Background.G-protein-coupled receptors (GPCRs) are one of the most important molecules that transfer signals across the plasma membrane, and play central roles in physiological systems.The molecular architecture of GPCRs allows them to bind to diverse chemicals, including environmental contaminants.Methods.To investigate the effects of benzo(a)pyrene (B[a]P) on GPCR signaling, GPCR and the protein kinase A (PKA) catalytic subunit of Perinereis aibuhitensis were cloned.The expression patterns of these two genes during B(a)P exposure were determined with real-time fluorescence quantitative PCR.The PKA content in P. aibuhitensis under B(a)P exposure was examined Results.The full-length cDNAs of PaGPCR and the PaPKA catalytic subunit were 1,514 and 2,662 nucleotides, respectively, encoding 338 and 350 amino acids, respectively.Multiple sequence alignments indicated that the deduced amino acid sequence of PaGPCR shared a low level of similarity with the orphan GPCRs of polychaetes and echinoderms, whereas PaPKA shared a high level of identify with the PKA catalytic subunits of other invertebrates.B(a)P exposure time-dependently elevated the expression of PaGPCR and PaPKA.The expression of both PaGPCR and PaPKA was also dose-dependent, except at a dose of 10 μg/L B(a)P.The PKA content in concentration group was elevated on day 4, with time prolonging the PKA content was down-regulated to control level.Discussion.These results suggested that GPCR signaling in P. aibuhitensis was involved in the polychaete's response to environmental contaminants.
In order to demonstrate the toxic effects of single and/or combined pollution of polycyclic aromatic hydrocarbons(PAHs) and heavy metals on the early development of polychaete Pernereis aibuhitensis,the 72 h acute toxic experiments of benzo(a)pyrene(BaP) and cadmium(Cd) on the three-setiger juvenile of P.aibuhitensis,which is a common species in the bays and estuaries of China,was investigated.As a result,under single B\P pollution,a significant decrease of the percentage of normally hatched larvae and abnormality was observed,however,as to the increasing concentration of Cd solutions,even exposure to the highest concentration,2000 μg/L,the percentage of successful development of juveniles can also reached as high as 82.3%,and there's no obvious abnormality,therefore,the single toxic effects of Cd on larvae development is insignificant,and the abnormal development of medium concentration(EC50) is 125.03 μg/L for B\P,13.3 g/L for Cd respectively.On the other hand,joint toxic effects caused by the combined pollution appear more complicated.Different concentration of the mixture lead to distinct kind of joint toxic effect,the influence on the percentage of normality is significant.As in the former four combinations of low concentration,the joint toxic effects is antagonism,but it gives priority to synergism when expose to the latter four high concentration of mixture exposure.
Background.G-protein-coupled receptors (GPCRs) are one of the most important molecules that transfer signals across the plasma membrane, and play central roles in physiological systems.The molecular architecture of GPCRs allows them to bind to diverse chemicals, including environmental contaminants.Methods.To investigate the effects of benzo(a)pyrene (B[a]P) on GPCR signaling, GPCR and the protein kinase A (PKA) catalytic subunit of Perinereis aibuhitensis were cloned.The expression patterns of these two genes during B(a)P exposure were determined with real-time fluorescence quantitative PCR.The PKA content in P. aibuhitensis under B(a)P exposure was examined Results.The full-length cDNAs of PaGPCR and the PaPKA catalytic subunit were 1,514 and 2,662 nucleotides, respectively, encoding 338 and 350 amino acids, respectively.Multiple sequence alignments indicated that the deduced amino acid sequence of PaGPCR shared a low level of similarity with the orphan GPCRs of polychaetes and echinoderms, whereas PaPKA shared a high level of identify with the PKA catalytic subunits of other invertebrates.B(a)P exposure time-dependently elevated the expression of PaGPCR and PaPKA.The expression of both PaGPCR and PaPKA was also dose-dependent, except at a dose of 10 μg/L B(a)P.The PKA content in concentration group was elevated on day 4, with time prolonging the PKA content was down-regulated to control level.Discussion.These results suggested that GPCR signaling in P. aibuhitensis was involved in the polychaete's response to environmental contaminants.
Background.G-protein-coupled receptors (GPCRs) are one of the most important molecules that transfer signals across the plasma membrane, and play central roles in physiological systems.The molecular architecture of GPCRs allows them to bind to diverse chemicals, including environmental contaminants.Methods.To investigate the effects of benzo(a)pyrene (B[a]P) on GPCR signaling, GPCR and the protein kinase A (PKA) catalytic subunit of Perinereis aibuhitensis were cloned.The expression patterns of these two genes during B(a)P exposure were determined with real-time fluorescence quantitative PCR.The PKA content in P. aibuhitensis under B(a)P exposure was examined Results.The full-length cDNAs of PaGPCR and the PaPKA catalytic subunit were 1,514 and 2,662 nucleotides, respectively, encoding 338 and 350 amino acids, respectively.Multiple sequence alignments indicated that the deduced amino acid sequence of PaGPCR shared a low level of similarity with the orphan GPCRs of polychaetes and echinoderms, whereas PaPKA shared a high level of identify with the PKA catalytic subunits of other invertebrates.B(a)P exposure time-dependently elevated the expression of PaGPCR and PaPKA.The expression of both PaGPCR and PaPKA was also dose-dependent, except at a dose of 10 μg/L B(a)P.The PKA content in concentration group was elevated on day 4, with time prolonging the PKA content was down-regulated to control level.Discussion.These results suggested that GPCR signaling in P. aibuhitensis was involved in the polychaete's response to environmental contaminants.
Influence of salinity on growth, development and survival of \%Asplanchna brightwelli\% was studied outdoors at water temperature of 25℃ at salinity gradient of 0,1,2 and 3. The results indicated that intrinsic growth rate of increase(rm), finite incremental rate, net rate of proliferation, reproductive times and total reproductive quantity all peaked at salinity of 2, which was 1.6658, 5.2899, 20.1, 4 9 and 23 2, respectively. At this salinity level it also possessed the longest life span, on average, reaching 98 4 days but the shortest developmental stage of pre-reproduction descending to 18 71 days. At salinity of 3 its lifetime was the shortest, namely 1 4414 days. Salinity of 2 is considered to be the optimal for existence of \%Asplanchna brightwelli\%.
Effects of water temperature(12,18,24 and 30℃) on oxygen consumption and ammonia-N excretion of triploid(3n) and diploid oyster(2n)(Crassostrea gigas) were studied in laboratory.At 12-24℃,oxygen consumption rate increased with accelerated temperature,peaks at 24℃ for 3n and 2n oyster.At 30℃,however,oxygen consumption decreased.Ammonia-N excretion rate of the oyster increased with increase in water temperature.Under controlled temperature of 12-30℃,the regressive equation between body weight of the oyster(W) and oxygen consumption rate(R) is described as R=aW~(b-1),the ranges of a and b were 1.532-1.737,0.728-0.887 for triploid;1.197-2.173,0.823-0.854,for diploid.Under 12-30℃,the relationship between body weight(W) of oyster and ammonia-N excretion rate(N)is described as regressive equation N=cW~(d-1),the means of c and d were 194.992 and 0.669 in diploid,and(251.746),0.610 in triploid.ANOVA showed that oxygen consumption rate was significantly affected by temperature,and the triploid had higher value than diploid;the ammonia-N excretion rate was significantly affected by the water temperature and ploidity.
Willa Cather's My Antonia deserves the honor of a classic model of character novels in American letters. The major feature of its character depiction is the abundant use of character juxtaposition, which results in the perfect mixture of character, structure and theme. This article analyzes how Willa Cather's My Antonia reflects the features of the novel of character, as stated in Muir's The Structure of Novel, in terms of plot and character, and explains Cather's unique technique of character juxtaposition by way of the relationship among character, structure and theme.
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