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  • Springer  (486)
  • Oxford University Press  (59)
  • 1990-1994  (545)
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  • 1
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    The design of the Tokamak Physics Experiment (TPX) (1993)
    Springer
    Details
    Publication Date: 1993-09-01
    Print ISSN: 0164-0313
    Electronic ISSN: 1572-9591
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by Springer
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    PAPER CURRENT
  • 2
    Electronic Resource
    Electronic Resource
    Band 3 antagonists, p-azidobenzylphlorizin and dids, mediate erythrocyte shape and flexibility changes as characterized by digital image morphometry and microfiltration (1994)
    Springer
    The journal of membrane biology 141 (1994), S. 91-100 
    Details
    ISSN: 1432-1424
    Keywords: Erythrocyte ; Cytoskeleton ; Cell deformability ; Anion transport inhibitors ; Band 3 ; Sickle cell disease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Two nonpenetrating membrane probes, p-azidobenzylphlorizin (p-AzBPhz) and 4,4′-diisothiocyano-2,2′-stilbene disulfonate (DIDS), have been shown in earlier studies to induce dose-dependent changes in red blood cell (RBC) shape and volume at the same low concentrations that inhibit anion transport. In the present work, these ligand-induced morphology and rheology changes were studied using video digital image morphometry (VDIM) and microfiltration techniques. The results of these experiments corroborate our earlier investigation. RBCs were filmed using a Nomarski optics microscope with video camera attachment and cell size and shape changes were computer analyzed using VDIM. Low μm p-AzBPhz or DIDS levels caused collapse of the cell's biconcave structure and cell flattening occurred within 1–2 sec after drug exposure. Higher doses of either agent converted cells to a new steady-state in which a concurrent limited increase in erythrocyte volume and blunt membrane protrusions were produced. These changes were reversed in less than 2 sec by washing the drug from the membrane. Both ligands increased the deformability of RBCs in a dose-dependent manner as determined by filtration through Nuclepore polycarbonate filters (3 μm pore diameter). The improvement in deformability of drug-treated sickle cells was much more dramatic than for normal cells at low p-AzBPhz concentrations. These results support our earlier conclusions that the ligands, through a common interaction with band 3, induce volume-associated cytoskeletal alterations which lead to changes in morphology and flexibility.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00232877
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of gibberellin biosynthesis inhibitors on shoot regeneration from hypocotyl explants of Albizzia julibrissin (1993)
    Springer
    Plant cell reports 13 (1993), S. 115-118 
    Details
    ISSN: 1432-203X
    Keywords: adventitious shoot formation ; gibberellic acid ; paclobutrazol ; prohexadione calcium ; tissue culture ; uniconazole
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Hypocotyl explants of Albizzia julibrissin were placed on Gamborg's B5 medium supplemented with various levels of paclobutrazol, uniconazole, prohexadione calcium, or GA3. Callus formation was evident within one week after placement of the explants on the culture media. Green nodule-like structures protruded from the distal end of the explants within 10 days and developed into shoots within a month. These shoots readily formed adventitious roots when placed on fresh culture medium. All three of the gibberellin biosynthesis inhibitors increased shoot formation compared to the control. The number of shoots per explants was increased 107, 79, and 168% by 0.3–0.4 μM paclobutrazol, uniconazole, and prohexadione calcium, respectively. In contrast to the gibberellin biosynthesis inhibitors, GA3 decreased shoot formation. These results indicate that modification of gibberellin status can have a strong impact on the number of shoots formed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00235303
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  • 4
    Electronic Resource
    Electronic Resource
    Influence of growth regulators on somatic embryogenesis, plantlet regeneration, and post-transplant survival of Echinochloa frumentacea (1992)
    Springer
    Plant cell reports 11 (1992), S. 368-371 
    Details
    ISSN: 1432-203X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract After placement on Murashige and Skoog's basal medium supplemented with 3–5 mg/l 2,4-D, immature inflorescence expiants of Echinochloa frumentacea gave rise to three distinct types of callus: a) loosely arranged and soft; b) compact and translucent; c) compact, sticky and mucilaginous. Somatic embryo formation occurred in type ‘b’ callus in about 18–24 d. Callus types ‘a’ and ‘c’ did not produce somatic embryos. The highest percentage of cultures exhibiting somatic embryogenesis occurred on the medium containing 5 mg/l 2,4-D and 0.5 mg/l kinetin. Somatic embryos also formed directly on the inflorescence (without intervening callus formation) in about 15% of the expiants placed on this medium. The addition of paclobutrazol or uniconazole (0.25 or 1 mg/l) to the medium had no influence on the percentage of cultures exhibiting direct somatic embryogenesis, but paclobutrazol slightly increased the mean number of somatic embryos per culture. Many of the callus-derived somatic embryos germinated when subcultured on basal MS medium supplemented with kinetin. Addition of paclobutrazol or uniconazole to the culture medium at 0.25 or 1 mg/l decreased somatic embryo germination and shoot elongation but increased root length and leaf width. Both paclobutrazol and uniconazole increased survival of the plantlets following transplanting to soil. Increased post-transplant survival was accompanied by reduced water loss from plantlets produced on culture media containing triazoles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00233368
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  • 5
    Electronic Resource
    Electronic Resource
    Mediation of deep supercooling of peach and dogwood by enzymatic modifications in cell-wall structure (1991)
    Springer
    Planta 184 (1991), S. 254-260 
    Details
    ISSN: 1432-2048
    Keywords: Prunus ; Cornus ; Cold hardiness ; Supercooling ; Xylem parenchyma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Treatment of stem sections of peach (Prunus persica (L.) Batsch) and flowering dogwood (Cornus florida L.) with macerase, an enzyme mixture rich in pectinase, for 24–48 h resulted in a complete flattening of the low-temperature exotherm (LTE) as determined by differential thermal analysis (DTA). Ultrastructural analysis of macerase-treated tissue demonstrated a nearly complete digestion of the pit membrane (black cap and primary cell-wall) of nearly 100% of the xylem-parenchyma cells examined after 48 h of exposure to the enzyme. Additionally, the underlying amorphous layer was partially degraded in up to 57% of the cells examined. The macerase treatment had no visible effect on secondary cell-walls of xylem tissue. In contrast, treatment of stem tissue with cellulysin (mostly cellulase) resulted in a shift of the LTE to warmer temperatures as determined by DTA, and a digestion of only the outermost layer of the pit membrane in nearly 100% of the cells examined, with little or no effect on the underlying layers. Treatment of tissue with 25 mM sodiumphosphate buffer also resulted in a shift of the LTE to warmer temperatures but the shift was not as great as in cellulysin-treated tissue. The shift was associated with a partial degradation of the outermost layer of the pit membrane in dogwood (33–45% of the cells examined) but not in peach (3–7% of the cells). Collectively, the data indicate that pectins may be an integral structural element of the pit membrane and that this portion of the cell-wall, along with the underlying amorphous layer, play a major role in forming a barrier to water movement and growth of ice crystals. This barrier allows xylem parenchyma of some species of woody plants to undergo deep supercooling.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01102426
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  • 6
    Electronic Resource
    Electronic Resource
    Mediation of deep supercooling of peach and dogwood by enzymatic modifications in cell-wall structure (1991)
    Springer
    Planta 184 (1991), S. 254-260 
    Details
    ISSN: 1432-2048
    Keywords: Prunus ; Cornus ; Cold hardiness ; Supercooling ; Xylem parenchyma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Treatment of stem sections of peach (Prunus persica (L.) Batsch) and flowering dogwood (Cornus florida L.) with macerase, an enzyme mixture rich in pectinase, for 24–48 h resulted in a complete flattening of the low-temperature exotherm (LTE) as determined by differential thermal analysis (DTA). Ultrastructural analysis of macerase-treated tissue demonstrated a nearly complete digestion of the pit membrane (black cap and primary cell-wall) of nearly 100% of the xylem-parenchyma cells examined after 48 h of exposure to the enzyme. Additionally, the underlying amorphous layer was partially degraded in up to 57% of the cells examined. The macerase treatment had no visible effect on secondary cell-walls of xylem tissue. In contrast, treatment of stem tissue with cellulysin (mostly cellulase) resulted in a shift of the LTE to warmer temperatures as determined by DTA, and a digestion of only the outermost layer of the pit membrane in nearly 100% of the cells examined, with little or no effect on the underlying layers. Treatment of tissue with 25 mM sodiumphosphate buffer also resulted in a shift of the LTE to warmer temperatures but the shift was not as great as in cellulysin-treated tissue. The shift was associated with a partial degradation of the outermost layer of the pit membrane in dogwood (33–45% of the cells examined) but not in peach (3–7% of the cells). Collectively, the data indicate that pectins may be an integral structural element of the pit membrane and that this portion of the cell-wall, along with the underlying amorphous layer, play a major role in forming a barrier to water movement and growth of ice crystals. This barrier allows xylem parenchyma of some species of woody plants to undergo deep supercooling.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00197955
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  • 7
    Electronic Resource
    Electronic Resource
    Survivorship of penstemon grandiflorus in an oak woodland: combined effects of fire and pocket gophers (1991)
    Springer
    Oecologia 86 (1991), S. 113-118 
    Details
    ISSN: 1432-1939
    Keywords: Penstemon grandiflorus ; Geomys bursarius ; Fire ; Disturbance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The effects of fire and pocket gophers, Geomys bursarius, on the survivorship of Penstemon grandiflorus growing in an oak woodland in Minnesota were studied from 1986 to 1990. Plants growing in sparse vegetation experienced mortality rates twice that of plants growing in dense vegetation. This difference was due partly to pocket gophers whose earth moving activities reduce the density of vegetation and bury and kill individual Penstemon plants. Laboratory feeding trials showed that gophers readily eat Penstemon, particularly the fleshy roots. An experiment involving the removal of 25–75% of the root tissue in 90 plants showed that root loss significantly reduced survivorship, suggesting that gopher herbivory might also kill plants. When gophers were experimentally excluded, plants growing in sparse vegetation exhibited significantly lower mortality rates than those growing in dense vegetation. Plants in the smallest size class exhibited reduced survivorship following a late spring burn; however, overall patterns of survivorship of plants in burned areas did not differ markedly from those in the unburned areas. A longitudenal analysis of plants with different reproductive histories revealed no survivorship cost to reproduction. Mortality rates decreased with increasing plant size. Small plants were more likely to be killed by fire and by being buried under gopher mounds. Differences in underground energy reserves of small and large plants can account for most of the survivorship patterns observed in this study. The study shows that within openings of the oak woodland, fire and gophers reduce the survival of individual Penstemon plants. Nevertheless, since both gophers and fire also serve to perpetuate suitable habitat in the woodland, Penstemon is ultimately dependent on both for its long term persistence in the landscape.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317397
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  • 8
    Electronic Resource
    Electronic Resource
    Estimates of bacterial productivity in marine sediments and water from a temperate saltmarsh lagoon (1992)
    Springer
    Microbial ecology 23 (1992), S. 195-209 
    Details
    ISSN: 1432-184X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Tritiated thymidine incorporation (TTI) into DNA was used to estimate bacterial productivity in sediment and water samples from two sites in Langebaan Lagoon, South Africa. Routine analysis of isotope dilution showed seasonal variations of approximately threefold in the thymidine precursor pool sizes for bacterial assemblages from each site. Dual label incorporation of [3H]-thymidine and 14C-leucine into DNA and protein, respectively, showed that pelagic but not sediment assemblages were in a balanced state of growth during TTI. This is the first report of dual label measurements of bacterial production in sediments. Sediments supported bacterial productivities that exceeded those in the water column by factors from five- to 950-fold, whereas bacterial abundance supported by sediments exceeded that in the water column by more than 3 orders of magnitude. Estimates of bacterial productivities in sediments were coincident with levels of organic content in sediments, but not with bacterial abundance. Measurements of TTI activity for 5 different benthic microhabitats at one lagoon site showed highest activity associated with seagrass beds (2.11 ± 0.84 nmol thymidine hours−1 g-1 dry weight), whereas activities decreased with depth (0.46 ± 0.21 nmol thymidine hours−1 g−I dry weight) below sediment surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00164096
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  • 9
    Electronic Resource
    Electronic Resource
    Alkaloids and ascidian chemical defense: Evidence for the ecological role of natural products fromEudistoma olivaceum (1991)
    Springer
    Marine biology 111 (1991), S. 375-379 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The surface of the colonial ascidianEudistoma olivaceum (Van Name) is almost completely free of fouling organisms. I provide evidence that this epibiont-free surface is maintained by the alkaloids, Eudistomins G and H. These alkaloids were extracted from colonies collected in the shallow subtidal of Indian River Lagoon, Florida. USA, in November 1987. Concentrations of less than one-fifth of those found in the living ascidian inhibited the settlement of the larvae of five invertebrate species relative to appropriate controls in laboratory and field trials. Standard pharmacological assays have revealed that Eudistomins G and H were not the most biologically active of the eudistomins, indicating that these standard assays are not necessarily good predictors of antifouling activity. In an examination of possible alternate roles for these eudistomins, they proved ineffective as a fish antifeedant. PinfishLagadon rhomboides consumed agar pellets to which Eudistomins G and H had been added at concentrations 10- to 100-fold higher than those effective against settling larvae. These findings indicate that biologically active marine natural products may serve specific ecological roles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01319409
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  • 10
    Electronic Resource
    Electronic Resource
    Feeding ecology and interannual variations in diet of larval jack mackerel, Trachurus declivis (Pisces: Carangidae), from coastal waters of eastern Tasmania (1992)
    Springer
    Marine biology 113 (1992), S. 11-20 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Crustacean microzooplankton were the main prey of larval Trachurus declivis collected in the summers of 1988, 1989 and 1990 from coastal waters of eastern Tasmania. The diet was dominated by harpacticoids (Microsetella rosea), cyclopoids (mainly Oithona spp.), calanoids and the calyptopis stage of the euphausiid Nyctiphanes australis. Bivalve veligers were occasionally eaten. Diets of larvae were affected by interannual variations in plankton composition, particularly in 1989 when intrusions of low-nutrient subtropical water exclused large zooplankters (e.g. N. australis) from the study area. Larvae≤6 mm selected for copepod nauplii; all larvae selected for M. rosea, cyclopoids, and the calyptopis stage of N. australis. Even though calanoids were a major prey taxon, there were proportionally fewer eaten than were present in the environment. In all, 78% of larvae taken during the daytime had food in their stomachs, as opposed to 38% of the larvae from night samples. Feedmid-morning and late afternoon. A gut evacuation rate of ∼4 to 6 h was estimated. We calculated that the larvae ate between 9 and 13% of their body weight in food per day. The larvae of T. declivis in this study were not sufficiently abundant to have an impact on their prey.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00367633
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