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  • Microtubules  (40)
  • Nicotiana
  • nitrogen
  • phosphorus
  • Springer  (86)
  • Blackwell Publishing Ltd
  • National Academy of Sciences
  • 1990-1994
  • 1980-1984  (86)
  • 1925-1929
  • 1983  (33)
  • 1980  (53)
Collection
Keywords
Publisher
  • Springer  (86)
  • Blackwell Publishing Ltd
  • National Academy of Sciences
  • Wiley-Blackwell  (1)
Years
  • 1990-1994
  • 1980-1984  (86)
  • 1925-1929
Year
  • 1
    Electronic Resource
    Electronic Resource
    Fertilizer regime and changes in the phosphate and potash status of a silty marine clay soil during 25 years (1980)
    Springer
    Nutrient cycling in agroecosystems 1 (1980), S. 95-101 
    Details
    ISSN: 1573-0867
    Keywords: soil fertility ; phosphorus ; potassium ; green manure ; crop rotation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Changes in the soil phosphorus and potassium status on three farming systems in the Northeast Polder during 25 years are related to the fertilizer regime over this period. The changes in the nutrient status of the soil are reflected in fertilizer policy. High rates of phosphate dressings markedly increased the phosphate status of the soil and built up a reserve of phosphate. In contrast, the potassium status decreased by about half, because only potatoes in the rotation were dressed with potassium. Methods of fertilization are discussed and suggestions are made with regard to possible improvements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01073181
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  • 2
    Electronic Resource
    Electronic Resource
    Migration and division of cleavage nuclei in the gall midge,Wachtliella persicariae (1980)
    Springer
    Development genes and evolution 188 (1980), S. 65-73 
    Details
    ISSN: 1432-041X
    Keywords: Nuclear migration ; Cleavage ; Microtubules ; Ultrastructure ; Gall midge
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In the eggs ofWachtliella persicariae the cleavage nuclei move relative to the surrounding ooplasm. This ‘active’ migration is caused by an organelle whose ultrastructure was studied throughout the mitotic cycle. It consists of a greatly enlarged polar cytaster derived from the mitotic apparatus, linked to the nucleus by 100 Å filaments. The microtubules of the cytaster were found only during periods of active nuclear migration, i.e., from the onset of anaphase to the early prophase of the next mitotic cycle. They are always solitary and follow the course of the astral rays, which are known to temporarily adhere to peripheral structures of the egg cell and to exert tractive forces. In contrast to the cytaster microtubules, the microtubules in the spindle are bundled and persist from early metaphase through late telophase. During ontogenesis the first migration cytaster is built up between 3 and 12 min after oviposition near the anterior egg pole, in the vicinity of the sperm nucleus. In non-inseminated eggs time lapse films show a migration cytaster to develop autonomously in a region free from nuclei, but it does not follow the normal path of the male pronucleus. In several cases the female pronucleus, which remains without a cytaster of its own, was observed to move to the cytaster generated in the absence of the male pronucleus. Whether or not it is adhering to a nucleus, the cytaster divides into two at the correct time, i.e, corresponding to the first cleavage division in fertilized eggs. In some non-inseminated eggs this type of ‘pseudocleavage’ has been observed to occur repeatedly, giving rise to an increasing number of anucleate cytasters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00848611
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  • 3
    Electronic Resource
    Electronic Resource
    Comparison of proteins synthesized in vivo and in vitro by mRNA from isolated protoplasts (1980)
    Springer
    Planta 148 (1980), S. 453-454 
    Details
    ISSN: 1432-2048
    Keywords: mRNA ; Protein synthesis ; Protoplasts ; Nicotiana ; Translation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Studies of proteins synthesized in vitro by messenger RNA (mRNA) extracted from tobacco protoplasts showed that the changes in protein synthesis and especially the lack of certain proteins observed previously in isolated protoplasts did not result from a failure of translation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02395314
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  • 4
    Electronic Resource
    Electronic Resource
    Influence of leaves and roots on meristem development inNicotiana tabacum L. cv. Wisconsin 38 (1980)
    Springer
    Planta 148 (1980), S. 462-467 
    Details
    ISSN: 1432-2048
    Keywords: Flower formation ; Leaves (in flower formation) ; Meristem (shoot) ; Nicotiana ; Roots (and flower formation)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The terminal, apical shoot meristem ofN. tabacum cv. Wisconsin 38 normally differentiates into a flower after producing 30 to 40 nodes. The influence of leaves and roots on the regulation of flowering was evaluated by counting the number of nodes produced after removal of leaves or the induction of adventitious roots. Leaf removal has no effect on the number of nodes produced before flower formation. Root induction significantly increases the number of nodes produced before flower formation. The plant behaves as if it were measuring the number of nodes between the meristem and the roots as a means of regulating meristem conversion from vegetative to floral differentiation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02395316
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  • 5
    Electronic Resource
    Electronic Resource
    Polysomes from expanded tobacco leaves (1980)
    Springer
    Planta 148 (1980), S. 491-497 
    Details
    ISSN: 1432-2048
    Keywords: Leaves (polysomes) ; Nicotiana ; Polysomes ; Poly(A)+ RNA ; Protein synthesis ; RNA (polysomal, polyA+)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The isolation of intact polysomes from leaves of tobacco (Nicotiana tabacum L.) is dependent on the age and state of development of leaves. Undegraded polysomes from young leaves in the early stages of expansion can be isolated easily by extracting the leaves in ice-cold extraction buffer (200 mM tris(hydroxymethyl)aminomethylmethane(Tris)-HCl, pH 9.0; 400 mM KCl; 200 mM sucrose; 35 mM MgCl2). Medium-size leaves give best yields of undegraded polysomes when extractions are carried out in the above buffer and in the presence of ethyleneglycol-bis-(β-amino-ethyl ether)-N,N′-tetracetic acid (EGTA) and mercaptoethanol. Isolation of polysomes from large, nearly fully expanded (mature) leaves requires all of the above plus diethyldithiocarbamate (DIECA) in the extraction medium. An extraction medium consisting of 25 mM EGTA, 0.01 M mercaptoethanol, 25 mM DIECA and 0.5% of the nonionic detergent, Nonidet-P40 (NP 40) was found to be very suitable for extraction of polysomes from all developmental stages of leaves. The polysomes extracted in the above medium showed active translation of protein in the wheat-germ in-vitro protein-synthesizing system. The translational products were similar when translations were carried out directly with polysomes or polysomal RNA, or polysomal poly(A)+ RNA from tobacco leaves. Poly(A)− polysomal RNA was a poor template in the in-vitro wheat-germ system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02395320
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  • 6
    Electronic Resource
    Electronic Resource
    Nutritional requirements of protoplast-derived, haploid tobacco cells grown at low cell densities in liquid medium (1980)
    Springer
    Planta 149 (1980), S. 7-18 
    Details
    ISSN: 1432-2048
    Keywords: Auxin metabolism ; Cell suspensions (low density) ; Medium conditioning ; Nicotiana ; Nitrogen metabolism ; Protoplasts ; Vitamin requirements
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Preliminary attempts to define a completely synthetic medium able to support divisions of haploid tobacco mesophyll protoplasts at low initial densities have failed. High protoplast concentrations together with large amounts of naphtaleneacetic acid in the medium (3 mg l-1 NAA) were required for maximal induction of protoplast division. However, cell suspensions derived from haploid protoplasts after four days of preculture at high initial cell densities could be diluted to densities as low as 1–4 cells ml-1, provided the concentration of NAA in the medium was lowered to below 0.3 mg l-1. The optimal NAA supply for low cell density growth was affected by the nature of the nitrogen source. A simple minimal medium which supports the growth of these haploid cells with a plating efficiency of 30–40%, independent of the cell density in the range of 1–4 to 3·104 cells ml-1, has been established. In this medium inositol was the only vitamin stringently required for growth. Growth of cells at low densities was also possible in a medium initially containing 3 mg l-1 NAA, provided it was conditioned by the growth of protoplasts at high densities. Preliminary experiments with [14C]NAA showed that the amount of free NAA remaining in the medium after preincubation at high densities was drastically reduced. Simultaneously, NAA conjugates accumulated in the medium. The implications of these results are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00386221
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  • 7
    Electronic Resource
    Electronic Resource
    Characterization of a cytoplasmic auxin receptor from tobacco-pith callus (1980)
    Springer
    Planta 149 (1980), S. 44-47 
    Details
    ISSN: 1432-2048
    Keywords: Auxin receptor ; Callus ; Nicotiana
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cultured tobacco-pith tissue contains a cytoplasmic receptor for indoleacetic acid (IAA). The concentration of binding sites is very low in comparison to that of several auxin receptors found by other investigators. A few obvious possible causes (degradation or inactivation) were investigated. From the results we conclude that the low number of binding sites is real. The receptor binds IAA optimally at pH 7.5–7.8 and at a temperature of 24–30°C, when incubated for 25–30 min. The binding is very specific, as is shown by competition experiments. The concentration of the receptor in the callus tissue changes dramatically during each culture period, which suggests a possible role in development. The receptor was partly purified by gel filtration on Sepharose 6B followed by ion-exchange chromatography on DEAE-cellulose.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00386225
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  • 8
    Electronic Resource
    Electronic Resource
    Reorganization of cortical microtubules and cellulose deposition during leaf formation in Graptopetalum paraguayense (1980)
    Springer
    Planta 149 (1980), S. 181-195 
    Details
    ISSN: 1432-2048
    Keywords: Cell walls ; Cellulose ; Graptopetalum ; Microtubules
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In the “regeneration” of a shoot from a leaf of the succulent, Graptopetalum paraguayense E. Walther the first new organs are leaf primordia. The original arrangement of cellulose microfibrils and of microtubules (MTs) in the epidermis of the leaf-forming site is one of parallel, straight lines. In the new primordium both structures still have a congruent arrangement but it is roughly in the form of concentric circles that surround the new cylindrical organ. The regions which undergo the greatest shift in orientation (90°) were studied in detail. Departures from the original cellulose alignment are detected in changes in the polarized-light image. Departures from the original cortical MT arrangement are detected using electron microscopy. The over-all reorganization of the MT pattern is followed by the tally of MT profiles, the various regions being studied in two perpendicular planes of section. This corrects for the difference in efficiency in counting transverse versus longitudinal profiles of MTs. Reorientation takes place sporadically, cell by cell, for both the cellulose microfibrils and the MTs, indicating a coordinated reorientation of the two structures. That MTs and cellulose microfibrils reorient jointly in individual cells was shown by reconstruction of the arrays of cortical MTs in paradermal sections of individual cells whose recent change in the orientation of cellulose deposition had been detected with polarized light. Closeness of the two alignments was also indicated by images where the MT and microfibril alignments co-varied within a single cell. The change-over in alignment of the MTs appears to involve stages where arrays of contrasting orientation co-exist to give a criss-cross image. During this critical reorganization, the frequency of the MTs is high. It falls during subsequent enlargement of the organ. It was found that the rearrangement of the cortical MTs to approximate a series of concentric circles on the residual meristem occurred before the emergence of leaf primordia. Through their apparent influence on microfibril alignments, the changes in MT disposition, described here, have the potential to generate major biophysical changes that accompany organogenesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00380881
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  • 9
    Electronic Resource
    Electronic Resource
    The effect of light on the production of ethylene from 1-aminocyclopropane-1-carboxylic acid by leaves (1980)
    Springer
    Planta 149 (1980), S. 196-199 
    Details
    ISSN: 1432-2048
    Keywords: 1-Aminocyclopropane-1-carboxylic acid ; Avena ; Ethylene ; Etiolation ; Light (ethylene production) ; Nicotiana
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract White light inhibits the conversion of 1-amino-cyclopropane-1-carboxylic acid (ACC) in discs of green leaves of tobacco (Nicotiana tabacum L.) and segments of oat (Avena sativa L.) leaves by from 60 to 90%. Etiolated oat leaves do not show this effect. The general nature of the effect is shown by its presence in both a mono- and a dicotyledon. Since the leaves have been grown and pre-incubated in light, yet can produce from 2 to 9 times as much ethylene in the dark as in the light, it follows that the light inhibition is fully reversible. The inhibition by light is about equal to that exerted in the dark by CoCl2; it can be partly reversed by dithiothreitol and completely by mercaptoethanol. Thus the light is probably acting, via the photosynthetic system, on the SH group(s) of the enzyme system converting ACC to ethylene.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00380882
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  • 10
    Electronic Resource
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    Correlation between the nicotine content of tobacco plants and callus cultures (1980)
    Springer
    Planta 149 (1980), S. 205-206 
    Details
    ISSN: 1432-2048
    Keywords: Callus cultures ; Nicotiana ; Nicotine ; Tissue cultures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Callus cultures of two low-alkaloid lines of Nicotiana tabacum L. had considerably lower nicotine contents than cultures from the respective highalkaloid cultivars which were isogenic except for the two loci for alkaloid accumulation. Thus, there was a strong correlation between the nicotine content of callus cultures and the plants from which they were derived.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00380884
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  • 11
    Electronic Resource
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    Anti-microtubular herbicides and fungicides affect Ca2+ transport in plant mitochondria (1980)
    Springer
    Planta 149 (1980), S. 336-340 
    Details
    ISSN: 1432-2048
    Keywords: Ca2+ transport ; Fungicides ; Herbicides ; Microtubules ; Mitochondria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The herbicides amiprophosmethyl (APM) trifluralin, and oryzalin as well as the fungicides methylbenzimidazolyl carbamate (MBC), O-isopropyl N-phenyl carbamate (IPC), and chlorisopropyl N-phenyl carbamate (CIPC), which are known to cause the destruction of microtubules in vivo but do not interfere with tubulin polymerization in vitro, have been examined with respect to their ability to affect Ca2+ transport in isolated cell organelles. In contrast to colchicine which has no effect on Ca2+ transport in isolated mitochondrial and microsomal fractions, all of the substances investigated caused considerable reduction of ca2+ net uptake into mitochondrial but not into microsomal fractions. This reduction has been shown to be due to an increase in passive Ca2+ efflux. These results have been extrapolated to in vivo situations where they are postulated to act by raising cytoplasmic Ca2+ levels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00571167
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  • 12
    Electronic Resource
    Electronic Resource
    Auxin-binding by particulate fractions from tobacco leaf protoplasts (1980)
    Springer
    Planta 150 (1980), S. 9-12 
    Details
    ISSN: 1432-2048
    Keywords: Auxin binding ; Nicotiana ; Plasma membrane ; Protoplast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In vitro binding of 1-naphthaleneacetic acid (NAA) to particulate fractions from tobacco leaf protoplasts was studied. In freshly isolated protoplasts no specific binding could be detected, whereas it was present in particulate fractions from tobacco leaves. It is concluded that the NAA-binding-sites are probably located at the external face of the plasma membrane; they are destroyed during protoplast isolation by proteolytic enzymes in the cellulase and macerozyme preparations. After culturing the protoplasts for 3–4 d, the first cell divisions were observed and at the same time specific NAA-binding became detectable. The affinity constant for NAA was approx. 2·106 mol-1 and the number of binding sites increased during further culture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00385607
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  • 13
    Electronic Resource
    Electronic Resource
    Factors influencing the incidence of habituation for cytokinin of tobacco pith tissue in culture (1980)
    Springer
    Planta 150 (1980), S. 264-268 
    Details
    ISSN: 1432-2048
    Keywords: Cytokinin habituation ; Habituation, cytokinin ; Nicotiana ; Position effects (habituation) ; Size effects (habituation) ; Tissue culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Pith tissue of Nicotiana tabacum L. cv. “Havana 425” exhibits a gradient in its tendency to habituate for cytokinin on an auxin-containing medium at 35° C, about 10° C above the standard culture temperature. Explants of pith from below the 8th to 11th internode, counting from the bottom of the plant, rarely habituate for cytokinin; explants from above this threshold habituate rapidly. The explants must also be above a critical size, about 20–30 mg, to habituate. There was a pronounced interaction between size and position effects; the threshold position for cytokinin habituation shifted upward with decreasing explant size.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00390836
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  • 14
    Electronic Resource
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    Stimulation by abscisic acid of RNA synthesis in discs from healthy and tobacco mosaic virus-infected tobacco leaves (1980)
    Springer
    Planta 150 (1980), S. 349-353 
    Details
    ISSN: 1432-2048
    Keywords: Abscisic acid ; Nicotiana ; Ribonucleic acid synthesis ; Tobacco mosaic virus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Uptake of abscisic acid from the culture medium by discs of healthy and tobacco mosaic virus-infected tobacco leaves was measured. Small (two to five-fold) increases in abscisic acid concentration in discs caused increases in rates of [3H]uridine and [3H]adenine incorporation into total nucleic acid, virus RNA and host ribosomal RNA. Net accumulation of virus RNA was also enhanced by abscisic acid. This evidence for stimulation of RNA synthesis is compared with previous reports showing inhibition of RNA synthesis in other tissues. It is suggested that the increase in endogenous abscisic acid caused by tobacco mosaic virus infection may be at least partly responsible for observed increases in rates of RNA synthesis after infection.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00390168
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  • 15
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    The role of peroxidase isoenzyme groups of Nicotiana tabacum in hydrogen peroxide formation (1980)
    Springer
    Planta 147 (1980), S. 467-470 
    Details
    ISSN: 1432-2048
    Keywords: Hydrogenperoxide ; Lignification ; Nicotiana ; Peroxidase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Three peroxidase isoenzyme-groups found in cell walls of tobacco were tested for their capacity to form H2O2. Isoenzyme-group GI, located only in cell walls (GII and GIII are also found in protoplasts) showed the highest Kapp-value for H2O2-formation. The lowest Kapp-value, i.e., maximal H2O2-formation was received for group GIII which is ionically bound to the cell wall. As shown before, GI yields maximal polymerization rates for coniferyl- and p-coumarylalcohol. These facts indicate that each of the peroxidase isoenzyme groups of the cell wall is involved with different catalytic functions within the same pathways of H2O2-formation and succeeding lignification. H2O2-formation catalyzed by all 3 groups was increased by very low concentrations of Mn2+-ions. The required amount of Mn2+ leading to maximal stimulation was in each case dependent on the basic rate of H2O2-formation. Maximal stimulation of H2O2-formation by phenolic compounds was achieved by coniferylalcohol at a concentration of 10-4M for all groups. Stimulation by p-coumaryl-and by sinapylalcohol was not as significant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00380189
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  • 16
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    The induction of cytokinin habituation in primary pith explants of tobacco (1980)
    Springer
    Planta 149 (1980), S. 402-407 
    Details
    ISSN: 1432-2048
    Keywords: Cytokinin ; Habituation rates ; Nicotiana ; Temperature and habituation ; Tissue culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Pith parenchyma tissue ofNicotiana tabacum L. cv. “Havana 425” becomes cytokinin habituated when incubated at 35°C on an auxin-containing medium. Under these conditions, habituated, hyperplastic nodules appear on the tissues. We used these nodules to estimate the incidence of habituation by a statistical method. The rate of habituation varied with the season. Tissue isolated from plants in the spring habituated approx. 7 times faster than did tissue isolated from plants in winter. The fact that the average rate, 〉4×10−3 per cell generation, was 100–1,000 times faster than the rate of somatic mutation inNicotiana species and depended on the physiological state of the tissue provides further evidence that habituation involves epigenetic changes rather than rare, random genetic mutations. We also found that kinetin (6-furfurylaminopurine) induced habituation and that the concentration required depended on the duration of cytokinin treatment. For long incubation times, approx. 6×10−10 M kinetin, which is about 1,000-fold lower than the concentration optimal for growth of cytokinin-requiring pith tissue, was sufficient to induce habituation. These results support the hypothesis that the habituated state is maintained by a positive feedback loop in which cytokinins either induce their own synthesis or inhibit their own degradation.
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    URL: http://dx.doi.org/10.1007/BF00571176
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  • 17
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    Fatty-acid composition and biosynthesis in cell suspension cultures of Glycine max (L.) Merr., Catharanthus roseus G. Don and Nicotiana tabacum L. (1980)
    Springer
    Planta 147 (1980), S. 384-388 
    Details
    ISSN: 1432-2048
    Keywords: Acetate incorporation ; Catharanthus ; Cell suspension cultures ; Fatty acids ; Glycihe ; Nicotiana ; Temperature and fatty-acid synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The fatty-acid composition of C. roseus and N. tabacum cell suspension cultures was unaffected by subculture on Wood and Braun, Murashige and Skoog, or Gamborg B5C media. However, placing the cultures — which were normally grown at 25° C — at 15° C reduced growth but resulted in enhanced formation of oleic and linolenic acids in C. roseus cultures and increased levels of linoleic and linolenic acids in cultures of G. max and N. tabacum, respectively. The incorporation of [14C]acetate into [14C]linoleic acid was more rapid in N. tabacum cells than in G. max cells, but was very poor in C. roseus where the [14C] label was distributed mainly between palmitic and oleic acids.
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    URL: http://dx.doi.org/10.1007/BF00380177
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  • 18
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    Expression of nuclear and chloroplastic genes coding for fraction-1 protein in somatic hybrids of Nicotiana tabacum + rustica (1980)
    Springer
    Planta 147 (1980), S. 414-417 
    Details
    ISSN: 1432-2048
    Keywords: Fraction-1 protein ; Hybrid, somatic ; Nicotiana ; Protein (Fraction 1) ; Ribulose-1,5-bisphosphate carboxylase ; Somatic hybrid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In the sexual interspecific cross, Nicotiana rustica L.xN. tabacum L., N. rustica can serve as the female but not as the male parent. By fusion of protoplasts, the barrier to fertilization was overcome and somatic hybrids containing N. tabacum cytoplasm were produced as shown by isoelectric focusing of the Fraction-1 protein (F-1-protein). All somatic hybrids displayed polypeptides of the large subunit of F-1 protein (which is coded by the chloroplast genome) characteristic of only one or the other parental species. Two hybrids had large subunits of the N. tabacum type and two hybrids had those of the N. rustica type. Three hybrids contained three smallsubunit polypeptides (coded by the nuclear genome), one being characteristic of N. rustica, one characteristic of N. tabacum, and one with an isoelectric point common to both species. A fourth hybrid contained only two small-subunit polypeptides of the N. tabacum type but in a F-1 protein macromolecule whose large subunits were of the N. rustica type. One somatic hybrid was self-fertile and its F2 progeny contained large- and small-subunit polypeptides indistinguishable in their isoelectric points from those in the parent F1 hybrid. All somatic hybrids showed an aneuploid chromosome number and morphological characteristics intermediate between those of N. rustica and N. tabacum.
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    URL: http://dx.doi.org/10.1007/BF00380181
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  • 19
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    The effect of different temperatures on fatty-acid synthesis and polyunsaturation in cell suspension cultures (1980)
    Springer
    Planta 147 (1980), S. 389-395 
    Details
    ISSN: 1432-2048
    Keywords: Catharanthus ; Cell suspension cultures ; Glycine ; Fatty acids (synthesis, desaturation) ; Nicotiana ; Linoleic, linolenic, oleic, acids ; Temperature and fatty acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cell suspension cultures of Catharanthus roseus G. Don, Glycine max (L.) Merr. and Nicotiana tabacum L. were incubated with [14C]acetate, [14C]oleic acid and [14C]linoleic acid at five different temperatures ranging from 15 to 35° C. When the incubation temperature was increased, [14C]acetate was incorporated preferentially into [14C]palmitate, with a concomitant drop in [14C]oleate formation. Between 15 and 20° C, [14C]oleic acid accumulated in C. roseus cells. In all cultures, optimum desaturation of [14C]oleic acid to [14C]linoleic acid occurred between 20 and 25° C, and in G. max this was also the optimal range for desaturation of [14C]linoleic acid to [14C]linolenic acid. Elongation of [14C]palmitic acid was inhibited when cultures grown at 15° C for 25 h were subsequently incubated with [14C]acetate at 25° C. [14C]oleic acid accumulated in G. max and C. roseus cultures grown at 35° C for 25 h and subsequently incubated at 25° C. Desaturation of [14C]oleic acid increased up to 25° C, but then decreased or leveled off depending on the cell line and on the temperature prior to incubation.
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    URL: http://dx.doi.org/10.1007/BF00380178
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  • 20
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    Polarity and growth of caulonema tip cells of the moss Funaria hygrometrica (1980)
    Springer
    Planta 147 (1980), S. 405-413 
    Details
    ISSN: 1432-2048
    Keywords: Caulonema ; Cell growth (tip) ; Funaria ; Microtubules ; Organelle modification ; Polarity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In the caulonema tip cells of Funaria hygrometrica, chloroplasts, mitochondria, and dictyosomes have differences in structure which are determined by cell polarity. In contrast to the slowly growing chloronema tip cells the apical cell of the caulonema contains a tip body. Colchicine stops tip growth; it causes the formation of subapical cell protrusions, redistribution of the plastids, and a loss of their polar differentiation. Cytochalasin B inhibits growth and affects the position of cell organelles. After treatment with ionophore A23 187, growth is slower and shorter and wider cells are formed. D2O causes a transient reversion of organelle distribution but premitotic nuclei are not dislocated. In some tip cells the reversion of polarity persists; they continue to grow with a new tip at their base. During centrifugation, colchicine has only a slight influence on the stability of organelle anchorage. The former polar organization of most cells is restored within a few hours after centrifugation, and the cells resume normal growth. In premitotic cells the nucleus and other organelles cannot be retransported, they often continue to grow with reversed polarity. Colchicine retards the redistribution of organelles generally and increases the number of cells that form a basal outgrowth. The interrelationship between the peripheral cytoplasm and the nucleus and the role of microtubules in maintaining and reestablishing cell polarity are discussed.
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    Polysomes from expanded tobacco leaves (1980)
    Springer
    Planta 148 (1980), S. 491-497 
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    ISSN: 1432-2048
    Keywords: Leaves (polysomes) ; Nicotiana ; Polysomes ; Poly(A)+ RNA ; Protein synthesis ; RNA (polysomal, polyA+)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The isolation of intact polysomes from leaves of tobacco (Nicotiana tabacum L.) is dependent on the age and state of development of leaves. Undegraded polysomes from young leaves in the early stages of expansion can be isolated easily by extracting the leaves in ice-cold extraction buffer (200 mM tris(hydroxymethyl)aminomethylmethane(Tris)-HCl, pH 9.0; 400 mM KCl; 200 mM sucrose; 35 mM MgCl2). Medium-size leaves give best yields of undegraded polysomes when extractions are carried out in the above buffer and in the presence of ethyleneglycol-bis-(β-amino-ethyl ether)-N,N′-tetracetic acid (EGTA) and mercaptoethanol. Isolation of polysomes from large, nearly fully expanded (mature) leaves requires all of the above plus diethyldithiocarbamate (DIECA) in the extraction medium. An extraction medium consisting of 25 mM EGTA, 0.01 M mercaptoethanol, 25 mM DIECA and 0.5% of the nonionic detergent, Nonidet-P40 (NP 40) was found to be very suitable for extraction of polysomes from all developmental stages of leaves. The polysomes extracted in the above medium showed active translation of protein in the wheat-germ in-vitro protein-synthesizing system. The translational products were similar when translations were carried out directly with polysomes or polysomal RNA, or polysomal poly(A)+ RNA from tobacco leaves. Poly(A)− polysomal RNA was a poor template in the in-vitro wheat-germ system.
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    Microtubules and coated vesicles in guard-cell protoplasts ofAllium cepa L. (1980)
    Springer
    Planta 149 (1980), S. 389-401 
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    ISSN: 1432-2048
    Keywords: Allium ; Cell wall Coated vesicles ; Guard cells ; Microtubules ; Protoplasts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Protoplasts were prepared from the guard cells ofA. cepa. Epidermal peels taken from expanding green leaves and largely free of mesophyll were treated with Cellulysin, and protoplasts were harvested after 18 h of digestion. That the protoplasts were derived from guard cells was ascertained from their characteristic vacuolar autofluorescence and from observations showing that all other epidermal cells are killed in the peeling procedure. The protoplasts proved to be a good system with which to view the cell cortex and inner surface of the plasmalemma. The lysis of cells adhering to polylysine-treated, Formvar-coated grids, followed by negative staining in uranyl acetate, showed that many microtubules normally present in ordered arrays in situ remain closely applied to the inner surface of the plasmalemma in protoplasts. In addition, numerous vesiculate elements including coated vesicles and/or pits are present amongst the microtubules. Similar vesicles are evident in thin sections of fixed, embedded guard cells and protoplasts. The significance of these structures in the cell cortex is discussed.
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    URL: http://dx.doi.org/10.1007/BF00571175
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    Suitable conditions for characterization, identification, and isolation of the mRNA of the small subunit of ribulose-1,5-bisphosphate carboxylase from Nicotiana sylvestris (1980)
    Springer
    Planta 148 (1980), S. 211-216 
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    ISSN: 1432-2048
    Keywords: mRNA ; Nicotiana ; Protein synthesis ; Ribulose-1,5-bisphosphate carboxylase ; RNA (messenger) ; Translation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The products synthesized in vitro by messenger RNA (mRNA) extracted from Nicotiana sylvestris were analyzed by electrophoresis on polyacrylamide slab gels. Only three of the major polypeptides synthesized are considered here: P55, P32, and P20. P55 and P32 were translated from chloroplast mRNA. P55 corresponds to the large subunit of ribulose-1,5-bisphosphate (RuP2) carboxylase; P32 is probably a chloroplast membrane protein. P20, the polypeptide synthesized from cytoplasmic poly(A)+ RNA, is the precursor of the small subunit of RuP2 carboxylase. The balance between P20 and P32, in which their relative proportions varied inversely, was regulated by the age of the leaves and the time of illumination; we took advantage of this phenomenon to isolate the mRNA from the small subunit in relatively large amounts. This mRNA has a molecular weight of 350,000.
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    Properties and regulation of adenosine 5′-phosphosulfate sulfotransferase from suspension cultures ofNicotiana sylvestris (1980)
    Springer
    Planta 150 (1980), S. 140-143 
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    ISSN: 1432-2048
    Keywords: Adenosine 5′-phosphosulfate sulfotransferase ; Cell suspension culture ; Cysteine ; Enzyme regulation ; Nicotiana
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The properties and the regulation of adenosine 5′-phosphosulfate sulfotransferase extracted from cell suspension cultures ofNicotiana sylvestris was investigated. Optimal adenosine 5′-phosphosulfate sulfotransferase activity was obtained from the cells by extraction with 0.1 M tris-HCl, pH8.0, containing 2 M MgSO4 and 10 mM dithioerythritol. The K m for adenosine 5′-phosphosulfate in the sulfotransferase reaction was about 11 μM. Adenosine 5′-phosphosulfate in concentrations above 50 μM were inhibitory. The extratable adenosine 5′-phosphosulfate sulfotransferase activity decreased during cultivation with sulfate as the sole sulfur source, but after about 3 days it reached a constant level (50 to 100 nmol activated sulfate transferred h-1 mg-1 protein) which was maintained for at least 24 h. Addition of 0.5 mM cysteine to the culture medium decreased the extractable adenosine 5′-phosphosulfate sulfotransferase activity and blocked growth completely. With 0.1 mM cysteine an enzyme level of about 10% of the initial value was reached within 6 to 12 h without significant inhibition of growth. The added cysteine was absorbed rapidly and after 24 h cysteine could no longer be detected in the medium. Before the cysteine was completely depleted, the activity of adenosine 5′-phosphosulfate sulfotransferase started to increase, reaching ultimately a level which was comparable to the initial value.
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    Ribosylzeatin and zeatin in tobacco crown gall tissue (1980)
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    Planta 147 (1980), S. 269-273 
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    ISSN: 1432-2048
    Keywords: Crown gall ; Cytokinins ; Nicotiana
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cytokinins were extracted from two cultures of tobacco crown gall tumor tissue: an unorganized tissue and a teratoma which produced leafy shoots. On Sephadex LH-20 column chromatography, extracts of both types of tissue yielded two peaks of cytokinin activity with elution volumes similar to ribosylzeatin and zeatin. Ribosylzeatin and zeatin were detected and quantified by coupled gas chromatography — mass spectrometry selected ion monitoring (GC/MS SIM), comparable quantities being found in the two extracts. Full mass spectral evidence for the presence of ribosylzeatin in both tissues was obtained. No evidence was found for the presence of N6-(Δ2-isopentenyl)adenosine (i6Ade) or N6-(Δ2-isopentenyl)adenine (i6Ade) although these compounds have been reported to occur in cytokinin-habituated tobacco callus tissues.
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    Multistage disruption of protoplasts by dikegulac (1980)
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    Planta 147 (1980), S. 274-276 
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    ISSN: 1432-2048
    Keywords: Cell division ; Dikegulac ; Lysis ; Nicotiana ; Plasmalemma ; Protoplasts ; Tonoplast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Dikegulac (2,3:4,6 di-o-isopropylidine-2-keto-I-gulonate) is a growth regulator used to differentially kill terminal apices, and it analogously inhibits basic metabolic functions in dividing cells, but not stationary cells, in suspension culture. This report demonstrates an analogous situation in isolated tobacco protoplasts. At the lowest concentrations, dikegulac partially suppresses division of the protoplasts. Higher concentrations are required to produce visual cytoplasmic damage to the protoplasts, which probably first occurs at the level of the plasmalemma, as the vacuoles can be released intact. Later, tonoplast disruption occurs.
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    Microtubules, protoplasts and plant cell shape (1980)
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    Planta 147 (1980), S. 500-506 
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    ISSN: 1432-2048
    Keywords: Cell shape ; Colchicine ; Daucus ; Immunofluorescence ; Microtubules ; Protoplasts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Indirect immunofluorescence has been used to study the function of cytoplasmic microtubules in controlling the shape of elongated carrot cells in culture. Using a purified wall-degrading preparation, the elongated cells are converted to spherical protoplasts and the transverse hoops of bundled microtubules are disorganised but not depolymerised in the process. Since microtubules remain attached to fragments of protoplast membrane adhering to coverslips and are still seen to be organised laterally in bundles, it would appear that re-orientation of the transverse bundles is due to loss of cell wall and not to the cleavage of microtubule bridges. After 24 h treatment in 10-3 M colchicine, microtubules are depolymerised in elongated cells but, at this time, the cells retain their elongated shape. This suggests that wall which was organised in the presence of transverse microtubule bundles can retain asymmetric shape for short periods in the absence of those tubules. However, after longer periods of time the cells become spherical in colchicine. Neither wall nor tubules therefore exert individual control on continued cellular elongation and so we emphasize the fundamental nature of wall/microtubule interactions in shape control. It is concluded that the observations are best explained by a model in which hooped bundles of microtubules—which are directly or indirectly associated with molecules involved with cellulose biosynthesis at the cell surface—act as an essential template or scaffolding for the orientated deposition of cellulose.
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    Topographical features of the membrane of Poterioochromonas malhamensis after colchicine and osmotic treatment (1980)
    Springer
    Planta 148 (1980), S. 84-88 
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    ISSN: 1432-2048
    Keywords: Colchicine ; Membrane structure ; Microtubules ; Osmotic treatment ; Plasmalemma ; Poterioochromonas
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Changes in membrane topography in the flagellate Poterioochromonas malhamensis, as a result of colchicine and osmotic-stress treatments, have been studied using freeze-fracturing and thin sectioning. Ridges, but not rows of intramembrane particles, in the PF-face which denote the position of underlying cortical microtubules, together with the ridge associated with their point of origin (flagellar root fibre 1), dissappear after colchicine or short-term (5 min) osmotic treatments. Cortical microtubules are destroyed as a result of the former, but not the latter treatment. Longer periods in osmoticum allow a recovery of the microtubule — associated membrane ridges. Despite careful isosmotic fixations distinct cross-bridges between microtubules and the plasmalemma were not discernible in thin section.
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    Isolation of abscisic acid-resistant variants from tobacco cell cultures (1980)
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    Planta 148 (1980), S. 97-102 
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    ISSN: 1432-2048
    Keywords: Abscisic acid ; Cell cultures ; Nicotiana ; Variants, resistant ; Water stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The goal of this work was to begin a genetic study of the molecular mode of action of abscisic acid (ABA), by isolating variant cultured cells resistant to the hormone, or to a factor which induces ABA synthesis, namely water stress. Cell cultures of Nicotiana tabacum L. cv. Wisconsin 38 and N. silvestris Speg. and Comes were chosen as the experimental materials. Studies of the effects of the two stresses on the growth of the cultures demonstrated that ABA or water stress imposed by mannitol could completely inhibit growth. These effects arose in both cases from a constant reduction of the growth rate of the cells throughout the culture period. Mannitol also induced an increase in ABA content of the cells and media of suspension cultures, although not to the concentrations required to achieve the same degree of growth inhibition when the hormone was applied exogenously.
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    Isolation of abscisic acid-resistant variants from tobacco cell cultures (1980)
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    Planta 148 (1980), S. 103-107 
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    ISSN: 1432-2048
    Keywords: Abscisic acid ; Cell cultures ; Nicotiana ; Variants, resistant ; Water stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Variant clones were isolated from Nicotiana silvestris Speg. et Comes cell cultures at low frequencies following severe abscisic-acid (ABA) or mannitol-induced water-stress treatments of plated cells. N. tabacum L. variants were not recovered. Variants from the ABA selection experiments exhibited a 10-fold increase in resistance to the hormone. This trait was stable in non-selective conditions for as long as was tested (200 days), but did not alter the response of the cells to water stress. Cell lines from the waterstress selection were not more resistant to mannitol than the parent line, and had a wide range of response to ABA.
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    Comparison of proteins synthesized in vivo and in vitro by mRNA from isolated protoplasts (1980)
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    Planta 148 (1980), S. 453-454 
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    ISSN: 1432-2048
    Keywords: mRNA ; Protein synthesis ; Protoplasts ; Nicotiana ; Translation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Studies of proteins synthesized in vitro by messenger RNA (mRNA) extracted from tobacco protoplasts showed that the changes in protein synthesis and especially the lack of certain proteins observed previously in isolated protoplasts did not result from a failure of translation.
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    Influence of leaves and roots on meristem development inNicotiana tabacum L. cv. Wisconsin 38 (1980)
    Springer
    Planta 148 (1980), S. 462-467 
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    ISSN: 1432-2048
    Keywords: Flower formation ; Leaves (in flower formation) ; Meristem (shoot) ; Nicotiana ; Roots (and flower formation)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The terminal, apical shoot meristem ofN. tabacum cv. Wisconsin 38 normally differentiates into a flower after producing 30 to 40 nodes. The influence of leaves and roots on the regulation of flowering was evaluated by counting the number of nodes produced after removal of leaves or the induction of adventitious roots. Leaf removal has no effect on the number of nodes produced before flower formation. Root induction significantly increases the number of nodes produced before flower formation. The plant behaves as if it were measuring the number of nodes between the meristem and the roots as a means of regulating meristem conversion from vegetative to floral differentiation.
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    Effect of microtubule-disrupting drugs on protein and RNA synthesis in Physarum polycephalum amoebae (1980)
    Springer
    Archives of microbiology 128 (1980), S. 34-40 
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    ISSN: 1432-072X
    Keywords: Protein ; RNA synthesis ; Microtubules ; Microfilament-disrupting drugs ; Heat ; Cold shock ; Recovery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effects of the microtubule-disrupting drugs, colchicine, vinblastine, podophyllotoxin, griseofulvin, and lumicolchicine (10-5 M), on protein and RNA synthesis were studied in Physarum polycephalum amoebae in culture. All, except lumicolchicine, were found to simultaneously reduce the rate of protein synthesis and stimulate RNA synthesis. These results parallel the effects seen in cells exposed to heat shock. Treatment of the cells with a microfilament-disrupting drug, cytochalasin B (10 μg/ml in ethanol), resulted in a reduced rate of protein synthesis after 2 h compared to a similar effect by vinblastine in 5–15 min. A morphological abnormality, microtubule paracystals, were seen associated with centrioles in vinblastine-treated cells in which protein synthesis had been reduced by 50%. Vinblastine and podophyllotoxin were shown to interfere with the recovery of protein synthesis after inhibition by low or elevated temperatures. The possible role of microtubules in regulating the translational response of a cell to an external environmental stimulus is discussed.
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    Genetic behavior of somatic hybrids in the genus Nicotiana: N. otophora + N. tabacum and N. sylvestris + N. tabacum (1983)
    Springer
    Theoretical and applied genetics 65 (1983), S. 93-101 
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    ISSN: 1432-2242
    Keywords: Nicotiana ; Somatic hybrids ; Protoplast fusion ; Genetic variability ; Variegation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Somatic hybrids have been produced between N. tabacum and two closely related species in the genus Nicotiana, N. otophora and N. sylvestris, to evaluate interclonal variation and genetic behavior of these hybrids. As with the previously reported N. nesophila+ N. tabacum somatic hybrids, we have detected variation for morphological and isoenzyme characters between somatic hybrid clones, despite stability of chromosome number. One clone of N. sylvestris+N. tabacum was marked by variation in leaf spot frequency. The inheritance of this unstable trait was monitored through two sexual generations. Transmission of the Su gene marker was monitored in self-fertilized and back-crossed progeny of the N. sylvestris+N. tabacum somatic hybrids. Segregation ratios were similar to those previously reported for amphiploid N. sylvestris x N. tabacum sexual hybrids.
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    Genetic processes in intergeneric cell hybrids Atropa + Nicotiana (1983)
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    Theoretical and applied genetics 65 (1983), S. 269-276 
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    ISSN: 1432-2242
    Keywords: Atropa ; Nicotiana ; cell hybrids ; Somatic hybrids ; Chromosome elimination ; DNA content
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The genetic constitution of the cell hybrids Atropa belladonna + Nicotiana chinensis, obtained by cloning of individual heteroplasmic protoplast fusion products (Gleba et al. 1982) and cultured in vitro for 12 months, has been studied. The study comprised 11 hybrid cell clones of independent origin and included analysis of a) chromosome number, size, morphology, and relative position in metaphase plates, b) multiple molecular forms of the enzymes esterase and amylase, and c) relative nuclear DNA content. The data obtained permit us to conclude that, after one year of unorganized growth in vitro, the cells of most (8) clones had retained chromosomes of both parents, while species-specific elimination of nearly all Atropa chromosomes had occurred in three clones. About half of the non-segregating clones possess 120–150 chromosomes including 50–70 of Atropa and 50–90 of Nicotiana. Other clones are polyploid and possess 200–250 chromosomes with a predominance of either Atropa or Nicotiana chromosome types. Only a few chromosomal changes (reconstituted chromosomes, ring chromosomes) have been detected. In some metaphase plates, chromosomes of the two parents tend to group separately, indicating non-random arrangement of chromosomes of the two parents within the hybrid nucleus. Cytophotometric studies of the relative nuclear DNA content showed that distribution histograms for cell clones were similar to those of non-hybrid cultured cells. Cell populations were relatively homogenous and do not indicate any genetic instability as a result of hybridization between remote plant species. Biochemical analysis of isoenzyme patterns confirmed that in most cell clones, species-specific multiple molecular forms of esterase and amylase from both parents were present, i.e. genetic material of both parental species was expressed in the cell hybrids.
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    Somatic hybridization in Nicotiana: behavior of organelles after fusion of protoplasts from male-fertile and male-sterile cultivars (1983)
    Springer
    Theoretical and applied genetics 65 (1983), S. 213-217 
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    ISSN: 1432-2242
    Keywords: Somatic hybridization ; Organelle segregation ; Nicotiana ; Male sterility ; Nitrate reductase ; Deficient mutant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Protoplasts from a nitrate reductase-deficient mutant of Nicotiana tabacum (cnx−68) were fused with protoplasts of 3 different cytoplasmically male-sterile cultivars of tobacco. Two cultivars had no stamens in the mature flowers and the third had petaloid structures in place of the stamens. Plants were regenerated from the fused protoplasts and characterized with respect to stamen development, chromosome number, and two chloroplast-coded traits. Nearly all hybrid plants displayed the chloroplast traits of only one parent, indicating that chloroplast segregation had occurred. The frequency of appearance of each chloroplast type differed according to the species origin of the chloroplasts. Chloroplasts from N. undulata competed much better than those from N. tabacum; N. suaveolens somewhat better than N. tabacum; and N. glauca about equally with N. tabacum. These results are compatible with an interpretation that equal frequency of appearance of chloroplast type among the regenerated plants occurs if the chloroplast DNAs of the parents are similar, whereas a bias of chloroplast type appears among the regenerated plants when the chloroplast DNAs are different. The appearance of aberrations in stamen development resembling the cytoplasmic male-sterile parental types was infrequent among the hybrid plants in all three crosses. Thus sterility factors were generally overcome by fertility factors following somatic hybridization.
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    Detection of two different nuclear genomes in parasexual hybrids by ribosomal RNA gene analysis (1983)
    Springer
    Theoretical and applied genetics 64 (1983), S. 117-118 
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    ISSN: 1432-2242
    Keywords: Nicotiana ; Somatic hybrids ; Ribosomal RNA genes ; Restriction endonucleases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Restriction endonucleases discriminated between the rDNAs contained in callus tissues derived from Nicotiana glauca, N. langsdorffii, and their somatic hybrids produced by protoplast fusion. With XbaI, a single repeat fragment of 7.5 × 106 daltons was produced from N. glauca rDNA compared to a single repeat fragment of 4.2 × 106 daltons produced from N. langsdorffii rDNA. Both kinds of XbaI fragments were found in somatic hybrids.
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    A heteroplasmic state induced by protoplast fusion is a necessary condition for detecting rearrangements in Nicotiana mitochondrial DNA (1983)
    Springer
    Theoretical and applied genetics 66 (1983), S. 203-207 
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    ISSN: 1432-2242
    Keywords: Nicotiana ; Mitochondrial DNA-cybrids ; Somatic hybrids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Mitochondrial DNA (mtDNA) restriction patterns were studied in mutant, cybrid and somatic hybrid plants regenerated from Nicotiana protoplasts. It has been shown that neither components of the culture media used for protoplast culture and plant regeneration, nor the antibiotics streptomycin and lincomycin used for the mutant selection induced alterations in the mtDNA. No rearrangements were detected in the mtDNA of plants derived from homoplasmic fusions where the mtDNA of the parents was identical as judged by mtDNA restriction patterns. There were rearrangements, however, in the mtDNA of each of the cybrid plants derived from heteroplasmic fusions. Restriction patterns generated by BamHI and SalI restriction endonucleases were different from those of both parents, and were composed of parental and non-parental fragments.
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    Restoration of fertility in cytoplasmic male sterile (CMS) Nicotiana Sylvestris by fusion with X-irradiated N. tabacum protoplasts (1980)
    Springer
    Theoretical and applied genetics 58 (1980), S. 121-127 
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    ISSN: 1432-2242
    Keywords: Nicotiana ; Cytoplasmic-male-sterility ; Somatic hybridization ; Plastid segregation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Restoration of male fertility was achieved by fusing protoplasts from male sterile (CMS) Nicotiana sylvestris plants with X-irradiated protoplasts derived from fertile N. tabacum plants. The CMS N. sylvestris plants were derived from a previous somatic hybridization experiment and contained alien (Line 92) cytoplasm. About one quarter of the regenerated plants were found to be cybrids. i.e. they consisted of N. sylvestris nuclei combined with all or some components of N. tabacum cytoplasm. In one half of these cybrids male fertility was restored to different levels. The chloroplasts of the two parental donors differ in respect to tentoxin sensitivity: chloroplasts of CMS N. sylvestris are sensitive while those of N. tabacum are insensitive. It could therefore be demonstrated that there was an independent segregation of chloroplast type and male fertility/sterility: several somatic cybrids were male fertile but tentoxin sensitive and others were tentoxin insensitive yet they were male sterile. Only in about one half of the somatic cybrids was male fertility restored together with restoration to tentoxin insensitivity.
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    Reduction of mechanical sensitivity in an insect mechanoreceptor correlated with destruction of its tubular body (1983)
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    Cell & tissue research 234 (1983), S. 451-461 
    Details
    ISSN: 1432-0878
    Keywords: Mechanoreception ; Sensory transduction ; Microtubules ; Vinblastine ; Insect sensillum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The modified cilium (dendrite) of epithelial mechanoreceptors of insects contains microtubules in different arrangements: (1) microtubules distributed over the entire receptor and not fixed in a special configuration, therefore called free microtubules, (2) densely packed, interconnected microtubules called the tubular body, and (3) 9 doublet microtubules. These groups of microtubules have been discussed in relation to mechanotransduction. In a preceding paper the free microtubules were proved to be not involved in mechanotransduction. In this paper the hypothesis is examined that the tubular body may be essential to mechanotransduction. For this purpose the effect of the microtubule-disassembling drug vinblastine on both the tubular body and the sensitivity is examined in a femoral mechanoreceptor of the cricket Acheta domesticus. After 6- to 26-h exposure to vinblastine the tubular body is partially or totally destroyed. Simultaneously, mechanical sensitivity decays to zero. In contrast, the pacemaker property for nerve impulses of the apical dendritic segment is only slightly altered. We conclude from these results that the tubular body is essential to mechanotransduction. Three experiments in which a (small) response persisted, despite a totally destroyed tubular body, suggest that receptor potentials can in principle be evoked without an intact tubular body. In addition to the irreversible reduction of receptor sensitivity, vinblastine causes a reversible reduction during repetitive stimulation. This adaptation is supposed to be the consequence of altered properties of the tubular body.
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    URL: http://dx.doi.org/10.1007/BF00213781
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    Microtubules, dendritic spines and spine apparatuses (1980)
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    Cell & tissue research 208 (1980), S. 171-181 
    Details
    ISSN: 1432-0878
    Keywords: Microtubules ; Dendritic spine apparatus ; Synapse ; Development ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Using techniques for enhanced microtubular preservation, including albumin pretreatment (Gray, 1975), occipital cortex of rats was studied electron microscopically at various ages of development. A close structural relationship was seen between microtubules, sacs of SER and the postsynaptic “thickening” in primordial spines and with the dense “plate” material of spine apparatuses. Stereoscopic preparations in addition show a more complicated substructure than previously described for the “plate”. Microtubules may contribute to the formation of the “plate” of the spine apparatus which in turn is associated with the postsynaptic “thickening” of the mature spine. Possible functional correlates are discussed.
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    URL: http://dx.doi.org/10.1007/BF00234868
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    Dry matter content and mineral composition of potatoes grown in Cyprus (1980)
    Springer
    Potato research 23 (1980), S. 371-375 
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    ISSN: 1871-4528
    Keywords: nitrogen ; phosphorus ; potassium ; calcium ; sodium ; nitrate ; sulphate ; micronutrients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The specific gravity and dry matter content of 193 tuber samples (cultivars: Arran Banner, Spunta, Up-to-Date, Cara) from crops grown at Kokkinochoria, the major potato growing area of Cyprus, were related to each other as follows: Dry matter (%)=−269.59+268.24×specific gravity. This regression accounted for 82.4% of the variation; the fiducial limits (P〈0.05) for single determinations of specific gravity were±1.54 percentage units. The mineral contents of the tubers were similar to those reported in other countries.
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    Intracellular transport in axonal microtubular domains II. Velocity profile and energetics of circumtubular flow (1983)
    Springer
    Protoplasma 114 (1983), S. 198-209 
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    ISSN: 1615-6102
    Keywords: Axoplasmic transport ; Zones of exclusion ; Microtubules ; Saltatory movement ; Transport mechanisms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The microtubule is a highly efficient vectorial structure that could orient a transport force generating mechanism and also absorb the recoil produced by vectorial force generation. We have assumed that a nonspecific shear force is generated in a narrow annulus around the microtubule and have calculated the velocity profiles in the shear flow and drag flow regions that result from such a mechanism. This circumtubular flow of low visocosity cytoplasm is thought to be the basic carrier stream that produces the observed axoplasmic transport phenomena. These carrier streams are devoid of neurofilaments and form the halos or exclusion zones seen around microtubules in electron micrographs. Individual carrier streams may merge hydrodynamically to produce transport domains that are capable of moving large organelles in a saltatory manner. Exchange of material between the low viscosity transport domains and the high macroviscosity neurofilament regions produces mass fluxes akin to those found in chromatographic columns. Calculations of energy required to maintain streaming and of the energy available to the transport system show a close correspondence and demonstrate that a continuous carrier stream activity is energetically feasible.
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    Intracellular transport in axonal microtubular domains I. Theoretical considerations on the essential properties of a force generating mechanism (1983)
    Springer
    Protoplasma 114 (1983), S. 179-197 
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    ISSN: 1615-6102
    Keywords: Axoplasmic transport ; Force generating mechanism ; Microtubules ; Nerve cell ; Saltatory movement ; Viscosity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In this article the mode of force generation of axoplasmic transport is examined on theoretical grounds. We use as criteria the experimental evidence available, the biophysical boundary conditions, energetical feasibility, and earlier theoretical treatments of this topic. The following results are obtained: 1. Comparison of the energy available and the energy required to move organelles through the viscous cytoplasm shows that the viscosities reported preclude such movement of larger vesicles or mitochondria. This suggests that transport should occur in microregions of low viscosity. 2. For ultrastructural, pharmacological, and biochemical reasons such low viscosity regions are expected to be located around microtubules. 3. Out of the 11 theoretical possibilities to generate the driving force we had to rule out four because of obvious violations of verified data. Four other modes of force generation would require one or several additional transport mechanisms to explain the entire phenomenon. Models which imply streaming of low viscosity axonal regions are found to be in good agreement with the experimental findings. 4. The comparison of intracellular sites for the location of the force generating mechanism suggests that they are located at the microtubular surface. We have shown that the properties of axoplasmic transport fit most easily the concept that the proposed low viscosity domains be located around microtubules and microtubule bundles and that these domains represent streaming regions of cytoplasm. This concept is found to be in agreement with the presented list of criteria any hypothesis of axoplasmic transport must satisfy.
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    Structure and formation of fibrillar mucilages in seed epidermis cells (1983)
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    Protoplasma 114 (1983), S. 210-221 
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    ISSN: 1615-6102
    Keywords: Cell wall structure ; Elementary fibrils ; Microtubules ; Mucilage ; Seed epidermis ; Collomia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The seed epidermis cells ofCollomia grandiflora Dougl. contain a mucilage with an amorphous and a fibrillar component. The elementary fibrils are very long and usually measure about 2.0 2.5 nm in thickness after negative staining but more than 5 nm in thin sections. They seem to consist of cellulose but are stained also with aniline blue; the emitted fluorescence light is polarized. The elementary fibrils are surrounded by the amorphous component of the mucilage and are loosely associated to form mucilage strands and, more densely, a massive spiral (or rings) which is embedded in the mucilage. During mucilage formation, microtubules run parallel with the elementary fibrils, both are oriented circumferentially. Microtubules are dense in regions where mucilage strands are formed and especially frequent where the spiral is being produced. Within the outer cell wall of the epidermis cells, lacuna-like spaces develop underneath the cuticle. They become partly filled with stacks of electron transparent lamellae, embedded in an electron dense material and resemble layers of waxes but are thicker than common “wax layers”.
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    Structure and formation of fibrillar mucilages in seed epidermis cells (1983)
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    Protoplasma 114 (1983), S. 222-234 
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    ISSN: 1615-6102
    Keywords: Cell wall growth ; Elementary fibrils ; β-1,3 and β-1,4 glucan ; Microtubules ; Mucilage ; Seed epidermis ; Ruellia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The seed epidermis cells of differentRuellia species rupture the cuticle to form unicellular hairs. They become filled with mucilage which consists of very long elementary fibrils and an amorphous matrix. After negative staining, the elementary fibrils appear to be about 2.0–2.5 nm thick. They stain with zinc-chloride-iodine and with the fluorochromes Calcofluor White and aniline blue, perhaps indicating β-1,4 and β-1,3 glucans. The emitted fluorescence light is polarized demonstrating a longitudinal arrangement of the dye molecules. The elementary fibrils aggregate into mucilage strands which helically extend through the cell parallel to the lateral cell wall. Different helices form layers which are arranged more or less concentrically. During hair elongation and during mucilage production, microtubules are aligned parallel with the elementary fibrils. There is a 1∶1 relationship between microtubules and mucilage strands. Frequently, the strand lies opposite the microtubule. Regions without microtubules but with imcomplete mucilage strands and vice versa have also been observed. There are several possibilities to explain the structure and the staining reactions of the elementary fibrils of the mucilage on a molecular basis and the role of the microtubules during microfibril formation and orientation. The pattern of microfibrils in developing hairs is compatible with the multinet hypothesis.
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    Microtubules and their organizing centres in differentiating guard cells ofAdiantum capillus veneris (1983)
    Springer
    Protoplasma 115 (1983), S. 176-192 
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    ISSN: 1615-6102
    Keywords: Microtubules ; Microtubule organizing centres ; Adiantum capillus veneris ; Guard cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The cortical cytoplasm of the young guard cells ofAdiantum capillus veneris is locally differentiated. At an early post-telophase stage, numerous microtubules diverge from the cytoplasm occupying the junctions of the midregion of the ventral wall with the periclinal ones, towards the periclinal and ventral wall faces as well as towards the inner cytoplasm. Microtubule-vesicle complexes (MVCs) are detected in these regions. Their appearance is accompanied by the initiation of local wall thickenings in the same areas. Afterwards, more distinct MVCs anchored to the plasmalemma were seen in the cortical cytoplasm of the periclinal walls, close to the growing thickenings, usually at a distance up to 3μm from them. Sometimes, they seemed to contain an electron dense substance in which the microtubules were embedded. Cortical microtubules converging from more than one direction terminate at the MVCs. Besides, the microtubule population lining the periclinal walls radiate from the regions where the above cytoplasmic formations are localized. The overlying cellulose microfibrils exhibit the same orientation. The vesicles localized at the MVCs appear to be of dictyosomal origin, very electron dense and react positively to periodic acid-thiocarbohydrazide-silver proteinate (PA-TCH-SP) test. Another population of microtubules fan out from the MVCs, entering deeper into the cytoplasm. They become associated with the nucleus and mitochondria, and traverse the peridictyosomal cytoplasm. In some instances the nucleus formed a protrusion towards an MVC and appeared associated with it via microtubules which radiate from the MVC and flank the nuclear envelope. The observations favour the hypothesis that prominent microtubule organizing centres (MTOCs) function in the cortical cytoplasm of the midregion of the periclinal walls surrounding the ventral one for a relatively long time. The MVCs and/or their adjacent plasmalemma sites may represent MTOCs or at least they specify the cortical cytoplasmic sites where microtubules are nucleated.
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    Motility and microtubule stability of Antarctic algae at sub-zero temperatures (1983)
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    Protoplasma 115 (1983), S. 240-242 
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    ISSN: 1615-6102
    Keywords: Algae ; Antarctic ; Microtubules ; Motility ; Sub-zero temperatures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Most ectothermic organisms become immobile at a few degrees above zero. The unicellular planktonic algaeDunaliella sp., andChlamydomonas sp. from Antarctic hypersaline lakes remain motile at temperatures as low as −14 °C.Pyramimonas gelidicola from the same habitat stops swimming at −10 °C but its flagella continue to beat at −14 °C. Further, the characteristic shape ofPyramimonas, which is maintained by cytoskeletal microtubules, is unaffected by such low temperature.
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    Orientation of microtubules against transverse cell walls in roots ofAzolla pinnata R. Br. (1983)
    Springer
    Protoplasma 116 (1983), S. 78-85 
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    ISSN: 1615-6102
    Keywords: Azolla ; Microtubules ; Root apex ; Cell expansion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Orientation of cortical microtubules against transverse cell walls was examined inAzolla root primordia at different stages of development. All transverse walls in the zone of formative divisions, where the rate of increase in girth of the root is maximal and contributed to by all cell layers, show circumferential orientation of their associated microtubules with respect to the shape of the root as a whole. In the zone of proliferative divisions, expansion of inner cortex cells remains predominantly radial and they retain the same microtubule orientation. However, in the endodermal cells which bound the stele and alter very little in radial dimension, circumferential orientation gives way to radial orientation. In none of these zones or cell types is the orientation of cortical microtubules against transverse walls “random”. Individual cells in the root can deploy their microtubules in specific, and different, orientations on different cell faces. The hypothesis that, inAzolla, nucleation of microtubules occurs along selected cell edges receives further support from the observations.
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    Microtubule organization and morphogenesis in young spores of the mossTetraphis pellucida Hedw (1983)
    Springer
    Protoplasma 116 (1983), S. 115-124 
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    ISSN: 1615-6102
    Keywords: Microtubules ; Moss ; MTOC ; Sporogenesis ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Microtubule systems appear sequentially at the distal and proximal poles of tetrad members during mid-sporogenesis in the mossTetraphis pellucida Hedw. The distal microtubule system emanates from a microtubule organizing center (MTOC) located between the single plastid and the nucleus. The distal MTOC and associated microtubules, which appear immediately after cytokinesis, are ephemeral and do not appear to be associated with the deposition of exine occuring at the same time. The proximal microtubule system, which appears slightly later than the distal system, is a more stable component of mid-sporogenesis. The proximal MTOC is an irregularly lobed, patelliform aggregation of electron-dense granules located beneath the plasma membrane at the proximal spore pole. Several bundles of microtubules radiate from the proximal MTOC and traverse the cell, enclosing the nucleus in an cone of microtubules. The proximal microtubule system is thought to function in aperture development and organelle migration. The relatively large nucleus migrates a short distance in the small spore early in the tetrad stage and maintains its acentric position at the proximal pole throughout later stages of sporogenesis. The plastid migrates later in the tetrad stage from its meiotic position parallel to the distal surface to a position perpendicular to the distal surface with one tip in close proximity to the proximal MTOC. The proximal microtubule system reaches its maximum development by the end of the tetrad stage and all micrographic evidence of it is lost in the maturation stages of late sporogenesis.
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    Cytoskeletal control of nuclear migration and anchoring in developing cells ofMicrasterias denticulata and the change caused by the anti-microtubular herbicide amiprophos-methyl (APM) (1983)
    Springer
    Protoplasma 118 (1983), S. 75-90 
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    ISSN: 1615-6102
    Keywords: Nuclear migration ; Cytoskeleton ; Microtubules ; Microfilaments ; Amiprophos-methyl (APM) ; Micrasterias
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Postmitotic nuclear migration and anchoring inMicrasterias seems to be mediated by two distinct microtubule (MT)-systems: the moving MT-system, called “posttelophase system of MT” (PTS) which arises from a node-like structure, possibly a microtubulecenter (MC) and the anchoring MT-system, called “isthmus system of MT” (IS) which surrounds the nucleus at its central position. The nucleus or parts of its envelope seems to be involved in the nucleation and orientation of these MT-systems. The moving force of the nuclear migration process obviously originates from interaction between the MT-system (PTS) and its adjacent microfilaments. Under the influence of the herbicide amiprophos-methyl (APM) a destruction of both of the MT-systems followed by a disoriented nuclear migration occurs. Recovery experiments after APM treatment revealed a reestablishment of both the PTS and the IS although a disoriented formation could often be observed. Depending on the orientation of the reestablished MT-system (PTS) either remigration of the nucleus or dislocated anchoring at one of the lobe invaginations of the cell takes place. An interaction between the nucleus and distinct sites of the plasma membrane is discussed.
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    Ultrastructural and biochemical characterisation of the cytoskeleton ofPhysarum polycephalum myxamoebae (1983)
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    Protoplasma 118 (1983), S. 181-191 
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    ISSN: 1615-6102
    Keywords: Actin ; Cytoskeleton ; Microtubules ; Physarum polycephalum ; Tubulin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The detergent-resistant cytoskeleton ofPhysarum polycephalum myxamoebae was isolated by extraction of cells in buffers containing Triton X-100. The cytoskeleton of myxamoebae was seen to be composed of a network of 6 nm microfilaments and microtubules when examined in the electron microscope as negatively stained whole mount preparations, or in thin sections. Cytoplasmic microtubules originated from a microtubule organising centre which remained in close association both with the nucleus and centrioles in detergent-lysed preparations. Nuclear pore complexes remained attached to the nuclear surface despite the removal of nuclear membranes during Triton extraction. Preparations were examined using SDS-polyacrylamide gel electrophoresis and two-dimensional polyacrylamide gel electrophoresis. Actin and tubulin were major components of the Triton-resistant structure. Two dimensional polyacrylamide gel electrophoresis indicated the presence of tubulin and actin species in the myxamoebal cytoskeleton. Other prominent protein components had apparent relative molecular masses of approx. 27 K and 220 K. Lysis of cells in buffers containing Ca2+ resulted in the removal of microtubules from the cytoskeleton and a specific decrease in the amount of tubulin in gels of Ca2+-treated material; some tubulin spots did however remain, possibly representing centriolar tubulins.
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    Some effects of colchicine on microtubules and cell division in roots ofAzolla pinnata (1980)
    Springer
    Protoplasma 102 (1980), S. 31-51 
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    ISSN: 1615-6102
    Keywords: Microtubules ; Morphogenesis ; Cell Walls ; Roots ; Colchicine ; Cell division
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Removal and subsequent reformation of microtubules in cells of the root-tips ofAzolla pinnata R. Br. was achieved by short pulse treatments with the drug colchicine. Loss of microtubules led to the formation of multinucleate cells more frequently than to the arrest of mitosis at metaphase, and primary and secondary wall formation was also disrupted. Recovery of root development was limited. Growth of all roots ceased 5–6 days after the pulse treatment. Following the reappearance of microtubules, renewed deposition of normal wall thickenings occurred in developing xylem elements. Multinucleate cells became subdivided by walls in the apparent absence of a phragmoplast. The plane in which the new wall was formed was often located as it would have been in an untreated root, but in a number of cases abnormal or precious positioning of new walls was observed. Clusters of microtubules, matrix material, and vesicles or particles, taken to indicate microtubule initiation, were observed during the recovery from treatment.
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    Purification of lumicolchicine for use in studies of plant development (1980)
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    Protoplasma 103 (1980), S. 105-114 
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    ISSN: 1615-6102
    Keywords: Colchicine ; Lumicolchicine ; Microtubules ; Mitosis ; Wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Lumicolchicine was purified by preparative thin-layer chromatography. Tests for purity were ultraviolet absorption spectrophotometry, analytical thin-layer chromatography, and a bioassay using wheat roots. Wheat roots treated for 3 days with 10−3 M lumicolchicine showed no c-mitosis, but had reduced growth compared with controls.
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    The organization of cortical microtubule arrays in the radish root hair (1980)
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    Protoplasma 103 (1980), S. 205-229 
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    ISSN: 1615-6102
    Keywords: Cell wall ; Cytochalasin B ; Microfibril orientation ; Microtubules
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Cortical microtubule arrays in the radish root hair were analyzed from reconstructions of serial ultra-thin sections in order to test extant hypotheses concerning the role of microtubules in the deposition of oriented microfibrils of cellulose. Passing away from the tip, root hairs exhibit a transition from random to oriented deposition of microfibrils at approximately 25 μm. Along the root hair, passing back from the tip, the microtubules: a) increase in number to a plateau at 25 μm; b) change their length profiles from approximately 60% less than 1 μm long in the hair tip to approximately 40% less than 1 μm long at 60 μm; c) maintain a constant pattern of angular deviation from the long axis, which is similar to the deviation pattern of the oriented wall fibrils; d) maintain a constant (approximately 70% of tubules) close (within 50 nm) proximity to the plasma membrane (PM); e) maintain a low (approximately 20%) degree of inter-microtubule proximity (i.e., within 50 nm of one another); f) show evidence for some variable long range (〉50 nm) association. Fixation with glutaraldehyde in a complete microtubule polymerization medium (MTPM), or pretreatment with cytochalasin B cause an approximate twofold increase in 1. the proportion of long microtubules in the tip region and 2. microtubules within 50 nm of one another. Fixation in incomplete MTPM (without GTP) produces results similar to phosphate buffer controls. Alternative explanations for these results are examined. A new hypothesis accounting for microtubule involvement in oriented microfibril deposition is described.
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    Griseofulvin-induced alterations in site of dividing nuclei and structure of septa in a dikaryon ofSchizophyllum commune (1980)
    Springer
    Protoplasma 103 (1980), S. 323-331 
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    ISSN: 1615-6102
    Keywords: Dikaryon ; Griseofulvin ; Microtubules ; Nuclear division ; Septal development ; Septal dissolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Ultrastructural study of a dikaryon of the basidiomyceteSchizophyllum commune showed that treatment with griseofulvin affected the site of the dividing nuclei and the location and structure of the septa. The microtubules were considered to be the primary target of griseofulvin, since they participate in nuclear division and movement in the hyphae, and their assembly is known to be in other organisms than fungi inhibited by griseofulvin. It is pointed out that dikaryotic hyphae with two nuclei and a clamp connection per cell are more sensitive indicators of the effect of griseofulvin than homokaryotic hyphae, whose structure is less complex.
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    Microtubules, organelle movement, and cross-wall formation at the sporangial-rhizoidal interface in the fungus,Chytridium confervae (1980)
    Springer
    Protoplasma 104 (1980), S. 201-221 
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    ISSN: 1615-6102
    Keywords: Cell wall ; Chytridiomycetes ; Chytridium confervae ; Cross-wall ; Microtubules ; Ribosomes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Chytridium confervae is a eucarpic, monocentric chytrid. We have used light and electron microscopy to study the relationship between the nutrient absorbing rhizoids and the asexually reproductive sporangium during growth. We have also examined the induction of zoosporogenesis by starvation, and subsequent differentiation until zoospore release. During growth the cytoplasm of the rhizoids and the developing sporangium was continuous and similar. At the start of starvation a bundle of fibers that were visible with light microscopy appeared at the junction between the rhizoids and the sporangium. Two hours after initiation of starvation a wall, that was also visible with light microscopy, formed to separate the rhizoids from the sporangium. Electron microscopy revealed a large, ordered array of microtubules in the thallus at the same time that the fibers appeared, and a sharp difference in the density of ribosomes in the cytoplasm of the sporangium and that of the rhizoids that was apparent immediately after starvation. This cytoplasmic difference was preserved by the formation of a cross-wall that was penetrated by plasmodesmata. After the wall was formed the cytoplasm of the rhizoids senesced. Comparison ofC. confervae with other organisms that use arrays of microtubules to move organelles is made and speculation on the role of the microtubules in organelle movement and wall formation inC. confervae is offered.
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    Cell shape and microtubules in zoospores of the green algaChlorosarcinopsis gelatinosa (Chlorosarcinales): Effects of low temperature (1980)
    Springer
    Protoplasma 104 (1980), S. 283-293 
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    ISSN: 1615-6102
    Keywords: Cell shape ; Chlorosarcinopsis ; Low temperature ; Microtubules
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The effect of low temperature (2 °C) on cell shape and microtubules in zoospores of the green algaChlorosarcinopsis gelatinosa has been investigated. The zoospores are 4–6 times longer than wide with a mean length of 12,5 μm and can be kept in the dark for several hours without changes in cell shape. Cell shape changes have been evaluated quantitatively by measuring changes in cell length. Low temperature induces a decrease in cell length which exhibits a two-step kinetic: during the first 30 minutes a rapid rate of decrease in cell length was measured, while during the next 4 hours a slow rate of decrease in cell length was observed. Complete regeneration of zoospore length occurs when cold-treated cells are subjected to the original zoospore induction temperature (30 °C) for two hours. Observation of numbers, disposition and types of microtubules in the zoospore during decrease in cell length has shown that within 30 minutes after cold application the secondary cytoskeletal microtubules (scmt) disappear, while flagellar root microtubules are unaffected. During this period most cells develop a prominent posterior appendage (tail). Sections demonstrate the presence of several microtubules in these tails. Flagellar root microtubules probably extend into the tails and disappearance of scmt starts at the posterior pole of the cell. Regeneration of zoospores to original cell length is coupled with reappearance of scmt starting at the anterior pole of the cell. It is concluded that secondary cytoskeletal microtubules constitute the main cytoskeleton inChlorosarcinopsis zoospores and that flagellar root microtubules contribute to only a minor extent to the cytoskeleton, because they cannot retain the cell shape. The results are discussed with respect to the functional significance of flagellar root microtubules in green algae.
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    Distribution of cortical microtubules in tobacco protoplasts. An immunofluorescence microscopic and ultrastructural study (1980)
    Springer
    Protoplasma 105 (1980), S. 27-43 
    Details
    ISSN: 1615-6102
    Keywords: Immunofluorescence ; Microtubules ; Plant protoplasts ; Tobacco
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The arrangement of cortical microtubules in tobacco protoplasts is described using the following techniques: 1. Transmission electron microscopy (TEM) of thin sections of whole protoplasts, 2. TEM of negatively stained protoplast ghosts, and 3. Indirect immunofluorescence microscopy of protoplast ghosts. Ghosts were prepared by attaching freshly isolated protoplasts to glass coverslips or formvar/carbon-coated grids with poly-L-lysine and then bursting them either osmotically or by detergent treatment in the presence of a microtubule stabilizing buffer. Osmotic bursting of protoplasts yielded large pieces of plasma membrane with attached microtubules. These preparations proved very useful for measuring the density and length of cortical microtubules. Detergent treatment dissolved the plasma membrane and altered the distribution of cortical microtubules.
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    Influence of the antimicrotubule agent, mebendazole, on the secretory activity of intestinal cells ofAscaridia galli (1980)
    Springer
    Protoplasma 105 (1980), S. 69-76 
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    ISSN: 1615-6102
    Keywords: Mebendazole ; Ascaridia ; Secretion ; Microtubules ; Anthelmintic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The anthelmintic compound mebendazole caused the disappearance of microtubules in the intestinal cells ofAscaridia galli. Electron microscopy revealed that soon after the microtubules disappeared there was an accumulation of secretory vesicles near the golgi areas. subsequently many of these vesicles aggregated forming dense large vesicles near the terminal web of the intestinal cells. This provides further evidence for the involvement of microtubules in the secretion of products from eukaryotic cells. It seems likely that inhibition of microtubule directed secretory functions in various cell types is an important function in the anthelmintic activity of the benzimidazole carbamates.
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    URL: http://dx.doi.org/10.1007/BF01279850
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    Selection of embryogenic pollen from cold-treated buds ofNicotiana tabacum var. badischer burley and their development into embryos in cultures (1980)
    Springer
    Protoplasma 105 (1980), S. 161-167 
    Details
    ISSN: 1615-6102
    Keywords: Embryogenic pollen ; Nicotiana ; Pollen culture ; Selection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary By using density gradient centrifugation, employing 55% percoll and 4% sucrose as suspension medium, it is possible to select embryogenic pollen from buds after cold treatment at 10 °C for 8 or more days. These buds at the uninucleate stage of pollen were collected from plants grown in 8 hours photocycles at 18 °C and supplied with mineral salts. The embryogenic pollen are small, starch-free with a clear cytoplasm whereas large starch-filled ones are nonembryogenic. The embryogenic pollen regularly form embryos at a frequency of 2% on a mineral medium supplemented with glutamine, asparagine and sucrose at pH 6.5. These results demonstrate, for the first time, that it is possible to have embryos in appreciable frequencies in “ab initio” pollen cultures raised from cold treated anthers.
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    Protoplasmic streaming in the giant unicellular green algaAcetabularia mediterranea (1980)
    Springer
    Protoplasma 102 (1980), S. 295-306 
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    ISSN: 1615-6102
    Keywords: Acetabularia ; Inhibitors ; Microcinematography ; Microfilaments ; Microtubules ; Protoplasmic streaming
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The sensitivity of the dual intracellular transport system inAcetabularia mediterranea (Koop andKiermayer 1979 a) to cytochalasin B (CB, 10−5 mol), chlorisopropyl-N-phenylcarbamate (CIPC, 2.10−4 mol), and amiprophosmethyl (APM, 3.10−5 mol) has been studied by microcinematography. Vegetative cells before cap formation, 2–3 cm in length, and cells with a maximum sized cap, containing secondary nuclei, were used for the experiments. All intracellular movements ceased under the influence of CB, while in contrast to “headed streaming bands” and to the migration of the secondary nuclei, the movement of chloroplasts at “thin filaments” was found to be insensitive to Col, CIPC, and APM. All inhibitory effects of the drugs on protoplasmic streaming were completely reversible within a time of less than 10–20 minutes recovery from the drugs. The results suggest an involvement of microfilaments in all intracellular movements while, in addition, microtubules seem to be connected with the movement on “headed streaming bands”, including the migration of secondary nuclei.
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    Algal dynamics and nitrogen and phosphorus cycling in a cypress stand in the seasonally flooded Great Dismal Swamp (1983)
    Springer
    Hydrobiologia 106 (1983), S. 115-122 
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    ISSN: 1573-5117
    Keywords: cypress swamp ; nitrogen ; nutrient cycling ; periphytic algae ; phosphorus ; phytoplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Both periphytic and planktonic algae are found in areas of the seasonally flooded Great Dismal Swamp (Virginia, U.S.A.). The dynamics of these algae were studied in a cypress stand and the periphytic algae appeared to be important as nutrient conservers. Clear temporal patterns in phytoplankton dominance were also observed.
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    Origin and production of phosphatases in the acid Lake Gårdsjön (1983)
    Springer
    Hydrobiologia 101 (1983), S. 49-58 
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    ISSN: 1573-5117
    Keywords: forest water ecosystems ; phosphatases ; phosphorus ; phosphatase budget ; acid lakes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The activity of acid phosphatases was followed for one year in Lake Gårdsjön as well as in the inlet and the outlet of the lake. A budget of the phosphatases was calculated, including an estimation of the production of phosphatases. The phosphatase activity was also measured in two basins upstream of L. Gårdsjön: the north basin and the south basin of L. Stora Hästevatten. The acid phosphatase activity was very high compared with reported alkaline phosphatase activities in other lakes. About 95% of the phosphatases in L. Gårdsjön was produced in the lake, and the production was highest in early summer. Small Chrysophyceae (〈 10 µm) probably produced the majority of the acid phosphatases in the investigated lakes, and accordingly could be favoured in environments with low phosphorus supply due to their ability to produce large amounts of phosphatases.
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    Ammonia nitrogen and inorganic phosphorus excretion by the planktonic rotifers (1983)
    Springer
    Hydrobiologia 104 (1983), S. 231-236 
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    ISSN: 1573-5117
    Keywords: rotifers ; phosphorus ; nitrogen ; excretion ; temperature ; body weight
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Two series of experiments were carried out to determine the relation of the rate of phosphorus and nitrogen excretion by the planktonic rotifers to ambient temperature and individual body weights of these animals. The following formulas describing this relation were obtained: EP=0.0154 W−1.27 e0.096T EN=0.0879 W−1.01 e0.088 T, where EP and EN denote the rate of P and N excretion, respectively, in µg · mg dry wt−1 · h−1, W is body weight in µg dry weight, and T is temperature in °C.
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    Somatic hybridization between Nicotiana rustica and N. sylvestris (1983)
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    Plant cell, tissue and organ culture 2 (1983), S. 269-283 
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    ISSN: 1573-5044
    Keywords: tissue culture ; protoplast fusion ; organogenesis ; isozyme analysis ; chloroplasts ; ribulose-1,5-bisphosphate carboxylase ; hybridization ; Nicotiana
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Protoplasts isolated from cell cultures of chlorophyll-deficient Nicotiana rustica cv. chlorotica and wild-type N. sylvestris were fused. The scheme for selection of somatic hybrids was based on the inability of the protoplast-derived colonies of the parental species to turn green; N. sylvestris protoplasts also had a very low plating efficiency in the medium employed. A total of 777 green colonies which were presumptive hybrids were isolated within four weeks of the fusion experiments. One hundred and eight green colonies formed shoots in vitro and 16 lines were rooted and grown in the greenhouse. Each of these hybrid plants displayed vegetative and floral traits intermediate to those of the parental species, except for plant height which in almost all cases was greater in the hybrids. Isozyme analyses by gel electrophoresis and isoelectric focussing of the small subunit of ribulose 1,5-bisphosphate carboxylase/oxygenase (RUBPCase) demonstrated that the nuclear genomes of both parents were expressed by the hybrids. Each of the eight somatic hybrid plants analyzed expressed only the N. rustica chloroplast genome as shown by isoelectric focussing of the large subunit of RUBPCase. This study demonstrated the value of N. rustica cv. chlorotica as a parental line in somatic hybridization with N. sylvestris and it might have widespread use with wild-type lines of other species.
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    Algal bioassays and algal growth controlling factors in eutrophic shallow lakes (1983)
    Springer
    Hydrobiologia 100 (1983), S. 59-64 
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    ISSN: 1573-5117
    Keywords: bioassays in situ ; algal growth ; nitrogen ; phosphate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Bioassays with water of eutrophic Lake Tjeukemeer were carried out in the laboratory, and, in the lake itself, by placing plexiglass tubes (∅ 9 cm) firmly in the mud. In the laboratory nitrogen had a strong growth-promoting effect on the concentrations of chlorophyll a, N-cell and COD-cell. In the bioassays in situ nitrogen increased the concentration of chlorophyll a, but not those of cellular N and cellular COD. It is argued that chlorophyll a is not a good indicator for algal growth in bioassays and that the extrapolation of laboratory experiments — where nitrogen limited algal growth — to the field situation — where light limited algal growth — often leads to erroneous results, especially in shallow eutrophic lakes. The main reason is probably that in bioassays in the laboratory the nutrient supply — both from external loading and from sediments — is often different and that processes like denitrification occur in the lake, but not in the bioassays.
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    Phosphorus limitation in some tropical African lakes (1983)
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    Hydrobiologia 100 (1983), S. 101-112 
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    ISSN: 1573-5117
    Keywords: nutrient limitation ; phosphorus ; nitrogen ; phytoplankton biomass ; tropical lakes ; Kenya
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Two of three Kenyan lakes studied between November 1979 and October 1980 have very short 33PO4 turnover times, indicating a high phosphorus (P) demand throughout the year. The P turnover time in Lakes Oloidien and Sonachi is as rapid as in the most P deficient temperate zone lakes. The third lake, Lake Naivasha, has a lower overall P demand and a wide seasonal range, with lowest demand between November 1979 and February 1980 when a P deficiency was unlikely. On an annual basis the Lake Naivasha status is, however, not statistically different from that recorded during the summer in Lake Memphremagog, a generally P-limited temperate zone lake. Lake Naivasha and Lake Oloidien fit well to the line of best fit for the Dillon-Rigler relationship relating total phosphorus (TP) and chlorophyll a derived in temperate zone lakes. Thus, temperate zone models predicting aspects of lake behaviour on the basis of TP may also be applicable to these two tropical lakes. Saline lake Sonachi had not only a short P turnover time but also responded dramatically to the fertilization of enclosures with P. However, it does not fit the TP-chla or the total nitrogen-chla plots from the temperate zone. This suggests that, in this saline lake at least, much of the TP is unavailable to the algae, with some of it in a particulate form that is readily extracted with boiling water. The epilimnetic N:P ratios also characterize lakes Oloidien and Sonachi lakes as highly P deficient and lake Naivasha as more moderately P limited. A single set of measurements in Winam Gulf (Lake Victoria) also showed a rapid P turnover time and thus P limitation, but as in lake Sonachi much of the TP was in a non-algal particulate form. Occasional measurements in three other hypertrophic and saline lakes suggest them to be primarily light limited on the basis of their very high photosynthetic cover. These findings support the hypothesis of a primary P limitation for those lakes not light limited, and contradicts literature suggestions that nitrogen is the primary limiting element in tropical lakes.
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    Seasonal distribution of quantities of phosphorus in different component organs of mango (Mangifera indica L) CV Langra (1983)
    Springer
    Nutrient cycling in agroecosystems 4 (1983), S. 151-154 
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    ISSN: 1573-0867
    Keywords: phosphorus ; proportion ; mango ; whole tree ; leaves ; bark ; wood ; roots
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Quantities of phosphorus present in different component parts of mango trees were estimated from July 1977 to June 1978 at the Horticultural Farm of the Gujarat Agricultural University, India. Because of high variation in the dry weight of the trees it was not possible to assess annual requirement of P by the trees. Hence a measure of comparability between P present in different months was sought to be established by expressing the quantity of P in a part of the tree as percentage of that in the whole tree.
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    Fertilization with phosphorus and nitrogen in young spruce stands (Picea abies Karst.) (1983)
    Springer
    Nutrient cycling in agroecosystems 4 (1983), S. 155-164 
    Details
    ISSN: 1573-0867
    Keywords: nitrogen ; phosphorus ; fertilization ; Norway spruce ; quartz-porphyry site ; reforestation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Growth of young Norway spruce plantations on quartz-porphyry sites can be improved by applying phosphorus fertilizer as this acid parent rock is extremely poor in phosphorus. If fertilization is performed in connection with reforestation, the increment in height and volume of the developing crop increases for a period of about ten years. Additional liming prolongs the duration of the P-fertilization effect up to 20 years. Liming stabilizes phosphorus in an available form in the humus layer and upper soil horizon. Nitrogen deficiency occurs only 10 to 15 years after planting and N applied up to then has no positive effect on spruce growth.
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    Response of mango (Mangifera indica L) to foliar application of phosphorus (1983)
    Springer
    Nutrient cycling in agroecosystems 4 (1983), S. 281-285 
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    ISSN: 1573-0867
    Keywords: mango ; foliar spray ; orthophosphoric acid ; phosphorus ; urea ; utilisation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Orthophosphoric acid (0.5%) was sprayed along with and without 2 per cent urea on the mango (Mangifera indica L) cv. Langra trees in the months of September, November or March as well as in all the three months. There was an improvement of fruit set in the sprayed treatments which was high after March sprays. Significantly higher yields were obtained in triple spray treatments along with urea. The percentage of phosphorus in the fruits was raised by the sprays. The yield of phosphorus in the fruits was highest in March spray treatment and progressively less in November and September spray treatments. It was concluded that the urea given along with phosphorus improved the utilisation of phosphorus in the fruits by providing a better balance of nutrients.
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    Thermal conductivity of nitrogen at high pressures (1980)
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    International journal of thermophysics 1 (1980), S. 375-381 
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    ISSN: 1572-9567
    Keywords: thermal conductivity ; high pressure ; nitrogen ; computer simulation ; modified Enskog theory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The results of the measurements of the thermal conductivity coefficients of nitrogen at 298.15 K from atmospheric pressure up to 1 GPa are reported. The experimental values are used to test the Modified Enskog Theory and the corresponding state principle. The experimental values are also compared with the results of computer simulation of the thermal conductivity of a Lennard Jones fluid.
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    The responses of lake waters to organic matter additions (1983)
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    Hydrobiologia 107 (1983), S. 203-212 
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    ISSN: 1573-5117
    Keywords: lake waters ; organic matter ; nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The increase of inorganic nitrogen subsequent to the addition of organic matter was investigated in replicate lake-water aliquots. Two experiments used freshly killed bacteria as the organic addition. In both, inorganic nitrogen in the water column increased only after a lag period following the organic addition, and only if the amount of organic matter added exceeded a threshold value. Two other experiments used freshly killed algae as the organic addition; in these, neither the lag period nor the threshold value were seen. A qualitative explanation for these observations is offered.
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    Annual changes of nitrogen and phosphorus in two aquatic macrophytes (Nymphaea Tuberosa and Ceratophyllum Demersum) (1980)
    Springer
    Hydrobiologia 70 (1980), S. 31-35 
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    ISSN: 1573-5117
    Keywords: macrophyte ; nitrogen ; phosphorus ; nutrients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The nitrogen and phosphorus content of Nymphaea tuberosa and Ceratophyllum demersum, in Lake Onalaska, Wisconsin, was studied for a year. On a yearly basis, N. tuberosa exhibited nitrogen and phosphorus differences among seasons and among plant parts. Variation among plant parts was also evident in C. demersum. However, within individual plant structures, no seasonal differences were observed.
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    Decay rates and nitrogen dynamics of decomposing watercress (Nasturtium officinale R.Br.) (1983)
    Springer
    Hydrobiologia 99 (1983), S. 207-214 
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    ISSN: 1573-5117
    Keywords: ammonification ; aquatic macrophyte ; decomposition ; Nasturtium officinale ; nitrification ; nitrogen ; stream ecology ; watercress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We examined the decomposition of watercress in the laboratory at 10° and 20 °C, and in the field. Rates varied from 0.058 g g−1 day−1 in the laboratory to 0.115 g g−1 day−1 in the field. There was a rapid generation of particles of size 〈500 µm. It is thought that washout of these from the litterbags in the field accounted for high field decomposition rate. Formation of dissolved nitrogen compounds during decomposition followed a time series from NH inf4 sup+ to NO in2 sup− to NO inf3 sup− withdissolved organic nitrogen accumulating at the end of decomposition. Ammonification rates were 480 and 657 g NH4-N g−1 (dry wt) day−1 and nitrification rates on the decomposing tissue were 640 and 571 µg NO3-N g−1 (dry wt) day−1 at 10° and 20 °C respectively. Fifty-six per cent of the initial plant N was regenerated as NO3-N 21% as DON and 25% remained as refractory particulate N.
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    Sensitivity of an insect mechanoreceptor after destruction of dendritic microtubules by means of vinblastine (1983)
    Springer
    Cell & tissue research 229 (1983), S. 673-684 
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    ISSN: 1432-0878
    Keywords: Mechanoreception ; Sensory dendrite ; Microtubules ; Vinblastine ; Insect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Microtubules (Mt) are present in the modified cilium of epithelial mechanoreceptors of insects in three different arrangements: (1) 9 doublet Mt in the proximal region of the outer segment, (2) densely packed, interconnected Mt of the tubular body in the dendritic tip receiving the adequate stimuli, and (3) Mt between ciliary neck and tubular body, which are not fixed in a special configuration and therefore called free Mt. The free Mt are considered by some authors to be elements of intracellular signal transmission. This hypothesis was examined by electrophysiological and morphological studies on a tibial hair-mechanoreceptor of a cricket (Acheta domesticus). Exposure of the receptor from the apical side to vinblastine disassembled the free Mt within 2 to 4 h, while Mt of the tubular body were only little affected during this time interval. In this state of Mt disassembly (up to 7 h of application) mechanosensitivity of the receptor is only slightly reduced or not at all. The pacemaker property of the dendrite for nerve impulse is also preserved. It is concluded that the free Mt are not elements of intracellular signal transmission and are not directly involved in mechanotransduction.
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    Microtubule polarity in the nutritive tubes of insect ovarioles (1983)
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    Cell & tissue research 233 (1983), S. 133-141 
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    ISSN: 1432-0878
    Keywords: Microtubules ; Polarity ; Elongation ; Cytoplasmic transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The enormous numbers of microtubules within the nutritive tubes of hemipteran ovarioles are amenable to the hook-decoration technique for determining microtubule structural polarity, as they can be microdissected from ovarioles intact. This has allowed the correlation between the polarity of this continuously elongating complex of microtubules within a nutritive tube and the direction of transport along its length; and has shown that the plus or fast growing ends of the microtubules are all situated at the anterior end of a nutritive tube proximal to the trophic region from which synthesised materials are passed back towards the developing oocytes.
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    The microtubular system of crayfish retinula cells and its changes in relation to screening-pigment migration (1983)
    Springer
    Cell & tissue research 232 (1983), S. 335-348 
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    ISSN: 1432-0878
    Keywords: Cytoskeleton ; Crayfish ; Microtubules ; Photoreceptors ; Pigment migration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The organization of the microtubular system in crayfish retinula cells and its changes in relation to the light-dependent migrations of the screening pigment were studied by electron microscopy. A massive column of microtubules extends longitudinally throughout each retinula cell and its axon. The column is formed by overlapping fascicles of microtubules that originate from the vicinity of the rhabdomeres at multiple levels along the rhabdom. The pigment granules and other organelles are in general aligned with these fascicles and peripheral to the microtubular column. Close associations between microtubules and pigment granules are frequent. The total number of microtubules decreases nucleofugally from an average of about 500 at the middle of the rhabdom, to 390 at the proximal end of the rhabdom, and 240 in the axon below the basement membrane. The longitudinal distribution of microtubules was found similar for cells with the screening pigment in opposite extreme positions. In cells with the pigment in an intermediate position the number of microtubules was found to be nearly doubled in each of the mentioned levels; however, this change was correlated with a parallel increase in the cross-sectional area of the cells during the intermediate state. Thus, the density of microtubules tends to remain fairly constant throughout the light/dark adaptation cycle. These observations suggest that the microtubular system of the crayfish retinula cells constitutes a relatively stationary framework during screening-pigment movements, and could possibly act as a supportive guiding track for pigment transport.
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    Ultrastructural observations on changes in cell shape in chromatophores of the sea urchin Centrostephanus longispinus (1980)
    Springer
    Cell & tissue research 206 (1980), S. 21-33 
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    ISSN: 1432-0878
    Keywords: Chromatophores ; Light-sensitivity ; Alteration in cell shape ; Microtubules ; Echinoids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Alterations in cell shape of the light-sensitive chromatophores of the sea urchin Centrostephanus longispinus were studied by scanning- and transmission electron microscopy. Transition of the aggregated to the dispersed state is accompanied by incorporation of vesicles into the membrane of the pigment cell. During dispersion a system of microtubules originating from centriole-like structures is established throughout the stellate cell. Within restricted areas of the cell, cytoplasmic differentiation and condensation is found. The possible functional significance of the findings is briefly discussed.
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    Inhibition of intracellular protein transport in the mouse exocrine pancreas induced by vinblastine (1980)
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    Cell & tissue research 206 (1980), S. 73-81 
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    ISSN: 1432-0878
    Keywords: Exocrine pancreas (mouse) ; Electron microscopic autoradiography ; Microtubules ; Protein transport ; Vinblastine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The effect of vinblastine on the intracellular transport of newly synthesized protein in the mouse exocrine pancreas in vivo was studied by electron microscopic autoradiography after administration of 3H-leucine. Vinblastine (1.1 μmole/mouse; i.v. injection) was in general given 1 h before radioleucine and 2–4 h before fixation of the pancreas by perfusion with glutaraldehyde. Vinblastine causes the disappearance of microtubules, mainly present in controls in the apical portion of the acinar cell. After injection of vinblastine, zymogen granules form clusters located throughout the cell but often associated with Golgi areas. The latter are enlarged mainly due to the accumulation of small vesicles. In addition, Golgi areas are displaced, most often in an apical direction. Electron microscopic autoradiography demonstrated that vinblastine delays the appearance of labeled protein in zymogen granules; even 2 h after injection of radioleucine the majority of silver grains is located over the rough endoplasmic reticulum while very few grains are related to zymogen granules. This finding might be related to the structural changes of the Golgi areas observed. Although intracellular migration of protein is retarded, zymogen granules are formed. However, many of the labeled granules are found in peculiar locations, often distant from the acinar lumen. The present study suggests that vinblastine, possibly due to its effect on microtubules, influences both the formation and the translocation of zymogen granules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00233609
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  • 81
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    Role of microtubules in milk secretion — Action of colchicine on microtubules and exocytosis of secretory vesicles in rat mammary epithelial cells (1980)
    Springer
    Cell & tissue research 207 (1980), S. 361-376 
    Details
    ISSN: 1432-0878
    Keywords: Microtubules ; Colchicine ; Secretory vesicles ; Milk secretion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Effect of colchicine on microtubules was studied in mammary epithelial cells treated both in vivo and in vitro with the alkaloid. Three hours after the intramammary infusion of colchicine, secretory activity of mammary epithelia ceased, milk constituents accumulated and were randomly distributed within the cytoplasm, sometimes leaking into the perialveolar connective tissue, and autophagic vacuoles were prevalent. It appeared that an accelerated involutionary process was occurring. No microtubules were observed after this treatment. In vitro treated cells appeared to be less affected by the alkaloid. Although numerous casein-containing secretory vesicles accumulated in the cytoplasm, lipid droplet accumulation was less, and fewer autophagic vacuoles were observed, although lysosomes were commonly observed. Occasionally, obliquely sectioned microtubules were found in cells treated with low concentrations of colchicine but were absent at higher colchicine concentrations; however, paracrystalline inclusions (tubulin aggregates) were observed in some cells at all concentrations of the drug. These observations provide evidence that drugs which interfere with microtubule integrity reduce the secretory activity in mammary epithelia. This evidence is consistent with the concept of an association of the microtubular system and the secretory process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00224613
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  • 82
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    Cold and metabolic inhibitor effects on cytoplasmic microtubules and the Golgi complex in cultured rat epiphyseal chondrocytes (1980)
    Springer
    Cell & tissue research 210 (1980), S. 403-415 
    Details
    ISSN: 1432-0878
    Keywords: Chondrocytes ; Golgi complex ; Microtubules ; Colchicine ; Metabolic inhibitors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Previous work has shown that exposure of cultured chondrocytes to colchicine leads to disappearance of microtubules and dispersion of the dictyosomes of the Golgi complex throughout the cytoplasm. Here, the effects of cold and metabolic inhibitors on cultured chondrocytes have been investigated in order to characterize further the relationship between these organelle systems. After incubation of cells for 24 h at 4° C most, but not all microtubules disappeared, indicating the existence of cold-resistant microtubules. Dictyosomes remained united in one area, until transfer of cultures to 37° C, when they dispersed throughout the cytoplasm in about one-third of the cells. In cells exposed simultaneously to cold and colchicine, microtubules disappeared completely, but spreading of dictyosomes occurred only in some cells and became generalized first upon warming. Application of the metabolic inhibitors sodium azide or sodium fluoride (10-2 M) or 2-deoxyglucose (5×10-2 M) together with sodium cyanide (10-2 M) inhibited microtubule removal by colchicine. Consequently, spreading of the Golgi complex was prevented. These findings support the concept of an important role of microtubules in the organization of the Golgi complex. Moreover, depolymerization of microtubules by colchicine appears to be an energy dependent process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00220198
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  • 83
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    Ultrastructural observation of paracrystalline aggregates of microtubules in anterior pituitary cells of the chinchilla (Chinchilla laniger) (1980)
    Springer
    Cell & tissue research 213 (1980), S. 433-440 
    Details
    ISSN: 1432-0878
    Keywords: Anterior pituitary ; Microtubules ; Paracrystalline aggregates ; Ultrastructure ; Chinchilla
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Unusual paracrystalline aggregates of microtubules which have not been described in any other mammalian species were observed in cultured anterior pituitary cells of normal chinchillas as well as in situ in the pituitary glands of these animals. These aggregates appeared as regularly arranged tubular structures in the longitudinal plane, and as a checkerboard pattern of closely and regularly packed microtubules when examined in transverse section. Supplementation with vinblastine, colcemide or colchicine in the culture medium did not change these structures morphologically. Each unit of tubules consisted of an outer wall or parellelogram profile and an inner wall composed of a single hexagonal doublet or in a figure “8” form. The outer wall of the parallelogram was 35×28 nm in length for both sides, while the diagonal of the inner wall was 18×28 nm. These paracrystalline aggregates of microtubules in the chinchilla pituitary cells are morphologically distinct from the paracrystalline assembly of cytoplasmic microtubules induced by vinblastine or other alkaloids. The function and significance of these paracrystalline aggregates in anterior pituitary cells of the chinchilla are uncertain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00237889
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  • 84
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    Multiple effects of colchicine on oogenesis in Drosophila: Induced sterility and switch of potential oocyte to nurse-cell developmental pathway (1983)
    Springer
    Cell & tissue research 228 (1983), S. 21-32 
    Details
    ISSN: 1432-0878
    Keywords: Drosophila ; Oogenesis ; Colchicine ; Microtubules ; Sterility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Adult female fruitflies exposed to colchicine admixed to the culture medium show a series of dosage-related abnormalities that affect oogenesis and may induce sterility. Among the effects observed were decreased fecundity and hatchability of laid eggs, formation of oocytes lacking chorionic appendages, abnormal distribution and diminution in number of yolk spheres, inhibition of oocyte growth and abnormally located oocyte nuclei. Potentially the most significant effect was the development of egg chambers which contained the normal complement of 16 cells but in which all the cells had the nuclear morphology of nurse cells. The approach provides for the first time an experimental means to divert a potential oocyte into the developmental pathway of the nurse cell in a wild-type fly, and hence should be helpful in the elucidation of factors which control oocyte and nurse cell differentiation. In addition, the results serve to expand the usefulness of oogenesis in Drosophila as a model system for the evaluation of drug-induced metabolic-morphologic abnormalities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00206261
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  • 85
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    Morphometry of the small intestinal enterocytes of the fasted rat and the effects of colchicine (1983)
    Springer
    Cell & tissue research 231 (1983), S. 289-299 
    Details
    ISSN: 1432-0878
    Keywords: Enterocytes ; Microtubules ; Colchicine ; Cell membrane ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The function of the microtubules that are present in the villus enterocytes of the mammalian small intestine is virtually unknown. In order to advance our knowledge about enterocyte microtubules, a quantitative ultrastructural comparison was carried out on enterocytes from rats injected intraperitoneally with colchicine (0.5 mg/100 g body weight) in saline and from rats injected with saline alone. Our morphometric and stereologic study demonstrates that colchicine treatment results in 1) an absolute decrease in microtubules, 2) a reduction in microvilli, essentially in length, 3) an increased thickness of the terminal web, 4) an increase in total lysosomal volume, apparently by an increased number of smaller lysosomes, and 5) a decrease in the number of Golgi lamellae. These results along with those from other studies suggest to us that enterocyte microtubules are involved in the biogenesis of microvillus plasma membrane. Our morphometric data from the saline-treated rats essentially agree with comparable data from other studies. However, comparison with comparable data from hamster enterocytes demonstrates species differences.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00222181
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  • 86
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    Synaptic development and microtubule organization (1983)
    Springer
    Cell & tissue research 231 (1983), S. 93-102 
    Details
    ISSN: 1432-0878
    Keywords: Synapses ; Microtubules ; Presynaptic dense projections ; Development
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Using techniques for enhanced microtubular preservation (albumin pretreatment of Gray) occipital and pyriform cortices of rats were studied by electron microscopy at various stages of development. A close structural relationship was seen between microtubules (mts), focal membrane densities, synaptic vesicles, and presynaptic dense projections (pre-dps) during maturation. Mts were seen in the neonates to be focused onto the inner surface of immature axonic profiles merging or sometimes fragmenting there. Focal densities occur at these attachment sites and thereafter synaptic vesicles clothe the mts and abut onto these presumed primordial pre-dps. Thus, mts may contribute to the initial formation of pre-dps as well as their maintenance in the adult and may act to channel the first synaptic vesicles to the site of eventual synaptic contact and transmitter release.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00215777
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