and closing rates, and conductance of batrachotoxin (BTX)-activated Na channels were studied in planar lipid bilayers. External divalent cations shifted the midpoint of the P o versus membrane potential (V m) relation (gating curve) to more depolarized potentials. Of the group IIA divalent cations tested, Ca2+ caused the largest depolarizing shift followed by Ba2+, Sr2+ and Mg2+ in that order. In contrast, the order of decreasing efficacy for block of the single channel conductance was Ca2+, Mg2+, Sr2+ and Ba2+. Thus, because it is a relatively good shifter but a poor blocker, Ba2+ was used to study the effects of divalent cations on gating. External Ba2+ decreased the Na channel opening rate and increased the closing rate. At voltages close to the midpoint of the gating curve, the opening rate decreased by a factor of 1/2.8 while the closing rate increased by 2.0-fold. Although Ba2+ would be expected to increase the external surface potential by interacting with negatively charged residues on the channel, this preferential effect on the opening rate indicates that the effects of external Ba2+ cannot be attributed solely to an increase in the potential gradient across the voltage sensing apparatus. Our results can be explained if two different mechanisms are involved in the modulation of Na channel gating by extracellular divalent cations in neutral membranes: (1) the screening or binding of Ba2+ at negatively charged groups on the extracellular side of the channel, leading to an increase in the transmembrane electric field at the voltage sensor, as well as an increase in the closing rate and decrease in the opening rate by the same proportion, plus (2) a direct modulatory action on the channel protein which stabilizes the closed state of the channel and accounts for the larger effect of external divalent cations on the opening rate.
    Materialart: Digitale Medien
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  • 13
    ISSN: 1432-1017
    Schlagwort(e): Erythrocytes ; Aggregation ; Phospholipid ; Calcium ; Red cell shape
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Physik
    Notizen: Abstract Reversible aggregation of erythrocytes was investigated after alteration of the phospholipid content in the membrane outer leaflet either by disturbance of endogenous transmembrane lipid asymmetry through changes in cellular free calcium, or by incorporation of exogenous lyso-derivatives. It was found that both calcium loading and lyso-phosphatidylcholine (LPC) addition induce a strong increase in red cell-red cell adhesive energy, whereas lyso-phosphatidylserine (LPS), added in the same amount as LPC, does not. Red cell morphological studies show differences in the shape change efficiency of LPS, LPC and calcium loading. However, it was further demonstrated that shape change is not directly responsible for the observed adhesive energy increase, since neuraminidase or trypsin treatment abolish this increase, even though the shape changes induced by alteration of phospholipid organization are not affected. The latter experiment strongly suggests that the red cell adhesive energy increase results from an alteration of the glycocalyx structure, which could be in turn a consequence of the shape change.
    Materialart: Digitale Medien
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  • 14
    Digitale Medien
    Digitale Medien
    Springer
    European journal of pediatrics 149 (1990), S. 800-803 
    ISSN: 1432-1076
    Schlagwort(e): Caesarean section ; Calcitonin ; Calcium ; Newborn ; Parathyroid hormone
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Serum levels of calcium (Ca), calcitonin (CT) and parathyroid hormone (PTH) were determined in cord blood of 229 newborns. In 136 newborns the tests were repeated 24h later. The probands were divided into four groups according to mode of delivery: (1) spontaneous; (2) elective caesarean section without labour; (3) elective caesarean section in labour; (4) emergency caesarean section with fetal distress. Newborns in group 2 had significantly lower Ca and CT levels and significantly higher PTH concentrations in cord blood than the other three groups. In all groups Ca and PTH concentrations were negatively correlated. At 24 h, mean Ca levels had decreased and mean CT and PTH concentrations had increased in all four groups. Newborns in group 2 still had lower Ca levels but higher CT and PTH concentrations. At that time there were negative correlations between Ca and CT levels in groups 1 and 2 and between Ca and PTH concentrations in group 1. These data demonstrate that without labour, cord blood Ca and CT levels are lower and PTH concentrations are higher. The low 24h calcium in newborns delivered without labour is explained by the lower Ca levels at birth and a tremendous increase of CT. The PTH secretion in full-term newborns is very substantial and negatively correlated with Ca levels.
    Materialart: Digitale Medien
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  • 15
    ISSN: 1432-072X
    Schlagwort(e): Klebsiella pneumoniae ; Chemostat culture ; Glucose metabolism ; Glucose dehydrogenase ; Pyrroloquinoline quinone ; Magnesium ; Calcium
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Magnesium-limited chemostat cultures of Klebsiella pneumoniae NCTC 418 with 20 μM CaCl2 in the medium showed a low rate of gluconate plus 2-ketogluconate production relative to potassium- or phosphate-limited cultures. However, when the medium concentration of CaCl2 was increased to 1 mM, the glucose dehydrogenase (GDH) activities also increased and became similar to those observed in potassium- or phosphate limited cultures. It is concluded that this is due to Mg2+ and Ca2+ ions being involved in the binding of pyrroloquinoline quinone (PQQ) to the GDH apoenzyme. There seems to be an absolute requirement of divalent cations for proper enzyme functioning and in this respect Ca2+ ions could replace Mg2+ ions. The high GDH activity which has been found in cells grown under Mg2−-limited conditions in the presence of higher concentrations of Ca2+ ions, is compatible with the earlier proposal that GDH functions as an auxiliary energy generating system involved in the maintenance of high transmembrane ion gradients.
    Materialart: Digitale Medien
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  • 16
    ISSN: 1432-2013
    Schlagwort(e): Calcium ; Calmodulin ; Salivary ; Muscarinic ; Cell line ; Naphthalenesulfonamides
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract We have investigated the effect of W-7, a calmodulin (CaM) antagonist, on Ca2+ mobilization in a human salivary epithelial cell line, HSG-PA, after muscarinic receptor stimulation. In a medium containing 1.5 mmol/l Ca2+, W-7 reduced both the maximum peak increase in cytosolic Ca2+ ([Ca2+]i) which follows stimulation by carbachol (Cch, 100 μmol/l) and the sustained nature of the response. Using an experimental approach which allows separate visualization of the intracellular Ca2+ release and extracellular Ca2+ entry phases, W-7 was shown preferentially to inhibit Ca2+ release. At 100 μmol/l W-7, Cch-induced Ca2+ release was completely inhibited, but Cch-induced Ca2+ entry was partially (∼40%) maintained. This W-7 residual Ca2+ entry response was abolished when cells were depolarized with high K+ or gramicidin D. W-7 also substantially inhibited Cch-induced inositol trisphosphate (IP3) production (∼75%). W-5, a less potent CaM antagonist than W-7, had markedly smaller effects on Cch-induced Ca2+ mobilization and IP3 formation. W-7 (100 μmol/ l) completely blocked (comparable to 10 μmol/l atropine) the binding of the muscarinic antagonist [3H] quinuclidinyl benzilate (QNB) to muscarinic receptors on cell membranes, whereas Cch (at 100 μmol/l) had minimal effects on ligand binding. W-7 and W-5 were equipotent in their ability to inhibit [3H] QNB binding. These results suggest that W-7 reduces Ca2+ mobilization in HSG-PA cells by a mechanism which likely involves the antagonism of a CaM regulatory step(s) but may also involve at least a partial blockade of the muscarinic receptor. In addition, in the presence of W-7, Ca2+ entry can occur via a receptor-operated Ca2+ pathway which is modulated by membrane potential.
    Materialart: Digitale Medien
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  • 17
    ISSN: 1432-2013
    Schlagwort(e): Vascular smooth muscle ; Calcium
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The changes in isometric force and the underlying fluctuations in intracellular free calcium concentration ([Ca2+]i) were monitored simultaneously in thin sheets of rabbit inferior vena cava loaded with the fluorescent Ca2+ indicator fura-2. In resting tissues bathed in physiological saline solution, the estimated [Ca2+]i was approximately 105 nM. The α-adrenergic agonist norepinephrine (10 μM) caused an initial rise in [Ca2+]i to 264 nM during force development, which dropped to 216 nM during force maintenance. The maintained norepinephrine-induced increase in force and [Ca2+]i was reversed in Ca2+-free (2 mM EGTA) solution. Membrane depolarization by high K+ (80 mM) significantly increased [Ca2+]i to 234 nM. Compared to norepinephrine, high K+ caused about the same steady-state increase in [Ca2+]i, but a smaller increase in force. [Ca2+]i/force curves were constructed at different concentrations of extracellular Ca2+, with either norepinephrine or high K+ as a stimulant. The curve generated with norepinephrine was located to the left of that generated with high K+.
    Materialart: Digitale Medien
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  • 18
    Digitale Medien
    Digitale Medien
    Springer
    Pflügers Archiv 417 (1990), S. 309-316 
    ISSN: 1432-2013
    Schlagwort(e): Heart ; Adenosine triphosphate ; HCO3/Cl Exchanger ; Arrhythmia ; Calcium ; pH
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Adenosine triphosphate (ATP) is released during neural stimulation and cardiac hypoxia and several mechanims of its action have been reported in different tissues. ATP stimulates P1 and P2 purinergic receptors; it also activates receptor-operated channels and increases membrane permeability to small ions. In single rat ventricular cells under whole-cell patch-clamp, a stepwise application of ATP in the micromolar range affects the resting potential and membrane currents through an entirely novel mechanism of action which involves several steps. Extracellular ATP induces an inward current and depolarization of the cell, leading to automaticity. The inward current is non-specific for cations, its reversal potential is around −5 mV. The conductance change evoked by ATP is suppressed by 4,4-diisothiocyanostilbene 2,2-disulphonic acid (DIDS) and low-chloride media and is prolonged by adding intracellular bicarbonate. These effects are specific for ATP in the presence of magnesium and are not evoked by a non-hydrolysable analogue of ATP or in the presence of vanadate. Other nucleotides are ineffective. We propose that ATP hydrolysis activates the chloride/bicarbonate (C1−/HCO 3 − ) exchanger. The induced local acidification could then increase intracellular free calcium and as a consequence, increases the sarcolemmal conductance. Thus, a sudden release of ATP in pathological conditions would induce a depolarization which could generate ventricular arrhythmias.
    Materialart: Digitale Medien
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  • 19
    ISSN: 1432-2013
    Schlagwort(e): Basal metabolism ; Papillary muscle ; Extracellular potassium ; Calcium ; Myothermic
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The effect of elevating extracellular K+ concentration on the basal metabolism of the isolated rat left ventricular papillary muscle has been investigated. The preparation was mounted on a thermopile and connected to a force transducer, to allow simultaneous measurement of muscle heat production and force. The resting heat rate (RHR) of the quiescent preparation was measured as an index of basal metabolism. Throughout all of the experiments, the muscles were maintained under a resting force of 10 mN and all measurements of RHR were made at times when there was no active force present above this passive level. Elevating the extracellular K+ concentration from 5.9 to 20, 40, then 80 mM produced graded increases in the RHR. The increase in RHR produced by 40 mM K+ was observed to be time-dependent, its effect being significantly greater at 5–7 h than at 2–4 h after cardiectomy. Averaged over all times, the percentage increases in RHR produced by 20, 40, and 80 mM K+ in the presence of 2 mM Ca2+ were 6.4±2.0%, 28.7±2.3%, and 51.3±8.9% (mean±SEM) respectively. The high K+-induced increase in basal metabolism was also shown to be Ca2+-dependent, the increase in RHR produced by 40 mM K+ being greater the higher the extracellular Ca2+ concentration (0.5–8.0 mM). The addition of verapamil was found to partially inhibit the K+-induced increase in resting metabolism. These results show that elevation of the extracellular K+ concentration produces a graded increase in the RHR that is Ca2+-dependent. It is suggested that the increases in RHR observed in this investigation are in part associated with elevated levels of myoplasmic free Ca2+ which stimulate the internal Ca2+ pumps.
    Materialart: Digitale Medien
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  • 20
    Digitale Medien
    Digitale Medien
    Springer
    Pflügers Archiv 417 (1990), S. 168-173 
    ISSN: 1432-2013
    Schlagwort(e): Rod photoreceptor ; Retina ; Calcium ; Quinidine
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The effect of quinidine on the membrane current generated by the Na∶Ca,K exchange has been investigated in the outer segment of isolated rod photoreceptors from the retina of the larval tiger salamander. The inward exchange current associated with the efflux of Ca2+ was selectively recorded by introducing a Ca2+ load through the light-sensitive channels, and then shutting these channels with a bright light. Quinidine (20–1000 μM) reduced the magnitude of the exchange current and slowed its decay during the removal of a Ca2+ load. Quinidine did not alter the form of the relation between the exchange current and the total concentration of exchangeable calcium remaining within the outer segment, [Ca]T, showing that it does not change the affinity of the exchange mechanism for internal Ca2+. The relation between exchange current inhibition and the quinidine concentration could be described by a simple Michaelis relation with a K i of 287 μM and a maximum inhibition of 50%. The incomplete block of the Na∶Ca,K exchange current by quinidine shows that it does not act by simple competition with external Na+, and suggests that the inhibition of the exchange by quinidine may be non-specific.
    Materialart: Digitale Medien
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  • 21
    Digitale Medien
    Digitale Medien
    Springer
    Journal of mathematical biology 28 (1990), S. 585-593 
    ISSN: 1432-1416
    Schlagwort(e): Calcium ; Viscoelasticity ; Stability ; Pattern generation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Mathematik
    Notizen: Abstract The Goodwin and Trainor model of pattern generation in calcium-regulated strain fields is studied in the case where calcium input and calcium output processes are involved. It is shown that the properties of the original model may still remain provided that the input-output processes are not unstable. In this last case, despite the eventual stabilizing effect of the calcium exchange term, perturbations of the generalized system can grow and lead to inhomogeneous solutions. Applications to cell differentiation and cell growth are discussed.
    Materialart: Digitale Medien
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  • 22
    Digitale Medien
    Digitale Medien
    Springer
    Heart and vessels 5 (1990), S. 206-211 
    ISSN: 1615-2573
    Schlagwort(e): Calcium ; Nifedipine ; Vascular endothelium
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The purpose of this study was to examine contractile properties of endothelin-1, a newly discovered vasoactive peptide, in guinea pig coronary resistance vessels and abdominal aorta. Changes in perfusion pressure after injections of endothelin-1 were measured using a constant-flow modified Langendorff preparation. The ED10 values of coronary perfusion pressure were about 100-fold less for endothelin-1 than for prostaglandin F2α. After the endothelium was damaged by exposure to free radicals, maximal coronary constriction in response to endothelin-1 (10−9 moles) was not altered, whereas dilator responses to low doses of endothelin-1 were converted to constrictor responses. Removal of the endothelium from aortic rings significantly increased responsiveness to endothelin-1 and the maximal response to the peptide. In calcium-free medium, endothelin-1 induced small increases both in perfusion pressure in coronary vessles and in tension in the aorta. Reintroduction of calcium in the coronary and aortic preparations produced a rapid increase in perfusion pressure and tension, respectively. Further, endothelin-1-induced coronary constriction was inhibited 59%±7% by nifedipine (10−7 moles). We conclude that endothelin-1 is a more potent constrictor than prostaglandin F2α in the coronary vasculature. Endothelin-1-induced constriction in the coronary vasculature of the guinea pig is not mediated through an endogenous constricting factor released from the endothelium or a constrictor prostaglandin. Further, endothelin-1-induced dilation in the coronary vasculature and attenuation of endothelin-1-induced contraction in the abdominal aorta of the guinea pig are mediated through the release of a factor from the endothelium. Endothelin-1-induced coronary constriction and abdominal aortic contraction require extracellular calcium, entering, in part, through nifedipine-sensitive channels.
    Materialart: Digitale Medien
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  • 23
    ISSN: 1615-6102
    Schlagwort(e): Endoplasmic reticulum ; Calcium ; Actin filaments ; DiOC6 ; Onion epidermis cells ; Confocal laser scanning microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The influence of substances interfering with the cellular calcium distribution on the organization of the endoplasmic reticulum has been investigated in live epidermal cells of onion bulb scales. The endoplasmic reticulum was visualized by vital staining with the fluorochrome DiOC6(3). It constitutes in these cells an anastomosing membrane system which is composed of three forms: cisternae, short tubules forming a peripheral network, and long tubular strands deeper in the cytoplasm. In the presence of all tested calcium interfering substances, e.g. the ionophore calcimycin (5 μM), the cryptate 221 (0.5 mM), the calmodulin antagonist calmidazolium (10 μM), the tubular ER elements disappear and huge cisternae form instead. The potassium-selective cryptate 222 (1 mM) chemically very similar to the effective cryptate 221 does not cause this change in ER pattern. Actin filaments which are indispensable for ER distribution in the epidermis cells appear to fragment in the presence of the drugs indicating some similarity with the action of cytochalasin D (Quader et al. 1989). Removal of the drugs initiates a characteristic sequence of recovery. The cisternae disintegrate at their edges into tubular loops which are pulled away from this cellular site as long tubular strands. In the presence of cytochalasin D (2 μM) the disintegration of the cisternae is inhibited indicating that kinetic forces are necessary to generate and maintain the spatial distribution of at least parts of the tubular ER meshwork. For the first time the decay of cisternae is described in live cells. The effect of the calcium agents is also compared with changes in ER organization caused by other chemical or natural means.
    Materialart: Digitale Medien
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  • 24
    Digitale Medien
    Digitale Medien
    Springer
    Protoplasma 154 (1990), S. 172-178 
    ISSN: 1615-6102
    Schlagwort(e): Cell motility ; Endoplasmic reticulum ; Calcium ; Calciosomes ; Acetabularia ; Inositol phosphate ; Signal transduction ; Intracellular particle motions ; Actin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Recent fluorescence, AVEC-DIC, and confocal laser scanning microscopic studies have revealed the dynamic nature and structural extent of a calcium-sequestering endoplasmic reticulum (ER) in plant cells. Various investigators have proposed different roles for the ER in cell motility. One, the ER plays a direct role in the generation of intracellular particle motions or two, the ER regulates particle motions indirectly. We show that the ER can be extruded fromAcetabularia cells, stains brightly with the fluorescent dye DiOC6(3), and small (ca. 100 nm diameter) fluorescent vesicles are observed to move in or along the ER tubules. Intracellular particle movements in the giant algal cellAcetabularia can be transiently inhibited by IP4, IP3, and IP2, compounds which in animal cells are known to cause the release of free calcium ions. A model is proposed which clarifies the possible relationships between the ER, calciosomes, calcium ions, and the microfilament-generated intracellular particle movements observed in plant cells.
    Materialart: Digitale Medien
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  • 25
    Digitale Medien
    Digitale Medien
    Springer
    Protoplasma 157 (1990), S. 182-192 
    ISSN: 1615-6102
    Schlagwort(e): Caffeine ; Cell plate ; Phragmoplast ; Endoplasmic reticulum ; Golgi vesicles ; Microtubules ; Calcium
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Caffeine is a potent inhibitor of cell plate formation in dividing plant cells. Previous studies living cells reveal that the drug always permits the cell plate to arise and grow normally until about 80% complete, but then causes it to break down. In the present investigation we examine this formation/degradation cycle at the ultrastructure level. Our results show that during the formation phase the caffeine treated plate is indistinguishable from untreated controls. Phragmoplast microtubules arise and align in the interzone, Golgi vesicles are produced and aggregate in a line that defines the young cell plate, and considerable fusion of these vesicles occurs to form islands of plate material. However, under the influence of caffeine these islands do not fuse to form the enlarged lamellar expanses characteristic of maturing cell plates. Instead, the partially fused material reverts to small vesicles which appear to become resorbed by the cellular membrane systems. The resorption process continues leaving no evidence of the previously developing plate, although occasionally we observe a stub of fused vesicles attached to the parent wall. Following cell plate disintegration the reformed nuclei move close together and occupy the central region of the cell. These observations focus attention on the consolidation phase of cell plate formation as the one being maximally affected by caffeine.
    Materialart: Digitale Medien
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  • 26
    Digitale Medien
    Digitale Medien
    Springer
    Protoplasma 158 (1990), S. 182-190 
    ISSN: 1615-6102
    Schlagwort(e): Aplanospores ; Calcium ; Ca-channels ; Germination ; Vaucheria
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary InVaucheria longicaulis var.macounii aplanospore germination and filament growth are severely inhibited by the Ca2+-channel antagonists (−)202–791, diltiazem, nifedipine and verapamil, whereas the agonists (+)202–791, Bay K-8644 and CGP-28392 stimulate those processes. Both antagonist and agonist actions suggest that voltage-controlled Ca2+ influx plays a major role in the regulation of the initial events of germination and filament growth. Increases in45Ca2+ influx are observed after pretreatment of the aplanospores with low temperature shocks of brief duration or FCCP. Both agents are known to depolarize the surface membrane.45Ca2+ influx is reduced in material treated with FC, an agent known to hyperpolarize cell membranes. The results indicate that Ca2+ influx takes place through voltage-sensitive Ca-channels.
    Materialart: Digitale Medien
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  • 27
    ISSN: 1435-5604
    Schlagwort(e): Calcium ; Oyster shell electrolysate ; Bioavailability ; Bioavailability ; Balance study ; Calcium ; Oyster Shell Electrolysate
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Balance studies were conducted on 4 normal elderly subjects, 2 males and 2 females, ranging in age between 66 and 86 years in order to compare the bioavailability of oyster shell electrolysate with that of calcium carbonate and calcium lactate, in a crossover design. In each subject, 600 mg oyster shell electrolysate was more effective than calcium carbonate or calcium lactate containing the same 600 mg calcium to restore the negative calcium balance found on 600 mg/day calcium intake, suggesting a better bioavailability of oyster shell electrolysate than the two kinds of calcium salts.
    Materialart: Digitale Medien
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  • 28
    ISSN: 1435-5604
    Schlagwort(e): Calcium ; Insulin-like growth factor-I ; Osteoblast
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The effect of insulin-like growth factor-I (IGF-I) on calcification in cloned osteoblast-like MC3T3-E1 cells was studied by measuring accumulation of45Ca into sodium dodecyl sulfate-insoluble, EDTA-extractable structure that appeared after 2 weeks of culture. The accumulation of45Ca was markedly enhanced by incubating cells with IGF-I after 6 weeks of culture. The enhancement was dose-dependent in a range between 0.1 nM and 100 nM. IGF-I stimulated alkaline phosphatase activity in the cells cultured for 7 weeks dose-dependently between 0.1 nM and 100 nM. DNA synthesis examined in the cells cultured for 7 weeks was not influenced by 100 nM IGF-I. These results suggest that IGF-I stimulates Ca-accumulation in osteoblast-like cells without stimulating their proliferation.
    Materialart: Digitale Medien
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  • 29
    ISSN: 1432-136X
    Schlagwort(e): Neurospora ; Calcium ; cAMP ; Protein phosphorylation ; Circadian rhythm
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Pulses of some Ca2+ channel blockers (dantrolene, Co2+, nifedipine) and calmodulin inhibitors (chlorpromazine) lead to medium (maximally 5–9 h) phase shifts of the circadian conidiation rhythm ofNeurospora crassa. Pulses of high Ca2+, or of low Ca2+, a Ca2+ ionophore (A23187) together with Ca2+, and other Ca2+ channel blockers (La3+, diltiazem), however, caused only minor phase shifts. The effect of these substances (A 23187) and of different temperatures on the Ca2+ release from isolated vacuoles was analyzed by using the fluorescent dye Fura-2. A 23187 and higher temperatures increased the release drastically, whereas dantrolene decreased the permeation of Ca2+ (Cornelius et al., 1989). Pulses of 8-PCTP-cAMP, IBMX and of the cAMP antagonist RP-cAMPS, also caused medium (maximally 6–9 h) phase shifts of the conidiation rhythm. The phase response curve of the agonist was almost 180° out of phase with the antagonist PRC. In spite of some variability in the PRCs of these series of experiments all showed maximal shifts during ct 0–12. The variability of the response may be due to circadian changes in the activity of phosphodiesterases: After adding cAMP to mycelial extracts HPLC analysis of cAMP metabolites showed significant differences during a circadian period with a maximum at ct 0. Protein phosphorylation was tested mainly in an in vitro phosphorylation system (with35S-thio γ-ATP). The results showed circadian rhythmic changes predominantly in proteins of 47/48 kDa. Substances and treatments causing phase-shifts of the conidiation rhythm also caused changes in the phosphorylation of these proteins: an increase was observed when Ca2+ or cAMP were added, whereas a decrease occurred upon addition of a calmodulin inhibitor (TFP) or pretreatment of the mycelia with higher (42° C) temperatures. Altogether, the results indicate that Ca2+-calmodulin-dependent and cAMP-dependent processes play an important, but perhaps not essential, role in the clock mechanism ofNeurospora. Ca2+ calmodulin and the phosphorylation state of the 47/48-kDa proteins may have controlling or essential functions for this mechanism.
    Materialart: Digitale Medien
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  • 30
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Bioluminescence and Chemiluminescence 5 (1990), S. 131-139 
    ISSN: 0884-3996
    Schlagwort(e): Calcium ; ATP ; Luc ; Phot ; gene ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: The Luc gene from the firefly Photinus pyralis has been isolated by cloning it in pcDV1 PL plasmid primer and Honjo linker and the Phot gene isolated from Aequorea victoria using the polymerase chain reaction. A method has been established using SP6 RNA polymerase for transcribing and translating bioluminescent genes in vitro. It should now be possible to engineer these genes to measure intracellular ATP and the covalent modification of proteins in single, live cells, providing unique insights into the molecular basis of disease.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 31
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 26 (1990), S. 366-376 
    ISSN: 1040-452X
    Schlagwort(e): In vitro capacitation ; Sperm domains ; Calcium ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: Calmodulin has been postulated as a mediator in the calcium-dependent processes that culminate in the acrosome reaction. Changes in calmodulin compartmentalization as a consequence of the increased permeability to extracellular calcium during capacitation and acrosome reaction have been suggested. In the present study the temporal localization of calmodulin in guinea pig spermatozoa was studied during in vitro capacitation and acrosome reaction by indirect immunofluorescence. Capacitation was achieved by incubation in Tyrode medium supplemented with pyruvate, lactate, and glucose in the presence and in the absence of calcium. Acrosome reaction was elicited in three different conditions: 1) by transfer to minimal culture medium containing pyruvate and lactate (MCM-PL) after in vitro capacitation, 2) by 0.003% Triton-X 100 treatment, and 3) by A 23187 addition to sperm samples incubated in MCM-PL. During capacitation, calmodulin was observed both in the acrosome and in the flagellum; this localization seemed to be independent of the presence of extracellular calcium and of exogenous substrates. Throughout the acrosome reaction, different stages of calmodulin compartmentalization were observed. It became clustered around the equatorial region just before or a little after the acrosome reaction had occurred. Later, it was observed around the postacrosomal region in the acrosome-reacted sperm. The changes in calmodulin distribution were found to be dependent on the stage in the acrosome reaction.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 32
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 26 (1990), S. 69-77 
    ISSN: 1040-452X
    Schlagwort(e): Calcium ; Hyperactivation ; Motility ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: The majority of sperm from mice carrying the tw32 haplotype undergo hyperactivation sooner than sperm from +/+ mice of the same strains (Olds-Clarke, Dev Biol 131:475-482, 1989). To investigate the mechanism underlying this abnormal motility, the Ca2+ sensitivity of their flagellar apparatus was compared to that of age- and strain-matched controls using Triton X-100-extracted sperm. Under these conditions, the curvature of the sperm flagellum is controlled by the free calcium concentration. Sperm from mice carrying the tw32 haplotype consistently exhibited a change in flagellar curvature at lower free calcium concentrations than controls. In addition, intact sperm from tw32/+ mice were much more likely than congenic control sperm to have a hook-like bend in the midpiece, which persisted throughout most of the beat cycle. Sperm exhibiting the hooked middle piece could be converted to a more normal appearance by 2mM procaine, which immobilizes cytoplasmic calcium. Thus an increased sensitivity of the sperm motor apparatus to calcium could be the cause of the precocious hyperactivation of sperm from mice carrying the tw32 haplotype.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 33
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 2 (1968), S. 296-298 
    ISSN: 1432-0827
    Schlagwort(e): Calcium ; Lipid ; Bacteria ; Calcification
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Beschreibung / Inhaltsverzeichnis: Résumé On a fait ce travail pour determiner si le facteur responsable pour la liaison de calcium par un calcifableBacterionema matruchotii est dans la fraction lipide de la cellule. Des cellules congelees et sechees ont ete extraites par le chloroform-methanol. La fraction de chloroform-methanol, les cellules extraites et les cellules non traitees ont ete examinees pour la liaison de calcium. La fraction du chloroform-methanol et les cellules non traitees avaient la liaison de calcium. Les cellules extraites n'en avaient pas.
    Kurzfassung: Zusammenfassung Diese Arbeit wurde durchgeführt um festzustellen, ob sich der Faktor für die Calcium-bindung, durch das calcifizierendeBacterionema matruchotii, in der Lipoidfraktion befindet. Die lyophiilisierten Zellen wurden mit Chloroform-Methanol extrahiert. Die Chloroform-Methanol-Fraktion, die extrahierten Zellen, sowie die nicht behandelten Zellen wurden auf eine Calciumbindung hin untersucht. Die Chloroform-Methanol-Fraktion und die nicht behandelten Zellen demonstrierten eine Calciumbindung. Die extrahierten Zellen hingegen nicht.
    Notizen: Abstract This work was done to determine whether the factor responsible for calcium binding by a calcifiableBacterionema matruchotii is in the lipid fraction of the cell. Freeze-dried cells were extracted with chloroform-methanol. The chloroform-methanol fraction, the extracted cells and untreated cells were examined for calcium binding. The chloroform-methanol fraction and the untreated cells bound calcium. The extracted cells did not.
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  • 34
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 2 (1968), S. 67-76 
    ISSN: 1432-0827
    Schlagwort(e): Calcergy ; Calciphylaxis ; Calcium ; Metals
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Beschreibung / Inhaltsverzeichnis: Résumé Chez le rat, des expériences ont montré que, sauf de rares exceptions, les calcifications produites au site d'injection d'acétate de plomb, de chlorure de cérium, chlorure de calcium ou de permanganate de potassium sont complètement prévenues ou fortement inhibées par l'application locale simultanée de provocateurs calciphylactiques, mais non par des agents non provocateurs. Malgré quelques exceptions (attribuées à des interrelations chimiques spécifiques entre certaines des substances utilisées), cette curieuse corrélation entre l'efficacité calciphylactique provocatrice et le pouvoir anticalcergique est, d'après le test χ2, hautement significative (P〈0,001).
    Kurzfassung: Zusammenfassung Nach subcutaner Injektion von Bleiacetat, Ceriumchlorid, Calciumchlorid oder Kaliumpermanganat tritt an der Injektionsstelle eine starke Verkalkung auf. Bis auf sehr wenige Ausnahmen kann diese durch gleichzeitige lokale Anwendung von calciphylaktischen Provokatoren verhütet oder weitgehend unterdrückt werden. In dieser Beziehung sind nicht provolatorisch wirkende Stoffe inaktiv. Trotz der wenigen Ausnahmen (die wahrscheinlich auf spezifische, chemische Wechselwirkungen zwischen manchen der untersuchten Substanzen beruhen) ist dieser merkwürdige Zusammenhang zwischen calciphylaktisch provozierender und anticalcergischer Aktivität, nach dem χ2-Test berechnet, statistisch hochsignifikant (P〈0,001).
    Notizen: Abstract Experiments on rats indicate that, with very few exceptions, the calcification which occurs at subcutaneous sites of treatment with lead acetate, cerium chloride, calcium chloride or potassium permanganate is completely blocked or severely inhibited by simultaneous topical application of calciphylactic challengers but not of non-challengers. Despite the few exceptions (which are thought to depend upon specific chemical interactions between some of the compounds tested) this singular correlation between calciphylactic challenging and anticalcergic potency, is highly significant by the Chi-square-test (P〈0.001).
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  • 35
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 2 (1968), S. 253-261 
    ISSN: 1432-0827
    Schlagwort(e): Calcium ; Ion ; Binding ; Chondroitin ; Cartilage
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Beschreibung / Inhaltsverzeichnis: Résumé La liaison du calcium par le sulfate de chondroitin C a été étudiée en utilisant des méthodes biologiques et physicochimiques pour la détermination quantitative du calcium ionique. Les valeurs moyennes pour logK j, le logarithme de la constante de formation non corrigée d'un complexe calcium-sulfate de chondroitin C, sont 1,64 par la technique de cœur de grenouille, 1,55 par la méthode de murexide, 1,39 par l'ultrafiltration et 1,04 par l'électrode sélective du calcium. L'ordre de grandeur de ces valeurs suggèrent que le sulfate de chondroitin C a une capacité de liaison pour calcium relativement élevée, mais les valeurs calculées pour un paramètre d'échangeK p indiquent que le calcium a une affinité faible pour le polysaccharide.
    Kurzfassung: Zusammenfassung Die Bindung von Calcium mit Chondroitinsulfat C wurde untersucht mittels biologischer und physikalisch-chemischer Methoden für die quantitative Bestimmung des ionischen Calciums. Im Durchschnitt ergab logK j, der Logarithmus der unkorrigierten Formationskonstante für einen Calciumchondroitinsulfatkomplex, 1,64 mit der Technik des Froschherzens, 1,55 mit der Murexidmethode, 1,39 mittels Ultrafiltration und 1,04 mit den Calciumselektiven Elektroden. Die Größe dieser Werte zeigt, daß Chondroitinsulfat eine relativ hohe Bindungskapazität für Calcium hat, die berechneten Werte für einen AustauschparameterK p jedoch, daß Calcium eine kleine Affinität für Polysaccharide hat.
    Notizen: Abstract The binding of calcium by chondroitin sulfate C was studied by employing biological and physicochemical methods for the quantitative determination of ionic calcium. Mean values for logK j, the logarithm of the uncorrected formation constant for a calcium-chondroitin sulfate complex, were 1.64 with the frog heart technique, 1.55 with the murexide method, 1.39 with ultrafiltration and 1.04 with the calcium selective electrode. The magnitude of these values suggests that chondroitin sulfate has a relatively high binding capacity for calcium, but calculated values for an exchange parameterK p indicate that calcium has a low affinity for the polysaccharide.
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  • 36
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 2 (1968), S. 301-313 
    ISSN: 1432-0827
    Schlagwort(e): Calcium ; Absorption ; Vitamin D
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Materialart: Digitale Medien
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  • 37
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 2 (1968), S. 20-29 
    ISSN: 1432-0827
    Schlagwort(e): Bone Atrophy ; Bone Resorption ; Calcium ; Collagen ; Osteoporosis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Beschreibung / Inhaltsverzeichnis: Résumé Atrophie osseuse d'immobilisation était induite par section de la plexus brachial et/ou désarticulation de la coude. Après 9 bis 12 semaines de désuétude huméri intactes furent examinés par rayons X et leur qualités physiques déterminés. Les humérientiers furent isolés, dégraissés, desséchés au poids constant, et leur teneur en cendre d'os et collagène déterminés. Huit des 10 huméri immobilisés monstrérent radiodensité diminué. La jambe inusitée monstra perte parallèle en poids sec et poids sans gras (−23.2%), en collagène (−25.3%), et en cendre d'os (−26.1%) en comparaison de la jambe normale. Les données monstrèrent que la portion plus grande du tissu osseux perdu en atrophie osseuse d'immobilisation est remplacée par de l'eau, du gras, et des autres matériels organiques inconnus plutôt que par tissu fibreux, et que collagène est perdu en proportion du minéral. La perte proportionellement plus grande du collagène et de la cendre d'os que du poids sec et poids san gras semble dû à une augmentation du matériel organique, non-collagéne, non-lipide, kprobablement protéine.
    Kurzfassung: Zusammenfassung Immobilisations-Knochenatrophie wurde in 10 erwachsenen Hunden herbeigeführt durch Brachialplexusschnitt und/oder Ellenbogenexartikulation. Nach 9–12 Wochen der Immobilisation wurden die intakten Humeri unter Röntgenstrahlen untersucht und ihre physischen Eigenschaften bestimmt. Derintakte Humerus wurde isoliert, entfettet, zu konstantem Gewicht getrocknet und der Knochenaschengehalt und Kollagengehalt bestimmt. Acht der 10 experimentellen (immobilisierten) Humeri demonstrierte Beweis von verringerter Röntgendichte. Die immobilisierte Extremität zeigte ähnlichen Verlust in trockenem, fettfreiem Gewicht (−23,2%) in Kollagen (−25.3%) und Knochenasche (−26,1%) im Vergleich zur normalen Extremität. Die Date deuten an, daß der Hauptanteil des Verlustes des Knochengewebes (bei Immobilisations-Knochenatrophie) von Wasser, Fett und anderen unidentifizierten organischen Substanzen ersetzt wird, als von Faserngewebe und daß Kollagen und Knochenasche im gleichen Verhältnis verloren gehen. Der größere, proportionale Verlust an Kollagen und Knochenasche, eher als der Verlust an fettfreiem Gewicht, scheint in der Zunahme an nicht kollagener, nicht lipoider, organischer Substanz, vermutlich Protein, zu liegen.
    Notizen: Abstract Disuse bone atrophy was induced in 10 adult dogs by means of brachial plexus section and/or elbow disarticulation. After 9 to 12 weeks of disuse intact humeri were examined by X-ray, and their physical properties determined. Thewhole humeri were isolated, defatted, dried to constant weight, and their mineral and collagen content determined. Eight out of 10 experimental (non-used) humeri demonstrated evidence of decreased radiodensity. The non-used limb demonstrated parallel loss in dry, fat-free weight (−23.2%), in collagen (−25.3%), and in mineral (−26.1%), as compared to the normal limb. The data indicated that the major portion of the lost bone tissue in disuse osteoporosis is replaced by water, fat, and other unidentified organic materials rather than fibrous tissue, and that collagen is lost in equal proportion to mineral. The proportionatelly greater loss of collagen and mineral than of dry, fat-free weight appears to be due to an increase of non-collagenous, non-lipid organic material, presumably protein.
    Materialart: Digitale Medien
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  • 38
    Digitale Medien
    Digitale Medien
    Springer
    Pflügers Archiv 300 (1968), S. 23-34 
    ISSN: 1432-2013
    Schlagwort(e): Electro-Physiology ; Ranvier-Node ; Stationary Current-Voltage Relation ; Calcium ; Elektrophysiologie ; Ranvierscher Schnürring ; Stationäre Strom-Spannungscharakteristik ; Calcium
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Erhöht man die extracelluläre Calcium-Konzentration, so verschieben sich die Stromextrema der Strom-Spannungsbeziehung des Ranvier-Knotens nach Depolarisationsrichtung. Mit Hilfe einer Gleichung zur Darstellung der Kennlinien läßt sich diese Wirkung durch Änderung eines einzigen Parameters V Tγ beschreiben. Dieser gibt die Spannungslage des Abfalles einer Stufenfunktion wieder, die im Rahmen der Ionentheorie der Kaliumleitfähigkeitsvariablen n ∞ 4 (V) entspricht. Durch Erhöhung von [Ca··] a wird V Tγ nach Depolarisationsrichtung verschoben. Darüber hinaus konnte eine deutliche Abhängigkeit dieses Parameters von [K·] a festgestellt werden. Der Calcium-Einfluß auf das Membranpotential konnte als Konsequenz der Vt r −-Verschiebung interpretiert werden.
    Notizen: Summary An increase of the extracellular calcium-concentration shifts the extreme current values of the current-voltage-relation of a Ranvier-node towards depolarization. This influence can be described by the change of one single parameter V Tγ of an equation representing the current-voltage-characteristic. V Tγ referres to the potential at which the s-shaped step-function of resistance change assumes the arithmetical mean of its limiting values. The step-function compares to the variable of potassium conductance n ∞ 4 (V). An increase of [Ca··] a shifts V Tγ towards depolarizing potentials. V Tγ is also found to depend on [K·] a . The influence of calcium on membrane potential is interpreted as a consequence of the observed shift of V Tγ .
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  • 39
    Digitale Medien
    Digitale Medien
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 260 (1968), S. 444-455 
    ISSN: 1432-1912
    Schlagwort(e): Chlorpromazin ; Calcium ; Zellmembran ; Muskelproteine ; Chlorpromazine ; Calcium ; Cell Membrane ; Muscle Proteins
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Summary 1. The calcium induced increase in ATPase and the rate of calcium uptake of the vesicular fragments of sarcoplasmic reticulum isolated from rabbit skeletal muscle are reduced by reserpine, prenylamine, chlorpromazine and imipramine. 3×10−5M reserpine, prenylamine, chlorpromazine and ∼3×10−4M imipramine are required to produce 50% inhibition of both activities. 2. In the presence of the drugs the rate of calcium exchange at the cessation of calcium uptake is reduced to the same extent as the initial rate of calcium uptake. 3. Neither the calcium storing capacity nor the ability to concentrate calcium are impaired by the drugs. 4. The drugs do not affect the calcium dependent phosphate exchange between ATP and ADP and the calcium dependent formation of phosphoprotein.
    Notizen: Zusammenfassung 1. Reserpin, Prenylamin, Chlorpromazin und Imipramin hemmen sowohl die Geschwindigkeit der Calcium-Aufnahme als auch die der Calcium-induzierten Extra-ATP-Spaltung an isolierten Vesikelmembranen des sarkoplasmatischen Reticulums von quergestreifter Muskulatur des Kaninchens. Die für eine 50%ige Hemmung erforderlichen Konzentrationen betragen beim Reserpin, Prenylamin und Chlorpromazin 3×10−5M, beim Impiramin ∼3×10−4M. 2. Calcium-Efflux und -Influx werden durch die Pharmaka in gleichem Ausmaß gehemmt. 3. Das Konzentrationsvermögen der Vesikel für Calcium wird deshalb durch die Hemmstoffe nicht beeinflußt. 4. Der erste Reaktionsschritt des aktiven Calciumtransports der Vesikel — die Übertragung des Phosphates des ATP auf das Vesikelprotein — wird durch die Pharmaka nicht beeinflußt.
    Materialart: Digitale Medien
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  • 40
    Digitale Medien
    Digitale Medien
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 260 (1968), S. 298-308 
    ISSN: 1432-1912
    Schlagwort(e): Anesthetics, Local ; Adrenal Medulla ; Calcium ; Catecholamines
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Local anesthetics (LA's) were examined for their ability to inhibit medullary catecholamine release from perfused cat adrenal glands in response to calcium (0.5 mM) in the presence of 56 mM KCl. LA's which are esters of p-aminobenzoic acid (including benzocaine), or which possess either an amide group (dibucaine), an amidine group (phenacaine), or an amino alkyl ether linkage (diphenhydramine) all produced a graded inhibition of the action of calcium, which was reversed by excess calcium (3 mM). Benzocaine, which does not possess an alkyl amino nitrogen, was five times more potent than procaine in depressing calciumevoked secretion; benoxinate, as well as tetracaine, which differ from procaine and its dimethyl analogue by possessing substituent groups on the aromatic ring were over thirty times more potent than procaine and dimethyl-procaine. Increasing the pH of the perfusion medium from 7.0–8.3 produced no marked alteration in the ability of procaine, tetracaine, and benzocaine to inhibit the stimulant actions of calcium. It is concluded that the aromatic ring of the LA molecule is more important than the alkyl nitrogen in determining the activity of a given agent in blocking the action of calcium.
    Materialart: Digitale Medien
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  • 41
    Digitale Medien
    Digitale Medien
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 260 (1968), S. 342-365 
    ISSN: 1432-1912
    Schlagwort(e): Myocardium ; Frequency of Contraction ; Action Potential ; Calcium ; Excitation-Contraction Coupling ; Myokard ; Kontraktionsfrequenz ; Aktionspotential ; Calcium ; Elektromechanische Kopplung
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The influence of stimulation frequency on the course of the transmembrane action potential (AP) and on the isometric tension of isolated guinea pig papillary muscles has been investigated. Special attention has been paid to the question whether the observed changes can be due to a frequency dependent increase of the extracellular concentration of Ca2+ and K+. The following results have been obtained: 1. The amplitude of the AP decreases at a stimulation frequency above 2/sec due to a diminished membrane-resting-potential (MRP) and a decrease in overshoot. 2. The duration of the AP is influenced biphasically by increasing the stimulation frequency at relatively low external calcium concentrations (1.2 and 2.4 mM). When the frequency of stimulation is increased, starting at 0.125/sec, the AP duration is prolonged at first and then shortened. At frequencies below 0.125/sec (down to 0.004/sec) the AP duration again increases. The prolongation of the AP in the medium frequency range (between 0.125 and 0.5/sec) is minimal at a higher calcium concentration (4.8 mM). The marked shortening of the AP duration caused by an increase in stimulation frequency above 1/sec corresponds to the frequency dependent increase in isometric tension of the papillary muscle. 3. The AP duration is shortened by 70 msec when the stimulation frequency is raised from 1/sec to 5/sec. After switching back to the lower frequency (1/sec) the disappearance of the frequency effect on the duration of the AP starts with a lower and continues with a higher speed than that on the force of contraction, the original values of both parameters being reached at the same time. 4. The extent of the frequency induced change of the AP duration is almost equal at 30%, 60% and 90% repolarisation. Consequently, the duration of the “plateau” (at 30% repolarisation) is shortened relatively more than the AP duration at 90% repolarisation. 5. The AP duration at 90% repolarisation is influenced by Ca2+ and Na+ antagonistically according to the relation [Ca2+]/[Na+]2 in the frequency range between 0.125/sec and 4.0/sec. In contrast, the extent of the shortening of the “relative duration of the plateau” depends on the external sodium concentration ([Na+] e ). The lesser shortening of the “relative duration of the plateau” at a decreased [Na+] e (70 mM instead of 140 mM) corresponds to a decreased positive inotropic frequency effect. 6. The MRP is decreased by 8 mV when the stimulation frequency is increased from 1/sec to 5/sec. Considering the relation between MRP and [K+] e at a stimulation frequency of 1/sec a frequency induced increase of [K+] e from 5.9 mM to 8–9 mM can be assumed. Such an increase in [K+] e , however, only causes a shortening of the AP duration by 6 msec. Concomitantly, the relative duration of the plateau is prolonged. 7. The shortening of the AP duration of about 70 msec due to an increase of the stimulation frequency from 1/sec to 5/sec equals—as does the augmentation of the contractile force of the muscle—the effect of a two—or threefold elevation of the external calcium concentration. Similarly the lengthening of the AP duration by an increase in stimulation frequency from 0.125 to 0.5/sec at a relatively low external calcium concentration (1.2 mM) equals the effect of raising the [Ca2+] e . 8. The results lead to the conclusion that the influence of the frequency of stimulation on the duration of the action potential is caused mainly by an increase of the calcium concentration at the outside of the cell membrane while the decrease of the membrane-resting-potential as well as of the overshoot may be the result of an extracellular accumulation of K+.
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  • 42
    ISSN: 1432-1912
    Schlagwort(e): Chlorpromazin ; Calcium ; Zellmembran ; Muskelproteine ; Lipide ; Chlorpromazine ; Calcium ; Cell Membrane ; Muscle Protein ; Lipids
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Summary 1. Reserpine, chlorpromazine, prenylamine and imipramine are bound to vesicles isolated from the sarcoplasmic reticulum of rabbit striated muscle cells as well as by the lipids which can be extracted from the vesicular preparations. 2. At concentrations of 5×10−7 M reserpine, chlorpromazine and prenylamine, drug binding can just be detected. At drug concentrations of 10−4 M the drug uptake amounts to 0.1 μmol per mg vesicular protein, 0.2 μmol drug per mg vesicular lipid and ∼0.4 μmol drug per mg phosphatidylcholine. 3. Drug binding is reversible and temperature independent. 4. Drug binding is not diminished when the phospholipids are hydrolysed by phospholipase A, C or D. 5. Drug binding is abolished by hydrogenation of the isolated lipids as well as of the lipids bound to the membranes. 6. In addition calcium uptake the Ca++ induced increase in ATP breakdown and the phosphate transfer reaction are inhibited when the lipids in the membranes are hydrogenated. 7. The normal ATPase as well as the lipid free proteins myokinase and actin are not affected by hydrogenation.
    Notizen: Zusammenfassung 1. Reserpin, Chlorpromazin, Prenylamin und Imipramin werden sowohl von den isolierten Vesikeln des sarkoplasmatischen Reticulums (quergestreifte Muskulatur von Kaninchen) als auch von den aus diesen mit Chloro-form-Methanol (2:1) extrahierten Lipiden gebunden. 2. Bei einer Konzentration von 10−4 M werden Reserpin, Chlorpromazin und Prenylamin von dem intakten Lipoproteinkomplex der Vesikelmembran in Mengen von 0,1 μmol/mg Vesikelprotein, von 0,2 μmol/mg vesikulärem Total-Lipid und von ∼0,4 μmol/mg Phosphatidylcholin (Lecithin) gebunden. Lipidfreies Vesikelprotein hat keine Bindungsfähigkeit. 3. Die Bindung der Pharmaka ist reversibel und temperaturunabhängig. 4. Die Bindungsfähigkeit der Phospholipide ist nicht beeinträchtigt, wenn diese durch Phospholipase A, C oder D hydrolysiert werden. Sie wird jedoch aufgehoben durch Hydrierung der isolierten bzw. der membrangebundenen Lipide. Nach Hydrierung ist auch die Calcium-Aufnahme, die ATP-Extraspaltung und die Phosphatübertragung aufgehoben. 5. Die lipidfreien Proteine Myokinase und Actin werden durch den Hydrierungsvorgang funktionell nicht beeinflußt.
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  • 43
    Digitale Medien
    Digitale Medien
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 258 (1967), S. 59-68 
    ISSN: 1432-1912
    Schlagwort(e): Calcium ; Noradrenaline ; ß-Blockers ; Quinidine ; Guinea-pig auricles. ; Calcium ; Noradrenalin ; ß-Adrenolytica ; Chinidin ; Meerschweinchenvorhof
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Isometrische Kontraktionen von elektrisch konstant gereizten linken Meerschweinchenherzohren wurden unter Einwirkung von Noradrenalin, MHIP, Pronethalol und Chinidin bei extracellulären Calciumkonzentrationen ([Ca] e ) zwischen 0,45 und 7,2 mM untersucht. Noradrenalin führte gegenüber den Kontrollwerten bei verschiedenen [Ca] e zu einer Linksverschiebung der Calcium-Konzentrations-Wirkungskurve. Für die ß-Adrenolytica MHIP und Pronethalol zeigte sich eine Abhängigkeit ihrer negativ inotropen Wirkung von der [Ca] e . In niedriger [Ca] e fand sich eine stärkere Verminderung der Kontraktionsamplitude als in höherer [Ca] e . Die Wirkung von Chinidin auf die Kontraktionskraft der Vorhöfe war von der [Ca] e unabhängig. Die ß-adrenolytische Wirkung von MHIP und Pronethalol bei Kombination mit Noradrenalin war bei allen untersuchten [Ca] e gleich. Außer bei 0,45 mM [Ca] e hatte Chinidin keine Wirkung auf den positiv inotropen Noradrenalineffekt.
    Notizen: Summary Isometric contractions of electrically driven (180/min) left guinea-pig auricles were recorded under the influence of norepinephrine, ß-blocking agents and quinidine at different extracellular calcium concentrations ([Ca] e ) between 0.45 to 7.2 mMol/l. Norepinephrine shifted the concentration-response curve for calcium to the left. The negativ inotropic effects of the ß-blocking agents MHIP and pronethalol depended on the [Ca] e . At low [Ca] e the force of contraction decreased to a larger extent than at high [Ca] e . The action of quinidine on the contractile force of the guinea-pig auricles was independent of the [Ca] e . The ß-adrenergic blocking action of MHIP and pronethalol was the same at all [Ca] e .
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  • 44
    Digitale Medien
    Digitale Medien
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 258 (1967), S. 108-122 
    ISSN: 1432-1912
    Schlagwort(e): Heart ; Noradrenaline release ; Acetylcholine ; Calcium ; Cations ; Herz ; Noradrenalin-Freisetzung ; Acetylcholin ; Calcium ; Kationen
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Die Wirkung veränderter Elektrolyt-Konzentrationen auf die Nordrenalin-Abgabe durch Acetylcholin wurde am isolierten, perfundierten Kaninchenherzen untersucht. Acetylcholin wurde in einer Konzentration von 3 × 10−5 g/ml 30 sec lang in die Aortenkanüle infundiert. Die Perfusionsflüssigkeit enthielt Atropin (3 × 10−6 g/ml) während der ganzen Versuchsdauer. Die von den Herzen in das Perfusat abgegebenen Catecholamine wurden fluorimetrisch bestimmt; außerdem wurden die Herzfrequenz, die Kontraktionsamplitude und der Coronardurchfluß registriert. Bei verminderter Ca++-Konzentration wurde die Noradrenalin-Abgabe durch Acetylcholin herabgesetzt und bei erhöhter Ca++-Konzentration gesteigert; die Spontanabgabe von Noradrenalin wurde durch veränderte Ca++-Konzentrationen nicht beeinflußt. Erhöhung der Mg++-Konzentration beeinflußte die Noradrenalin-Abgabe durch Acetylcholin bei normaler oder verminderter Ca++-Konzentration nicht. Herabsetzung der Konzentrationen von Na+ oder K+ steigerte die Noradrenalin-Abgabe durch Acetylcholin, sofern die Ca++-Konzentration vermindert war. Erhöhung der K+-Konzentration steigerte die Spontanabgabe von Noradrenalin nicht; die Noradrenalin-Abgabe durch Acetylcholin wurde aber herabgesetzt. Aus den Ergebnissen wird gefolgert, daß die Noradrenalin-Freisetzung durch Acetylcholin aus peripheren, sympathischen Nerven einem Ca++-Na+-Antagonismus unterliegt, wie er schon für die Noradrenalin-Freisetzung durch Acetylcholin aus der chromaffinen Zelle beschrieben worden ist (Douglas). Die Versuche, in denen CaCl2 durch MgCl2 und NaCl durch Saccharose oder LiCl substituiert wurden, brachten Hinweise dafür, daß die Noradrenalin-Freisetzung durch Ca-Ionen gefördert und durch Na-Ionen gehemmt wird. Beim Vergleich der vorliegenden Befunde mit entsprechenden Untersuchungen an der chromaffinen Zelle (Douglas) ergaben sich wesentliche Unterschiede hinsichtlich der Bedeutung der Mg++- und besonders einer gesteigerten K+-Konzentration.
    Notizen: Summary The following experiments were done in order to study the effects of alterations in the ionic composition of the perfusion fluid of the isolated rabbit heart on the noradrenaline release caused by acetylcholine. The perfusion fluid contained 3 × 10−6 g/ml atropine throughout the whole experiment. Acetylcholine was infused into the aortic cannula for 30 sec at a concentration of 3 × 10−5 g/ml and this effect was repeated at time intervals of 15 min. Heart rate, contractile amplitude and coronary flow were recorded. The noradrenaline output into the perfusate was measured fluorometrically. Lowering of the calcium concentration decreased the noradrenaline output following administration of acetylcholine. Conversely, elevation of the calcium concentration increased the noradrenaline output. The resting output of noradrenaline was not affected by alterations of the calcium concentration of the perfusion fluid. Magnesium neither antagonized the action of calcium on the noradrenaline release by acetylcholine nor was it effective as a substitute for calcium. Lowering of the sodium or potassium concentration of the perfusion fluid caused an increase in the noradrenaline output following acetylcholine provided the noradrenaline output was initially kept at a submaximal level by decreasing the external calcium concentration. Substantial elevation of the potassium concentration of the perfusion fluid did not affect the resting output of noradrenaline but decreased the output caused by acetylcholine. It is concluded that the release of noradrenaline from the sympathetic nerve ending evoked by acetylcholine is dominated by a calcium-sodium antagonism as previously described for the chromaffin cell (Douglas). The experiments in which CaCl2 was substituted by MgCl2 and NaCl was substituted by sucrose or LiCl provided evidence that calcium ions promote and sodium ions inhibit noradrenaline release. The above findings obtained on the sympathetic nerve endings differ markedly from the results on the chromaffin cell (Douglas) as far as the actions of magnesium or excess potassium are concerned. The effects on noradrenaline output brought about by variations of the ionic concentrations cannot be explained by concomitant alterations of the coronary flow.
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  • 45
    Digitale Medien
    Digitale Medien
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 258 (1967), S. 238-250 
    ISSN: 1432-1912
    Schlagwort(e): Hypothalamus ; Noradrenaline ; Storage ; Calcium ; Acetylcholine ; Hypothalamus ; Noradrenalin ; Speicherung ; Calcium ; Acetylcholin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Schweine-Hypothalami wurden durch Differentialzentrifugieren fraktioniert und der Noradrenalin- sowie der Eiweiß-Stickstoff-Gehalt der gewonnenen sechs Fraktionen bestimmt. Die Fraktionen III (30 000 g), IV (60 000 g) und V (100 000 g) enthalten den größten Noradrenalin-Gehalt pro mg Eiweiß und stellen somit die spezifischen Fraktionen dar, in denen das Noradrenalin hauptsächlich partikulär gebunden vorliegt. Der molare Quotient Noradrenalin/ATP der Fraktion 30 000–100 000 g beträgt 0,56. Die aminspeichernden Vesikel der Fraktion 30 000–100 000 g wurden 60 min lang bei 37°C inkubiert. Die spontane Noradrenalin-Freisetzung ist mit 31% des Ausgangsgehaltes etwa gleich groß wie die spontane Adrenalin-Freisetzung aus isolierten Nebennierenmark-Granula. Reserpin sowie kleine Prenylamin-Konzentrationen (60 nmol/ml) hemmen die spontane Noradrenalin-Freisetzung, während große Prenylamin-Konzentrationen (1,2 μmol/ml) eine fast vollständige Noradrenalin-Verarmung der Vesikel verursachen. Inkubation mit verschiedenen Calcium-Konzentrationen verursacht eine dosisabhängige Noradrenalin-Freisetzung. Acetylcholin ist ebenfalls in der Lage, die spontane Noradrenalin-Freisetzung zu erhöhen. Bei der gleichzeitigen Inkubation mit Calcium und Acetylcholin konnte keine Addition der Wirkungen der beiden Substanzen festgestellt werden. Reserpin vermag die durch Calcium bedingte Noradrenalin-Freisetzung zu hemmen.
    Notizen: Summary In order to study the subcellular distribution of noradrenaline in the hypothalamus this region was removed from pig brains and fractionated by differential centrifugation. From the six obtained fractions fraction III (30,000 g), IV, (60,000 g), and V (100,000 g) contain the highest amounts of noradrenaline per mg protein (69, 60 and 47 ng/mg protein respectively). These fractions represent therefore the main noradrenaline storing fractions of the hypothalamus. The molar ratio noradrenaline/ATP of the vesicles of the fraction 30,000–100,000 g is 0.56. The noradrenaline storing vesicles of the fraction 30,000–100,000 g of the hypothalamus were incubated for 60 min at 37°C. The spontaneous release of noradrenaline amounts to 31% of the original noradrenaline content of the vesicles. It is therefore of the same order of magnitude as the spontaneous release of adrenaline from isolated granules of the suprarenal medulla. Reserpine and prenylamine (60 nmoles/ml) inhibit the spontaneous release of noradrenaline whereas 1.2 μmoles prenylamine/ml deplete the vesicles almost completely. Incubation of the hypothalamus vesicles with calcium chloride (0.31–5.0 μmoles/ml) causes a dose dependent release of noradrenaline. Acetylcholine (55 nmoles/ml) is also able to increase the spontaneous release of noradrenaline. By simultaneous incubation with calcium and acetylcholine no addition of the effects of both substances on the release of noradrenaline could be observed. Reserpine prevents the calcium-induced release of noradrenaline.
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  • 46
    Digitale Medien
    Digitale Medien
    Springer
    Diabetologia 3 (1967), S. 47-49 
    ISSN: 1432-0428
    Schlagwort(e): Calcium ; Magnesium ; Insulin ; Secretion Rabbit ; Pancreas ; Foetus
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Résumé Le glucose, le glucagon, le tolbutamide et la L-leucine stimulent la libération d'insuline par le pancréas de lapin étudié in vitro. Cette stimulation n'a pas lieu lorsque le milieu d'incubation est préparé sans calcium. L'absence de magnésium n'a pas d'effet sur la sécrétion insulinique stimulée par le glucose, alors que le magnésium à la concentration de 10mM exerce un effet inhibiteur. La concentration optimale du calcium extracellulaire pour la sécrétion insulinique est de 2.64 mM. La stimulation de la sécrétion insulinique par le glucose est également supprimée par l'absence de calcium pour le pancréas de foetus de lapin âgé de 27 jours.
    Kurzfassung: Zusammenfassung Die Freisetzung von Insulin aus Kaninchen-Pankreas in vitro wird durch Glucose, Glucagon, Tolbutamid oder L-Leucin stimuliert. In allen diesen Fällen bleibt die Stimulation in Abwesenheit von Calcium in Inkubationsmedium aus. In Abwesenheit von Magnesium stimulierte Glucose die Insulinsekretion weiter, währenddem eine Erhöhung der Magnesiumkonzentration auf 10 mM deutlich hemmend wirkte. Die optimale Sekretion von Insulin erfolgte bei einer Calciumkonzentration von 2.64 mM. In Abwesenheit von Calcium wurde die Freisetzung von Insulin auch aus dem Pankreas von 27 Tage alten Foeten gehemmt.
    Notizen: Summary Glucose, glucagon, tolbutamide and L-leucine stimulated insulin secretion from rabbit pancreas studiedin vitro. In each case stimulation was inhibited by omitting calcium from the incubation medium. The omission of magnesium had no effect on glucose stimulated insulin secretion but 10 mM magnesium inhibited secretion. Optimal secretion of insulin occurred at an extracellular calcium concentration of 2.64 mM. The omission of calcium inhibited glucose-stimulated insulin secretion from pancreas of 27 day rabbit foetuses.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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