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  • Cell culture  (6)
  • Springer  (6)
  • American Physical Society
  • 1
    Electronic Resource
    Electronic Resource
    Nitrate reductase activity in Paul's scarlet rose suspension cultures and the differential role of nitrate and molybdenum in induction (1978)
    Springer
    Planta 141 (1978), S. 183-189 
    Details
    ISSN: 1432-2048
    Keywords: Antimetabolites ; Cell culture ; Enzyme induction ; Molybdenum ; Nitrate reductase ; Rosa, Paul's Scarlet
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Induction of nitrate reductase (EC 1.6.6.1) activity was measured in Paul's Scarlet rose cell suspensions cultured in media containing nitrate (NO 3 - ) or urea (U) as nitrogen source, and with (+Mo) or without molybdenum (-Mo). There was a lag of 30 min during induction by NO 3 - in +Mo cultures but no lag occurred during induction after adding Mo to NO 3 - -Mo or to U-Mo cultures preincubated with NO 3 - . Actinomycin D, cycloheximide, and puromycin completely blocked induction by NO 3 - , but had no effect on the initial rate of induction by Mo. Cycloheximide and puromycin blocked induction by NO 3 - more quickly than actinomycin D. Induction by NO 3 - appeared to involve mRNA-dependent synthesis of apoprotein followed by rapid activation with molybdenum in intact cells independently of protein synthesis. Nitrate-induced apoprotein appeared less stable than the holoenzyme. When induced by NO 3 - in the absence of Mo, apoprotein concentration was about half the amount of maximally induced nitrate reductase. Cycloheximide stabilised preformed nitrate reductase which disappeared steadily in the presence of puromycin. Apoprotein was not stabilised by either antimetabolite.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00387887
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  • 2
    Electronic Resource
    Electronic Resource
    Nitrate reductase activity and growth in Paul's Scarlet rose suspension cultures in relation to nitrogen source and molybdenum (1976)
    Springer
    Planta 133 (1976), S. 27-34 
    Details
    ISSN: 1432-2048
    Keywords: Rose ; Paul's Scarlet ; Cell culture ; Nitrate reductase ; Molybdenum ; Enzyme induction ; Enzyme assay
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Growth and nitrate reductase activity were measured in Paul's Scarlet rose cell suspensions, cultured in media purified from molybdenum and containing nitrate or urea as sole nitrogen source with or without added Mo. Urea could replace nitrate to yield 80% of the fresh weight in nitrate medium. Nitrate reductase activities were compared by in vivo and in vitro assays. The latter varied due to inactivation during extraction. Compared with activities in cells in complete NO3 - medium, activity in NO3 --Mo cells was reduced to 30% and, in urea-grown cells, to trace amounts. Increases in nitrate reductase activity were found when NO3 - alone was added to NO3 - or urea+Mo cultures. In NO3 --Mo cultures, Mo alone or with NO3 - caused a similar increase in activity, whereas urea-Mo cultures required both NO3 - and Mo for enzyme induction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00386002
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  • 3
    Electronic Resource
    Electronic Resource
    Morphological and physiological aspects of melanophores in primary culture from tadpoles of Xenopus laevis (1979)
    Springer
    Cell & tissue research 198 (1979), S. 397-409 
    Details
    ISSN: 1432-0878
    Keywords: Melanophores ; Xenopus laevis ; Tadpole ; Cell culture ; Melanophore-stimulating hormone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Melanophores from tadpoles of Xenopus laevis (Daudin) were isolated by digestion of tail fins with acetyltrypsin and collagenase and maintained in primary culture for 6 weeks up to 3 months. Within 36 to 72 h the melanophores develop one to eight dendritic processes per cell; secondary and tertiary branchings of the processes were frequently observed. The melanophores in primary culture disperse under the influence of α-MSH or cyclic AMP; upon rinsing out these substances the cells aggregate. In darkness, about 40 % of the cells disperse their pigment, whereas under illumination the pigment of the melanophores aggregates. To date, attempts to initiate cell division in melanophores have not been successful.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00234185
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  • 4
    Electronic Resource
    Electronic Resource
    The morphology of cultured melanophores from tadpoles of Xenopus laevis: Scanning electron microscopical observations (1980)
    Springer
    Cell & tissue research 211 (1980), S. 179-189 
    Details
    ISSN: 1432-0878
    Keywords: Melanophores ; Pigment migration ; Xenopus laevis ; Cell culture ; Scanning electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Tail-fin melanophores of tadpoles of Xenopus laevis (Daudin) in primary culture were examined scanning electron microscopically in the aggregated and in the dispersed state. After isolation, the melanophores are spherical, but within 24 h they develop thin filopodia for attachment to the substratum. Subsequently, cylinder-like as well as flat sheet-like processes are formed, which adhere to the substratum with terminal pseudopodia and filopodia. The processes of adjacent melanophores contact each other, thus forming an interconnecting network between the melanophores. In the aggregated state the central part of the melanophore is spherical and voluminous. Both the central part and the processes bear microvilli. In melanophores with dispersed melanosomes the central part is much flatter; the distal parts have a thickness that equals a monolayer of melanosomes. The surface of the cell bears only scarce microvilli. These features indicate that melanophores do not have a fixed shape and that pigment migration is accompanied by reciprocal volume transformation between the cell body and its processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00236441
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  • 5
    Electronic Resource
    Electronic Resource
    Variability among plants and their progeny regenerated from protoplasts of Su/su heterozygotes of Nicotiana tabacum (1983)
    Springer
    Theoretical and applied genetics 66 (1983), S. 67-75 
    Details
    ISSN: 1432-2242
    Keywords: Cell culture ; Mesophyll protoplasts ; Somaclonal variation ; Mutagenesis ; Aurea mutant ; Tobacco
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Mesophyll protoplasts of Nicotiana tabacum, heterozygous for the sulfur locus (Su/su), were isolated and more than 2,200 calli were cultured. More than 8,000 regenerated shoots were analyzed for leaf colour. Cell culture regimes included media for normal and stressed growth conditions with both short and long culture periods. An additional treatment included N-methyl-N′-nitro-N-nitrosoguanidine mutagenesis. An analysis of the regenerated shoots showed that an extended culture period led to an enhanced frequency of variant colony types, i.e. colonies producing both parental (Su/su) and non-parental (Su/Su or su/su) plants. NNG at 10 mg/l also enhanced the frequency of variant colony types. In some treatments there was also an increase in non-morphogenic colonies but this was independent of genetic changes at the sulfur locus. The frequency of dark green spots and twin spots, presumed to result from somatic crossing-over, was higher in the leaf cells of regenerated plants after both prolonged cell culture and chemical mutagenesis. Genetic analysis of the progeny of selfed regenerants revealed additional tissue culture induced variability with respect to segregation ratios of the different sulfur phenotypes. About two thirds of the lines tested segregated in accordance with a 1∶2∶1 Mendelian ratio. The remainder deviated from the expected segregation pattern and some lines also showed heterogeneity between progeny families derived from different seed capsules of the same plant. These results demonstrate that genetic changes affecting a specific locus and segregation patterns in progeny of regenerated plants are induced during cell culture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00281851
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  • 6
    Electronic Resource
    Electronic Resource
    Characteristics of cells derived from the girdle region of the pre-implantation blastocyst of the donkey (1986)
    Springer
    Cell & tissue research 246 (1986), S. 343-352 
    Details
    ISSN: 1432-0878
    Keywords: Blastocyst ; Cell culture ; PMSG ; Donkey
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The establishment of a monolayer culture of cells derived from the girdle region of a 34-day-old donkey conceptus is described. These cells have had over 100 repeated passages in culture. Low levels of pregnant mares' serum gonadotrophin (PMSG, eCG) could be detected in the cells by indirect immunofluorescence using some monoclonal anti-eCG antibodies, but the cells did not secrete eCG as measured by radioimmunoassay or inhibition of haemagglutination. There was marked nuclear polymorphism with binucleate and occasional multinucleate cells. The cells were strongly reactive with wheatgerm agglutinin and concanavalin A suggesting the synthesis of many glycosylated products. Some cells were reactive with antisera to prekeratin, others with antisera to vimentin. The cells also contained actin (showing peculiar intercellular communications), α-actinin and tubulin. They were able to metabolize certain steroid precursors, but there was no definitive evidence for the presence of aromatase or Δ5-3β-hydroxysteroid dehydrogenase in these cells. This cell line appears to resemble trophectodermal girdle epithelium at a stage of development prior to the onset of eCG production, and may be useful in studies on the control of expression of this substance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00215896
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