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971.
Eniko Kadar Antonio G. Checa Alfredo N. D. P. Oliveira Jorge P. Machado 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2008,178(1):123-130
This study describes the micro-morphological features of the shell nacre in the vent mytilid Bathymodiolus azoricus collected along a bathymetric gradient of deep-sea hydrothermal vents of the mid-Atlantic ridge (MAR). Pressure-dependent crystallisation patterns were detected in animals subjected to post-capture hydrostatic simulations. We provide evidence for the following: (1) shell micro morphology in B. azoricus is similar to that of several vent and cold-seep species, but the prismatic shell layers may vary among bathymodiolids; (2) nacre micro-morphology of mussels from three vent sites of the MAR did not differ significantly; minor differences do not appear to be related to hydrostatic pressure, but rather to calcium ion availability; (3) decompression stress may cause drop off in pH of the pallial fluid that damages nascent crystals, and in a more advanced phase, the aragonite tablets as well as the continuous layer of mature nacre; and (4) adverse effects of decompression on calcium salt deposition in shells was diminished by re-pressurisation of specimens. The implications of the putative influence of hydrostatic pressure on biomineralisation processes in molluscs are discussed. 相似文献
972.
973.
André Luiz Seccatto Garcia Carlos Antonio Lopes de Oliveira Hanner Mahmud Karim César Sary Humberto Todesco Ricardo Pereira Ribeiro 《Journal of applied genetics》2017,58(4):527-533
Improvement of fillet traits and flesh quality attributes are of great interest in farmed tilapia and other aquaculture species. The main objective of this study was to estimate genetic parameters for fillet traits (fillet weight and fillet yield) and the fat content of fillets from 1136 males combined with 2585 data records on growth traits (body weight at 290 days, weight at slaughter, and daily weight gain) of 1485 males and 1100 females from a third generation of the Aquaamerica tilapia strain. Different models were tested for each trait, and the best models were used to estimate genetic parameters for the fat content, fillet, and growth traits. Genetic and phenotypic correlations were estimated using two-trait animal models. The heritability estimates were moderate for the fat content of fillets and fillet yield (0.2–0.32) and slightly higher for body weight at slaughter (0.41). The genetic correlation between fillet yield and fat was significant (0.6), but the genetic correlations were not significant between body weight and fillet yield, body weight and fat content, daily weight gain and fillet yield, and daily weight gain and fat content (? 0.032, ? 0.1, ? 0.09, and ? 0.4, respectively). Based on the genetic correlation estimates, it is unlikely that changes in fillet yield and fat content will occur when using growth performance as a selection criterion, but indirect changes may be expected in fat content if selecting for higher fillet yield. 相似文献
974.
Marianna Trebuňová Galina Laputková Imrich Géci Igor Andrašina Ján Sabo 《Central European Journal of Biology》2013,8(4):357-365
The aim of the study was to investigate the effect of high-frequency electromagnetic field of 900 MHz at 8 W input power on metabolic activity of human breast adenocarcinoma MCF-7 cells. With the aid of the colorimetric MTT assay, it was shown that there is significant change in cell culture survival exposed to docetaxel in field-free conditions in comparison with cells treated with docetaxel simultaneously exposed to high-frequency electromagnetic field. 相似文献
975.
M. Antonio Todaro 《ZooKeys》2013,(289):13-24
A new species of marine Gastrotricha from Brazil is described and discussed. Ptychostomella lamelliphorasp. n. is one of the several new taxa that were found during an extensive survey of the gastrotrich fauna carried out in 2002 and 2003 along the coastline of the State of São Paulo. The new species is unique in that it possesses cuticular ornamentations in the form of plate-like structures (scales) along the lateral borders of the body and two massive clusters of densely packed adhesive tubes on the ventral surface, near the ano-genital opening. Both these features appear to be adaptations to challenge the high energy waters that characterize the species’ microhabitat: the coarse sublittoral sand in the channel between the mainland and the largest island in the State, Ihlabela. Additionally, a key to the described Ptychostomella species of the world is provided. 相似文献
976.
14alpha-Demethylase (CYP51) is a key enzyme in all sterol biosynthetic pathways (animals, fungi, plants, protists, and some bacteria), catalyzing the removal of the C-14 methyl group following cyclization of squalene. Based on mutations found in CYP51 genes from Candida albicans azole-resistant isolates obtained after fluconazole treatment of fungal infections, and using site-directed mutagenesis, we have found that fluconazole binding and substrate metabolism vary among three different CYP51 isoforms: human, fungal, and mycobacterial. In C. albicans, the Y132H mutant from isolates shows no effect on fluconazole binding, whereas the F145L mutant results in a 5-fold increase in its IC(50) for fluconazole, suggesting that F145 (conserved only in fungal 14alpha-demethylases) interacts with this azole. In C. albicans, F145L accounts, in part, for the difference in fluconazole sensitivity reported between mammals and fungi, providing a basis for treatment of fungal infections. The C. albicans Y132H and human Y145H CYP51 mutants show essentially no effect on substrate metabolism, but the Mycobacterium tuberculosis F89H CYP51 mutant loses both its substrate binding and metabolism. Because these three residues align in the three isoforms, the results indicate that their active sites contain important structural differences, and further emphasize that fluconazole and substrate binding are uncoupled properties. 相似文献
977.
Marcilla A Rubia JE Espert A Carpena I Esteban JG Toledo R 《Experimental parasitology》2004,106(1-2):56-58
Protein tyrosine phosphorylation (PY) is a well-known signalling mechanism which is also involved in host-parasite interactions. Despite its transcendence, PY has been poorly studied in parasitic helminths. The aim of this study is to examine the effect of bile salts on the PY pattern in parasitic trematodes. Two distinct adult models were analysed: Echinostoma friedi, of intestinal habitat, and Fasciola hepatica, naturally inhabitant of host biliary channels. Our results show that bile salts induce specific and distinct protein PY in both trematode species, indicating that this signalling process seems to be also involved in host-trematode relationships. 相似文献
978.
Forest management modified the original structure of most European forests, and in the most extreme cases, genuinely natural and semi-natural forests were turned into plantations through clear felling and replanting, often using non-native species. We compared the bird community structure of native oak woods of northern Italy with that of their anthropogenic counter-parts: black locust and sweet chestnut woods. The three stand types were compared in terms of vegetation structure, bird species richness, diversity and abundance of foraging guilds. We analysed both the overwintering and the breeding community, to assess whether management had specific seasonal effects on bird diversity. Forestry-imposed disturbances affected bird diversity more consistently in winter than in breeding time: bird species richness and diversity were significantly greater in oak and chestnut stands, which were the preferred habitat for bark foragers and foliage gleaners. In the breeding period, bird diversity of black locust woodlands increased, and inter-stand differences were not significant. At this time of year, understorey gleaners were more abundant in black locust stands (where shrubs were denser). In winter, species richness, diversity and the abundance of several guilds were positively correlated with stand age, whereas in the breeding period canopy gleaners preferred younger woodlots. Despite the lack of inter-stand differences in breeding bird diversity, young-managed woods benefited generalist birds that need no particular conservation efforts. Conversely, priority species for forest conservation such as specialised bark foragers positively selected native and mature stands throughout the year. We suggest that detailed year-round studies on diversity and community composition could sharpen the precision with which it is possible to prescribe conservation measures in forested areas. 相似文献
979.
Morsch M Girardi LG Cechinel-Filho V Meyre-Silva C Rodrigues CA 《Zeitschrift für Naturforschung. C, Journal of biosciences》2004,59(9-10):649-652
Heptaldehyde-modified chitosan (heptyl-chitosan, CH-Hp) was investigated as adsorbent for chromatograhic separation of the flavonoids from A. moluccana. The amount of 2"-O-rhamnosylswertisin isolated (30.0 mg) was approx. twice as high as swertisin (17.5 mg). The improved surface hydrophobicity effected by the heptyl groups promoted the separation of flavonoids. From the results obtained, CH-Hp seems to be more suitable for separation of glycosylated flavonoids than other flavonoids. Thus, modified chitosan described here can be used for hydrophobic interaction chromatography as sucessfully illustrated with flavonoids. 相似文献
980.
The growth rate and CO2 biofixation rate of a photosynthetic organism depend basically on the availability of light, all other factors being optimum.
In dense cultures of cyanobacteria or micro-algae intended for biomass production, incident irradiance on the reactor surface
is not the same as the intensity which is received by cells, as irradiance is attenuated by cell absorption and the self-shading
effect. In a well-mixed, dense culture, only the average irradiance, I
av, can be considered responsible for the photosynthetic response. In this study, the photosynthetic response of Synechocystis sp., estimated from its specific growth rate, was measured for each I
av in batch cultures irradiated with different levels of external irradiance, I
ext. The specific growth rate of Synechocystis sp. depends on I
av, in accordance with the model proposed by Muller-Feuga (J Exp Mar Biol Ecol 236:1–13, 1999). A non-linear regression analysis estimated a maximum specific growth rate of 0.108 h−1, at an I
av of 930 μmol photons·m−2·s−1. This reveals that Synechocystis sp. is a highly light-tolerant strain, suitable for outdoor cultures. Higher I
av levels caused photoinhibition in batch cultures. Parameters obtained from the Muller-Feuga model show that the minimum irradiance
needed to start growth mechanisms becomes less as light availability decreases, i.e. cells become more efficient in the use
of light when it is scarce. This observation suggests that choosing for low-light adaptation may be a good strategy to improve
productivity in dense cultures, where light is a limiting factor. 相似文献