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991.
Cements from two species of barnacles, Balanuseburneus Gould and Balanus crenatus Bruguiére, were analyzed to identify the number and nature of proteins present. B. crenatus cement was composed mainly of a small peptide cross-linked into aggregates ranging in size from ˜ 3 kD to 40–50 kD. These
aggregates could be reduced with 2-mercaptoethanol (2-ME) in the presence of sodium dodecyl sulfate (SDS) but only after incubation
at 40 °C for 12 to 24 h and only when the cement was recently formed. Reductive alkylation of cysteine residues with 4-vinylpyridine
produced a water-soluble peptide of less than 5 kD. By comparison, the cement of B. eburneus could be dissolved only partially in SDS and 2-ME when heated at 100 °C for 10 min. Five major proteins were identified by
SDS-PAGE: 7, 22, 36 and 58 kD bands for which N-terminal sequence and amino acid compositions are presented; and a 52 kD band
for which sequence data are given. A minor protein band of ˜ 80 kD has the same N-terminus as the 36 kD band. CNBr digests
of individual proteins produced peptides for which sequence and composition data are also presented. The study was conducted
during 1993 to 1995. In general, the proteins identified from B. crenatus cement are similar to those characterized from B. eburneus, and they are different in composition and sequence than those previously reported from Mytilus edulis.
Received: 7 August 1996 / Accepted: 8 October 1996 相似文献
992.
In French Guiana, parabiotic societies (natural mixed colonies) are frequently found in ant gardens. Crematogaster limata parabiotica (Myrmicinae), often associated with Camponotus femoratus (Formicinae), was found for the first time in parabiosis with ponerine ants: Pachycondyla goeldii and Odontomachus mayi. A detailed study of the relationships between Cr. l. parabiotica and O. mayi showed that each species is aggressive towards allospecific or conspecific individuals belonging to another colony, but tolerates
allospecific individuals from the multi-species society. Studies of cuticular substances of the four ant species were made
using gas chromatography. The results showed that each species, living alone or in parabiosis, possesses a specific chemical
profile. Thus, the ants are able to recognise nestmate and non-nestmate individuals of the associated species, even though
their cuticular profiles are different. The hypothesis that the nestmate allospecific profile is learned is suggested to explain
this pattern of recognition.
Received: 5 June 1996 / Accepted after revision: 17 October 1996 相似文献
993.
L. E. C. Conceição T. van der Meeren J. A. J. Verreth M. S. Evjen D. F. Houlihan H. J. Fyhn 《Marine Biology》1997,129(2):255-265
The present paper studied the influence of different food regimes on the free amino acid (FAA) pool, the rate of protein
turnover, the flux of amino acids, and their relation to growth of larval turbot (Scophthalmus maximus L.) from first feeding until metamorphosis. The amino acid profile of protein was stable during the larval period although
some small, but significant, differences were found. Turbot larvae had proteins which were rich in leucine and aspartate,
and poor in glutamate, suggesting a high leucine requirement. The profile of the FAA pool was highly variable and quite different
from the amino acid profile in protein. The proportion of essential FAA decreased with development. High contents of free
tyrosine and phenylalanine were found on Day 3, while free taurine was present at high levels throughout the experimental
period. Larval growth rates were positively correlated with taurine levels, suggesting a dietary dependency for taurine and/or
sulphur amino acids. Reduced growth rates in Artemia-fed larvae were associated with lower levels of free methionine, indicating that this diet is deficient in methionine for
turbot larvae. Leucine might also be limiting turbot growth as the different diet organisms had lower levels of this amino
acid in the free pool than was found in the larval protein. A previously presented model was used to describe the flux of
amino acids in growing turbot larvae. The FAA pool was found to be small and variable. It was estimated that the daily dietary
amino acid intake might be up to ten times the larval FAA pool. In addition, protein synthesis and protein degradation might
daily remove and return, respectively, the equivalent of up to 20 and 10 times the size of the FAA pool. In an early phase
(Day 11) high growth rates were associated with a relatively low protein turnover, while at a later stage (Day 17), a much
higher turnover was observed.
Received: 19 March 1997 / Accepted: 14 April 1997 相似文献
994.
995.
Polychaetes belonging to the genus Capitella are often present in high numbers in organic-rich sediments polluted with, e.g., oil components, and Capitella spp. may have a great impact on the biogeochemistry of these sediments. We examined the influence of Capitella sp. I on microbial activity in an organic-rich marine sediment contaminated with the polycyclic aromatic hydrocarbon, fluoranthene.
Capitella sp. I were added to microcosms (10 000 ind m−2) and the impact of a pulse-sedimentation of fluoranthene-contaminated sediment (3 mm layer) was studied for a period of 12
d after sedimentation. The sediment oxygen uptake and total sediment metabolism (TCO2 production) increased in cores with worms (71 to 131%), whereas the anaerobic activity, measured as sulfate reduction rate
12 d after sedimentation, was lower compared to cores without worms. The effect of fluoranthene on sulfate reduction was most
pronounced in the presence of worms, with a 34% reduction versus 16% in cores without worms. The reduced sulfur pools in cores
with worms were smaller than in cores without worms, suggesting that the reduced anaerobic activity was caused by increased
oxidation of the sediment, which may favor O2 and other electron-acceptors (e.g. NO3
−, Fe3+, Mn4+) in organic matter decomposition. The sediment oxygen uptake and TCO2 production did not show significant changes due to fluoranthene treatment, indicating that these parameters were either less
sensitive to fluoranthene stress or recovered more rapidly (i.e. within 48 h) than sulfate reduction rates. Bioturbation by
Capitella sp. I altered the depth profile of fluoranthene such that fluoranthene was found in deeper sediment layers (down to 2 cm)
where diffusional loss and microbial breakdown probably are reduced relative to surface layers. In cores without worms, fluoranthene
was found down to 1 cm, with 75% remaining in the upper 5 mm.
Received: 5 December 1996 / Accepted: 11 February 1997 相似文献
996.
997.
Background
Earthworm heavy metal concentrations (critical body residues, CBRs) may be the most relevant measures of heavy metal bioavailability in soils and may be linkable to toxic effects in order to better assess soil ecotoxicity. However, as earthworms possess physiological mechanisms to secrete and/or sequester absorbed metals as toxicologically inactive forms, total earthworm metal concentrations may not relate well with toxicity.Objective
The objectives of this research were to: i) develop LD50s (total earthworm metal concentration associated with 50% mortality) for Cd, Pb, and Zn; ii) evaluate the LD50 for Zn in a lethal Zn-smelter soil; iii) evaluate the lethal mixture toxicity of Cd, Pb, and Zn using earthworm metal concentrations and the toxic unit (TU) approach; and iv) evaluate total and fractionated earthworm concentrations as indicators of sublethal exposure.Methods
Earthworms (Eisenia fetida (Savigny)) were exposed to artificial soils spiked with Cd, Pb, Zn, and a Cd?Pb?Zn equitoxic mixture to estimate lethal CBRs and mixture toxicity. To evaluate the CBR developed for Zn, earthworms were also exposed to Zn-contaminated field soils receiving three different remediation treatments. Earthworm metal concentrations were measured using a procedure devised to isolate toxicologically active metal burdens via separation into cytosolic and pellet fractions.Results and Discussion
Lethal CBRs inducing 50% mortality (LD50, 95% CI) were calculated to be 5.72 (3.54–7.91), 3.33 (2.97–3.69), and 8.19 (4.78–11.6) mmol/kg for Cd, Pb, and Zn, respectively. Zn concentrations of dead earthworms exposed to a lethal remediated Zn-smelter soil were 3-fold above the LD50 for Zn and comparable to earthworm concentrations in lethal Zn-spiked artificial soils, despite a 14-fold difference in total soil Zn concentration between lethal field and artificial soils. An evaluation of the acute mixture toxicity of Cd, Pb, and Zn in artificial soils using the Toxic Unit (TU) approach revealed an LD50 (95% CI) of 0.99 (0.57–1.41) TU, indicating additive toxicity.Conclusions
Total Cd, Pb, and Zn concentrations in earthworms were good indicators of lethal metal exposure, and enabled the calculation of LD50s for lethality. The Zn-LD50 developed in artificial soil was applicable to earthworms exposed to remediated Zn-smelter soil, despite a 14-fold difference in total soil Zn concentrations. Mixture toxicity evaluated using LD50s from each single metal test indicated additive mixture toxicity among Cd, Pb, and Zn. Fractionation of earthworm tissues into cytosolic and pellet digesis yielded mixed results for detecting differences in exposure at the sublethal level.Recommendation and Outlook
CBRs are useful in describing acute Cd, Pb, and Zn toxicity in earthworms, but linking sublethal exposure to total and/or fractionated residues may be more difficult. More research on detoxification, regulation, and tissue and subcellular partitioning of heavy metals in earthworms and other invertebrates is needed to establish the link between body residue and sublethal exposure and toxicity.998.
Lipid synthesis from acetate by the in vitro incubated ovaries of the penaeid shrimp Penaeus semisulcatus 总被引:1,自引:0,他引:1
The present research was aimed at studying the synthesis of lipids from 14C-acetate in vitro by ovarian tissue in relation to oogenesis and at examining the binding of newly synthesized lipids to ovarian proteins. Lipid synthesis gradually increased during oogenesis. Fifty percent of the newly synthesized lipids was phosphatidyl choline; triacylglycerols reached 30 to 35%; diacylglycerol was a relatively important component of the synthesized neutral lipids in immature ovaries. Cholesterol was not synthesized. Only saturated (73%) and monounsaturated (26%) fatty acids were labeled. Polyunsaturated fatty acids were not synthesized. Bound lipids in developing ovaries were associated mainly with vitellin. Lipids were bound also to two other proteins in immature ovaries. Binding of lipids to vitellin was observed at the commencement of vitellogenesis. Up to a third of the newly synthesized lipids was bound to vitellin, with triacylglycerols and phosphatidyl choline as the main bound lipids. Peneaus semisulcatus individuals examined in the present study were collected in Haifa Bay, Israel during the years 1990 to 1992. 相似文献
999.
The presence and characteristics of a membrane-bound adenylate cyclase from Mytilus galloprovincialis Lmk posterior adductor muscle have been investigated. The enzyme has a Michaelis constant (K
m) of 0.38 mM at 20°C and requires divalent cations (Mg2+/Mn2+) for its activity. Optimal GTP concentrations are between 10-5 and 10-4
M. The non-hydrolizable GTP-analogues GMPpNHp and GTPS increase the activity of the enzyme four- to ten-fold. Sodium fluoride stimulates the enzymatic activity seven- to eight-fold. Forskolin increases the enzymatic activity two- to three-fold. Serotonin stimulates the adenylate cyclase activity in a dose-dependent manner. These experiments were performed with mussels collected from the estuary of Muros, Spain, in 1990. 相似文献
1000.
Nicola M. Marples 《Chemoecology》1993,4(1):29-32
Garden black ants,Lasius niger L., in a laboratory colony, attacked three species of live ladybirds found near their nest, killing the smaller two species. A second colony was offered artificial diets containing crushed ladybirds of two species, and the ants' choice of feeding site noted. Both the diets were aversive compared to control, but that containing 7spot,Coccinella septempunctata L., was more aversive than the diet containing 2spot,Adalia bipunctata L. The implications of this lesser protection for 2spots in terms of the chemical defence of the species are discussed. 相似文献