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  • Ultrastructure  (10)
  • Lepidoptera  (4)
  • 42.55
  • Scolytidae
  • healthy volunteers
  • Springer  (21)
  • American Chemical Society
  • American Geophysical Union
  • Frontiers Media SA
  • 1980-1984  (21)
  • 1920-1924
  • 1981  (21)
Collection
Keywords
Publisher
  • Springer  (21)
  • American Chemical Society
  • American Geophysical Union
  • Frontiers Media SA
Years
  • 1980-1984  (21)
  • 1920-1924
Year
  • 1
    Electronic Resource
    Electronic Resource
    Ultrastructure of the sperms ofPlumbago zeylanica (1981)
    Springer
    Protoplasma 107 (1981), S. 85-107 
    Details
    ISSN: 1615-6102
    Keywords: Male cytoplasmic inheritance ; Plumbago ; Pollen grain ; Pollen tube ; Sperm ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Male gametes ofPlumbago zeylanica were examined in pollen grains and tubes using light and electron microscopy of chemically and physically fixed tissues, and Nomarski interference microscopy of isolated, living sperm cells. Male gametes are elongate, spindleshaped cells containing a nucleus, mitochondria, ER, ribosomes, vesicles, dictyosomes, probable microfilaments, and a variable number of plastids. In mature pollen grains ofP. zeylanica, the two sperm cells are directly linked; they share a transverse cell wall with plasmodesmata and are enclosed together by the inner vegetative cell plasma membrane. One of these two sperms is also associated with the vegetative nucleus as a consistent feature of pollen grain organization. The basis of this association appears to be a long, narrow projection of the sperm cell (averaging 〈 1 μm wide and about 30 μm long) which wraps around the periphery of the vegetative nucleus and occupies embayments of that nucleus. This association is maintained throughout pollen tube growth but becomes less extensive near the completion of tube growth and is severed following tube discharge. The consistent occurrence of the sperm-vegetative nucleus association in pollen grains, tubes and isolated pollen cytoplasm suggests that the two structures may be directly connected, but attempts to visualize this type of connection were unsuccessful. Possibly, the entwining nature and extent of complementary interfaces between vegetative nucleus and sperm may have a role in stabilizing their association. Functionally, the two sperms and vegetative nucleus appear to travel as a linked unit within the pollen tube, possibly increasing the effectiveness of gamete delivery and helping to ensure nearly simultaneous transmission of sperms into the receptive megagametophyte.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01275610
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  • 2
    Electronic Resource
    Electronic Resource
    Ecdysteroids during pupal development of female Xyleborus ferrugineus (1981)
    Springer
    Entomologia experimentalis et applicata 30 (1981), S. 151-156 
    Details
    ISSN: 1570-7458
    Keywords: Xyleborus ferrugineus ; pupae ; ecdysteroids ; pharate adult ; radioimmunoassay ; Coleoptera ; Scolytidae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung Der Ecdysteroidtiter weiblicher Puppen von Xyleborus ferrugineus (Fabr.) wurde geschätzt, indem ganze Tiere homogenisiert und radioimmunologisch untersucht wurden. Ein ausgeprägtes Maximum an Ecdysteroiden wurde bei 36 Stunden Puppenent-wicklung beobachtet (743 pg/mg Körpergewicht). Der Titer nahm ab auf 299 pg/mg im Pharatstadium und auf 193 pg/mg unmittelbar vor Schlüpfen der Adulten. Qualitative Studien mit HPLC ergaben in frischen Puppen ein Verhältnis von 3:1 Ecdyson zu 20-Hydrooxyecdyson. Pharatstadien enthielten vor allem 20-Hydrooxyecdyson. Das beobachtete einzige Maximum im Titer stimmt überein mit den Resultaten bei andern untersuchten Coleopteren.
    Notes: Abstract Ecdysteroid titers were estimated on the whole body homogenates of Xyleborus ferrugineus (Fabr.) female pupae during development by radioimmunoassay. A distinct peak of ecdysteroids was observed at 36-hr pupal development (743 pg/mg body wt). Titer declined to 299 pg/mg by the pharate adult stage and to 193 pg/mg body wt just before adult emergence. Qualitative studies by HPLC revealed a ratio of 3:1 ecdysone to 20-hydroxyecdysone in the initial pupal stage. Pharate adults had mainly 20-hydroxyecdysone. The observed single peak in ecdysteroid titer agrees with findings in other studied coleopteran species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00300880
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  • 3
    Electronic Resource
    Electronic Resource
    Repellency of pheromones released by females of Heliothis armigera and H. zea to females of both species (1981)
    Springer
    Entomologia experimentalis et applicata 30 (1981), S. 123-127 
    Details
    ISSN: 1570-7458
    Keywords: Sex Pheromones ; Repellent ; Heliothis armigera ; Heliothis zea ; Lepidoptera ; Noctuidae ; cotton bollworm ; corn earworm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Résumé L'examen en olfactomètre a porté sur les réactions face à d'autres femelles de la même espèce, de femelles vierges ou ayant copulé d'Heliothis armigera Hübner et H. zea Boddie. Le lot comprenait 8 femelles, vierges ou ayant copulé en présence d'une femelle vierge ou ayant copulé. Les 4 combinaisons possibles de femelles vierges et de femelles ayant copulé ont été examinées avec 12 répétitions pour chaque espèce. Un extrait de l'extrémité de l'abdomen de femelles vierges d'une espèce a été présenté aux femelles de l'autre espèce pour examiner les possibilités de réactions interspécifiques aux phéromones. Pour chaque espèce, les réactions interspécifiques de répulsion entre femelles ont été hautement significatives par rapport aux témoins, à l'exception toutefois des réactions de femelle ayant copulé face à des femelles ayant elles aussi copulé. Les répulsions moyennes chez H. armigera et H. zea pour les 8 femelles de chaque expérience ont été: a) vierges en présence d'une vierge: 7,33 et 7,66; b) vierges en présence d'une femelles ayant copulé: 5,76 et 5,58; c) femelles ayant copulé en présence d'une vierge: 4,67 et 4,83. Les différences sont hautement significatives entre chaque paire de moyennes et entre chaque paire et le lot témoin; 3,17; 3,17; 3,42; 4,00 pour H. armigera; 3,17; 3,50; 2,83 et 3,75 pour H. zea. Les femelles vierges des deux espèces, H. armigera et H. zea ont présenté une réaction de répulsion en présence d'un extrait de l'abdomen de l'autre espèce; les répulsions moyennes étant respectivement 5,53 et 5,33 contre 3,83 et 3,58 pour le lot trémoin. On peut en conclure que ces répulsions doivent entraîner une tendance à la répartition uniforme.
    Notes: Abstract An olfactometer was used to determine the effect of pheromones released by females of the bollworms Heliothis armigera (Hübner) and H. zea (Boddie) on females of the same species. Four combinations of virgin and mated females were tested for repellency of one to the other. Evidence is presented that females of the two bollworms were repelled by females of the same species. In addition, extracts of virgin female abdomens of each species repelled virgin females of the other species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00300876
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  • 4
    Electronic Resource
    Electronic Resource
    The effects of nitrogen limitation on the ultrastructure of the cyanobacterium Agmenellum quadruplicatum (1981)
    Springer
    Archives of microbiology 130 (1981), S. 204-212 
    Details
    ISSN: 1432-072X
    Keywords: Agmenellum quadruplicatum ; Nitrogen starvation ; Ultrastructure ; PATO poststain ; Cyanobacteria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effects of nitrogen limitation on the ultrastructure of the unicellular cyanobacterium, Agmenellum quadruplicatum, were studied by thin sectioning transmission electron microscopy. Nitrogen became limiting for growth 14–15 h after transfer to nitrogen-limiting medium, but cultures retained full viability for at least 45 h. The c-phycocyanin: chlorophyll a ratio and cellular nitrogen content of the culture dropped rapidly after 14–15 h, as a progressive deterioration of major cell structures took place. Phycobilisomes were degraded first, followed by ribosomes and, then, thylakoid membranes. These structures were virtually depleted from the cells within 26 h. Intracellular polysaccharide accumulated in place of the normal cell structures throughout this period. Nitrogen limitation did not affect polyphosphate bodies, carboxysomes, lipid granules, the cell envelope, or the extra-cellular glycocalyx. All of the ultrastructural changes resulting from nitrogen limitation were reversed upon addition of nitrate to a starved culture. Most cell structures were restored within 3 h, and restoration was complete within 9 h.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00459520
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  • 5
    Electronic Resource
    Electronic Resource
    A magnetically stabilized coaxial laser discharge (1981)
    Springer
    Applied physics 26 (1981), S. 161-167 
    Details
    ISSN: 1432-0649
    Keywords: 52.80 ; 42.55
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A new magnetic discharge stabilization technique for coaxial laser systems is described. The approach utilizes crosses electric and magnetic fields to create and maintain a large and rapidly rotating plasma volume which does not experience glow-to-arc transitions. Very high cw specific discharge power loadings have been achieved even without the benefit of external gas cooling or circulation. Performance is insensitive to gas composition and pressure such that high power coaxial discharges have been run in CO2 laser gas mixtures up to several hundred torr. Stable cw discharges have also been obtained in mixtures containing several torr of SF6. The technique appears to be readily scalable to give very large excited volumes in systems with comparatively small overall physical dimensions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00692441
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  • 6
    Electronic Resource
    Electronic Resource
    Ultrastructure of differentiating preameloblasts from tooth germs of the permanent dentition ofMacaca mulatta andMacaca arctoides (1981)
    Springer
    Calcified tissue international 33 (1981), S. 603-618 
    Details
    ISSN: 1432-0827
    Keywords: Preameloblasts ; Tooth germs ; Monkey ; Enamel ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Cytodifferentiation of inner enamel epithelium and the adjacent connective tissue from the tip of the cervical loop to the initiation of enamel elaboration in twoMacaca species was examined. Ten- to twelve-month-old specimens were fixed by perfusion and the permanent tooth buds were prepared for transmission electron microscopy. At the cervical loop proper, inner enamel epithelium cells have lobed nuclei, a paucity of cytoplasm, and wide extracellular spaces; the basal lamina facing the dental papilla is straight. With increasing distance from the tip of the cervical loop, the following changes occur gradually: (a) preameloblasts elongate from 15 to 45 µm, and their organelles, particularly mitochondria and profiles of rough endoplasmic reticulum, become more numerous; (b) extracellular spaces decrease between preameloblasts starting at the basal (infranuclear) end; (c) the basement membrane becomes convoluted and associated with aperiodic fibers; (d) preodontoblast projections penetrate the aperiodic fibers; (e) collagen fibers subjacent to the basement membrane increase in density, with particularly thick fibers paralleling the aperiodic fibers. These modifications occur within three-fourths of the distance from the tip of the cervical loop to the mineralization front. The condensation of preodontoblasts is followed immediately by predentin synthesis. Concomitantly, the basement membrane breaks down and the aperiodic fibers are engulfed by preameloblasts. Preameloblast projections penetrate junctional predentin, contact mineralized dentin, and enamel synthesis ensues. At this stage the ameloblast is 45 µm long, the nucleus is central or basal, the Golgi apparatus has migrated apically, but the Tomes' process has not yet formed. The results indicate that odontogenesis inMacaca monkeys more closely resembles human odontogenesis than does that in the murine rodents.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02409498
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  • 7
    Electronic Resource
    Electronic Resource
    Radiocarbon dating by infrared laser spectroscopy (1981)
    Springer
    Applied physics 24 (1981), S. 381-386 
    Details
    ISSN: 1432-0630
    Keywords: 33 ; 42.55
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A tunable diode laser and a multipass optical cell are used to investigate the feasibility of performing radiocarbon dating by means of infrared spectroscopy. We show that the detection of14CO2 at concentrations of14C/12C≲10−12 is not limited by interferences from the background of normal CO2 molecules, provided the gas sample is cooled. Using short-time constants, the present sensitivity of the infrared technique is comparable to that of an ideal disintegration counter. The experimental results are extrapolated to long time constants to demonstrate that radiocarbon dating by infrared spectroscopy is feasible, and that carbon samples with a mass of less than 1 gm can be dated by this technique.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00899738
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  • 8
    Electronic Resource
    Electronic Resource
    Effect of dose on bioavailability of oral digoxin (1981)
    Springer
    European journal of clinical pharmacology 19 (1981), S. 53-55 
    Details
    ISSN: 1432-1041
    Keywords: digoxin ; bioavailability ; dose-dependency ; urinary excretion ; healthy volunteers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Nine healthy volunteers received single 0.25, 0.5, 1.0, 1.5, and 2.0 mg doses of oral digoxin tablets in random sequence on five occasions separated by at least 4 weeks. Urinary excretion of immunoassayable digoxin was determined from 8 consecutive 24 h urine samples collected after each dose. Mean values of cumulative urinary excretion of digoxin at the 5 doses were: 40.9, 35.6, 36.4, 34.1, and 33.5% of the dose (F=0.64; d. f.=4.32; N. S.). Mean values of urinary excretion half-life were: 2.48, 2.03, 2.20, 2.07, and 1.87 days (F=2.87; d. f.=4.32;p=0.05). Thus, the bioavailability of orally administered digoxin tablets in healthy volunteers is dose-independent over an 8-fold range of doses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00558384
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  • 9
    Electronic Resource
    Electronic Resource
    Ultrastructure of cell division and reproductive differentiation of male plants in theFlorideophyceae (Rhodophyta). Mitosis inDasya baillouviana (1981)
    Springer
    Protoplasma 106 (1981), S. 329-341 
    Details
    ISSN: 1615-6102
    Keywords: Dasya ; Mitosis ; Rhodophyta ; Spermatangia ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Mitosis in the marine red algaDasya baillouviana (Ceramiales, Florideophyceae) was observed with the electron microscope. Most details of the process are quite similar to those observed in the other macroscopic red algae studied to date. However, some minor variations were noted. At late prophase a very small nuclear envelope protrusion (NEP) is formed at each division pole subjacent to the “nucleus associated organelle” known as the polar ring (PR) and 2–3 cisternae of perinuclear endoplasmic reticulum (PER) are commonly present during metaphase-anaphase. In contrast, in the other florideophycean algae where mitosis has been reported, a prominent NEP is present at late prophase (McDonald personal communication,Scott et al. 1980) and only a single cisterna of PER is observed. Additionally, during mid-late interphase and in mitotically-quiescent cells ofDasya, a single cisterna of smooth-surfaced ER is always juxtaposed with each PR. The possible significance of PER in theFlorideophyceae and other multinucleate organisms is discussed as well as the likely functions of spindle-associated smooth ER. It is suggested that ultrastructural features of mitosis should be useful as criteria to aid in the interpretation of the phylogeny of red algae.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01275563
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  • 10
    Electronic Resource
    Electronic Resource
    Interspecific effects of pheromones on the attraction of the bark beetles,Dendroctonus brevicomis andIps paraconfusus in the laboratory (1981)
    Springer
    Journal of chemical ecology 7 (1981), S. 9-18 
    Details
    ISSN: 1573-1561
    Keywords: Dendroctonus brevicomis ; Ips paraconfusus ; Coleoptera ; Scolytidae ; Pinus ponderosa ; bark beetle ; exo-brevicomin ; frontalin ; myrcene ; verbenone ; ipsenol ; ipsdienol ; cis-verbenol ; attractants ; inhibition ; semiochemicals ; pheromones
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Dendroctonus brevicomis was attracted to a mixture of theIps paraconfusus pheromones, ipsenol,cis-verbenol, and ipsdienol at 10−9 g each/μl but was not attracted to these pheromones at higher and lower release rates.I. paraconfusus was not attracted to theD. brevicomis pheromonesexo-brevicomin, frontalin, and myrcene at any release rate tested. Increased release rates of a mixture of the three pheromones ofI. paraconfusus inhibited the attraction ofD. brevicomis to its synthetic pheromones. A mixture of ipsenol + ipsdienol orcis-verbenol alone failed to cause inhibition indicating that at least two of theI. paraconfusus pheromones are required to inhibit the response ofD. brevicomis. The pheromones ofD. brevicomis did not inhibit the attraction ofI. paraconfusus to its pheromones; however, verbenone was a potent inhibitor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00988631
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