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  • Articles  (197)
  • Electron microscopy  (141)
  • Auxin  (30)
  • Nicotiana  (27)
  • Springer  (197)
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  • 1980-1984
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  • 1978  (104)
  • 1977  (93)
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  • Articles  (197)
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  • Springer  (197)
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  • 1995-1999
  • 1980-1984
  • 1975-1979  (197)
  • 1925-1929
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  • 1
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    Calcified tissue international 25 (1978), S. 217-222 
    ISSN: 1432-0827
    Keywords: Bone mineral ; Electron microscopy ; X-ray diffraction ; Dark field
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Electron microscopical observations of the size and shape of bone mineral crystallites have not been in complete agreement with X-ray diffraction findings. The two prevalent viewpoints consider bone mineral crystals to be either rod, or plate like in habit. There appears to be agreement that the smallest dimension of the crystals is about 5 nm, but there is discrepancy in the reported c-axial lengths. The method of dark field imaging is used to obtain a quantitative measurement of the c-axial length distribution in rabbit, ox and human bone: mean c-axial lengths 32.6 nm, 36.2 nm and 32.4 nm, respectively, show no significant difference at the 5% level to the mean c-axial length measured by X-ray line broadening. Both bright and dark field images strongly suggest that bone mineral has a plate like form. Reasons for past discrepancies are discussed.
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  • 2
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    Mycopathologia 60 (1977), S. 175-177 
    ISSN: 1573-0832
    Keywords: Aspergillus fumigatus ; Spore formation ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
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  • 3
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    Mycopathologia 61 (1977), S. 117-119 
    ISSN: 1573-0832
    Keywords: Prototheca ; Colorless alga ; Plastids ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract An ultrastructural investigation of six different species of Prototheca showed that all of them contained starch grains enclosed in double-membrane-bounded structures recognized as plastids. It is concluded that these unicellular species of Prototheca must be considered as non-photosynthetic algae.
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  • 4
    ISSN: 1432-041X
    Keywords: Synaptogenesis ; Electron microscopy ; Visual acuity ; Fish development
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The morphogenetic differentiation of synapses of the optic tectum of the rainbow trout was investigated at different stages of development (from hatching to adult) and compared with the improvement in visual discrimination (minimum separable). (1) The main phase of synaptogenesis (increase in number of synapses, length of contact zone and number of vesicles) begins about one week after hatching and continues up to the age of one month, when the larvae start swimming freely. (2) Myelination begins 26 days after hatching and induces the end of the synaptogenesis period. (3) The visual discrimination (minimum separable) of trout larvae improves from 30 degrees of arc on the 10th day after hatching to 1 degree on day 30, then to about 14 to 18 min of arc in the adult. The results are discussed with special reference to previous biochemical investigations on changes in the ganglioside composition of the trout brain during comparable periods of development.
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  • 5
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    Calcified tissue international 26 (1978), S. 181-190 
    ISSN: 1432-0827
    Keywords: Cellular calcium ; Electron microscopy ; Osteoblasts ; Chondrocytes ; Mineralization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The calcium distribution in cartilage and bone cells during beginning ossification of fetal mouse long bones was studied after fixation with 2% K-pyroantimonate in 1% osmium. In the developing periosteum, the future osteoblasts showed a sparse cation-antimonate precipitate over the cytoplasm. In young osteoblasts the precipitate was accumulated on the mitochondrial membranes and the plasmalemma. Both organelles were sharply outlined by precipitate in the mature osteoblasts at the onset of mineralization. X-Ray microprobe analysis of these organelles demonstrated the presence of both Sb and Ca. In the extracellular compartment, a collagen-associated precipitate with 50 to 60 nm periodicity appeared during osteoblastic differentiation. During the initial phase of matrix mineralization, a random gross precipitate appeared in the matrix and seemed to be accumulated by osmiophilic matrix vesicles while the collagen fibrils lost their precipitate. Subsequently, during the confluent phase of matrix mineralization, the precipitate rapidly disappeared from the cells, leaving them devoid of precipitate once they were surrounded by mineralized matrix. Similar changes were found in the chondrocytes of the growth plate, but cartilage collagen, unlike osteoid collagen, did not bind precipitate. The results indicate that both osteoblasts and calcifying cartilage cells bind calcium prior to matrix mineralization. Bone collagen has strong pyroantimonate binding capacity, but it is not directly involved with initial stages of matrix mineralization, which starts in close association with matrix vesicles.
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  • 6
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    Calcified tissue international 23 (1977), S. 215-223 
    ISSN: 1432-0827
    Keywords: Amorphous mineral ; Bone ; Electron microscopy ; Ultracryotomy ; Ultramicro-incineration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The fine structure of the extracellular phase of avian medullary bone and embryonic chick femur was examined in thin sections prepared by ultracryotomy and ultramicroincineration. Since contact with solutions was completely avoided, little or no loss or dislocation of mineral constituents could occur. Amorphous bone mineral (ABM) was present in two forms: as 15–30 nm spheres and as a structure-free haze. Removal of all organic material by low temperature ashing left the ABM intact. Crystals were usually associated with the ABM. In newly ossifying regions clusters or nodules of randomly oriented crystals and ABM appeared to coalesce when they reached approximately 1 μm in diameter. In highly calcified regions crystals appeared to be oriented along collagen fibers. ABM did not appear to be associated with collagen. Unmineralized collagen was visible in osteoid after staining with dry OsO4 vapor and it appeared to be diverted around nodules. Structures which resembled matrix vesicles were present. Selected area electron diffraction patterns indicated the presence of hydroxyapatite.
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  • 7
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    Calcified tissue international 25 (1978), S. 179-190 
    ISSN: 1432-0827
    Keywords: Decalcification ; Electron microscopy ; Calcified matrices
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The ultrastructure of calcifying cartilage and bone has been examined under the electron microscope after using three different methods of decalcification. The first was carried out before embedding (by soaking specimens in EDTA or formic acid), the second after embedding (by floating ultrathin sections on formic acid), and the third after embedding (by soaking embedded specimens in EDTA or formic acid), and with later re-embedding. The first procedure invariably induces drastic changes in the fine structure of the cells and calcified matrix, probably as a results of the extraction of organic material along with extraction of mineral. The second and third procedures make it possible to preserve ultrastructural details perfectly in both cells and calcified matrix. Of the two, the third procedure is preferable because of its greater simplicity. In areas that are still calcifying, these post-embedding decalcification techniques reveal the presence of crystal-associated, filamentous organic structures which are not recognizable in specimens decalcified before embedding. These structures, which could have a key role in inducing and regulating crystal formation and growth, are less evident in fully calcified areas (but not at their borders). This may partly be due to the loss of glycan components in the matrix during calcification. The most important determinant, however, seems to be the fact that during calcification the components of the matrix, including collagen fibrils, are involved in an aggregation process which reduces the amounts of free chemical groups available for reaction with the stain solution. Because post-embedding decalcification does not disturb this state of aggregation, the stainability of the matrix and the electron microscopic evidence of its components remain very low.
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  • 8
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    Calcified tissue international 24 (1977), S. 191-197 
    ISSN: 1432-0827
    Keywords: Amelogenesis imperfecta ; Hypocalcification ; Hypoplasia ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary An ultrastructural study of teeth with amelogenesis imperfecta revelaed various aspects of microcavities in the enamel surface, which ranged from isolated imprints of ameloblasts corresponding to the mildest lesions at the end of amelogenesis, to pits caused by the death of 20 to 30 ameloblasts at the beginning of amelogenesis. Abnormalities in the shape of the prisms can be observed. Further, crystals are distributed randomly within a prism or at the junction of 2 contiguous prisms while intercrystalline spaces are widened, indicating in various places the lack of a preferred orientation of the crystals. In amelogenesis imperfecta, two different crystalline periods are found: 1 of about 250 Å, the other of about 500 Å and over. The fact that amorphous areas are found among the crystals of enamel may be related to different stages of crystallization. However, it was not possible to find any lattice defect.
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  • 9
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    Calcified tissue international 24 (1977), S. 239-242 
    ISSN: 1432-0827
    Keywords: Cementum ; Lysis ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Examination of microradiographs from the deciduous teeth of pigs revealed large lacunae or radiolucent zones close to the cemento-dentinal junction. Electron microscopic studies of the ground sections showed areas or irregularly shaped zones devoid of mineral and filled with collagen fibers. In the wide unmineralized zones, spherical clusters of crystallites were noted. Several cementum lacunae bordered by a broad rim of unmineralized collagen fibers were noted and some lacunae also contained zones of a moderately electron dense material. This material did not yield a diffraction pattern, while the mineralized part of the cementum gave the diffraction pattern typical of hydroxyapatite.
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  • 10
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    Calcified tissue international 25 (1978), S. 45-51 
    ISSN: 1432-0827
    Keywords: CaCO3 ; Amino acids ; Sheaths ; Ligament ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The aragonite crystals in the molluscan bivalve hinge ligament are surrounded by an organic sheath which is distinct from the remainder of the ligament matrix. Methods have been developed to isolate these sheathed crystals from the ligaments ofSpisula solidissima andMercenaria mercenaria employing a papain digestion of the matrix protein. The sheathed crystals fromSpisula have a CaCO3/protein ratio of 11.1 and those fromMercenaria a ratio of 29.6. The sheathed crystals and the empty crystal sheaths have been examined by electron microscopy for structural integrity. The sheath proteins exhibit much smaller proportions of the amino acids glycine and methionine than the hinge ligaments. These are characteristic amino acids of high concentration in the hinge ligaments of both species. The concentrations of acidic and basic amino acids are increased about two fold in the sheaths over those of the ligaments. Otherwise there is little similarity in the amino acid composition of the sheaths in the two species. However, SDS electrophoresis shows the sheaths of both to contain a major protein component with a molecular weight of about 25,000. The sheath protein from theMercenaria ligament contains about 5% carbohydrate and that ofSpisula sheaths less than 1% carbohydrate.
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  • 11
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    Calcified tissue international 25 (1978), S. 133-143 
    ISSN: 1432-0827
    Keywords: Osteon ; X-Ray diffraction ; Electron microscopy ; Calcification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary To obtain information on the changes in the inorganic bone fraction during calcification, low- and wide-angle X-ray diffraction techniques and electron microscopy have been applied to single osteon samples. The samples were cylindrically shaped and their axes corresponded to the axes of the Haversian canals. The selection was made according to the degree of calcification and the orientation of collagen bundles and inorganic particles. Osteons at both the initial and final stages of calcification were chosen. Arrangements of fiber bundles and inorganic particles in successive lamellae characteristic of three types of osteon were selected, that is, longitudinally structured osteons, transversely structured osteons, and alternately structured osteons. The results indicate that in osteonic lamellar bone there are two types of inorganic particles: (1) granules arranged in linear or needle-shaped entities with maximum width 40–45 Å, which are regularly distributed at the level of the main band of the collagen fibrils where their maximum length reaches the length of the main band itself; that is, about 400 Å; and (2) very long crystallites, with a diameter of 40–45 Å, which grow with their crystallographicc-axis parallel to the collagen fibrils and cover much more than a major collagen period.
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  • 12
    ISSN: 1432-2048
    Keywords: Antirrhinum ; Cellulose ; Nicotiana ; Protoplasts ; Scanning microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The formation of cell wall fibres at the surface of isolated leaf protoplasts has been studied by scanning electron microscopy. Fibres are not formed on incubated protoplasts until a lag period has elapsed. This period is about 8 h for leaf protoplasts of Nicotiana tabacum and about 45 h for leaf protoplasts of Antirrhinum majus. In the case of Antirrhinum protoplasts the length of the lag period is dependent on the concentration of osmoticum present during the incubation period. If regenerating protoplasts are briefly treated with dilute cellulase, the newly formed wall is completely digested. Such protoplasts are capable of producing new fibres at the surface within minutes of their return to a nutrient medium. These results are discussed in terms of the likely source of the lag period and its significance in wall regeneration studies.
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  • 13
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    Planta 139 (1978), S. 155-158 
    ISSN: 1432-2048
    Keywords: Avena ; Cell-wall regeneration ; Electrical potential ; Nicotiana ; Protoplast culture ; Turgor pressure ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Four independent kinds of observations indicate that the cell wall regenerated by oat (Avena sativa L.) and corn (Zea mays L.) protoplasts in culture is less well developed than that regenerated by tobacco (Nicotiana tabacum L.) protoplasts. Following wall regeneration the cereal protoplasts remained susceptible to osmotic shock upon transfer to water, showed great enlargement, stained poorly with calcofluor white, and maintained a positive internal electrical potential. The development of a negative membrane potential by tobacco protoplasts in culture often occurred simultaneously with the onset of cell division. Since division was observed only in protoplasts which had regenerated good cell walls and had re-established negative membrane potentials it is suggested that culture conditions which favor these two processes should improve protoplast viability.
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  • 14
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    Planta 134 (1977), S. 145-149 
    ISSN: 1432-2048
    Keywords: Affinity labels ; Auxin ; Cell membranes ; Hormone Receptors ; Receptors ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Two auxin analogues have been tested as affinity labels for auxin binding sites in coleoptile membranes of Zea mays L. Reacting the membranes at pH 8–9 with the diazonium salt of CAPA (2-chloro-4-aminophenoxyacetic acid) reduces their subsequent ability to bind NAA(1-naphthylacetic acid). Diazo-Chloramben (2,5-dichloro-3-aminobenzoic acid) is also effective in inhibiting NAA binding capacity and this inhibition is largely independent of reaction pH over the range pH 6–9. Similar experiments with sulphydryl reagents have shown that reaction of the membranes with p-mercuribenzoate (PMB) strongly inhibits subsequent auxin binding activity. Prior addition of NAA protects the binding sites against the action of diazo-Chloramben or PMB when the reactions are carried out at pH 6. From these results and from other considerations, several of the amino acid residues in the binding site environment have been tentatively assigned.
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  • 15
    ISSN: 1432-2048
    Keywords: Auxin ; Avena ; Helianthus ; pH drop ; Pisum ; Protoplast suspension
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Several indoleacetic acids, substituted in the benzene ring, were compared in the Avena straight growth bioassay. 4-Chloroindoleacetic acid, a naturally occurring plant hormone, is one of the strongest hormones in this bioassay. With an optimum at 10-6 mol l-1, it is more active than indoleacetic acid, 2,4-dichlorphenoxyacetic acid and naphthaleneacetic acid. 5-Chloro- and 6-chloroindoleacetic acids are very strong auxins as well. Other derivatives tested have a lower activity. 5,7-Dichloro- and 5-hydroxyindoleacetic acids have very low auxin activity at 10-4 mol l-1 and may be anti-auxins. Some of the derivatives were compared for their effect on pH decline in stem protoplast suspensions of Helianthus annuus L. and Pisum sativum L. The change of pH occurs without a lag period or with only a very short one. Derivatives which are very active in the Avena straight growth assay cause a larger pH decline than indoleacetic acid, while inactive derivatives cause effectively no pH decline.
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  • 16
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    Planta 140 (1978), S. 107-109 
    ISSN: 1432-2048
    Keywords: Auxin ; Leaf movement ; Phaseolus ; Pulvinus ; Turgor movement
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Auxin application to the upper side of the pulvinus of primary leaves of Phaseolus vulgaris L. promoted bending away from the place of application. The effect had a latency of less than 20 min and was specifically induced by substances known as active auxins in growth tests (indoleacetic and 1-naphthaleneacetic acid) but not by inactive auxin analogs (2-naphthaleneacetic, 3-indolepropionic and benzoic acid); 2,4-dichlorophenoxyacetic acid, and L-(-)-2,4-dichlorophenoxyisopropionic acid were of intermediate activity. Auxin-promoted bending was reversible and presumably caused by turgor increase in the treated cells.
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  • 17
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    Planta 140 (1978), S. 201-211 
    ISSN: 1432-2048
    Keywords: Auxin ; Cell elongation ; Coleoptiles ; Fusicoccin ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract To analyze early effects of auxin application, an apparatus was developed which continuously and simultaneously registered the curvature of 10 individual maize (Zea mays L.) coleoptiles. Resolution was less than 5 μm over a range of ±0.5 mm. The data were evaluated and plotted via paper tape and Hewlett-Packard-computer. Unilateral application of 3×10-5 M indoleacetic acid (IAA) resulted in a transient inhibition of growth on the side of application for ca. 10 min (Phase I), followed by a strong stimulation (Phase II). The phytotoxin fusicoccin (FC) caused an immediate stimulation of elongation. The initial negative reaction of Phase I is auxin-specific. Only active auxins such as IAA and 1-naphtaleneacetic acid produced this initial inhibition; chemical analogs-inhibitory or neutral in long-term growth tests, e.g. phenylacetic acid-did not show any significant effects on Phase I. When the coleoptiles were symmetrically preloaded with different levels of auxin, only a large step-up of subsequent unilateral auxin application resulted in a negative phase I; a small step-up led to an immediate positive reaction. The results are discussed in context with the parallel kinetics for various other auxin-induced reactions of coleoptile cells which have already been published.
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  • 18
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    Planta 135 (1977), S. 177-181 
    ISSN: 1432-2048
    Keywords: Cell division ; Cell wall regeneration ; Cellulose synthesis ; Nicotiana ; protoplast culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Addition of cellulose to the culture medium inhibited cell wall regeneration and nuclear and cell division in tobacco (Nicotiana tabacum L.) mesophyll protoplasts. When the activity of celllase was inhibited by cellobiose, the inhibition of nuclear and cell division was overcome. Cell wall formation thus appears to be a prerequisite for nuclear and cell division in tobacco protoplasts.
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  • 19
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    Planta 136 (1977), S. 97-102 
    ISSN: 1432-2048
    Keywords: Acid growth ; Auxin ; Ethylene ; Fusicoccin ; Growth inhibition ; Lens ; Root growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Both acid pH (4.0) and fusicoccin (FC) strongly stimulate root elongation in intact lentil (Lens culinaris Med.) seedlings. FC-induced elongation is apparently mediated by FC-enhanced H+ secretion since the toxin induces massive secretion of H+ in these roots after a latent period of less than 5 min. Auxin (indole-3-acetic acid) strongly inhibits elongation in control roots as well as acid-induced and FC-induced root elongation. Treatment of apical root segments with auxin causes only a slight apparent uptake of H+ and has no inhibitory effect on FC-induced H+ secretion, whether the hormone is given before or after the toxin. Auxin induces ethylene production in excised roots of lentil but the latent period is at least 30 min while inhibition of root elongation by IAA is maximal within 30 min. It is concluded that the inhibitory action of auxin on acid-and fusicoccin-induced root elongation is a direct effect, independent of auxin-induced ethylene production or auxin-mediated modification of cell-wall pH.
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  • 20
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    Planta 137 (1977), S. 97-105 
    ISSN: 1432-2048
    Keywords: Chloroplast ; Ferredoxin-coding-site ; Nicotiana
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Ferredoxins were isolated and purified from leaves of different species of Nicotiana and Petunia and from spinach leaves. Their spectral properties, degree of homogeneity, and molecular weights were determined. The preparations were further analyzed by polyacrylamide gel electrophoresis of tryptic hydrolysates. This allowed us to distinguish between not only ferredoxins of Nicotiana, Petunia, and spinach, but even ferredoxins of various Nicotiana species. We used the differences in tryptic peptide compositions as phenotypic markers to study the mode of inheritance of chloroplast ferredoxin to see whether the coding site is in the chloroplast or in the nucleus. Analysis of the tryptic peptide composition of ferredoxin from different interspecific hybrids of Nicotiana showed that the characteristics of both parental ferredoxins were present. The results indicate that the primary structure of at least the male ferredoxin is coded for in the nucleus. In some of the hybrids the relative contribution of the male parent appeared to be low, suggesting that the female genome (presumably that part located in the plastome) exerted a dominating influence.
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  • 21
    ISSN: 1432-2048
    Keywords: Chloroplast ; Ferredoxin ; Immunofluorescence ; Nicotiana
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Antibodies were raised in rabbits against 2Fe−2S ferredoxin from N. tabacum L. The antibodies showed partial cross-reactivity in the double diffusion test with ferredoxins from Spinacia oleracea L., Petunia inflata Fries., P. axillaris Lam., Phaseolus vulgaris L., Chlamydomonas remhardii Dang. A complete cross-reaction was observed with ferredoxins from five other Nicotiana species, thus with this test it was impossible to discriminate between these ferredoxins. Therefore the following test was performed. Heterologous ferredoxin (i.e., ferredoxin other than from N. tabacum) was coupled covalently to Sepharose beads. Rabbit anti-N. tabacum-serum was then pre-incubated with this ferredoxin which resulted in complete abolition of cross-reactivity with free heterologous ferredoxin. However, the serum retained antibody activity against specific antigenic determinants of N. tabacum ferredoxin. When this serum was tested against ferredoxin purified from the hybrid: N. tabacum (♀)xN. glutinosa (♂) it gave a positive reaction. The relative content of maternal N. tabacum ferredoxin in the hybrid was estimated by using a fluorescent derivative of this specific antibody and estimating the cross-reactivity compared with that of artificial mixtures of pure N. tabacum and N. glutinosa ferredoxins. The hybrid contained 50% of maternal ferredoxin. This technique was also applied to ferredoxins of other species of Nicotiana and to the ferredoxin from the hybrid N. clevelandii (♀)xN. glutinosa (♂). We conclude that it provides a good test system for the study of the expression of chloroplast ferredoxin in Nicotiana hybrids in general.
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  • 22
    ISSN: 1432-2048
    Keywords: Abelmoschus ; Auxin ; Gibberellin ; Root formation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Indole-3-acetic acid (IAA) and gibberellic acid (GA3) enhanced the formation of roots on the stem cuttings of Abelmoschus esculentus. The effect increased considerably when both IAA and GA3 were applied together.
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  • 23
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    Planta 138 (1978), S. 107-110 
    ISSN: 1432-2048
    Keywords: Auxin ; Nitrogen fixation (asymbiotic) ; Pisum ; Rhizobium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Treatment of epicotyls of dark-grown pea (Pisum sativum L.) seedlings with indole-3-acetic acid causes swelling of the tissue. Application of Rhizobium to the cut surface of the swollen tissue results in the development of an “infection”. The infection spreads in the cortical cells and proceeds 2–3 mm deep into the stem within 3–4 days. An acetylene reduction assay used for detecting nitrogen-fixation capacity of the infected tissue was negative at 10% [O2]; however, if [O2] was reduced to below 1%, some activity could be detected. Ultrastructural observations indicate that the cytoplasmic contents of the infected cells are destroyed and no membrane structure around the bacteria is formed during this infection. Rhizobium does not appear to have developed any symbiotic relationship with the host. Failure to develop symbiosis appears to result in a parasitic or saprophytic association and the nitrogen fixed under such conditions may not be of any use to the plant.
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  • 24
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    Planta 138 (1978), S. 181-184 
    ISSN: 1432-2048
    Keywords: Abscisic acid ; Auxin ; Cannabis ; Cytokinin ; Flowers (sex) ; Gibberellin ; Sex expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Application, through the root system, of growth regulators to hemp (Cannabis sativa L.) plants having 2–3 pairs of visible leaves caused pronounced shifts of sex expression in the adult individuals. Treatment with gibberellic acid (25 mg/l) resulted in more than 80% of the plants being male, i.e. having staminate flowers (controls, ca. 30%). Treatment with 6-benzylaminopurine and with indole-3-acetic acid (in either case, 15 mg/l) resulted in all plants being either female (pistillate flowers) or intersexes (bisexual flowers); treatment with abscisic acid (10 mg/l) had a similar but somewhat less pronounced effect.
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  • 25
    ISSN: 1432-2048
    Keywords: Auxin ; Ethylene ; Root formation ; Vigna
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Rooting responses and ethylene production by hypocotyl cuttings from etiolated mung-bean seedlings treated with the auxins α-naphthaleneacetic acid, γ-(indole-3)-n-butyric acid (IBA) and 2,4,5-trichloro-phenoxypropionic acid were determined. There was no relationship between the abilities of the auxins to induce root formation and their capacities for inducing ethylene production. Studies with mixtures of 3-indoleacetic acid, a poor stimulator of rooting but an effective inducer of ethylene production, and IBA, an effective rooting stimulator but a poor inducer of ethylene production, exposure of cuttings to ethylene or (2-chloroethyl) phosphonic acid (Ethephon), hypobaric storage (150 mb) of treated cuttings, and exposure of auxin-treated cuttings to 7% CO2 also indicated that ethylene is not directly involved in initiation of adventitious roots in this plant material.
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  • 26
    ISSN: 1432-2048
    Keywords: Auxin ; Fusicoccin ; Glucose transport ; Proton flux ; Roots ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Auxin and fusicoccin (FC) stimulate the active uptake of 3-O-methyl glucose (3-O-MG) in those materials in which they have been shown to activate an electrogenic proton extrusion (Pisum sativum L. stems, Zea mays L. coleoptiles and roots). In maize roots the curve relating 3-O-MG influx to external concentrations indicated that the values of the apparent Km increase in the 3-O-MG concentration range between 2×10-5 mol l-1 and 2×10-2 mol l-1. FC did not alter the Km values and its stimulating effect was nearly constant at all 3-O-MG concentrations tested. Basal and FC-induced uptake of 3-O-MG appeared associated with a transient proton influx suggesting that also in maize roots a sugar-proton contransport occurs. Diethyl stilbestrol, which inhibits proton extrusion, inhibited also basal and FC-induced 3-O-MG uptake. The data support the view that the stimulation by FC of 3-O-MG uptake is closely related to that of proton extrusion. The stimulation by FC of 3-O-MG uptake cannot be replaced by increasing extracellular proton concentration, nor may be explained only by the FC-induced hyperpolarization of transmembrane potential difference. The hypothesis is proposed that the effect of FC on 3-O-MG uptake depends on an increase of cytoplasmic pH, following the activation of the proton extruding system.
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  • 27
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    Planta 141 (1978), S. 179-181 
    ISSN: 1432-2048
    Keywords: Auxin ; Maize ; Root tip ; Zea
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    Topics: Biology
    Notes: Abstract [5-3H]Indol-3yl-acetic acid (IAA) applied to the shoot apices of intact 6-day-old maize (Zea mays L.) plants moved into the primary root and accumulated at the root apex. IAA from the shoot could partially satisfy the requirement of the primary root for IAA for growth.
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  • 28
    ISSN: 1432-2048
    Keywords: AMO-1618 ; Antiauxin ; Auxin ; Bromodeoxyuridine ; Cell (fiber) growth ; Gibberellin ; Gossypium ; Ovules (in-vitro culture)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effects of 5-bromo-2-deoxyuridine (BUdR, thymidine analogue), AMO-1618 (2-isopropyl-4-dimethylamino-5-methylphenyl-1-piperidine carboxylate methyl chloride), a growth retardant, and p-chlorophenoxyisobutyric acid (PCIB, an antiauxin) on growth (dry weight increase) and fiber development in unfertilized cotton (Gossypium hirsutum L.) ovules grown in vitro have been studied. BUdR (5 μM) causes about 70% inhibition of fiber production, with little effect on ovule growth, if applied during the first 6 d of culture in the presence of GA3 and IAA. AMO-1618, when used with GA3 alone, causes only a small reduction in both dry weight and fiber production, but when used with IAA alone reduces both fiber production and dry weight, the effect on the latter being predominant. In the presence of both IAA and GA3, AMO-1618 causes a small decrease in fiber production but a major decrease in dry weight. PCIB completely inhibits fiber growth but has little effect on dry weight, especially when GA3 is present. These results indicate that GA3 mainly promotes ovule growth while IAA is largerly responsible for fiber growth.
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  • 29
    ISSN: 1432-2048
    Keywords: Auxin ; Chlorophyll content ; Chloroplast ; Photosynthetic rate ; Raphanus
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    Topics: Biology
    Notes: Abstract Dark-grown radish seedlings (Raphanus sativus L.) were sprayed with 10-3 mol·l-1 2,4-dichlorophenoxyacetic acid and then were exposed to a 14:10 light: dark cycle. Cotyledon samples from these seedlings and unsprayed controls were taken for electron microscopy, chlorophyll determinations, and photosynthetic rate measurements at regular intervals for 72 h. A normal development of etioplasts to chloroplasts with formation of typical grana-fret work system was observed in the control cotyledons. The chloroplasts in the 2,4-D-treated cotyledons showed changes in the organization of the grana thylakoids; these thylakoids being more appressed to each other than in the controls. The chlorophyll content of treated plants was less than that of controls but the rate of chlorophyll biosynthesis was unaffected. The photosynthetic rate/mg chlorophyll was considerably higher for treated plants suggesting that 2,4-D treatment resulted in decreased size of the photosynthetic unit.
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  • 30
    ISSN: 1432-2048
    Keywords: Cell culture ; Cytokinin ; Funaria ; Protonema ; Nicotiana ; Photoaffinity labeling
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    Topics: Biology
    Notes: Abstract A cytokinin photoaffinity reagent, 8-azido-N 6-benzyladenine (8N3BA), was synthesized from 8-bromoadenosine via azide replacement, benzylation at N−1, rearrangement to the N-6-benzyl derivative and acid hydrolysis. The compound thus obtained was found to have full cytokinin activity in the moss and tobacco cell-suspension bioassays. Photolysis of 8N3BA was accomplished with long and short-wavelength ultraviolet light and produced compounds which had very little or no biological activity in the two bioassays. In-vivo photolysis of 8N3BA caused loss of the cytokinin activity of this compound in moss protonemata. This result was similar to earlier ones where the biological response of moss protonemata to benzyladenine was reversed following removal of the hormone by a short rinse with water.
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  • 31
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    Planta 144 (1978), S. 39-47 
    ISSN: 1432-2048
    Keywords: Aquatic plants ; Auxin ; Cell elongation ; Ethylene ; Ethylene biosynthesis ; Silverions
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    Topics: Biology
    Notes: Abstract Elongation of the shoots of three aquatic plants (Hydrocharis morsus-ranae, Regnellidium diphyllum and Ranunculus sceleratus) is stimulated by treatment with ethylene or IAA. The effects of the two hormones are additive, and experiments with an ethylene biosynthesis inhibitor and silver ions indicate that the mechanisms by which ethylene and IAA stimulate growth may be different. Hydrocharis and Ranunculus leaf discs synthesize [14C]ethylene from [14C]methionine, but no [14C]ethylene is formed by Regnellidium, suggesting the existence of an alternative pathway of ethylene biosynthesis in the fern.
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  • 32
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    Planta 136 (1977), S. 173-180 
    ISSN: 1432-2048
    Keywords: Auxin ; Immunoassay ; Nicotiana ; Radioimmunoassay
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    Topics: Biology
    Notes: Abstract We have developed a specific radioimmunoassay [RIA] for indole-3-acetic acid (IAA) in the 0.2 ng to 12 ng range which, in principle, can be extended to other indole auxins as well. Methods are presented for obtaining suitable antibody, for the RIA procedure, and for measuring IAA in methanolic extracts of plant tissues. Antibody specific for IAA was obtained from rabbits immunized with IAA bound to bovine serum albumin by formaldehyde treatment. In assays with this antibody, 2,4-dichlorophenoxyacetic acid and indoles structurally related to IAA reacted from 300- to 3000-fold less than did IAA itself. However, α-and β-naphthaleneacetic acid reacted significantly and hence interfered with the assay. Extracts of tobacco (Nicotiana tabacum L.) tissue were immunoassayed after partial purification by buffer-ether partition. Crown-gall tumor tissue, which is auxin-autotrophic, and pith tissue depleted of auxin by the diffusion method contained, respectively, 26.7 ng and 〈0.5 ng extractable IAA per gram fresh weight.
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  • 33
    ISSN: 1432-2048
    Keywords: Auxin ; Calcium ions ; Cell growth ; Gibberellin ; Membrane permeability ; Membrane potential ; Zea
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    Topics: Biology
    Notes: Abstract The membrane potential difference of dwarf maize coleoptile cells is increased by both 10-5moll-1 gibberellic acid (GA3) and indoleacetic acid (IAA) a few minutes after application. A final level is reached after 10–20 min. The membrane permeability ratio P Na:P K is altered by both hormones during the first 15 min after application, indicating a rapid effect on the membrane. Elongation growth of coleoptile segments, however, is only stimulated by IAA. The auxin-induced growth as well as the auxin effect on membrane permeability depends on the calcium ion concentration of the medium. It is concluded that IAA acts via a proton extrusion pump that is electrically balanced by a potassium ion uptake, driven by the electromotive force of the pump. The mode of action of GA3 on elongation growth is assumed to involve a process that depends on the physiologic state of the tissue and/or metabolic energy.
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  • 34
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    Planta 140 (1978), S. 31-35 
    ISSN: 1432-2048
    Keywords: Auxin ; Coleoptiles ; Electrical Potential ; Zea
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    Topics: Biology
    Notes: Abstract Following asymmetric application of indoleacetic acid to maize (Zea mays L.) coleoptiles the early time course of changes in lateral electrical potential was externally monitored with static-drop electrodes. First, an early negative potential change of ca.-1 mV was measured at the surface on the side of a strong auxin application. This negative auxin effect ended after ca. 15 min and was followed by a strong and lasting auxin stimulation of a positive lateral potential up to +12 mV at the auxin-treated side. The initial auxin effect appeared to depend on the size of the step-up in auxin concentration.
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  • 35
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    Planta 140 (1978), S. 137-142 
    ISSN: 1432-2048
    Keywords: Auxin ; Cell elongation ; Proton secretion ; Triticum
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    Topics: Biology
    Notes: Abstract Growth of Triticum aestivum L. cv. Cappelle Desprez coleoptiles is promoted by 5.7×10−5 M indole acetic acid (IAA) as effectively in pH 3.4 buffer as in water, but IAA is not effective in the presence of buffer at pH 3.0 or 3.2 A combination of 5.7×10−5 M IAA and pH 3.4 buffer promotes growth to a greater extent than pH 3.2 buffer alone, which is optimal for acid-induced growth. IAA employed at 10−7 M is still effective at promoting growth in the presence of pH 3.4 buffer, moreover, IAA at 10−7 M interacts synergistically with the acidic buffer to promote growth. It is concluded that IAA and acid promote growth via separate mechanisms, and that IAA does not promote cell wall loosening by rendering the cell wall more acid.
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  • 36
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    Planta 140 (1978), S. 293-294 
    ISSN: 1432-2048
    Keywords: Callus culture ; DPX-3778 ; Nicotiana ; Tissue culture ; Triazinone
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    Topics: Biology
    Notes: Abstract DPX-3778, the triethanolamine salt of 3-(p-chlorophenyl)-6-methoxy-s-triazine-2,4(1H,3H) dione, at concentrations of 0.124–2.48 μM enhanced ca. 4-5-fold the proliferation of tobacco (Nicotiana tabacum L. cv. Wisconsin 38) callus cultured in the presence of indole-3-acetic acid and kinetin, and retarded its senescence.
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  • 37
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    Planta 144 (1978), S. 79-84 
    ISSN: 1432-2048
    Keywords: Auxin ; Cell elongation ; Lead ; Triticum
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    Notes: Abstract In vitro studies of IAA-induced cell elongation in Triticum aestivum have demonstrated that lead causes a large reduction in elongation. Inhibition of elongation can be reduced by increasing the concentration of IAA, or by the addition of calcium. The inhibitory effect appears to be linked with changes in the properties of the cell walls. Experiments are described which show that lead becomes bound strongly to certain chemical substances involved in cell wall architecture.
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  • 38
    ISSN: 1432-2048
    Keywords: Hypersensitivity ; Nicotiana ; o-Diphenols ; O-Methyltransferases ; Tobacco mosaic virus
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    Topics: Biology
    Notes: Abstract Three distinct o-diphenol O-methyltransferases (OMTs) were found in leaves of Nicotiana tabacum, variety Samsun NN. They could be clearly distinguished by differences in elution pattern upon chromatography on DEAE-cellulose and in specificity towards 16 diphenolic substrates. The phenylpropanoids caffeic acid and 5-hydroxyferulic acid, whose importance as lignin precursors is well known, were the best substrates of OMT I, but they were also efficiently methylated by the two other OMTs that showed a broader substrate specificity. The highest rates of methylation were observed by assaying these latter enzymes with catechol, homocatechol and protocatechuic aldehyde. The flavonoid quercetin, the major o-diphenol of tobacco leaves, was a good substrate for OMTs II and III, but was also methylated significantly by OMT I. The tobacco OMTs showed both para-and meta-directing activities with protocatechuic acid, protocatechuic aldehyde and esculetin as substrates. Para-O-methylation of the former substrate arose almost exclusively from OMT I whereas that of the two latter substrates from all three enzymes. In healthy leaves the total O-methylating activity varied very much with the batch of plants whereas the relative contributions of the three enzymes were rather constant. On an average, OMTs I, II and III acounted towards caffeic acid, respectively. In tobacco mosaic virus-infected leaves carrying local necrotic lesions we found the same three OMTs with the same substrate specificities, but with increased activities. The degree of stimulation of both OMTs II and III was 2–3 times greater than that of OMT I when the leaves had a moderate number of lesions, and 3–5 times greater with large number of lesions. It is very likely that the changes in both the pattern of the O-methylating enzymes and the concentrations of the naturally occuring o-diphenolic substrates are related to an increased biosynthesis of lignins and of lignin-like compounds. These aromatic polymers could be involved in the cell wall thickening associated with the hypersensitive reaction and with the resistance to virus spread that occur in the cells surrounding the local lesions.
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  • 39
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    Planta 142 (1978), S. 207-210 
    ISSN: 1432-2048
    Keywords: Abscisic acid ; Auxin ; Cytokinin ; Flowers (sex) ; Gibberellin ; Sex expression ; Spinacia
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    Topics: Biology
    Notes: Abstract When 7-d-old plantlets of spinach (Spinacia oleracea L.) were immersed with their roots for 24 h in 25 mg/l gibberellic acid (GA3), or 15 mg/l 6-benzylaminopurine (6-BAP), or 15 mg/l indole-3-acetic acid (IAA), or 10 mg/l abscisic acid (ABA) and subsequently grown on long (18-h) days, the ratio of plants with male and female flowers, which in the controls was almost 1:1 (48 and 52%, respectively), was greatly altered. The treatments with 6-BAP, IAA and ABA raised the percentage of female plants to 88, 76 and 71%, respectively; the GA3 treatment increased the percent of male plants to 79%. When young, vegetative spinach plants (3 visible leaves) grown in 18-h days were cut a the root neck, and the shoots grown with their bases in nutrient solution, with adventitious roots either being allowed to develop or being systematically removed, 85% of the plants without roots became males, 85% of those with roots became females. But if the cut shoots were first, for 28 h, placed in a 15-mg/l 6-BAP solution and then grown in the absence of roots, the percent of female plants was restored to 84. These results fully agree with those obtained previously with hemp, namely, that plant growth regulators exert a regulating effect on the sex expression of dioecious plants when applied through the roots in early stages of development; that the root system plays an important role in determining the sex of these plants, that this role of the roots is associated with the synthesis of cytokinins in them. Dioecious short- and long-day plants do not differ in these respects.
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  • 40
    ISSN: 1432-2048
    Keywords: Cell wall formation ; Cytokinesis ; Inhibitors ; Mitosis ; Nicotiana
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    Topics: Biology
    Notes: Abstract The effect of cytochalasin B, colchicine, coumarin and 2,6-dichlorobenzonitrile on cell wall formation and cellular division was studied by light and electron microscopy with tobacco mesophyll protoplasts cultivated in vitro. 2,6-dichlorobenzonitrile was found to be the most effective and reversible inhibitor of cell wall formation. The other inhibitors caused irreversible damage and/or inhibited mitosis. In protoplasts cultivated in the presence of 2,6-dichlorobenzonitrile the total inhibition of cell wall formation had no effect on nuclear division, but cytokinesis was totally inhibited so that multinucleate protoplasts were obtained.
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  • 41
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    Planta 143 (1978), S. 29-32 
    ISSN: 1432-2048
    Keywords: Hybrids (somatic) ; Isoenzymes ; Kanamycin resistance ; Nicotiana ; Somatic hybrids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Fusion of Nicotiana knightiana Goodsp. and kanamycin resistant Nicotiana sylvestris Speg. et Com. protoplasts was induced by polyethylene glycol treatment. Heterokaryons were isolated by micropipette and transferred to nurse cultures of albino cells. Colonies originating from the heterokaryons could subsequently be distinguished by their green colour. The somatic hybrid nature of four such colonies was confirmed by isoenzyme pattern, kanamycin resistance and restored morphogenic potential. An additional kanamycin resistant line with characteristic Nicotiana knightiana isoenzymes was also found indicating that the drug resistance in the kanamycin resistant parent is under cytoplasmic control.
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  • 42
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    Planta 141 (1978), S. 77-82 
    ISSN: 1432-2048
    Keywords: Cell wall ; myo-Inositol ; Nicotiana ; Polysaccharides (cell wall) ; Tissue culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Tobacco (Nicotiana tabacum L.) cells were cultured in a liquid medium which contained sucrose as a source of carbon and energy. Various cell-wall constituents and wall precursors (L-arabinose, D-xylose, D-galactose, D-mannose, D-glucuronate, myo-inositol) were added to cells growing in this medium to by-pass possible rate-limiting steps in the relevant metabolic pathways. None of these compounds stimulated growth as measured by increase in fresh weight; myo-inositol did cause a slight increase and L-arabinose a decrease in dry weight accumulation compared to controls grown on sucrose only. Although myo-inositol was not needed for rapid growth, tracer level amounts of [2-3H]myo-inositol were rapidly absorbed and metabolized. Label was incorporated into the uronide and pentose residues of cell walls and exocellular polysaccharide.
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  • 43
    ISSN: 1432-2048
    Keywords: Auxin ; Benzoxazolinones ; Receptors ; Supernatant factor ; Zea
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    Topics: Biology
    Notes: Abstract A naturally-occurring material termed ‘supernatant factor’ [Ray, P.R., Dohrmann, U., Hertel, R.: Plant Physiol. 59. 357–364 (1977)], which has the property of modifying the binding affinity of auxins to receptor sites, has been isolated from corn (Zea mays L.) and characterised as a mixture of 6-methoxy-2-benzoxazolinone (MBOA) and 6,7-dimethoxy-2-benzoxazolinone (DMBOA). DMBOA is about 50 times more active than MBOA in inhibiting binding of the auxin 1-naphthylacetic acid to membrane-bound or solubilised receptors. The activity of these compounds and the parent analogue in inhibiting auxin binding is correlated with their ability to inhibit auxin-induced growth.
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  • 44
    ISSN: 1432-2048
    Keywords: Auxin ; Compartmental analysis ; Ion fluxes ; Petroselinum ; Suspension culture
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    Topics: Biology
    Notes: Abstract Transport of 86Rb+/K+, 22Na+, 36Cl−, and [3H]indole acetic acid (IAA) has been studied on suspension-cultured cells of the parsley, Petroselinum crispum (Mill) Nym. By compartmental analysis two intracellular compartments of K+, Na+, and Cl− have been identified and ascribed to the cytoplasm and vacuole; half-times of exchange were around 200 s and 5 h, respectively. According to the Ussing-Teorell flux equation, active transport is required for the influx into the cytoplasm at the plasmalemma (K+, Cl−) and the tonoplast (K+, Na+, Cl−). The plasmalemma permeability pattern, PK:PNa:PCl=1.00:0.24:0.38, features an increased chloride permeability compared with cells from higher plant tissues. IAA uptake showed an exponential timecourse, was half-maximal after 10 min, and a linear function of the IAA concentration from 10−9 to 10−5 M. IAA and 2,4-dichlorophenoxy acetic acid reduce the apparent influx of K+, Na+, Cl− during the initial 30 min after addition and subsequently accelerate both in- and efflux of these ions. We discuss that auxins could affect the ion fluxes in a complex way, e.g. by protonophorous activity and by control of the hypothetical proton pump.
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  • 45
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    Planta 142 (1978), S. 235-238 
    ISSN: 1432-2048
    Keywords: Brassica ; Cell-cell interaction ; Nicotiana ; Petunia ; Protoplasts (surface charge) ; Vigna
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    Topics: Biology
    Notes: Abstract ζ-potential of mesophyll protoplasts of tobacco (Nicotiana tabacum L.), petunia (Petunia hybrida Hort.), turnip (Brassica rapa L.) and cowpea (Vigna unguiculata L. Walpers) was determined by use of a cell electrophoresis apparatus. All protoplasts examined showed a constant negative value of-10 to-35 mV. The addition of CaCl2 nullified the ζ-potential of tobacco protoplasts. This phenomenon is explained by DLVO theory of colloid science, which has been successfully applied to animal cells. Furthermore, positively charged polymers reversed the ζ-potential to positive values. Treatment of the protoplast surface with several enzymes was carried out to characterize the chemical nature of suface charges. The removal of surface charges was most conspicuous by the treatment of acid phosphatase (EC 3.1.3.2), but did not occur upon treatment with α-neuraminidase (EC 3.2.1.18) or Streptomyces griseus pronase. Thus a major part of the surface charge originates from the phosphate groups at the cell membrane. The significance of these studies for the properties of the protoplast surface in cell adhesion is discussed.
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  • 46
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    Planta 138 (1978), S. 299-301 
    ISSN: 1432-2048
    Keywords: Bryophytes ; Funaria ; Nicotiana ; Protein pattern ; Pteridophytes
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    Topics: Biology
    Notes: Abstract Soluble proteins extracted with Tris-buffer pH 8.8 from different mosses are analysed by microgelelectrophoretic method for comparison to the specific proteins present only in the caulonema of Funaria hygrometrica. The protein patterns are also compared with those of liverwort, fern gametophytes and sporophytes and tobacco. It is observed that the “caulonema specific proteins” are only present in the caulonema of these mosses and are absent in other plants.
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  • 47
    ISSN: 1432-2048
    Keywords: Cell wall ; Cellulose ; Lycopersicum ; Nicotiana ; Plasmalemmasomes ; Plasma membrane ; Protoplasts ; Raphanus
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    Topics: Biology
    Notes: Abstract Freeze-etch observations of protoplasts isolated from tobacco (Nicotiana tabacum L.) mesophyll tissue and tomato (Lycopersicum esculentum Mill.) fruit locule tissue are described which clarify earlier observations (Burgess, J., Fleming, E.N., Planta 131, 173–178, 1976; Planta 133, 267–273, 1977), obtained using scanning electron microscopy. of “fibres” associated with “projections” from these cell surfaces. It is demonstrated (1) that the “fibres” consist of bundles of small numbers of microfibrils which have become artifactually thickened by the deposition of coating materials, and (2) that the apparent association between “fibres” and “projections” results from microfibrils being lifted preferentially from protoplast surfaces in regions rich in “projections” (plasmalemmasomes). With the higher resolution available using freeze-etching it can be demonstrated that microfibril deposition does not occur in discontinuous zones on these protoplast surfaces. Globules associated with microfibril termini in radish (Raphanus sativus L.) roots are illustrated and it is proposed that turgor pressure differences between isolated protoplasts and intact tissue may account for the absence of similar globules from isolated protoplast surfaces.
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  • 48
    ISSN: 1432-2048
    Keywords: Auxin ; Cytokinin ; 5-Fluorouracil ; Helianthus ; Ribosome synthesis and activity ; Tuber
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    Topics: Biology
    Notes: Abstract In order to examine the relation of protein synthesis to the onset of growth, changes in ribosome content and activity were compared in aged, metabolically active Jerusalem artichoke (Helianthus tuberosus L.) slices incubated in water or 2,4-dichlorophenoxyacetic acid+kinetin. In water, cells do not grow or divide and rRNA and protein levels remain constant. The percentage membrane-bound (mb) ribosomes drops from 25% to 16% during 24h. At the same time the proportion of ribosomes active in protein synthesis in both free and mb populations declines from about 69% to 54%. In auxin+kinetin, cell expansion occurs and is accompanied by a 3-fold increase in rRNA and a 50% increase in total protein content. The percentage mb ribosomes remains at 25% throughout 48 h of growth. During the first 24h of growth 70% of ribosomes in both free and mb populations are active; this value declines to near water levels at 48 h. Considering the large increase in total ribosomes the number of synthetically active ribosomes is substantially increased during growth. 5-Fluorouracil (5-FU) does not inhibit hormone induced growth but does depress total rRNA content by about one-third. It also reduces [3H]uridine incorporation into ribosomes by 70% and the newly made ribosomes are mostly inactive in protein synthesis. On the other hand, the inhibitor does not significantly affect the proportion of total ribosomes active in protein synthesis and only partially reduces protein accumulation during the second 24 h of growth. It is suggested that while ribosome production is reduced in 5-FU, ribosome turnover is also retarded resulting in retention of near normal capacity for protein synthesis and growth.
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  • 49
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    Planta 135 (1977), S. 289-295 
    ISSN: 1432-2048
    Keywords: Antiauxin ; Auxin ; Meristem differentiation ; Riella
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract During the development of the unistratose gemmae of Riella helicophylla, the single intercalary meristem of the very young gemmae is subdivided into two lateral meristems. The duration of the cell reproduction cycle increases from the margin to the median part of the gemmae. This polarization within the meristem disappears after addition of the antiauxin PCIB to the culture medium. PCIB leads to a retardation or blockage of the cell cycle during the light period of the culture. Under the influence of PCIB the amount of starch in the chloroplasts is strikingly increased, probably because of a reduction of starch degradation. Addition of sugars compensates the effect of PCIB on the cell cycle. The effects of PCIB are counteracted by auxin. The results are taken as evidence that auxin plays a role in directing the transport of substances needed for the continuation of the cell reproduction cycle between adjacent cells of the meristem.
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  • 50
    ISSN: 1432-2048
    Keywords: Nucleic acid synthesis ; Nicotiana ; Osmotic stress ; Protein synthesis ; Protoplasts
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    Topics: Biology
    Notes: Abstract The incorporation of labeled precursors into RNAs and proteins of isolated tobacco (Nicotiana tabacum L.) leaf protoplasts decreases with increasing osmotic pressure in the incubation medium. The incorporation of precursors into RNA and proteins is linear for 15–18 h after the isolation of the protoplasts, irrespective of the osmolarity of the culture media. The uptake of precursors is also affected by the osmolarity of the medium. However, the osmotic stress-induced inhibition of incorporation of precursors into RNA and proteins is also apparent if the differences in uptake are taken into consideration in the calculation. Incorporation of 32P into TMV-RNA is also inhibited by osmotic stress. As assayed by the double labeling ratio technique, osmotic stress has less unequivocal effect on TMV protein synthesis.
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  • 51
    ISSN: 1432-2048
    Keywords: Cell cultures ; Medicago ; Nicotiana ; Nitrogen sources ; TCA cycle ; Tissue culture ; Triticum
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    Topics: Biology
    Notes: Abstract Alfalfa (Medicago sativa L. cv. Canadian No. 1), tobacco (Nicotiana tabacum L. var. humilis) and wheat (triticum monococcum L.) cells were grown in a defined, liquid medium containing either ammonium sulfate, L-glutamine or potassium nitrate as the sole nitrogen source, and the effects of the tricarboxylic-acid (TCA) intermediates, citrate and α-ketoglutarate (5, 10, 15 mM), on the growth (dry-weight increase) of these cells was observed. The three cell suspension cultures exhibited a different growth response to the TCA-cycle intermediate supplied, depending upon the concentration of the additive and the nitrogen source. Citrate (5 mM) greatly enhanced growth of alfalfa and wheat cells in an ammonium-based medium but was less effective at higher concentrations, and in the case of alfalfa cells markedly inhibited growth. Tobacco cell growth was inhibited by all citrate concentrations tested. In contrast, all concentrations of α-ketoglutarate used stimulated the growth of all three cell cultures in an ammonium-based medium. Alfalfa and wheat cells grown in an L-glutamine-based medium were influenced by citrate in a manner similar to that in ammonium-based medium. The growth of tobacco cells was slightly enhanced by 5 mM citrate but inhibited by higher concentrations. α-Ketoglutarate, at all concentrations tested, was stimulatory to the growth of the cells of all three species in a glutamine-based medium, except for alfalfa cells which were inhibited at 15 mM. Both TCA-cycle acids inhibited the growth of alfalfa and tobacco cells grown on a nitrate-based medium whereas the growth of wheat cells was almost unaffected.
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  • 52
    ISSN: 1432-2048
    Keywords: Auxin ; Cambium ; Gibberellin ; Picea ; Tracheids-wood production
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    Topics: Biology
    Notes: Abstract The diameter and wall thickness of tracheids produced after indoleacetic acid treatment were not significantly different from those of the intact controls, for the first few weeks after treatment of disbudded shoots of Picea abies Karst. and Picea sitchensis (Bong.) Carr. However, lateral application of indoleacetic acid (IAA) to intact shoots increased both tracheid diameter and wall thickness; it is suggested that IAA acted synergistically with another endogenous growth regulator, which was also removed by disbudding. Increase in wall thickness after exogenous IAA was associated with increase in duration of the wall thickening phase of tracheid differentiation; this is discussed in relation to the seasonal change from early to latewood. Cambial dormancy was induced by disbudding during active wood production. Since this occurred with or without the presence of current leaves, it is concluded that in Picea continued cambial activity depends upon supply of auxin from the buds, and cannot be supplied from expanded leaves or from the internode itself. Neither indoleacetic acid nor gibberellic acid stimulated renewed cambial activity when applied after the cessation of wood production. With both disbudded and intact shoots, the effectiveness of exogenous IAA declined with time, probably due to decreasing penetration through callus developing at the wounded surface. It is suggested that this apparent change in IAA effectiveness may explain some discrepancies between the results of previous observers.
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  • 53
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    Planta 134 (1977), S. 295-299 
    ISSN: 1432-2048
    Keywords: Abscisic acid ; Apical dominance ; Auxin ; Gibberellin ; Hormone transport ; Phaseolus
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    Topics: Biology
    Notes: Abstract Abscisic acid (ABA) in lanolin, applied to the internode of decapitated runner bean plants enhances the outgrowth of lateral buds. The optimum concentration of the paste is 10-5 M. The effect of ABA is counteracted by indoleacetic acid (IAA) but not by gibberellic acid (GA3). There is no effect when ABA is applied to the apical bud or lateral buds of intact plants. However, 13.2 ng given to the lateral buds of decapitated plants stimulate their growth, whereas higher concentrations are inhibitory. Consequently, ABA enhances growth of lateral buds directly, but only when apical dominance is already weakened. The growth of the decapitated 2nd internode was not affected by ABA. Radioactivity from [2-14C] ABA, applied to nonelongating 2nd internode stumps of decapitated runner bean plants moves to the lateral buds, whereas [1-14C]IAA-and [3H]GA1-translocation is much weaker. ABA transport is inhibited if IAA or [3H]GA1 is applied simultaneously. In elongating internodes [14C]ABA is almost completely immobile. [14C]IAA-and [3H]GA1-translocation is not affected by ABA. The amount of radioactivity from labelled ABA, translocated to the lateral buds, is highest during the early stages of bud outgrowth.
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  • 54
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    Planta 134 (1977), S. 103-108 
    ISSN: 1432-2048
    Keywords: Amino-acid-analog resistance ; Auxin autotrophy ; Daucus ; Nicotiana ; Solanum ; Tissue culture ; Tryptophan
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Auxin autotrophy was studied in cultured carrot (Daucus carota L.), tobacco (Nicotiana tabacum L.), and potato (Solanum tuberosum L.) cell lines. Of 10 carrot lines resistant to 5-methyltryptophan (5MT), which accumulate free tryptophan (trp) because of an altered control enzyme, 5 were auxinautotrophic while the normal parent line was not. Carrot lines selected from the same parent line as resistant to other amino-acid analogs were not auxinautotrophic, like the parent. The only 5MT-resistant potato line studied was also auxin-autotrophic while the normal line was only partially auxin-autotrophic. The tobacco lines which accumulated free trp were not auxin-autotrophic, and no auxin-autotrophic tobacco lines were selected by screening for growth in medium lacking 2,4-dichlorophenoxyacetic acid (2,4-D). Several auxin-autotrophic carrot and potato lines were selected from the normal lines and none of these lines were resistant to 5MT. Length of time in culture and difficulty in selecting auxin-autotrophic lines were correlated on the 3 normal carrot lines studied. The addition of trp or indole to the culture medium would partially alleviate the auxin requirement of the normal lines studied. 2,4-D (0.4 mg/l) stimulated the growth of all auxin-autotrophic carrot lines.
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  • 55
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    Planta 135 (1977), S. 207-212 
    ISSN: 1432-2048
    Keywords: Auxin ; Cytokinin ; Explants ; Helianthus ; Tuber (explants) ; Xylem differentiation
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    Topics: Biology
    Notes: Abstract the culture of Jerusalem artichoke (Helianthus tuberosus L.) tuber explants on filter paper discs moistened with liquid medium resulted in rapid and consistent xylem differentiation. The number of tracheary elements increased in discrete steps, the first at 48 h with a second at 56–58 h, following partially synchronous mitoses at 20 and 30 h. Factors favouring xylem cell differentiation were optimum levels of both an auxin and a cytokinin, low medium nitrogen concentrations, small volumes of medium, and high culture temperatures. A cell counting method employing Feulgen-stained nuclei and suitable for quantifyings small numbers of immature tracheary elements is described.
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  • 56
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    Archives of microbiology 113 (1977), S. 197-204 
    ISSN: 1432-072X
    Keywords: Gliding bacterium ; Simonsiella ; Oral cavity ; Electron microscopy ; Morphology ; Dorsal-ventral differentiation ; Ultrastructure
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    Topics: Biology
    Notes: Abstract The morphology and ultrastructure of the aerobic, Gram-negative multicellular-filamentous bacteria of the genus Simonsiella were investigated by scanning and transmission electron microscopy. The flat, ribbon-shaped, multicellular filaments show dorsal-ventral differentiation with respect to their orientations to solid substrata. The dorsal surface, orientated away from the substrate, is convex and possesses an unstructured capsule. The ventral surface, on which the organisms adhere and glide, is concave and has an extracellular layer with fibrils extending at right angles from the cell wall. The cytoplasm in the ventral region contains a proliferation of intracytoplasmic membranes and few ribosomes in comparison to the cytoplasm in other parts of the cell. Centripetal cell wall formation is asymmetrical and commences preferentially in the ventral region. Quantitative differences in morphology and cytology exist among selected Simonsiella strains. Functional aspects of this dorsalventral differentiation are discussed with respect to the colonization and adherence of Simonsiella to mucosal squamous epithelial cells in its ecological habitat, the oral cavities of warm-blooded vertebrates.
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  • 57
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    Archives of microbiology 118 (1978), S. 67-69 
    ISSN: 1432-072X
    Keywords: Corynebacterium autotrophicum ; Outer Membrane ; Lipopolysaccharides ; Biochemical analysis ; Polymyxin B ; Electron microscopy
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    Topics: Biology
    Notes: Abstract Lipopolysaccharides (LPS) from Corynebacterium autotrophicum were isolated and analyzed. Autotrophically grown cells contained 2–5 mg of partly purified LPS per g dry weight of lyophilized cells. Serological cross reaction with Lipid A antigen of Salmonella minnesota confirmed the presence of LPS in C. autotrophicum. Electron microscopy of negatively stained Polymyxin B-treated cells showed formation of blebs on the Outer Membrane indicating an interaction of Polymyxin B specifically with LPS. Up to now, no Gram-positive organisms are known which contain any LPS. Thus, C. autotrophicum, though giving opposite results when the Gram-staining reaction was applied by several authors, has to be classified into the group of Gram-negative bacteria.
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  • 58
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    Archives of microbiology 119 (1978), S. 303-304 
    ISSN: 1432-072X
    Keywords: Vibrio cholera phage group II ; Properties ; Electron microscopy
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    Topics: Biology
    Notes: Abstract The basic physical, chemical and physiological properties of a group II cholera phage belonging to Mukerjee's classification has been described.
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  • 59
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    Archives of microbiology 119 (1978), S. 87-90 
    ISSN: 1432-072X
    Keywords: Salmonella typhimurium strain LT2 (ColIb) ; Cryptic plasmids ; Electron microscopy
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    Notes: Abstract Small cryptic plasmids of molecular weights ranging from 1 to 3 Mdal were detected by electron microscopy in Salmonella typhimurium strain LT2 (ColIb). They were divided into different size classes. Two of the cryptic plasmids were transferred simultaneously with ColIb to Escherichia coli.
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  • 60
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    Archives of microbiology 119 (1978), S. 227-229 
    ISSN: 1432-072X
    Keywords: Cell wall ; Electron microscopy ; Methylomonas albus ; Goblet sub-units
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    Notes: Abstract In surface view, the cell wall complex ofMethylomonas albus possesses a hexagonal pattern of ridges. Thin sections reveal a continuous layer of goblet-shaped elements attached to the outermost surface of the lipopolysaccharide membrane. A possible interpretation of the cell wall complex ofM. albus, based on the fine-structural data is presented.
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  • 61
    ISSN: 1432-072X
    Keywords: Acetobacterium woodii ; Hydrogen-oxidizing acetate-forming anaerobe ; Fine structure ; Electron microscopy
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    Notes: Abstract Acetobacterium woodii is a Gram-positive anaerobic nonsporeforming bacterium able to grow on H2 and CO2 as sole sources of energy. The product of fermentation is acetic acid. Fine structural analysis showed rod-shaped flagellated cells, and coccoid cells without flagella arranged predominantly in pairs and chains. The cell wall was found to be composed of three layers. The cell surface exhibited a periodic array of particles consisting of subunits. The cytoplasmic membrane showed particles either either in random distribution or in a hexagonal pattern. Intracytoplasmic membranes were rarely observed, whereas inclusion bodies of varying shapes, predominantly in an uncommon disc-shape, could frequently be observed. Their content was dissolved in ultrathin sections indicating hydrophobic nature.
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  • 62
    ISSN: 1432-072X
    Keywords: Defective lysogeny ; Alcaligenes eutrophus ; Simultaneous isolation technique ; Temperate bacteriophages ; Pseudomonas pseudoflava ; Biological characterization ; Electron microscopy
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    Notes: Abstract Widespread defective lysogeny was detected in Alcaligenes eutrophus by electron microscopic analysis of cultures. Mitomycin C treatment of the cultures resulted in the production of defective (inco-) particles. Polysheaths were produced both with and without induction. With the simultaneous isolation technique six phages were isolated for hydrogen-oxidizing strains of the new species Pseudomonas pseudoflava. The phages were able to replicate under autotrophic conditions and were found to have a very restricted host range. Electron microscopic analysis allowed classification into two structural groups. Group I contained phages with contractile tails; group II contained phages with flexible, noncontractile tails. All but one (gb) of the new phages were shown to be temperate by isolation of lysogens and induction with mitomycin C.
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  • 63
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    Archives of microbiology 112 (1977), S. 207-218 
    ISSN: 1432-072X
    Keywords: Cryptophyceae ; Algae ; Hemiselmis rufescens ; Chroomonas ; Cryptomonas ; Mitochondrial complex ; Cristae ; Electron microscopy
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    Notes: Abstract The unitary nature of the mitochondrion and the characteristic flattened finger-like morphology of the cristae were demonstrated in the Cryptophyceae. Hemiselmis rufescens contained an unbranched vermi-form mitochondrion in contrast to the variously branched complex, comprising an interconnected peripheral and central reticulum, in Chroomonas sp. and strains of Cryptomonas. The systematic value of the shape and distribution of the mitochondria in the examined genera was suggested.
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  • 64
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    Archives of microbiology 115 (1977), S. 185-198 
    ISSN: 1432-072X
    Keywords: Synechococcus lividus ; Cyanobacteria ; Carbon dioxide ; Electron microscopy ; Bleaching-regreening
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    Topics: Biology
    Notes: Abstract The effect of carbon dioxide on pigment and membrane content in Synechococcus lividus was studied by depriving cells of CO2 and examining cell populations biochemically and by electron microscopy. After 120 h of CO2 deprivation, S. lividus lost all detectable chlorophyll a and C-phycocyanin. Such bleached cultures were “mustard yellow”, the result of approximately 1.8 times more carotenoid per cell than green control cultures. Although cells from beached cultures appeared morphologically identical to control green cells when examined by light microscopy, electron microscopic examination revealed them to be devoid of detectable thylakoid membrane. Thylakoid membrane could not be recovered by physical isolation or revealed by freeze etching of bleached S. lividus. In addition, inclusion bodies characteristically found in S. lividus were also absent. Reintroduction of CO2 into bleached cultures resulted in a rapid resynthesis of both chlorophyll a and C-phycocyanin. Electron microscopic examination of these regreening cultures revealed that thylakoid membrane was also rapidly resynthesized. Growth of regreened cultures did not occur until there was the synthesis of a full complement of chlorophyll a, C-phycocyanin, and thylakoid membrane. A time course study of the cytological events occurring during bleaching and regreening is presented.
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  • 65
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    Archives of microbiology 118 (1978), S. 305-308 
    ISSN: 1432-072X
    Keywords: Carotenoid mutant strain R-26-Rhodopseudomonas sphaeroides ; Electron microscopy ; Intracellular membranes
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    Topics: Biology
    Notes: Abstract Stained thin-sections and freeze-fractured preparations of the carotenoid-less mutant strain R-26 of Rhodopseudomonas sphaeroides grown photosynthetically revealed 2 morphological kinds of intracellular membrane systems- spherical vesicles distributed throughout the cytoplasm and lamellae confined to the periphery of the cell. The lamellar membranes appeared to be large, flattened vesicles.
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  • 66
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    Archives of microbiology 116 (1978), S. 133-139 
    ISSN: 1432-072X
    Keywords: Lagenisma ; Coscinodiscus ; Infection ; Endosymbiotic bacteria ; Tip growth ; Wall-less thallus ; Host-parasite interface ; Membranes ; Electron microscopy
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    Topics: Biology
    Notes: Abstract Lagenisma coscinodisci is diplanetic and has two different cyst stages. The secondary cyst has a uniform cell wall of fibrillar material. It attaches to a Coscinodiscus frustule and germinates with an infection tube. The cyst becomes filled with an enlarging expulsion vacuole. The infection tube penetrates the diatom cell between the cingula. Inside the host cell the fungus grows as an irregularly branched wall-less thallus. In the hyphae apical vesicles are lacking. The infection tube is plugged by wall material. There are no microtubules which might participate in the morphogenesis of the thallus. The plasmalemma of the diatom is pushed inward but not pierced by the fungus. Along the host-parasite interface it lies closely paralled to the Lagenisma plasmalemma which is extremely straight here and measures about 10 nm instead of about 5–6 nm at the surfaces of other stages. The Coscinodiscus plasmalemma disintegrates at about the same time when the cytoplasm breaks down. The fungus allows bacteria to enter the diatom; there are also endosymbiontic bacteria in unattacked cells — The growth mechanisms are discussed and the host-parasite interface is compared with that of other fungi.
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  • 67
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    Biochemical genetics 15 (1977), S. 1143-1146 
    ISSN: 1573-4927
    Keywords: coupling factor 1 ; chloroplasts ; maternal inheritance ; Nicotiana
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    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract An analysis of interspecific hybrids of Nicotiana spp. in which one of the parents was sensitive to tentoxin showed that this sensitivity was transmitted only through the female parent. Since tentoxin acts by selectively binding to the α,β subunit complex of chloroplast coupling factor 1, the gene(s) specifying either one or both of these subunits is located in the cytoplasm.
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  • 68
    ISSN: 1432-2048
    Keywords: Auxin ; Avena ; Cell elongation ; Ion uptake ; Malate synthesis
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    Topics: Biology
    Notes: Abstract The short-term effects of auxin (indole-3-acetic acid) and fusicoccin (FC) on Rb+ uptake and malate accumulation in Avena sativa L. coleoptile sections have been investigated. FC stimulates 86Rb+ uptake within 1 min while auxin-enhanced uptake begins after a 15–20-min lag period. Auxin has little or no effect on 86Rb+ uptake at external pHs of 6.0 or less, but substantial auxin effects can be observed in the range of pH 6.5 to 7.5. Competition studies indicate that the uptake mechanism is specific for Rb+ and K+. After 3 h of auxin treatment the total amount of malate in the coleoptile sections is doubled compared to control sections. FC causes a doubling of malate levels within 60 min of treatment. Auxin-induced malate accumulation exhibits a sensitivity to inhibitors and pH which is similar to that observed for the H+-extrusion and Rb+-uptake responses. Both auxin- and FC-enhanced malate accumulation are stimulated by monovalent cations but this effect is not specific for K+.
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  • 69
    ISSN: 1432-2048
    Keywords: Anabaena ; Cell uptake ; Cyanobacterium ; Nicotiana ; Polyethylene glycol ; Protoplast
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    Notes: Abstract Auxotrophic cells of the filamentous cyanobacterium Anabaena variabilis Kütz. were introduced into protoplasts of Nicotiana tabacum L. in an attempt to engineer a nitrogen-fixing endosymbiosis. Conditions were established to maximize uptake of the cyanobacteria by use of polyethylene glycol. Culture of the novel association was not successful: tobacco protoplasts with Anabaena inside did not appear to divide. Most of the protoplasts expelled the cyanobacteria and simultaneously disintegrated. The reasons for the incompatibility are not known.
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  • 70
    ISSN: 1432-2048
    Keywords: Abscisic acid ; Auxin ; Cambium ; Picea
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    Topics: Biology
    Notes: Abstract Indole-3-acetic acid (IAA) and abscisic acid (ABA) were identified by combined gas chromatography-mass spectrometry (GCMS) in fractions obtained by diffusion and extraction from bark peelings of Sitka spruce. A procedure is described for the quantitative analysis of IAA and ABA levels in the same extract using the GCMS technique of single-ion current monitoring. This procedure was used to measure the diffusible, free, and bound fractions of IAA and ABA in the cambial region of Sitka spruce throughout one year; the range in concentration for these fractions was 0.06–0.30, 0.46–3.85, and 0.04–0.20 μg/g oven-dry weight, respectively, for IAA, and 0–0.08, 0.03–2.21, and 0.13–0.66 μg/g oven-dry weight, respectively, for ABA. Movement in the cambial region was found to be polar for endogenous IAA and nonpolar for endogenous ABA. Recoveries of [14C]IAA internal standards showed that 73–99.5% of the IAA was lost during purification, and that there could be up to 5-fold differences in recovery between purifications, indicating that IAA loss shold be measured in quantitative analyses.
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  • 71
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    Planta 134 (1977), S. 273-275 
    ISSN: 1432-2048
    Keywords: Cell culture ; Cytokinin metabolites ; Mitosis ; Nicotiana
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    Topics: Biology
    Notes: Abstract 14C-labelled benzyladenine-7-glucoside (0.57 μM) supplied to cytokinin-requiring Nicotiana tabacum (cv. Wisconsin 38) cells cultivated in liquid medium was slowly absorbed and resulted in rather large intracellular quantities of benzyladenine-7-glucoside (30 pmol/105 cells) but did not show any biological activity, while 0.01 μM benzyladenosine induced cell division. In this case the resulting intracellular quantity of benzyladenine-7-glucoside formed was 3.3 pmol/105 cells. Also, N6-(Δ2-isopentenyl)adenosine induced cell division in these tobacco suspensions without being significantly 7-glucosylated. These data provide strong evidence that the 7-glucosylation of cytokinins is not a prerequisite of the expression of their biological activity.
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  • 72
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    Planta 135 (1977), S. 1-5 
    ISSN: 1432-2048
    Keywords: Auxin ; Cell elongation ; Elongation ; Root growth ; Zea
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    Topics: Biology
    Notes: Abstract The effect of indole-3-acetic acid (IAA) on the elongation rates of 2 mm corn (Zea mays L.) root segments induced by citrate-phosphate buffer (or unbuffered) solutions of pH 4.0 and 7.0 was studied. At pH 7.0, auxin initially reduced the elongation rate in both buffered and unbuffered solutions. Only in buffer at pH 7.0 was auxin at a concentration of 0.1 μM found to promote the elongation rate though briefly. THis promoted rate represented only ca. 20% of the rate achieved with only buffer at pH 4.0. Auxin in pH 4.0 buffered and unbuffered solutions only served to reduce the elongation rates of root segments. Some comparative experiments were done using 2 mm corn coleoptile segments. Auxin (pH 6.8) promoted the elongation rate of coleoptile segments to a level equal or greater than the maximal H ion-induced rate. The two responses of root segments to auxin are compared to auxin action in coleoptile growth.
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  • 73
    ISSN: 1432-2048
    Keywords: Anaerobiosis inhibition ; C3/C3 plants ; Nicotiana ; Oxygen-release ; Photosynthesis ; Zea
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    Topics: Biology
    Notes: Abstract Tobacco leaves (Nicotiana tabacum var. Wisconsin 38) submitted to anaerobic conditions behave in a manner similar to that of maize, sugarcane, or sorghum leaves (C4-plants); more precisely, a lag time in O2 release is exhibited when the leaves are exposed to light after treatment in the dark under pure nitrogen. Although the conditions for the appearance of this phenomenon in tobacco are somewhat different, the main features are identical to those observed with maize: abolition of the lag time upon immediate exposure to light, release of CO2 under light (illumination burst of CO2), photochemical nature of the reactions involved in the abolition of the lag time, activation of oxygen release by far-red light, and the antagonistic effect of red and far-red light on the lag time. The high CO2 compensation point of tobacco leaves permits the classification of this plant among the C3 group. A comparison of these experimental results with others from the literature suggests than the distinguishing features between C3- and C4-plants are not as sharp as generally thought.
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  • 74
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    Theoretical and applied genetics 53 (1978), S. 49-55 
    ISSN: 1432-2242
    Keywords: Density gradient ; Nicotiana ; Protoplasts ; Selection ; Somatic hybridization
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    Topics: Biology
    Notes: Summary Buoyant density differences between different types of protoplasts were used in an iso-osmotic density gradient system to enrich protoplast fusion mixtures for heterokaryocytes. Protoplasts of maize stem and wheat mesophyll, as well as epidermis, stem parenchyma and mesophyll protoplasts of two amphihaploid, light sensitive tobacco mutants were fused with polyethylene glycol using conventional methods and a new rolling tube technique. The protoplast combinations used for fusion involved protoplast types with considerably different buoyant densities. Enriched fractions of maize-wheat heterokaryocytes of intermediate density were recovered which contained up to 31% mostly binucleate heterokaryocytes (a 2–7 fold relative enrichment). Tobacco heterokaryocytes recovered analogously from enriched intermediate fractions readily divided and gave rise to an increased number of light resistant calluses when compared with cultures from non-fractionated fusion mixtures. Maize-wheat fusion products, however, failed to divide.
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  • 75
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    Theoretical and applied genetics 53 (1978), S. 49-55 
    ISSN: 1432-2242
    Keywords: Density gradient ; Nicotiana ; Protoplasts ; Selection ; Somatic hybridization
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    Topics: Biology
    Notes: Summary Buoyant density differences between different types of protoplasts were used in an iso-osmotic density gradient system to enrich protoplast fusion mixtures for heterokaryocytes. Protoplasts of maize stem and wheat mesophyll, as well as epidermis, stem parenchyma and mesophyll protoplasts of two amphihaploid, light sensitive tobacco mutants were fused with polyethylene glycol using conventional methods and a new rolling tube technique. The protoplast combinations used for fusion involved protoplast types with considerably different buoyant densities. Enriched fractions of maize-wheat heterokaryocytes of intermediate density were recovered which contained up to 31% mostly binucleate heterokaryocytes (a 2–7 fold relative enrichment). Tobacco heterokaryocytes recovered analogously from enriched intermediate fractions readily divided and gave rise to an increased number of light resistant calluses when compared with cultures from non-fractionated fusion mixtures. Maize-wheat fusion products, however, failed to divide.
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  • 76
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    Cell & tissue research 176 (1977), S. 23-36 
    ISSN: 1432-0878
    Keywords: Lateral line organ ; Shark (Mustelus manazo) ; Neuromasts ; Cell types ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The lateral line organ of the spotted shark is characterized by its semi-cylindrical shape. Each organ (neuromast) is so closely apposed to the next that the individual neuromasts are almost continuous. The neuromast is composed of receptor cells, supporting cells and mantle cells. The receptor cells bear one kinocilium and up to 40 stereocilia. Bi-directional arrangement of the receptor cells as occurs in teleosts was demonstrated. Afferent and efferent nerve endings were found at the base of the receptor cells. The supporting cells extend from the basal lamina to the free surface. Long microvilli and a cilium-like “ciliary rod” project from the top of each supporting cell. The cell contains relatively few elements of the Golgi apparatus and little rough endoplasmic reticulum, but mitochondria and filaments are abundant. The mantle cell limits the lateral margin of the neuromast. It is distinguished from the supporting cell because of its long crescent-shaped nucleus and scarce, short microvilli. Myelinated nerve fibres are found in the subepithelial connective tissue but not in the epithelium. The fine structure of the shark lateral line organ suggests that this organ is in an intermediated step of evolution between that of lamprey and teleost.
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  • 77
    ISSN: 1432-0878
    Keywords: OsO4 ; Cholesterol ; Symbiotes ; Aphids ; Electron microscopy
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    Topics: Biology , Medicine
    Notes: Summary Pea aphids left for 48 h in unbuffered osmium tetroxide show heavy staining of many organelles in the symbiote-containing cells (mycetocytes and sheath), embryos and oenocytes very similar to that characteristic of mammalian sterol-synthesizing cells. However, the staining of the pea-aphid cells is, to a large extent, dependent on the presence of cholesterol benzoate, or free cholesterol, in the aphid's diet. In aphids cultured in vitro with 3H mevalonate in the presence of added cholesterol, the incorporation of label into the cholesterol and lanosterol fractions is significantly reduced. If the dietary cholesterol effects a similar inhibition in vivo, the cholesterol-dependent osmium staining could be due to precursors(s) of cholesterol accumulating in the intracellular sites described. There is also osmium staining of large (normally electron-transparent) vacuoles in mycetocytes, gut and fat body, irrespective of dietary cholesterol.
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  • 78
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    Cell & tissue research 176 (1977), S. 417-429 
    ISSN: 1432-0878
    Keywords: Fat body ; Galleria mellonella ; Basement membrane ; Ruthenium red staining ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The fat body lobes of Galleria mellonella are surrounded by basement membrane — a fine granular layer of connective tissue. This membrane has an affinity for ruthenium red. The results obtained after treatment of the fat body with neuraminidase, hyaluronidase, phospholipase C and proteolytic enzymes suggest that glycoproteins and phospholipoproteins are constituents of this basement membrane. The basement membrane also has the ability to bind concanavalin A-peroxidase, which is associated with the presence of mannoside residues.
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  • 79
    ISSN: 1432-0878
    Keywords: Skeletal muscle ; Protamine ; Endocytosis ; Autophagic vacuolation ; Electron microscopy
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    Topics: Biology , Medicine
    Notes: Summary The uptake in vitro of horseradish peroxidase (HRP) in mouse skeletal muscle was examined by electron microscopy and chemical determination. In muscles exposed to an HRP solution for 60 min at +37°C, HRP infiltrated the basal lamina of muscle fibres and caused an intense labelling of their sarcolemma. In addition HRP was found within the transverse tubules. Exposure to HRP for 30 min at +37°C followed by HRP together with a polycationic protein (protamine) for 30 min at +37°C caused an intracellular vesicular uptake of HRP. Intracellular HRP was found in numerous vesicles, membrane limited bodies and vacuoles. Protamine also induced focal autophagic vacuolation with progressive muscle fibre degeneration. An intracellular HRP uptake or muscle cell vacuolation could not be detected in the absence of protamine or when the incubation temperature was + 4°C. Chemical determination of HRP uptake was in general agreement with the morphological results. The uptake of HRP in the presence of protamine was stimulated at +31°C and blocked at +4°C. The results suggest that in skeletal muscle in vitro intracellular uptake of macromolecules occurs by endocytosis.
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  • 80
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    Keywords: Electron dense plaques ; Pancreatic islets ; Parathyroids ; Electron microscopy ; Calcium binding
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    Topics: Biology , Medicine
    Notes: Summary Small electron dense plaques (EDP) were found in the plasma membrane of pancreatic islet A-, B- and D-cells and parathyroid chief cells of mice and gerbils. The identification of the EDP was facilitated by the use of special fixation techniques. The EDP may represent sites of calcium binding in the cell membranes.
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  • 81
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    Cell & tissue research 177 (1977), S. 127-140 
    ISSN: 1432-0878
    Keywords: Microtubules ; Retina ; Electron microscopy ; Rainbow trout
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    Topics: Biology , Medicine
    Notes: Summary In the retina of the rainbow trout (Salmo gairdneri, Richardson) two types of microtubular structures are demonstrated. Besides the normal type of microtubules (about 200 Å in diameter), occurring in all cell types of the retina, a second type is described which is termed microtubule-like structure (MLS) because of its extracellular localization. These MLS have a diameter of about 250 Å under the same preparative conditions in which the normal microtubules appear 180–200 Å thick. The interspace between the tubules is smaller than between the microtubules. Specific MLS to membrane associations exist, which are analyzed by serial sectioning and tilting procedures. It is suggested that the MLS have their origin at small membranous extrusions of the plasmalemma. These extrusions could contain nucleation sites for the MLS-formation within the extracellular space. It remains unknown which cell type produces the MLS proteins and which factors are responsible for the aggregation of the subunits to intact MLS.
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  • 82
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    Cell & tissue research 177 (1977), S. 221-226 
    ISSN: 1432-0878
    Keywords: Actin-like filaments ; Myoid cell ; Testis ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Microfilaments in the myoid cells of the peritubular tissue in the mouse, swine and human testis bind heavy meromyosin (HMM) and form arrowhead complexes. The periodicity of the arrowhead complexes is about 35 nm. Individual filaments show arrowheads that point in the same direction. Opposing polarity of the HMM-bound filaments is also observed. The microfilaments do not bind HMM in the presence of 10 mM ATP. After treatment with the contraction medium of Hoffmann-Berling, the filaments appear to be undulated. These observations indicate that the microfilaments in the myoid cell are actin-like in nature. A small number of thicker filaments (about 10 nm in diameter) which do not bind HMM is also observed in the cell. Microfibrils which have been reported around the human myoid cell are also found in the swine.
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  • 83
    ISSN: 1432-0878
    Keywords: Optic neuropile ; Crustacea ; Catecholamine ; Fluorescence histochemistry ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Summary The crustacean optic neuropiles, the lamina ganglionaris and especially the medulla externa, show a specific pattern of green fluorescence with the fluorescence histochemical method of Falck-Hillarp. Normally, only the terminals and the cell bodies fluoresce, but in reserpine-treated animals exogenous catecholamines are taken up by the whole adrenergic neuron and are thus visualized as a whole. Incubating crayfish optic neuropiles in dopamine or α-methylnoradrenaline after reserpine treatment demonstrated a tangential neuron connecting the lamina and the medulla externa. The morphology of this tangential neuron differs from the two types of tangential neurons, Tan1 and Tan2, previously characterized with Golgi techniques. The catecholaminergic neuron thus constitutes a third tangential neuron type.
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  • 84
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    Cell & tissue research 182 (1977), S. 401-407 
    ISSN: 1432-0878
    Keywords: Microtubules ; Sciatic nerve (rat) ; Tannic acid ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Tannic acid in glutaraldehyde was used to stain microtubules in myelinated and unmyelinated axons of rat sciatic nerve. In the majority of areas the tannic acid failed to penetrate the unmyelinated axons whilst penetrating neighbouring myelinated axons, suggesting a difference in the ability of the two types of nerves to exclude tannic acid. Where tannic acid had penetrated the unmyelinated axons the 13 protofilament substructure and size of the microtubules appeared identical to those seen in the myelinated axons.
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  • 85
    ISSN: 1432-0878
    Keywords: Albinism ; Pigment epithelium ; Tyrosinase ; Electron microscopy ; Carassius auratus L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Ultrastructural studies, and cytochemical and biochemical determinations of tyrosinase activity were conducted on the pigment epithelium of albino and xanthic goldfish eyes. In eyes of xanthic goldfish, two types of melanosomes are present, spherical and elongated. Melanized melanosomes are absent in the eyes of the albino goldfish, but elongated lamellar premelanosomes are observed. Internal vesicles are present in both melanosome types in the pigment epithelium of the xanthic goldfish but are absent in premelanosomes of the albino. There are also differences in the distribution of lipid droplets, smooth endoplasmic reticulum and Golgi complexes with the latter two being more abundant in the albino. Tyrosinase was not identified cytochemically; however, the enzyme was demonstrated biochemically in the pigment epithelia of both albino and xanthic goldfish. The enzyme is associated with the particulate and soluble fractions of both types of eyes. Particulate albino tyrosinase may be solubilized by triton X-100 treatment. Tyrosinase inhibitors are present in the particulate fractions of both albino and xanthic goldfish eyes. Thus, in the goldfish, ocular albinism appears to be a multiple defect at the molecular and ultrastructural levels.
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  • 86
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    Cell & tissue research 176 (1977), S. 407-416 
    ISSN: 1432-0878
    Keywords: Chick embryo ; Electron microscopy ; Glial differentiation ; Neuron differentiation ; Reaggregation cultures
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    Topics: Biology , Medicine
    Notes: Summary Dissociation and reaggregation cultures from different portions of the chick embryo neural tube were made, and the resulting aggregates were fixed for electron microscopy after 1, 5, 8, 14, 16 and 22 days in vitro. All cultures (pure aggregates of telencephalon, optic lobe or neural retina, and combined aggregates made from mixtures of optic lobe plus neural retina or optic lobe plus telencephalon) show a common timing of neuronal and glial morphological differentiation. During the first week in vitro, some cells developed neuronal characteristics in the absence of morphological evidence of glial differentiation. Numerous axonic processes usually formed fascicles with all the fibers running parallel to each other. Axonic growth cones were abundant and a few immature synapses were also present. The second week in culture was characterized by the disappearance of growth cones and the increase in number and morphological maturation of synapses. Morphologically detectable glial differentiation began by the end of this week, and during the third week almost every neuronal element, including the axonic fascicles, became associated with glial cells showing astrocytic features.
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  • 87
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    Keywords: Gastric mucous cells ; Differentiation ; 3H-thymidine incorporation ; Histochemistry ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Gastric surface mucous cells (SMC), mucous neck cells (MNC) and their undifferentiated and immature precursors were studied by light and electron microscopic histochemistry. The secretory granules of SMC were smaller, more electron dense and more reactive to PAS and its analogues than those of MNC. Alcian blue demonstrated that the mucus of SMC was acidic and that of MNC was neutral. The periodic acid —thiocarbohydrazide —silver proteinate method revealed the presence of carbohydrates in the Golgi apparatus, condensing vacuoles, secretory granules, apical vesicles and tubules and cell coat. Maturation of SMC during their migration towards the free surface was reflected by an increase in size and number of secretory granules, an increase of RER and microfilaments, and a decrease of microvilli and apical vesicles and tubules. The secretory granules of older SMC were less acidic and possessed a proteinaceous core. Most MNC were fully differentiated, but some immature MNC containing only a few granules were found. Furthermore, undifferentiated cells and intermediates between SMC and MNC were also observed. The presence of both transitional and intermediate forms indicates that both SMC and MNC arise from the same population of undifferentiated cells. Incorporation of 3H-thymidine revealed that undifferentiated cells, isthmic SMC, MNC and intermediate cells are proliferative. No proliferative activity was found in foveolar SMC, parietal, chief, fibrillovesicular or endocrine cells.
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  • 88
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    Cell & tissue research 177 (1977), S. 159-180 
    ISSN: 1432-0878
    Keywords: Muscle transplantation ; Rat ; Electron microscopy
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    Topics: Biology , Medicine
    Notes: Summary Rat soleus muscles were autografted from right to left legs, and regeneration following necrosis of all original myofibres was studied after 7 to 250 days. The best regenerates were from grafts replacing all calf muscles and sutured to the tendon stumps. After 30 days the size of such regenerates was equal to those from minced gastrocnemius muscles: the cross sectional area of muscle tissue was 30% (1.7 mm2) and the number of fibres was 180% (4500) of normal soleus muscles; the fibre diameters were 10 to 40 μm. To increase the number of myoblasts before grafting some muscles were injured by Ringer solution of 70° C and transplanted after 2 days. Nevertheless, this did not influence regeneration. After 7 days clusters of myotubes occurred in the periphery of the muscle. These myotubes originated from myoblasts growing like endothelial cells on the inner face of the persisting basal lamina tubes of necrotic fibres. After 30 days the muscles were vascularized. Fibres formed in a common basal lamina detached and so looked “split”. Satellite cells of new fibres came from undifferentiated cells associated with myotubes, i.e. from myoblasts. After 30 days and more regenerates contained three sorts of fibres. 1. Thin (5 to 20 μm) fibres resembling fetal muscle fibres. They were most prominent after 30 days, and probably not yet innervated. 2. Thin (10 μm) degenerating fibres as in long-time denervated muscles. 3. Thick (more than 30 μm) mature looking fibres which were innervated and revealed end-plates. Half of the grafts studied after 30 and 60 days contained unmyelinated and myelinated axons which had grown along strands of surviving Schwann cells. After 250 days, only two muscles were studied which both lacked innervation. Almost all regenerates contained muscle spindles, which, however, were not innervated. Within the persisting spindle capsules new muscle fibres had been formed from satellite cells of the former intrafusal fibres.
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  • 89
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    Cell & tissue research 177 (1977), S. 247-268 
    ISSN: 1432-0878
    Keywords: Adrenal medulla ; In vitro ; Phase contrast microscopy ; Catecholamine histochemistry ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Explants and enzyme-dispersed cells of adrenal medulla from 10–12 day old rats were studied in culture for up to 3 weeks. Adrenomedullary chromaffin cells, nerve cells and satellite cells were clearly discernible. The nerve cells were few in number and did not show catecholaminespecific fluorescence. Chromaffin cells stored catecholamines, as judged by the Falck and Hillarp method, in varying amounts decreasing with age of the cultures and the distance from the explants. Exocytosis profiles observed with the electron microscope suggested that cultured chromaffin cells also released catecholamines. Moreover, the cells formed processes and frequently migrated into the outgrowth. After 6 days in culture, the great majority of chromaffin cells stored noradrenaline as revealed by electron microscopy with few adrenaline-storing cells being visible. Granular vesicles (∼ 80–240 nm in diameter) with cores of different electron densities were occasionally present in the same cell suggesting the occurrence of mixtures of primary and secondary amines. Apart from “chromaffin” granules, small clear and densecored vesicles (∼ 40–60 nm) were found both in the somata and cell processes. Chromaffin cells and their processes were often closely apposed and occasionally formed specialized attachment zones. As a whole, chromaffin cells in culture resembled small granule-containing cells in sympathetic ganglia. 0.5 mM dbcAMP prevented dedifferentiation of chromaffin cells as judged by the lack of processes, the size and amount of “chromaffin” granules and the high number of adrenaline-storing cells present after 6 days in culture. NGF caused a striking increase in the number of axons growing out from expiants.
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  • 90
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    Cell & tissue research 177 (1977), S. 291-305 
    ISSN: 1432-0878
    Keywords: Juxtaglomerular apparatus ; Tupaia ; Gap junctions ; Renin ; Freeze-fracturing ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The vascular pole of the juxtaglomerular apparatus in Tupaia belangeri was studied with special reference to the intercellular contacts of the periendothelial cells and the endothelium of the vas afferens. The periendothelial cells of the vascular pole of the glomerulum are connected by numerous gap junctions; and the granulated epithelial cells are suggested to form a functional unit. Probably there is a continuity of this system troughout the entire vascular pole including (1) all granulated cells, (2) all lacis cells, (3) the mesangium cells and (4) the adjacent smooth muscle cells of the vas afferens and vas efferens. Analysis of the endothelial junctions shows a zonular arrangement of tight junctions indicating a rather tight blood-tissue barrier next to the glomerular vascular pole. The ultrastructure of the different cell types of the vas afferens is also described, emphasizing the granulated epithelial cells and their innervation.
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  • 91
    ISSN: 1432-0878
    Keywords: Gut epithelium ; Ciona intestinalis, Mytilus edulis ; Endocrinecells ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Ultrastructural evidence has been found for the presence of polypeptide hormone-producing cells in the gut of Ciona intestinalis L. and Mytilus edulis L. which do not appear to have been described before. Due to their localization and ultrastructural characteristics, it is suggested that the cells in Mytilus edulis probably produce an insulin-like substance and that some of these cells in Ciona intestinalis may produce 5-HT (5-Hydroxytryptamine). In each species only one granulated cell type can be observed. The granules, which are electron dense and membrane bound, also show a halo. The average diameter of the granules is 100–200 nm for Ciona and 200–400 nm for Mytilus.
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  • 92
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    Cell & tissue research 177 (1977), S. 539-553 
    ISSN: 1432-0878
    Keywords: Sensory receptors ; Peripatopsis ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Three types of sensilla occurring on the lips and on the antennae of Peripatopsis moseleyi have been investigated by scanning and transmission electron microscopy. On the lips sensory spines can be found which contain numerous cilia originating from bipolar receptor cells. They reach the tip of the spine where the cuticle is modified. The perikarya of the sensory cells, a large supporting cell with a complicated surface and a second type of receptor, form a bud-like structure and are surrounded by a layer of collagen fibrils. The second receptor cell bears apical stereocilia as well as a kinocilium which are directed towards the centre of the animal — thus the cell appears to be turned upside down. The sensilla of the antennae are 1) sensory bristles containing two or three kinds of receptor cells, one of which bears an apical cilium and one kind of supportive cell and 2) sensory bulbs located within furrows consisting of receptor cells with branched cilia and two kinds of supportive cells which are covered by a modified thin cuticle. According to the electron microscopical findings the sensory spines on the lips are presumably chemoreceptors. The sensory bristles on the antennae can be regarded as mechanoreceptors and the sensory bulbs as chemoreceptors.
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  • 93
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    Cell & tissue research 178 (1977), S. 155-167 
    ISSN: 1432-0878
    Keywords: Electromotor system ; Oval nucleus ; Synapses, junctions ; Electron microscopy ; Torpedo marmorata
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The morphology of the oval nucleus of neonatal Torpedo marmorata is described at the light and electron microscopic level of examination. The nucleus is unique relative to other central electromotor centers of electric fish so far described being bilaterally symmetrical, composed of two nerve cell types, and possessing no gap junctions between neurons and their processes. This particular structural plan presents difficulties in accounting for presumed synchronous discharge since it has been strongly argued that electrotonic coupling by means of gap junctions is the primary process by which synchronization is accomplished. Close membrane apposition and dendritic bundling, common features within the nucleus, are discussed as possible alternative structural correlates.
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  • 94
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    Cell & tissue research 182 (1977), S. 1-16 
    ISSN: 1432-0878
    Keywords: Epithalamus (Rat) ; Supraependymal nerves ; Electron microscopy ; Circumventricular organs ; Medial habenular nucleus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Transmission and scanning electron microscopy of the rat epithalamus shows a regional variation in the distribution of Supraependymal nerves (SN) which correlates well with Supraependymal yellow fluorescence reported by Richards et al. (1974). The medial habenular nucleus, the intercommissural and suprahabenular recesses, the habenular commissure and the fibrae periventriculares thalami have the greatest density of SN/100 μm of ependymal surface. The floor of the suprahabenular and intercommissural recesses is covered by non-ciliated ependyma. The significance of these findings is discussed with respect to (1) a direct functional relationship of SN with ependyma, and (2) a possible participation of the non-ciliated ependyma of the suprahabenular and intercommissural recesses in secretory activity whereby the CSF serves as a vehicle for neuroendocrine communication.
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  • 95
    ISSN: 1432-0878
    Keywords: Ovary ; Oocyte elimination ; Peritoneal epithelium ; Primordial follicle ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Numerous ovarian oocytes of primordial follicles are lost postnatally by their elimination into the peritoneal cavity during days 1–6 in young mice. It is rarely found in animals over 2 weeks old. This phenomenon has been investigated by light and EM techniques. Oocytes that become extruded from the ovary this way appear to pass between the cells of the covering epithelium. The ultrastructural changes that take place during this process are described.
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  • 96
    ISSN: 1432-0878
    Keywords: Gastrin cells ; Electron microscopy ; Fixation ; Granule maturation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The ultrastructural appearance of gastrin cell (G cell) granules was studied after different fixation procedures. When the pH of prefixation was varied there was greater preservation of the electron density of granule cores after acidic (pH 5.0 and 6.0) than after neutral or alkaline (pH 7.0 and 8.0) prefixation. Increasing duration of prefixation at pH 7.3 resulted in progressive loss of electron density of the granule core with swelling and occasional rupture of the limiting membrane. In tissues where most granules had been rendered electron lucent by fixation, those granules remaining dense cored were preferentially located close to the Golgi zone. These findings indicate that the electron density of G cell granules is profoundly affected by conditions of fixation, and that immature granules are more resistant to loss of core density than mature granules. They also suggest that the gastrin granule in vivo, like other polypeptide granules, may have a “solid”, osmotically inactive core.
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  • 97
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    Cell & tissue research 176 (1977), S. 275-284 
    ISSN: 1432-0878
    Keywords: Neural lamella (wax moth) ; Ruthenium red ; Enzyme digestion ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The outer surface of the neural lamella, the connective tissue ensheathing the brain, shows the ability to bind ruthenium red in the wax moth larva. Ruthenium red-positive material is sensitive to neuraminidase, hyaluronidase and to some extent to phospholipase C, what suggests that the negative charge on the external surface of the neural lamella depends on the presence of the anionic groups of sialic and hyaluronic acids and phospholipids.
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  • 98
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    Cell & tissue research 186 (1978), S. 121-133 
    ISSN: 1432-0878
    Keywords: Proximal tubule ; Tight junctions ; Ultrastructure ; Electron microscopy ; Freeze fracturing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The morphology of tight junctions of the renal proximal tubule was studied comparing the pars convoluta and pars recta of rat, golden hamster, rabbit, cat, dog and tupaia. Though some interspecies variations were observed, the convoluted portions of the proximal tubules revealed quite uniformly very leaky tight junctions with mainly 1–2 strands. Along the whole proximal tubule of the rabbit kidney including the pars recta only minor differences of the zonulae occludentes were found. By contrast, the tight junctions of the pars recta in other species were much more elaborate, especially in cat and tupaia, having up to 6 strands and an overall depth of more than 150 nm. The implications of these findings are discussed with special regard to the functional differences between the pars convoluta and pars recta of the proximal tubule.
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  • 99
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    Cell & tissue research 187 (1978), S. 457-472 
    ISSN: 1432-0878
    Keywords: Ovarian follicles (sheep) ; Theca interna ; Oestrogen ; Androgen ; Capillaries ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The theca interna of non-atretic ovarian follicles from 2.0 mm in diameter up to the stage shortly following ovulation was studied by light and electron microscopy. In follicles 〈3.0mm in diameter, the theca interna consisted of about 8–12 layers of flattened cells, together with many capillaries and small bundles of collagen. Two main forms of cellular differentiation were seen. These were towards either fibroblast-like cells or presumed steroidogenic cells whose cytoplasm contained large amounts of predominantly smooth tubular endoplasmic reticulum, to which some ribosomes were attached. The majority of cells were of relatively undifferentiated or intermediate structure. In larger follicles up to the early stages of oestrus the theca interna cells became larger and less flattened, and cells rich in tubular endoplasmic reticulum became proportionately more numerous. By 18 h after the onset of oestrus the theca interna was oedematous, and many cells possessed pseudopodia. Many cells also contained numerous lipid droplets, but there were no signs of thecal cell degeneration or death. Shortly after ovulation the basal lamina of the membrana granulosa was incomplete, and it became more difficult to distinguish between theca and granulosa layers. Structural heterogeneity, with two major cell types and cells of intermediate structure, was present at all stages. It was concluded that: (1) the theca interna of 2.0–2.9 mm follicles contained many cells whose structure was compatible with a steroidogenic capacity; (2) changes in the differentiated thecal cells up to the early stages of oestrus were quantitative rather than qualitative, and suggestive of an increased steroidogenic capacity; (3) the accumulation of lipid in many cells of the theca interna by 18 h after the onset of oestrus probably reflected a reduction in steroidogenic activity; and (4) there was no evidence of any structural specialization to facilitate the transport of steroids from the theca interna to the membrana granulosa.
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  • 100
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    Cell & tissue research 188 (1978), S. 75-82 
    ISSN: 1432-0878
    Keywords: Drum muscles ; Piranha ; Degenerative changes ; Fine structure ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary In the posterior drum muscle of the piranha structural alterations are frequently observed. Electron microscopic studies revealed a disordering of the myofibrils in these regions, accompanied by conspicuous changes in the mitochondria. As the degree of disorder increases, the mitochondrial cristae initially swell to form vesicles. Eventually the mitochondria become filled with myelin-like lamellar structures, which in many cases coalesce to form a dense outer wall. A striking concentration of lysosomes into localized masses was also characteristic of these regions.
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