首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 46 毫秒
1.
Abstract Anopheles stephensi is the main vector of urban malaria in South Asia. Three ecological variants (‘type’, ‘mysorensisandintermediate’) of An. stephensi have been reported on the basis of ecology and egg morphology. However, it is unclear if there is any genetic isolation between the three variants. We analyzed the three variants of An. stephensi using eight microsatellite loci and found that large and significant genetic differentiation exists between them (mean FST= 0.393 and mean RST= 0.422). Pairwise estimates of genetic differentiation between the variants were ‘type’ versus ‘mysorensis’ (mean FST= 0.411 and mean RST= 0.308), ‘type’ versus ‘intermediate’ (mean FST= 0.388 and mean RST= 0.518) and ‘intermediate’ versus ‘mysorensis’ (mean FST= 0.387 and mean RST= 0.398) and all were statistically significant (P < 0.05). The greater sensitivity of RST in differentiation indicated that mutations and not genetic drift had generated the differences between three variants of An. stephensi. The present study indicated large genetic differentiation and presence of non-significant low level of gene flow between the three variants (‘type’, ‘mysorensisandintermediate’) of An. stephensi.  相似文献   

2.
In Vitro Cellular & Developmental Biology - Plant - Plants were regenerated from in vitro leaf and petiole tissues of Rubus spp. L. (red raspberry) ‘Joan J’ and ‘Polana’...  相似文献   

3.
Summary Ammonium fertilizer applied to tea soils is readily converted to nitrate by the nitrifying bacteria in soil. Excess nitrate in soil could undergo rapid leaching losses under high rainfall conditions. Data is presented in this paper to show that waste tea could be effectively used to retard and delay nitrate production and thereby prevent loss of nitrogen as nitrate by leaching. Evidence is also presented to show that waste tea readily liberates ammonium nitrogen in soil.  相似文献   

4.
Synopsis The cost of parental care in the maternal, mouthbrooding cichlid,Haplochromis ‘argens’ was measured in terms of parental survival, fecundity and breeding frequency. In comparison with non-parental females, those that mouthbrooded eggs for a period of 16 days took 33 % longer to respawn. Parental females also grew more slowly between spawnings, and this may affect their future fecundity. These costs were attributed to the cessation of feeding by parental females while mouthbrooding and/or the hormonal inhibition of oogenesis.  相似文献   

5.
Chronic oral anticoagulant treatment is obligatory in patients (class I) with mechanical heart valves and in patients with atrial fibrillation with CHADS2 score >1. When these patients undergo percutaneous coronary intervention with placement of a stent, there is also an indication for treatment with aspirin and clopidogrel. Unfortunately, triple therapy is known to increase the bleeding risk. For this group of patients, the bottom line is to find the ideal therapy in patients with indications for both chronic anticoagulation therapy and percutaneous intervention to prevent thromboembolic complications such as stent thrombosis without increasing the risk of bleeding. (Neth Heart J 2010;18:444-50.)  相似文献   

6.
A simple and efficient method for multiplication of vanilla (Vanilla planifolia) was developed using in vitro fragmented explants (IFEs) as propagules. IFEs were obtained after dissecting apices from in vitro propagated clusters of plantlets, by cutting the remaining base of these plant clusters into segments of about 1 cm in length. After 4 months of culture on multiplication medium, 100% of IFEs produced up to 15 new shoots per explant, providing an efficient additional method for in vitro propagation of vanilla that maximizes the use of available material. Cryopreservation of apices from in vitro grown plants was achieved using the droplet vitrification protocol. Maximum survival (30%) and further regeneration (10%) of new shoots were obtained for apices derived from clusters of in vitro plantlets produced from microcuttings through a three-step droplet vitrification protocol: 1-d preculture of apices on solid MS medium with 0.3 M sucrose; loading with a 0.4 M sucrose + 2 M glycerol solution for 20–30 min; and exposure to plant vitrification solution PVS3 for 30 min at room temperature. Even though the cryogenic protocol needs to be optimized to improve results, this work represents the first successful report of cryopreservation of vanilla apices.  相似文献   

7.
8.
9.
The effect of the cytokinins mT (meta-topolin), mTR (meta-topolin riboside), MemT (meta-methoxy topolin) and MemTR (meta-methoxy topolin riboside) on micropropagation of banana cultivars ‘Williams’ and ‘Grand Naine’ was studied and compared to BA (6-benzylaminopurine). In vitro cultures, at the third sub-culture level, were purchased from African Biotechnologies (Pty) Ltd., South Africa. These were then sub-cultured on MS media containing 7.5, 15 and 30 μM of all the cytokinins tested. Results recorded after 6 weeks of growth demonstrated that there were statistically significant differences between the parameters analyzed for the treatments. Superior multiplication rates were recorded for mT and mTR treatments. This result was consistent when compared to BA at 22.2 μM (previously published standard concentration). Contrary to previous findings with other species, these cytokinins inhibited rooting. The effect on somaclonal variation was not significantly different when BA, mT and mTR were tested at the seventh multiplication cycle for ‘Williams’ banana. These results support the possible use of topolins as an alternative to BA for Cavendish banana tissue culture. The role of these cytokinins on somaclonal variation however, requires a more stringent investigation as the results obtained in this investigation could have been influenced by carry-over effects from the initial cultures.  相似文献   

10.
11.
We tend to think that the difficulties in bioethics spring from the novel and alarming issues that arise due to discoveries in the new biosciences and biotechnologies. But many of the crucial difficulties in bioethics arise from the assumption we make about ethics. This paper offers a brief overview of bioethics, and relates ethical 'principlism' to 'ethical fundamentalism.' It then reviews some alternative approaches that have emerged during the second phase of bioethics and argues for a neo-Aristotelian approach. Misconceptions about ethical principles and ethical reasoning not only distort our views of the business of bioethics, but they also prevent us from facing up to the formidable problems posed by ethical pluralism in so-called liberal societies.  相似文献   

12.
The objective of this paper is the structural and narrative reconstruction of representations of ‘nature’, ‘wildlife’ and ‘landscape’, held by rural residents of the Dadia Forest Reserve. Data collection involved in-depth interviews. Employing a social representations’ approach, we recovered representational elements that are expected in the case of rural belief systems, such as negative dispositions towards wolves and foxes, as well as elements of an urban adherence, such as nature’s independence. Representational elements refer to visual aspects of the countryside, which seem compatible with the figurative nucleus of the rural idyll. Concerning ‘wildlife’, residents focused on vultures, which comprise the main tourist attraction of the reserve. Scientific knowledge adds to the complexity of the narrative schema, which corresponds to the representation of ‘wildlife’. Interviewees perceived the rural landscape as an interface between the natural and the human-conditioned environment. Our study shows that interviewees make no reference to environmental conservation or quality of life issues, as it could be expected according to relatively wide definitions of the term ‘environmentalism’. Environmental messages reinforced by ecotourism development seem to be recalled primarily in terms of their compatibility with the perceived economic benefit of local people. Despite ecotourism development, representational elements that diverge from a tourist version of ‘nature’, ‘wildlife’ and ‘landscape’ were not pronounced within rural belief-systems. Further interventions within the study area are needed, in order to address a variety of topics under the environmental conservation discourse and raise the environmental awareness of rural residents.  相似文献   

13.
14.
<正>We are pleased to announce a special issue on‘‘Metagenomics of Marine Environments’’of the journal Genomics,ProteomicsBioinformatics(GPB),aiming to provide a platform for high-quality papers focusing on the topic and we invite submissions for this special issue(to be published in the fall of 2015).With most microbes being difficult or impossible to culture  相似文献   

15.
Nucellar explants from the immature fruit of Ataulfo mango, 3–4 cm long, were used. The process had a very low efficiency (<10%); however, Ataulfo was more embryogenic than other cultivars such as Tommy Atkins or Haden in our hands. Overall, the process from nucellus to plantlet stage took 5 months. Twelve regenerated plants were obtained and are currently growing in the greenhouse. They appear to be normal and free of abnormalities. Some biochemical and molecular tests are currently being carried out.  相似文献   

16.
The aim of this study was to determine how size, age, somatic and reproductive condition, abundance and egg production of southern calamary spawning aggregations changed during the spawning season in each of 2 years. During the spawning period in at least one of the years there was a decline as much as 20% in average size, 50% in somatic condition, 28–34% in size-at-age, 26–29% in reproductive status, as well as abundance and reproductive output of the stock declining during the spawning season. However, this change was not a function of the population becoming reproductively exhausted, as the aggregation was composed of different individuals with different biological characteristics. In each month the average age of individuals was ca. 6 mo, indicating that squid that had hatched at different times had entered the spawning aggregations, suggesting that the aggregation was made-up of a succession of microcohorts. Currently, management of many squid populations assumes that there is a single cohort in the aggregation. Therefore, estimating stock biomass at the start of the spawning season cannot be used as the population is constantly changing as micro-cohorts move into the aggregation. An instantaneous estimate of the spawning biomass, independent of fishing activity may be obtained by quantifying the density of deposited eggs. The strategy of individuals with a diversity of life history characteristics coming together in a single spawning aggregation may ensure the phenotypic and genetic diversity required to guarantee successful recruitment of this short-lived species. Therefore, temporally structured protection from harvest throughout the spawning season will ensure maintenance of this population diversity.  相似文献   

17.
A series of dimeric picket fence porphyrinatocobalt(II) complexeses in which the length of the bridging chain controls the dioxygen affinity was newly derived from the coupling of two meso-mono- (β-o-aminophenyl)-tris-(α,α,α-o-pivaloylamidophenyl)- porphyrins with (CH2)n(COCl)2 (n = 1, 3, 5 or 7). Some of the dimeric complexes form a unique ‘sandwich structure’ upon binding with certain bidentate ligands, and their dioxygen affinities are greatly increased compared with those for corresponding monomeric complexes. The relationship observed between the length of the bridging chain and the dioxygen affinity of the dimer complex having a sandwich structure is interpreted in terms of the displacement mechanism of the metal atom from a porphyrin plane.  相似文献   

18.
Yams (Dioscorea rotundata) were processed and fermented to the traditional West African dried yam flour Elubo. Yam slices were blanched at 60°C for 10min and then fermented at 30°C for 24h. The microbial population increased with fermentation time during the first 24h of natural fermentation with a fall in the pH from 6.2 to 5.4. The dominant aerobic mesophilic bacteria consisted of Lactobacillus plantarum, Lactobacillus brevis, Lactobacillus delbrueckii and Bacillus subtilis. Significant contributions were also made by Lactococcus lactis, Klebsiella pneumoniae, Citrobacter freundii and the yeasts Pichia burtonii and Candida krusei. Accelerated natural lactic fermentation was achieved by repetitive use of the previous fermentation batch as an inoculum through back-slopping at a rate of 10% (w/v). After three consecutive fermentation cycles, the microflora was dominated by L. plantarum and L. brevis. Fermentation of blanched samples with pure cultures of the isolates showed L. plantarum L. brevis and B. subtilis to be the main species responsible for pH reduction and in changes in the browning levels of the reconstituted flour paste (amala). The typical colour of amala is disliked by many individuals and it seems possible that amala with a lighter colour which will be more acceptable can be produced by fermentation.  相似文献   

19.
Summary Christmas bush (Ceratopetalum gummiferum Sm) is a shrubby tree species of the east coast of New South Wales in Australia. It is much prized as a cut flower crop because of its bright, pinky red floral calyces. New varieties are being developed, the storage of which is an important issue. In this study, it was shown that shoot tips sampled from in vitro plantlets withstood cryopreservation using the encapsulation-dehydration technique. The protocol leading to optimal regrowth was the following: excised shoot tips were pretreated for 1 d in the dark on hormone-free Murashige and Skoog (MS) medium with 0.3 M sucrose, then encapsulated in 3% calcium alginate and precultured in liquid MS medium with 0.5 M sucrose for 3 d. Precultured beads were dehydrated for 6 h in the air current of the laminar flow cabinet to 24.3% moisture content (fresh weight basis) before rapid immersion in liquid nitrogen. Under these conditions, regrowth of shoot tips after cryopreservation reached 61.4%. Regrowth of cryopreserved shoot tips was not affected by the period of cold acclimation of in vitro mother plants.  相似文献   

20.
Apple exhibits gametophytic self-incompatibility (GSI) that is controlled by the multiallelic S-locus. This S-locus encodes polymorphicS ribonuclease (S-RNase) for the pistil-part 5 determinant. Information aboutS-genotypes is important when selecting pollen donors for fruit production and breeding of new cultivars. We determined the 5-genotypes of ‘Charden’ (S2S3S4), ‘Winesap’ (S1S28), ‘York Imperial’ (S2S31), ‘Stark Earliblaze’ (S1S28), and ‘Burgundy’ (S20S32), byS-RNase sequencing and S-allele-specific PCR analysis. Two newS-RNases, S31 and S32, were also identified from ‘York Imperial’ and ‘Burgundy’, respectively. These newS-alleles contained the conserved eight cysteine residues and two histidine residues essential for RNase activity. Whereas S31 showed high similarity to S20 (94%), S32 exhibited 58% (to S24) to 76% (to S25) similarity in the exon regions. We designed newS-allele-specific primers for amplifying S31- and S32-RNasc-specific fragments; these can serve as specific gene markers. We also rearranged the apple S-allele numbers containing those newS-RNases. They should be useful, along with anS-RNase-based PCR system, in determining S-genotypes and analyzing new alleles from apple cultivars.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号