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  • 1
    ISSN: 1432-1211
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Recently we reported that antigen-primed T cells from (H-2 u × H-2 s)F1 and (H-2 u × H-2 q)F1 mice responded poorly in vitro to antigen in the context of antigen-presenting cells of the non-H-2 u parent. It was suggested that this effect might be due to unbalanced expression of parental antigens in the F1 hybrid with the result that the non-H-2u A antigens were greatly reduced or absent in these mice. If this were the case, non-H-2u Ia-A cells might be expected to stimulate a mixed lymphocyte reaction (MLR) when cultured with Fl responder cells. When tested, (SJL × PL)F1 responder cells reacted strongly to SJL stimulator cells. There was no significant reaction to PL stimulator cells. The use of major histocompatibility complex (MHC) congenic mice showed the stimulatory antigens to be associated with the MHC. The MLR could be blocked significantly by monoclonal A-specific antibody of the appropriate specificity. When a monoclonal antibody reactivewith a private epitope associated with As was used to probe for the presence of As on the surface of (SJL × PL)F1 spleen cells, no antigen could be detected, indicating loss or alteration of this antigen. These findings suggest that an alteration of the expression of the parental As molecule may be responsible for this phenomenon.
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  • 2
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: SJL/J and (SJL × PL) F1 hybrid mice were immunized with intact human myelin basic protein (MBP) or the three major peptic fragments of MBP, residues 1–38, 39–89, and 90–170. Immune spleen cells were fused with mouse myeloma P3 × 63Ag8 (NS1) cells in the presence of polyethylene glycol. Hybridoma supernatant culture fluids were screened for antibody to MBP by a solidphase radioimmunoassay (RIA). The specificity of the monoclonal antibody (mAb) was characterized by RIA using the three major MBP peptic fragments and subfragments as well as MBP and MBP fragments of different species with known amino acid sequence differences. Six MBP mAbs were generated, one of them IgM isotype and the remainder IgG isotypes. One mAb each reacted against regions of residues 22–38, 39–69, 70–89, 90–116, and two reacted against residues 118–157. Immunoblots also showed that the five IgG mAbs were reactive against MBP and the peptic fragment of MBP containing the epitope. Immunohistochemical studies showed the IgG mAbs specifically stained myelinated fiber tracts in human brain tissue.
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  • 3
    ISSN: 1434-0879
    Keywords: Urinary tract infection ; Super-infection ; Anti-adherence factor ; Sialomucin layer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Pre-existing bacteriuria of 2 to 3 weeks' duration in the rabbit had no effect on either the histological integrity of the sialomucin layer (anti-adherence factor) of the bladder mucosa or the protective effect of this layer against super-infection.
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  • 4
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] T lymphocytes sensitized to MBP can cause clinical and histological EAE when adoptively transferred to naive recipients6"10. The ? cells that are transferred in these experimental systems are heterogeneous polyclonal populations capable of responding to various antigenic determinants on MBP9. It is ...
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  • 5
    ISSN: 1573-8477
    Keywords: allocation costs ; chemical defense ; epistasis ; genetic architecture ; hybridization ; selection experiments ; tolerance to damage ; tradeoffs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Hybridization is common and important to the adaptive evolution of plants. Hybridization has resulted in the formation of new species and the introgression of traits between species. This paper discusses the advantages of using hybrid systems to explore the evolution of tolerance to herbivore damage (i.e., the ability to diminish the negative effects of damage on fitness). The major consequence of hybridization likely to make it influential for tolerance evolution is that hybridization generates broad variation in traits that can be selected for or against. In addition to generating greater variation in tolerance to damage and its putative traits (e.g., traits associated with allocation patterns and meristem production), hybridization can generate greater independence among tolerance traits and between tolerance and defense traits. Greater independence may provide a greater ability to discern mechanisms of tolerance, give a greater probability of detecting allocation costs of tolerance, and provide an effective means to evaluate tradeoffs between tolerance and defense. Interspecific hybrid systems can also be used to evaluate the importance of co-adaptation of tolerance traits. Moreover, recombinant hybrids can be used in selection studies focusing on tolerance to damage to discern whether parental combinations of tolerance traits are favored over novel combinations. Research in hybrid systems that investigate the selective importance of tolerance, the patterns of inheritance of tolerance traits, and the genetic architecture of plant species involved can be vital to our evaluation of the adaptive role of tolerance to damage.
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  • 6
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    Oecologia 65 (1985), S. 194-200 
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Reproductive success and growth rate data were collected for individually marked crab spiders Misumena vatia (Clerck) in 1980, 1981, and 1982. All measures of reproductive success were found to be quite variable between individuals within years, but did not differ between years. Reproductive effort (mass of clutch/prereproductive mass of female) was the least variable measurement and was not correlated with female weight at reproduction. Clutch weight and number of eggs per clutch were highly correlated with female reproductive weight. Egg weight was not correlated with the number of eggs per clutch. Hatching success did not vary with clutch size and averaged 94.5%. Growth rates of spiders were highly variable, indicating large variation in feeding rate. In 1981 and 1982, approximately 20% of female spiders were unable to capture enough prey to grow and reproduce. Primary prey species differed in weight and in their contribution to spider egg production. Spiders attacked a larger percentage of bumblebees but captured a larger percentage of honeybees. There was no simple relationship between diet choice and reproductive success. Spiders which selected suboptimal umbels to forage on some or all of the time, however, had significantly lower reproductive success than spiders choosing the best umbels.
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  • 7
    ISSN: 1432-2013
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Zusammenfassung Am Froschnerven wird die Abhängigkeit der Rheobase von der elektrotonischen Ausgangslage am Reizort für verschiedene Milieubedingungen untersucht. Der Verlauf dieser Abhängigkeit wird durch die „elektrotonische Rheobasenkurve“ in von der bisher verwendeten etwas abweichender graphischer Darstellung wiedergegeben. Es wird gezeigt, daß die von früheren Autoren beschriebenen verschiedenen Verlaufstypen der elektrotonischen Rheobasenkurve auf ganz bestimmte Veränderungen des den Nerven umgebenden Mediums zurückgeführt werden können. Befindet sich die interpolare Nervenstrecke in Luft statt unterRinger-Lösung, so wird dadurch die elektrotonische Rheobasenkurve in Richtung höherer Reizschwellen verschoben. Ein ähnlicher Effekt wird erreicht, wenn in der den Nerven umgebendenRinger-Lösung der Gehalt an Calcium-Ionen noch innerhalb physiologisch zulässiger Grenzen erhöht wird. Diese Wirkung der Calcium-Ionen wird durch Kalium-Ionen antagonistisch beeinflußt, doch nur solange, als Calcium-Ionen gegenwärtig sind. In Abwesenheit von Calcium wirkt Kalium ebenfalls im Sinne einer Verschiebung der elektrotonischen Rheobasenkurve nach höheren Schwellenwerten. Für diese Verschiebung der elektrotonischen Rheobasenkurve nach höheren Schwellenwerten wird als gemeinsame Ursache eine Verzögerung der mit dem Reizprozeß einhergehenden lokalen Ladungsausgleichsvorgänge verantwortlich gemacht. Diese Verzögerung ist dann, wenn die interpolare Nervenstrecke sich in Luft befindet, auf das geringe Leitvermögen des umgebenden Mediums zurückzuführen, während bei Steigerung des Calciumgehaltes an eine Erhöhung desinneren Widerstandes durch die membranverdichtende Eigenschaft der Calcium-Ionen zu denken ist. Schließlich ergibt sich auch die Möglichkeit, für die Zunahme der Reizschwellen im Anelektrotonus, d. h. also für den gewöhnlichen Verlauf der elektrotonischen Rheobasenkurve die verdichtende Wirkung der Anode verantwortlich zu machen. Der hier an der elektrotonischen Rheobasenkurve des Nerven in Erscheinung tretende Antagonismus in der Wirkung der Kalium- und Calcium-Ionen zeigt eine auffallende Übereinstimmung mit anderweitigen Beobachtungen über den Kalium-Calcium-Antagonismus.
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  • 8
    ISSN: 1573-1561
    Keywords: Salicaceae ; willows ; hybrids ; hybridization ; phenolic glycosides ; salicortin 2′-cinnamoylsalicortin ; condensed tannins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Salix sericea andS. eriocephala differ markedly in secondary chemistry.S. sericea produces phenolic glycosides, salicortin and 2′-cinnamoylsalicortin, and low concentrations of condensed tannin. In contrast,S. eriocephala produces no phenolic glycosides, but high concentrations of condensed tannins. Hybrid chemistry is intermediate for both types of chemicals, suggesting predominantly additive inheritance of these two defensive chemical systems from the parental species. However, there is extensive variation among hybrids. This variation may be due to genetic variation among parental genotypes, which genes were passed on, or to subsequent back-crossing. The differences in chemistry are likely to exert a strong effect on the relative susceptibility of hybrid and parental willows to herbivores.
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  • 9
    ISSN: 1570-7458
    Keywords: Salix ; hybridization ; phenolic glycosides ; herbivore preference ; herbivore performance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We examined the preferences and performances of five beetle species (four chrysomelids and one scarab) on two species of willows (Salix sericea and S. eriocephala) and their interspecific hybrids. Beetle species differed markedly in their responses. In preference assays, two chrysomelid beetle species (Calligrapha multipunctata bigsbyana and Plagiodera versicolora) preferred hybrids, two chrysomelids (Chrysomela scripta and Ch. Knabi) preferred hybrids and S. sericea, and the scarab beetle ( Popillia japonica) preferred S. eriocephala. Experiments with purified salicortin indicated that salicortin concentration may contribute to these preferences. The relative performance (growth rate, pupal/adult weight and survivorship) of these beetles on the three willow taxa did not correspond with their feeding preferences. Three species exhibited intermediate performance on hybrid willows (the two Chrysomela spp. and P. japonica); the Chrysomela spp. performed best on S. sericea, while P. japonica performed best on S. eriocephala. One species performed equally well on all three taxa (C. multipunctata bigsbyana). The performance of Pl. versicolora was not tested. Our results support the general pattern that willow taxa with phenolic glycosides are more acceptable to specialist willow herbivores while those taxa without phenolic glycosides are more acceptable to generalist herbivores. We also show that to predict the relative susceptibility of hybrid and parental plants to herbivores, consideration must be given to the inheritance of traits affecting both preference and performance.
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  • 10
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The population structure of the spruce grouse (Canachites canadensis) was studied in the Adirondack Mountains of New York, U.S.A. Twenty-five isolated habitat patches exist and are occupied by spruce grouse, with 7 suitable but unoccupied patches existing at the periphery of the range. The regional distribution and abundance of spruce grouse is correlated with the amount of lowland coniferous forest habitat. Unoccupied patches were significantly smaller and significantly farther from occupied patches than were other occupied patches. For all patches, as distance from the nearest occupied patch increased, the percent of occupied patches decreased linearly. I incorporated birth and death rates for spruce grouse into the MacArthur-Wilson survivorship model which closely predicted the proportion of occupied patches for an average population density (2.8 ♀ spruce grouse/100ha). For the same demographic parameters, extinction times were calculated which indicate that the 15 habitat patches of a carrying capacity of ≦3 female spruce grouse (≦100 ha) would have an average extinction time of less than 6 years. This in part accounts for the high proportion of these patches which are unoccupied. Extinctions and recolonizations of patches were observed during the study. The patterns of patch occupancy can partially be predicted based on their size, spatial arrangement, and the demographic characteristics of the spruce grouse.
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