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  • 1
    Electronic Resource
    Electronic Resource
    Nuclear and cytosolic calcium levels in NIH 3T3 fibroblasts (1997)
    Springer
    Experimental biology online 2 (1997), S. 1-9 
    Details
    ISSN: 1430-3418
    Keywords: Cytosolic calcium ; Image analysis ; NIH3T3 fibroblasts ; Nuclear calcium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The spatial distribution of intracellular calcium in resting NIH 3T3 fibroblasts loaded with Fura-2 has been studied by digital image analysis. Calibration parameters were determined separately for the nucleus and the cytosol to take into account possible differences in the physico-chemical properties of the two compartments and were found not to differ significantly. The apparent resting calcium concentration in these cells was found to be significantly lower in the nucleus than in the cytoplasm; however, this difference appears to be an artefact arising from the presence in the cytoplasm of regions with higher calcium levels. Application of thapsigargin, to block active uptake of calcium into these compartments, substantially eliminated the differences between nuclear and cytosolic calcium concentrations. These observations indicate that nuclear and cytosolic calcium are in equilibrium in the resting fibroblasts and argue against the existence of diffusional barriers between these two compartments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00898-997-0009-4
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Ionic selectivity of the coupled and uncoupled currents carried by the amino acid transporter KAAT1 (1999)
    Springer
    Pflügers Archiv 438 (1999), S. 788-796 
    Details
    ISSN: 1432-2013
    Keywords: Intestinal cotransport Xenopus oocyte KAAT1
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. The ability of the intestinal amino acid cotransporter KAAT-1 expressed in Xenopus oocytes to transport different cations in either amino acid coupled or uncoupled manner was studied using voltage-clamp conditions. KAAT1-expressing oocytes exhibit a transporter-related current in the absence of organic substrate (uncoupled current). In the presence of various alkali cations the amplitude of this current follows the sequence: I Li〉I Na〉I K≅I Rb≅I Cs. Addition of 1 mM leucine causes large increases in K+ and Na+ currents, while the Li+ current undergoes a more complex change and Rb+ and Cs+ currents are only marginally affected. Pre-steady-state currents in the absence of organic substrate are apparent when Na+, K+, or Li+ are the bathing ions; analysis of these currents in terms of charge movement reveals that Na+, K+, and Li+ interact differently with the transporter. The uncoupled current in mixtures of Na+ and Li+ fails to exhibit anomalous mole-fraction behavior. Kinetic analysis of ion binding and uncoupled permeation argues against a multi-ion single-file mechanism in the KAAT1 cotransporter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004249900132
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  • 3
    Electronic Resource
    Electronic Resource
    Properties of the Ca2+-activated Cl− current of Xenopus oocytes (1997)
    Springer
    Cellular and molecular life sciences 53 (1997), S. 604-610 
    Details
    ISSN: 1420-9071
    Keywords: Key words. Calcium-dependent chloride current; Xenopus oocyte; calcium influx.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. The properties of the Ca2+-activated Cl− current of Xenopus oocytes have been investigated by voltage-clamp and injections of D-3-deoxy-3-fluoro-myo-inositol 1,4,5-trisphosphate (3-F-InsP3). Following 3-F-InsP3 injection, a transient phase of Ca2+-activated Cl− current occurred, caused by Ca2+ release from internal stores; subsequently, a secondary, long-lasting, current was recorded, signaling Ca2+ influx from the exterior (ICRAC). Changes in external Cl− during the sustained phase produced the expected shifts in reversal potential (Erev), while the conductance varied opposite to the predictions of simple electrodiffusional theory. Application of depolarizing pulses soon (10 s) after 3-F-InsP3 injection elicited membrane currents exhibiting a single exponential rise. During the sustained subsequent phase, the current elicited by depolarizations showed an early peak followed by a prominent decline. During the sustained phase, removal of calcium from the external solution, or its substitution with Ba2+, abolished voltage- and time-dependent components of the depolarization-induced current. Slope conductance analysis of the inactivating records revealed, in addition to the decline of the Ca2+-activated Cl− current, the presence of a second, inwardly directed current. This could be identified as a slowly inducible Na+ current already described in Xenopus oocytes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s000180050079
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  • 4
    Electronic Resource
    Electronic Resource
    Dietary spermine supplementation induces intestinal maturation in sea bass (Dicentrarchus labrax) larvae (1997)
    Springer
    Fish physiology and biochemistry 16 (1997), S. 479-485 
    Details
    ISSN: 1573-5168
    Keywords: polyamine ; spermine ; sea bass ; larvae ; intestinal maturation ; pancreatic enzymes ; intestinal enzymes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Sea bass (Dicentrarchus labrax) larvae were fed microparticulated compound diet containing 0 (FP0), 0.10 (FP10) and 0.33% (FP33) of a polyamine, spermine, from day 20 to day 38. LP group was fed live prey. This group exhibited the highest growth and survival. The addition of spermine did not lead to growth enhancement. A 33% survival improvement was obtained in FP33 group compared to FP0 group. The spermine addition affected the activity of pancreatic enzymes, trypsin, chymotrypsin and amylase, during larvae development. This non specific effect suggested that the action of spermine would be mediated by hormones. In the intestine, the FP33 group exhibited from day 31 higher activities of brush border membrane enzymes (leucine aminopeptidase and alkaline phosphatase) and lower level in a cytosolic enzyme (leucine-alanine peptidase) compared to FP10 and FP0 group. The diet containing the highest spermine level induced an enzymatic profile similar to that obtained in LP group and characteristic of a mature enterocyte. The initiation of enterocyte maturation at a proper development stage was associated to the survival improvement observed in FP33 group.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007786128254
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  • 5
    Electronic Resource
    Electronic Resource
    Amylase and trypsin responses to intake of dietary carbohydrate and protein depend on the developmental stage in sea bass (Dicentrarchus labrax) larvae (1996)
    Springer
    Fish physiology and biochemistry 15 (1996), S. 237-242 
    Details
    ISSN: 1573-5168
    Keywords: amylase ; trypsin ; proteins ; carbohydrates ; marine fish larvae ; pancreatic maturation ; enzyme adaptation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Sea bass (Dicentrarchus labrax) larvae were fed from day 15 to day 35 with 4 isoenergetic formulated diets that varied in protein (30, 40, 50, 60%) and carbohydrate (37, 27, 17, 7%) content. The diets were designated as P30, P40, P50 and P60, respectively. Best growth and survival were noted for P50 larvae. Poor growth and survival were observed for P30 larvae. The specific activity of amylase increased in direct relation to the dietary carbohydrate level from day 18 onwards. This increase was the result of extensive amylase synthesis. Trypsin activity was positively correlated with dietary protein level only at day 35. This study shows that the mechanisms involved in amylase regulation are efficient in very young sea bass larvae, while those related to trypsin appear later in ontogeny and thus suggests an age-dependent regulation of enzyme synthesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01875574
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  • 6
    Electronic Resource
    Electronic Resource
    Dietary regulation of activities and mRNA levels of trypsin and amylase in sea bass (Dicentrarchus labrax) larvae (1998)
    Springer
    Fish physiology and biochemistry 19 (1998), S. 145-152 
    Details
    ISSN: 1573-5168
    Keywords: sea bass ; larvae ; dietary adaptation ; gene regulation ; trypsin ; amylase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Specific activities and mRNA levels of trypsin and amylase were studied in sea bass larvae. From day 20 to day 40, Dicentrarchus labrax were fed two rations of one day old Artemia: satiation (LP) and one-eighth of the satiation ration (LP/8) or two isoenergetic compound diets that varied in protein (30 and 60%) and carbohydrate (37 and 7%) content (FP30 and FP60 respectively). Trypsin mRNA levels and specific activities were mainly influenced by the nature of dietary protein and the Artemia ration. By using fish meal as protein source, dietary protein concentration did not affect either mRNA level nor specific activity of trypsin. These results suggested that the trypsin synthesis was not affected at a transcriptional level by the protein ration, i.e., Artemia ration. Decrease in amylase mRNA observed from day 29 in the four dietary groups suggested that this decrease in amylase expression is genetically programmed during sea bass larvae development. Nevertheless, the composition and the quantity of the diet influenced the amylase specific activities revealing primarily translational regulation of amylase. This study shows for the first time that the molecular mechanisms which control the dietary adaptation of trypsin and amylase are independently regulated, age-dependent and influenced by the composition and the quantity of the diet.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007775501340
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    Paper (German National Licenses)
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