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61.
Michele K. Johnson Sally J. Holbrook Russell J. Schmitt Andrew J. Brooks 《Environmental Biology of Fishes》2011,91(4):429-448
Branching corals, like many in the genus Acropora, provide structurally complex habitats for reef fishes and other organisms. Fluctuations in the abundance, distribution and
characteristics of thicket-forming staghorn Acroporids may contribute to changes in the abundance and species composition
of reef fishes due to changes in the availability of shelter habitat and food. Farming damselfishes of the genus Stegastes can occur in high abundances in staghorn corals and actively defend food and nest space against organisms that threaten these
resources. Here we assess the value of staghorn as habitat for fishes in the central South Pacific, and how the presence of
territorial farming damselfishes may influence the assemblage of fishes that associate with staghorn corals. Surveys of 185
Acropora pulchra patches located in the lagoons surrounding the island of Moorea, French Polynesia revealed 85 species of fish from 25 families.
Total fish abundance and species richness values ranged from no fish on a patch to a high of 275 individuals and 26 species.
Patch area was the most important characteristic in explaining variation in attributes of the fish assemblage, with other
characteristics explaining little of the species composition or trophic structure. Behavioral observations revealed that farming
damselfishes were most aggressive toward corallivores, herbivores, and egg predators, while they ignored most carnivores and
omnivores. Despite this pattern, we observed positive covariance between Stegastes and the group of fishes that elicited the strongest aggressive response when the effect of patch area was removed, suggesting
these fishes remain drawn to the resources produced or enhanced by Stegastes on A. pulchra. 相似文献
62.
63.
Benedetti Ettore Iacovino Rosa Pedone Carlo Rossi Filomena Saviano Michele Isernia Carla Montesarchio Daniela de Napoli Lorenzo Piccialli Gennaro 《International journal of peptide research and therapeutics》1997,4(3):129-134
Summary An N- and C-protected derivative ofhomo-β-leucine, Fmoc-homo-β-(S)-leucine methyl ester, synthesized from the corresponding proteinogenic parent α-amino acid in enantiopure form has been
fully characterized in the solid state by X-ray diffraction analysis. The crystal conformation of this new residue indicates
and extended conformation for thishomo-β-residue, with the ϕ torsion angle being more constrained than the μ and ψ angles. 相似文献
64.
Physiological price of an induced chemical defense: photosynthesis, respiration, biosynthesis, and growth 总被引:8,自引:1,他引:8
A recurring theme in defense allocation theories is that defenses are costly. Most studies that attempt to quantify a cost
of defense seek to establish a trade-off between a component of plant fitness and the level of a constitutive defense. Such
estimates are ambiguous because they cannot discount the cost of traits that are correlated with defense but are not themselves
defensive. We examined the effects of damage-induced synthesis of furanocoumarins, known defense compounds, on the growth
of wild parsnip. Plants that had 2% of their leaf area removed accumulated 8.6% less total biomass and 14% less root biomass
than intact plants over a 4-week period. We also found that this small amount of leaf damage significantly reduced net photosynthetic
rates 0.5 h after damage; the effect was temporary, as photosynthetic rates were no longer significantly different after 48 h.
Lastly, we found that increases in respiration rates associated with damage coincided spatially and temporally with increases
in furanocoumarin production, and that respiration increases were phenotypically correlated with furanocoumarin production.
When damage-induced changes in furanocoumarin content and respiration rates were expressed in glucose equivalents and compared,
the energetic cost of furanocoumarin production (12.6 μg glucose cm−2) accounted for all of the increase in respiration (12.0 μg glucose cm−2). A comparison of other secondary compounds in damaged and intact leaflets revealed that myristicin, a furanocoumarin synergist,
is the only other compound aside from furanocoumarins that is inducible. The inducible defense system of wild parsnip thus
appears to involve a small subset of secondary compounds. Synthesis of these compounds is tightly linked to damage-induced
rates of respiration. Because the negative impact that damage had on the rate of net photosynthesis was short-lived, the impact
of damage on growth observed in this study was likely due to the cost of furanocoumarin synthesis elicited by damage rather
than the loss of photosynthetic tissue caused by damage.
Received: 4 April 1996 / Accepted: 29 August 1996 相似文献
65.
Mosca A D'Alagni M Del Prete R De Michele GP Summanen PH Finegold SM Miragliotta G 《Anaerobe》1995,1(1):21-24
In this study we describe two properties of the Gram-negative bacterium Bilophila wadsworthia, namely the ability to clot Limulus lysate and the capacity to induce the production of tissue factor-like procoagulant activity by human mononuclear cells in vitro. Although exhibited at a lower degree when compared with those of typical Gram-negative bacteria or Gram-negative endotoxin those activities may account in part for Bilophila's pathogenicity. The capacity indeed to induce fibrin formation through the interaction with mononuclear cells suggests one mechanism by which the microorganism might cause abscess formation in the host. Moreover, since this activity is dependent on the number of Bilophila interacting with mononuclear cells, we hypothesize that this biological activity is closely influenced by growth environment. 相似文献
66.
67.
Ubiquitin over-expression promotes E6AP autodegradation and reactivation of the p53/MDM2 pathway in HeLa cells 总被引:1,自引:0,他引:1
Crinelli R Bianchi M Menotta M Carloni E Giacomini E Pennati M Magnani M 《Molecular and cellular biochemistry》2008,318(1-2):129-145
It has been established that intracellular ubiquitin pools are subject to regulatory constrains. Less certain is the mechanism by which the pool of conjugated ubiquitin shift in parallel with total ubiquitin, and how this type of regulation affects the flux of substrates through the pathway. In this study we demonstrate that ubiquitin over-expression promotes the destabilization of the ubiquitin protein ligase E6AP, by a mechanism involving self-ubiquitination, and the stabilization of p53. These results represent the very first evidence that the levels of a ubiquitin ligase can be regulated in vivo by ubiquitin abundance, supporting the idea that a strict interrelationship between pathway component activities and ubiquitin pool size exists. Interestingly, ubiquitin-induced p53 accumulation did not induce cell-cycle arrest, suggesting that although fluctuations of the intracellular ubiquitin content may actively modulate the level of regulatory proteins, this event is not per se sufficient to elicit a cellular response in terms of proliferation. 相似文献
68.
69.
Cavarra E Fimiani M Lungarella G Andreassi L de Santi M Mazzatenta C Ciccoli L 《Biological chemistry》2002,383(1):199-206
Solar elastosis is characterized by accumulation of large amounts of material staining similarly to elastin in the dermis. The nature of this material and the process responsible for its accumulation are still unknown. Elastolytic proteases have important functions in the catabolism of the interstitial matrix and can also generate, by the digestion of the interstitial proteins, soluble peptides which can induce collagen and elastin synthesis and deposition. We investigated whether (i) elastolytic enzymes can be detected in samples from sun-exposed and non-exposed skin, and (ii) ultraviolet (UV) rays influence the production of elastolytic activities in cultured dermal fibroblasts. Immunoelectron microscopy showed a positive reaction for neutrophil elastase and cathepsin G in fibroblast-like cells from specimens of sun-exposed areas. Little or no reaction was found in biopsies of sun-protected skin. Fibroblast cultures from sun-exposed skin expressed higher levels of hydrolytic activity against synthetic substrates of elastases and cathepsin G than those obtained from sun-protected areas. Irradiation with UVA strongly stimulated the production of these activities in fibroblasts from sun-protected sites. No significant change was detected in parallel sets of cultures after UVB irradiation. Inhibition experiments indicated that the elastase-like activity expressed by fibroblasts can be attributed to at least two enzymes. 相似文献
70.
Svetlana P Chapoval Koji Iijima Eric V Marietta Michele K Smart Andrei I Chapoval Amy G Andrews Chella S David 《Journal of immunology (Baltimore, Md. : 1950)》2002,168(2):890-899
To investigate the role of HLA-DQ molecules and/or CD4(+) T cells in the pathogenesis of allergic asthma, we generated HLA-DQ6 and HLA-DQ8 transgenic mice lacking endogenous class II (Abeta(null)) and CD4 genes and challenged them intranasally with short ragweed allergenic extract (SRW). We found that DQ6/CD4(null) mice developed a strong eosinophilic infiltration into the bronchoalveolar lavage and lung tissue, while DQ8/CD4(null) mice were normal. However, neither cytokines nor eosinophil peroxidase in the bronchoalveolar lavage of DQ6/CD4(null) mice was found. In addition, the airway reactivity to methacholine was elevated moderately in DQ6/CD4(null) mice compared with the high response in DQ/CD4(+) counterparts and was only partially augmented by CD4(+) T cell transfer. The DQ6/CD4(null) mice showed Th1/Th2-type cytokines and SRW-specific Abs in the immune sera in contrast to a direct Th2 response observed in DQ6/CD4(+) mice. The proliferative response of spleen mononuclear cells and peribronchial lymph node cells demonstrated that the response to SRW in DQ6/CD4(null) mice was mediated by HLA-DQ-restricted CD4(-)CD8(-)NK1.1(-) T cells. FACS analysis of PBMC and spleen mononuclear cells demonstrated an expansion of double-negative (DN) CD4(-)CD8(-)TCRalphabeta(+) T cells in SRW-treated DQ6/CD4(null) mice. These cells produced IL-4, IL-5, IL-13, and IFN-gamma when stimulated with immobilized anti-CD3. IL-5 ELISPOT assay revealed that DN T cells were the cellular origin of IL-5 in allergen-challenged DQ6/CD4(null) mice. Our study shows a role for HLA-DQ-restricted CD4(+) and DN T cells in the allergic response. 相似文献