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1.
Summary We used an automated technique for the observation and quantification of zooplankton swimming behavior to study the behavioral responses of two congeneric, herbivorous, freshwater copepod prey to a copepod predator (Limnocalanus macrurus). One prey, Diaptomus sicilis, often co-occurs with Limnocalanus, while previous studies indicated that the zoogeographic distribution of the second prey, Diaptomus oregonensis, was independent of the predator. We found that in the presence of Limnocalanus, D. sicilis swims more slowly and with less hopping and jumping than D. oregonensis. Diaptomus sicilis is also attacked and consumed by the predator Limnocalanus macrurus less frequently than D. oregonensis. We suggest that the faster, noisier swimming of D. oregonensis increases its vulnerability to Limnocalanus. The behavioral defenses to both prey are induced by the presence of the predator, and may represent two different anti-predator strategies, crypsis and avoidance for D. sicilis and D. oregonensis respectively. In a zoogeographical analysis D. oregonensis occurs at densities below D. sicilis in lakes where Limnocalanus is at elevated abundances, while in low-predator lakes the opposite is true. This distribution pattern supports our experimental results, and suggests that D. sicilis is adapted to survive with Limnocalanus, while D. oregonensis is not. 相似文献
2.
Hardies SC; Martin SL; Voliva CF; Hutchison CA d; Edgell MH 《Molecular biology and evolution》1986,3(2):109-125
3.
Predator-induced bottom-up effects in oligotrophic systems 总被引:1,自引:1,他引:0
Five treatments (replication n=2) were applied to mesocosms in an oligotrophic lake (TP=6–10 µg 1-1) to assess the effects of fish on planktonic communities. The treatments were: (1) high fish (30 kg ha–1
Lepomis auritus, Linnaeus), (2) low fish (10 kg ha–1), (3) high removal of zooplankton, (4) low removal of zooplankton and (5) control. Total phosphorus, chlorophyll a, zooplankton biomass, and species richness decreased from high fish > low fish > control > low removal > high removal treatments. The fish treatments were dominated by crustacean zooplankton, while rotifers outnumbered the other zooplankters in the removal treatments. Calculations of zooplankton grazing rates suggested that clearance rates seldom exceeded 2% of the enclosure volume d–1 and were unlikely to have had much influence on phytoplankton biomass. Calculations from a phosphorus bioenergetics model revealed that when fish were present, their excretion rates were higher than the rates ascribed to zooplankton. Diet analysis showed that the fish derived most of their energy from the benthos and periphyton, and that fish excretion and egestion made significant contributions to the very oligotrophic pelagic phosphorus pool. In the absence of fish, zooplankton excretion was highest in the control treatments and lowest in the zooplankton removal treatments. Our results suggest that in oligotrophic systems, planktivorous fish can be significant sources of phosphorus and that fish and zooplankton induced nutrient cycling have significant impacts on planktonic community structure. 相似文献
4.
Ben M. De Rooij Jan N.M. Commandeur Jane R. Ramcharan Hilda C.P. Schuilenburg Ben L.M. Van Baar Nico P.E. Vermeulen 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1996,685(2):1402
Epichlorohydrin (ECH) is used in many industrial processes. Different toxic effects of ECH were found in rodents. The metabolism of ECH was investigated before in rats using [14C]ECH. The aim of this investigation was the development of non-radioactive quantitative analytical methods for measuring two urinary metabolites of ECH, namely 3-chloro-2-hydroxypropylmercapturic acid (CHPMA) and α-chlorohydrin (α-CH). The identity of CHPMA and α-CH excreted in urine of rats treated with 5 to 35 mg/kg ECH was confirmed by GC-MS. The quantitative analysis of CHPMA, involving ethyl acetate extraction from acidified urine and subsequent methylation and analysis by gas chromatography-flame photometric detection (GC-FPD), showed a method limit of detection of 2 μg/ml. The analysis of α-CH, based on ethyl acetate extraction and subsequent analysis by GC-ECD, showed a method limit of detection of 2 μg/ml. CHPMA and α-CH derivatives could be determined quantitatively down to concentrations of 0.5 and 0.4 μg/ml urine, respectively, by selected-ion monitoring GC-MS under EI conditions. Cumulative urinary excretion of CHPMA and α-CH by rats treated with ECH were found to be 31 ± 10 and 1.4 ± 0.6% (n = 13) of the ECH dose, respectively. For CHPMA, the dose-excretion relationship suggested partially saturated ECH metabolism. For α-CH, the dose-excretion relationship was linear. With fractionated urine collection it was found that approximately 74 and 84% of the total cumulative excretion of CHPMA and α-CH, respectively, took place within the first 6 h after administration of ECH. From these investigations it is concluded that the GC-FPD and GC-ECD based methods developed are sufficiently sensitive to measure urinary excretion of CHPMA and α-CH in urine from rats administered 5 to 35 mg/kg ECH. It is anticipated that the analysis of CHPMA and α-CH based on GC-MS may be sufficiently sensitive to investigate urinary excretion from humans occupationally exposed to ECH. 相似文献
5.
Summary Microsomal and soluble fractions of Pleurotus pulmonarius exhibited a reduced carbon monoxide difference spectrum with P450 maxima at 448nm and 450–452nm respectively. Substrate induced Type I spectra were observed on addition of benzo(a)pyrene to both fractions. Benzo(a)pyrene hydroxylation was measured using the aryl hydrocarbon hydroxylase assay and was observed to be P450 dependent as indicated by carbon monoxide inhibition together with the substrate binding characteristics. The activity of the fractions were observed to give Km of 200mM and 660mM and Vmax of 1.25 nmol/min/nmol P450 and 0.57 nmol/min/nmol P450 for the microsomal and cytosolic fractions respectively. 相似文献
6.
Yan Lu Shulin/SL Li Shiguo/SG Zhu Yabin/YB Gong Jun/J Shi Ling/ L Xu 《Biological procedures online》2017,19(1):2
DNA/RNA methylation plays an important role in lung cancer initiation and progression. Liquid biopsy makes use of cells, nucleotides and proteins released from tumor cells into body fluids to help with cancer diagnosis and prognosis. Methylation of circulating tumor DNA (ctDNA) has gained increasing attention as biomarkers for lung cancer. Here we briefly introduce the biological basis and detection method of ctDNA methylation, and review various applications of methylated DNA in body fluids in lung cancer screening, diagnosis, prognosis, monitoring and treatment prediction. We also discuss the emerging role of RNA methylation as biomarkers for cancer. 相似文献
7.
Out of Africa and back again: nested cladistic analysis of human Y chromosome variation 总被引:18,自引:3,他引:15
Hammer MF; Karafet T; Rasanayagam A; Wood ET; Altheide TK; Jenkins T; Griffiths RC; Templeton AR; Zegura SL 《Molecular biology and evolution》1998,15(4):427-441
We surveyed nine diallelic polymorphic sites on the Y chromosomes of 1,544
individuals from Africa, Asia, Europe, Oceania, and the New World.
Phylogenetic analyses of these nine sites resulted in a tree for 10
distinct Y haplotypes with a coalescence time of approximately 150,000
years. The 10 haplotypes were unevenly distributed among human populations:
5 were restricted to a particular continent, 2 were shared between Africa
and Europe, 1 was present only in the Old World, and 2 were found in all
geographic regions surveyed. The ancestral haplotype was limited to African
populations. Random permutation procedures revealed statistically
significant patterns of geographical structuring of this paternal genetic
variation. The results of a nested cladistic analysis indicated that these
geographical associations arose through a combination of processes,
including restricted, recurrent gene flow (isolation by distance) and range
expansions. We inferred that one of the oldest events in the nested
cladistic analysis was a range expansion out of Africa which resulted in
the complete replacement of Y chromosomes throughout the Old World, a
finding consistent with many versions of the Out of Africa Replacement
Model. A second and more recent range expansion brought Asian Y chromosomes
back to Africa without replacing the indigenous African male gene pool.
Thus, the previously observed high levels of Y chromosomal genetic
diversity in Africa may be due in part to bidirectional population
movements. Finally, a comparison of our results with those from nested
cladistic analyses of human mtDNA and beta-globin data revealed different
patterns of inferences for males and females concerning the relative roles
of population history (range expansions) and population structure
(recurrent gene flow), thereby adding a new sex-specific component to
models of human evolution.
相似文献
8.
Varnika Bhatia Jaya Maisnam Ajay Jain Krishan Kumar Sharma Ramcharan Bhattacharya 《Annals of botany》2015,115(4):581-591
Background and Aims Plant-synthesized sesquiterpenes play a pivotal role in chemotactic interactions with insects. Biosynthesis of functionally diverse sesquiterpenes is dependent on the availability of a pool of the precursor farnesyldiphosphate (FDP). In Arabidopsis thaliana, FPS2, encoding cytosolic farnesyldiphosphate synthase, is implicated in the synthesis of cytosolic FDP, but it is not known whether enhanced levels of FDP have a commensurate effect on sesquiterpene-mediated defence responses. This study examined transgenic arabidopsis plants generated to over-express FPS2 in order to determine if any effects could be observed in the response of aphids, Myzus persicae.Methods Transgenic arabidopsis plants were generated to over-express FPS2 to produce FPS2 in either the cytosol or the chloroplasts. Morphochemical analyses of the transgenic plants were carried out to detremine growth responses of roots and shoots, and for GC-MS profiling of sesquiterpenes. Aphid response to hyrdo-distillate extracts and head-space volatiles from transgenic plants was assessed using a bioassay.Key Results Either over-expression of FPS2 in the cytosol or targetting of its translated product to chlorplasts resulted in stimulatory growth responses of transgenic arabidopsis at early and late developmental stages. GC-MS analysis of hydro-distillate extracts from aerial parts of the plants revealed biosynthesis of several novel sesquiterpenes, including E-β-farnesene, an alarm pheromone of aphids. Both entrapped volatiles and hydro-distillate extracts of the transgenic leaves triggered agitation in aphids, which was related to both time and dose of exposure.Conclusions Over-expression of FPS2 in the cytosol and targeting of its translated product to chloroplasts in arabidopsis led to synthesis of several novel sesquiterpenes, including E-β-farnesene, and induced alarm responses in M. persicae. The results suggest a potential for engineering aphid-resistant strains of arabidopsis. 相似文献
9.
JG Hansen W Gao J Dupuis GT O’Connor W Tang M Kowgier A Sood SA Gharib LJ Palmer M Fornage SR Heckbert BM Psaty SL Booth SUNLIGHT Consortium Patricia A Cassano 《Respiratory research》2015,16(1)
Background
Vitamin D is associated with lung function in cross-sectional studies, and vitamin D inadequacy is hypothesized to play a role in the pathogenesis of chronic obstructive pulmonary disease. Further data are needed to clarify the relation between vitamin D status, genetic variation in vitamin D metabolic genes, and cross-sectional and longitudinal changes in lung function in healthy adults.Methods
We estimated the association between serum 25-hydroxyvitamin D [25(OH)D] and cross-sectional forced expiratory volume in the first second (FEV1) in Framingham Heart Study (FHS) Offspring and Third Generation participants and the association between serum 25(OH)D and longitudinal change in FEV1 in Third Generation participants using linear mixed-effects models. Using a gene-based approach, we investigated the association between 241 SNPs in 6 select vitamin D metabolic genes in relation to longitudinal change in FEV1 in Offspring participants and pursued replication of these findings in a meta-analyzed set of 4 independent cohorts.Results
We found a positive cross-sectional association between 25(OH)D and FEV1 in FHS Offspring and Third Generation participants (P = 0.004). There was little or no association between 25(OH)D and longitudinal change in FEV1 in Third Generation participants (P = 0.97). In Offspring participants, the CYP2R1 gene, hypothesized to influence usual serum 25(OH)D status, was associated with longitudinal change in FEV1 (gene-based P < 0.05). The most significantly associated SNP from CYP2R1 had a consistent direction of association with FEV1 in the meta-analyzed set of replication cohorts, but the association did not reach statistical significance thresholds (P = 0.09).Conclusions
Serum 25(OH)D status was associated with cross-sectional FEV1, but not longitudinal change in FEV1. The inconsistent associations may be driven by differences in the groups studied. CYP2R1 demonstrated a gene-based association with longitudinal change in FEV1 and is a promising candidate gene for further studies.Electronic supplementary material
The online version of this article (doi:10.1186/s12931-015-0238-y) contains supplementary material, which is available to authorized users. 相似文献10.
Histone H2AX is phosphorylated at sites of retroviral DNA integration but is dispensable for postintegration repair 总被引:7,自引:0,他引:7
Daniel R Ramcharan J Rogakou E Taganov KD Greger JG Bonner W Nussenzweig A Katz RA Skalka AM 《The Journal of biological chemistry》2004,279(44):45810-45814
The histone variant H2AX is rapidly phosphorylated (denoted gammaH2AX) in large chromatin domains (foci) flanking double strand DNA (dsDNA) breaks that are produced by ionizing radiation or genotoxic agents and during V(D)J recombination. H2AX-deficient cells and mice demonstrate increased sensitivity to dsDNA break damage, indicating an active role for gammaH2AX in DNA repair; however, gammaH2AX formation is not required for V(D)J recombination. The latter finding has suggested a greater dependence on gammaH2AX for anchoring free broken ends versus ends that are held together during programmed breakage-joining reactions. Retroviral DNA integration produces a unique intermediate in which a dsDNA break in host DNA is held together by the intervening viral DNA, and such a reaction provides a useful model to distinguish gammaH2AX functions. We found that integration promotes transient formation of gammaH2AX at retroviral integration sites as detected by both immunocytological and chromatin immunoprecipitation methods. These results provide the first direct evidence for the association of newly integrated viral DNA with a protein species that is an established marker for the onset of a DNA damage response. We also show that H2AX is not required for repair of the retroviral integration intermediate as determined by stable transduction. These observations provide independent support for an anchoring model for the function of gammaH2AX in chromatin repair. 相似文献