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  • Electron microscopy  (1,196)
  • Drosophila  (737)
  • Springer  (1,930)
  • 1
    Electronic Resource
    Electronic Resource
    Transfer of dye among salivary gland cells is not affected by genetic variations of the period clock gene in Drosophila melanogaster (1993)
    Springer
    The journal of membrane biology 136 (1993), S. 333-342 
    Details
    ISSN: 1432-1424
    Keywords: Drosophila ; per mutants ; pertransgenic ; Lucifer Yellow injections ; Gap junctions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Larval salivary gland cells of Drosophila melanogaster were injected with a fluorescent dye to assess strengths of intercellular communication among such cells, as influenced by mutations at the period locus and by a per transgene. This clock gene had been reported to increase the extent of dye transfer when mutated such that it shortens the period of biological rhythms; the previous study also showed that a per-null mutant decreased the strength of transfer among salivary gland cells. Our re-examination of this feature of larval physiology—in observer-blind analyses, using the per s and per o mutants as well as two per-normal strains—revealed no appreciable differences in extents of dye transfer among these four genotypes. These results are discussed in the context of emerging findings which suggest that the period gene's product controls pacemaker functioning as an intracellularly acting entity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00233672
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  • 2
    Electronic Resource
    Electronic Resource
    Renewing olfactory receptor neurons in goldfish do not require contact with the olfactory bulb to develop normal chemical responsiveness (1997)
    Springer
    Journal of comparative physiology 181 (1997), S. 425-437 
    Details
    ISSN: 1432-1351
    Keywords: Key words Olfactory receptor cells ; Olfactory bulbectomy ; Olfactory axotomy ; Electrophysiology ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract This study investigated whether contact with the olfactory bulb was necessary for developing and renewing olfactory receptor neurons (ORNs) to attain normal odorant responsiveness, and whether the anatomical and functional recoveries of the olfactory epithelium were similar in both bulbectomized (BE) and bilaterally axotomized (AX) preparations. In vivo electrophysiological recordings were obtained in response to amino acids, a bile acid [taurolithocholic acid sulfate(TLCS)] and a pheromonal odorant [17α, 20β,-dihydroxy-4-pregnen-3-one (17,20P)] from sexually immature goldfish. Both transmission and scanning electron microscopy indicated that the olfactory epithelium degenerated in BE and AX goldfish. Within 1–2 weeks subsequent to the respective surgeries, responses to high concentrations (〉0.1 mmol · l−1) of the more stimulatory amino acids remained, whereas responses were no longer obtainable to TLCS and 17,20P. At 4 weeks, responses to amino acid stimuli recovered to control levels, while responses to TLCS and 17,20P were minimal. By 7 weeks post bilateral axotomy, the olfactory epithelium recovered to a condition similar to control sensory epithelium; however, the rate of degeneration and proliferation of receptor neurons in BE preparations appeared to remain in balance, thus blocking further recovery of the olfactory epithelium. At 7 weeks post surgery, odorant responses of AX and BE goldfish to TLCS and 17,20P were still recovering.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003590050126
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  • 3
    Electronic Resource
    Electronic Resource
    Membrane topology of insulin receptors reconstituted into lipid vesicles (1994)
    Springer
    The journal of membrane biology 140 (1994), S. 215-223 
    Details
    ISSN: 1432-1424
    Keywords: Insulin receptor ; Membrane reconstitution ; Electron microscopy ; Quaternary structure ; Immunogold labeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Insulin receptors were incorporated into liposomes by two different procedures, one using dialysis and one using detergent removal by Bio-Beads. Receptor incorporation was analyzed by gradient centrifugation and electron microscopy. Reconstituted receptors projected up to 12 nm above the membrane and exhibited a T-shaped structure compatible with that previously described for the solubilized receptor. Insulin binding and autophosphorylation experiments indicated that approx. 50% of the receptors were incorporated right-side out. Such random orientation was confirmed by immunogold labeling of the α- and the β-subunit of the receptor. Immunogold labeling of the C-terminus of the β-subunit indicates that it resides about 6 nm off the membrane, while two α-subunit epitopes were labeled at about twice this distance, confirming that the α-subunit is harbored in the cross-bar of the T-structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00233710
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  • 4
    Electronic Resource
    Electronic Resource
    Lanthanum mimicks the trp photoreceptor mutant of Drosophila in the blowfly Calliphora (1989)
    Springer
    Journal of comparative physiology 166 (1989), S. 179-187 
    Details
    ISSN: 1432-1351
    Keywords: Blowfly ; Drosophila ; Photoreceptor ; Lanthanum ; trp mutant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The effect of lanthanum on the light response of blowfly (Calliphora erythrocephala) photoreceptors was studied. The electrophysiological behaviour of the photoreceptors in the presence of La can be summarized as follows: 1. Upon long stimulation the photoreceptors responded with a ‘transient receptor potential’, i.e. the cells depolarized at the onset of the stimulus and then repolarized to (or below) the resting potential. This effect was dependent on stimulus intensity and occurred only at high intensities. During illumination membrane noise was reduced. 2. The light-induced changes in membrane potential were paralleled by changes in membrane resistance. 3. The time course of the receptor response was slowed down. 4. Light adaptation led to an increase in response latency. 5. The recovery of the receptor response after light adaptation was slowed down. 6. The sensitivity of the receptor cells measured by the response to short light stimuli was reduced. In summary, the electrophysiological behaviour of Calliphora photoreceptors in the presence of La was very similar to that of the photoreceptors of the trp (transient receptor potential) mutant of Drosophila melanogaster. This result suggests that La and trp mutation affect the same cellular processes in the photoreceptors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00193462
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  • 5
    Electronic Resource
    Electronic Resource
    Defect structure of the low temperature α-cristobalite phase and the cristobalite ⇆ tridymite transformation in (Si-Ge)O2 (2000)
    Springer
    Physics and chemistry of minerals 27 (2000), S. 386-397 
    Details
    ISSN: 1432-2021
    Keywords: Key words Cristobalite ; Tridymite ; Phase transformation ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract Using minimum exposure techniques, it is feasible to perform high resolution electron microscopy on the α-cristobalite phase of (Si0.9 Ge0.1)O2, which is extremely radiation sensitive. Such images reveal atomic scale information of twins and tridymite-like stacking faults on (1 1 1)β planes, as well as of domain boundaries resulting from the β→α transition. Polytype structures are formed in certain cases. Morphological features suggest that the phase transformation cristobalite → tridymite proceeds by means of a zonal dislocation mediated synchro-shear process on (1 1 1)β planes; the geometry of this process is analyzed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002699900082
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  • 6
    Electronic Resource
    Electronic Resource
    High-pressure freezing of soybean nodules leads to an improved preservation of ultrastructure (1992)
    Springer
    Planta 188 (1992), S. 155-163 
    Details
    ISSN: 1432-2048
    Keywords: Bradyrhizobium ; Electron microscopy ; Glycine (root nodules) ; High-pressure freezing ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract High-pressure freezing of chemically untreated nodules of soybean (Glycine max (L.) Merr.), in sharp contrast to chemical fixation and prefixation, appears to preserve the ultrastructure close to the native state. This is supported by the observation that the peribacteroid membrane of high-pressure-frozen samples is tightly wrapped around the bacteroids, a finding that is fully consistent with the current views on the physiology of oxygen and metabolite transport between plant cytosol and bacteroids. In soybean root nodules, the plant tissue and the enclosed bacteria are so dissimilar that conventional aldehyde-fixation procedures are unable to preserve the overall native ultrastructure. This was demonstrated by high-pressure freezing of nodules that had been pre-fixed in glutaraldehyde at various buffer molalities: no buffer strength tested preserved all ultrastructural aspects that could be seen after high-pressure freezing of chemically untreated nodules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00216809
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  • 7
    Electronic Resource
    Electronic Resource
    Differential mutagenic response in selected lines of Drosophila melanogaster (1977)
    Springer
    Theoretical and applied genetics 50 (1977), S. 125-127 
    Details
    ISSN: 1432-2242
    Keywords: Drosophila ; Mutants ; Radiation ; Lethals ; Dose-Response
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The mutagenic efficiency of ionizing radiations has been tested on different lines of Drosophila melanogaster. It has been shown that differential lethal effects are obtained when irradiated females from different lines are mated to flies carrying heterozygous lethal genes. The results seem not to be attributable to differential expression of the lethality in the various crosses performed with the irradiated flies. This might suggest that gene activity is involved in the expression of the mutagenic effects of radiations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00276806
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  • 8
    Electronic Resource
    Electronic Resource
    Prediction of heterosis in crosses between inbred lines of Drosophila melanogaster (1990)
    Springer
    Theoretical and applied genetics 80 (1990), S. 321-325 
    Details
    ISSN: 1432-2242
    Keywords: Heterosis ; Genetic distance ; Drosophila ; Inbreeding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The aim of the experiment was to determine if the estimated genetic distance between two populations could be used to predict the amount of heterosis that would occur when they were crossed. Eight lines of known relatedness to each other were produced by eight generations of sib mating and sub-lining. This produced lines that varied in coefficient of coancestry from zero to 0.78. Fourteen reciprocal crosses of these lines were used to measure heterosis for larval viability and adult fecundity. Gene frequencies at six polymorphic enzyme loci were used to estimate the genetic distances between lines, which were then compared with the known degrees of coancestry. The estimated genetic differences were poorly correlated with the known coancestry coefficients (r=0.4), possibly due to the small number of loci typed. Also genetic distances were only about 1/3 of what was expected. Selection acting on blocks of genes linked to the enzyme loci probably prevented the expected increase in homozygosity. Coancestry coefficient was correlated with heterosis (r=0.44–0.71). This level of correlation implied differences in heterosis among parent lines with the same level of coancestry. This variability is expected if a small number of loci explain most of the heterosis. The average level of heterosis was less than expected after eight generations of sib mating. This is most likely due to selection opposing the increase in homozygosity caused by inbreeding. The combination of these two imperfect correlations resulted in no significant correlation between genetic distance estimated from markers and heterosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00210066
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  • 9
    Electronic Resource
    Electronic Resource
    Effect of rate of inbreeding on inbreeding depression in Drosophila melanogaster (1989)
    Springer
    Theoretical and applied genetics 77 (1989), S. 123-127 
    Details
    ISSN: 1432-2242
    Keywords: Inbreeding depression ; Drosophila ; Natural selection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary This experiment was designed to study the relationship between rate of inbreeding and observed inbreeding depression of larval viability, adult fecundity and cold shock mortality in Drosophila melanogaster. Rates of inbreeding used were full-sib mating and closed lines of N=4 and N=20. Eight generations of mating in the N=20 lines, three generations in the N=4 lines and one generation of full-sib mating were synchronised to simultaneously produce individuals with an expected level of inbreeding coefficient (F) of approximately 0.25. Inbreeding depression for the three traits was significant at F=0.25. N=20 lines showed significantly less inbreeding depression than full-sib mated lines for larval viability at approximately the same level of F. A similar trend was observed for fecundity. No effect of rate of inbreeding depression was found for cold shock mortality, but this trait was measured with less precision than the other two. Natural selection acting on loci influencing larval viability and fecundity during the process of inbreeding could explain these results. Selection is expected to be more effective with slow rates of inbreeding because there are more generations and greater opportunity for selection to act before F=0.25 is reached. Selection intensities seem to have been different in the three traits measured. Selection was most intense for larval viability, less intense for fecundity and, perhaps, negligible at loci influencing cold shock mortality.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00292326
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  • 10
    Electronic Resource
    Electronic Resource
    Heterosis in crosses between lines of Drosophila melanogaster selected for adaptation to different environments (1989)
    Springer
    Theoretical and applied genetics 77 (1989), S. 253-259 
    Details
    ISSN: 1432-2242
    Keywords: Heterosis ; Selection ; Drosophila ; Genotype x environment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Experiments were designed to examine whether heterosis would occur in crosses of Drosophila melanogaster populations adapted to 18 °C or 28 °C environments. Crosses were examined in parental environments, an intermediate environment (23 °C) and a mixed environment (alternating 18°/28°C). Parental populations did not show divergence for larval viability, cold shock or high temperature mortalities when tested in a common environment. However, the 28 °C population was less fecund than the 18 °C population, but had higher larval competitive ability and higher adult longevity. Heterosis for viability, cold shock mortality and high temperature mortality occurred in crosses between a population adapted to 18 °C and another adapted to 28 °C, but not in crosses between two populations adapted to the same temperature. The results suggest that, in the absence of drift, heterosis is expected in crosses between lines or populations with different histories of selection but not between lines with the same selection histories.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00266195
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