共查询到20条相似文献,搜索用时 531 毫秒
1.
V. V. Moiseenko R. N. Hamm A. J. Waker W. V. Prestwich 《Radiation and environmental biophysics》1998,37(3):167-172
Radiation-induced DNA single- and double-strand breaks were modeled for 660 keV photon radiation and scavenger capacity mimicking
the cellular environment. Atomistic representation of DNA in B form with a first hydration shell was utilized to model direct
and indirect damage. Monte Carlo generated electron tracks were used to model energy deposition in matter and to derive initial
spatial distributions of species which appear in the medium following radiolysis. Diffusion of species was followed with time,
and their reactions with DNA and each other were modeled in an encounter-controlled manner. Three methods to account for hydroxyl
radical diffusion in a cellular environment were tested: assumed exponential survival, time-limited modeling and modeling
of reactions between hydroxyl radicals and scavengers in an encounter-controlled manner. Although the method based on modeling
scavenging in an encounter-controlled manner is more precise, it requires substantially more computer resources than either
the exponential or time-limiting method. Scavenger concentrations of 0.5 and 0.15 M were considered using exponential and
encounter-controlled methods with reaction rate set at 3×109 dm3 mol–1 s–1. Diffusion length and strand break yields, predicted by these two methods for the same scavenger molarity, were different
by 20%–30%. The method based on limiting time of chemistry follow-up to 10–9 s leads to DNA damage and radical diffusion estimates similar to 0.5 M scavenger concentration in the other two methods.
The difference observed in predictions made by the methods considered could be tolerated in computer simulations of DNA damage.
Received: 3 June 1998 / Accepted in revised form: 16 July 1998 相似文献
2.
Suspensions of testicular germ cells from six species of mammals were prepared and stained for the DNA content with a fluorochrome
(ethidium bromide) adopting a common technique and subjected to DNA flow cytometry. While uniform staining of the germ cells
of the mouse, hamster, rat and monkey could be obtained by treating with 0.5% pepsin for 60 min followed by staining with
ethidium bromide for 30 min, that of the guinea pig and rabbit required for optimal staining pepsinization for 90 min and
treatment with ethidium bromide for 60 min. The procedure adopted here provided a uniform recovery of over 80% of germ cells
with each one of the species tested and the cell population distributed itself according to the DNA content (expressed as
C values) into 5 major classes-spermatogonia (2C), cells in S-phase, primary spermatocytes (4C), round spermatids (1C), and
elongating/elongated spermatids (HC). Comparison of the DNA distribution pattern of the germ cell populations between species
revealed little variation in the relative quantities of cells with 2C (8–11%), S-phase (6–9%), and 4C (6–9%) amount of DNA.
Though the spermatid cell populations exhibited variations (1C:31–46%, HCl:7–20% and and HC2:11–25%) they represented the
bulk of germ cells (70–80%). The overall conversion of 2C to 1C (1C:2C ratio) and meiotic transformation of 4C cells to 1C
(1C:4C ratio) kinetics were relatively constant between the species studied. The present study clearly demonstrates that DNA
flow cytometry can be adopted with ease and assurance to quantify germ cell transformation and as such spermatogenesis by
analysing a large number of samples with consistency both within and across the species barrier. Any variation from the norms
in germ cell proportions observed following treatment, fore.g. hormonal stimulation or deprivation can then be ascribed due to a specific effect of the hormone/drug on single/multiple
steps in germ cell transformation 相似文献
3.
Wu XC 《Biochemical genetics》2006,44(5-6):177-185
Species endangerment often derives from the “endangerment” of genetic diversity, thus loss of genetic diversity is an important cause of species extinction. Since historical specimens were unavailable, previous studies mainly described the genetic diversity status in the current population rather than the loss of genetic variation over time. In this study, we collected samples during1998–1999 and obtained historical specimens from 1957 to 1958. Based on the two sets of fish, we determined the changes in genetic diversity of Sichuan taimen using DNA fingerprinting. The differences in genetic parameters between the present samples and historical taimens revealed their loss of genetic variation. As a result, the existing populations have lower viability, and proper management has to be implemented to preserve genetic diversity. 相似文献
4.
Approximately 39 to 49% of the genome of finger millet consists of repetitive DNA sequences which intersperse with 18% of
single copy DNA sequences of 1900 nucleotide pairs. Agarose gel filtration and electrophoresis experiments have yielded the
sizes of interspersed repeated sequences as 4000–4200 nucleotide pairs and 150–200 nucleotide pairs. Approximately 20% of
the repeated DNA sequences (4000–4200 nucleotide pairs) are involved in long range interspersion pattern, while 60% of the
repeated DNA sequences (150–200 nucleotide pairs) are involved in short period interspersion pattern.
Based on the data available in literature and the results described here on DNA sequence organization in plants, it is proposed
that plants with haploid DNA content of more than 2.5 pg exhibit mostly the short period interspersion pattern, while those
with haploid DNA content of less than 2.5 pg show diverse patterns of genome organization.
NCL Communication No.: 2708 相似文献
5.
We describe a simple and efficient method for genomic DNA extraction from woody fruit crops containing high polysaccharide
levels. This method involves a modified CTAB or SDS procedure employing a purification step to remove polysaccharides by using
water-saturated ether and 1.25 M NaCl. Precipitation with an equal volume of isopropanol caused a DNA pellet to form. After
being washed with 70% ethyl alcohol, the pellet easily dissolved in TE buffer. Using this method, DNA was extracted from samples
of more than 1000Citrus spp., including young leaves, old leaves, frosted old leaves, withered old leaves, and callus lines. The average yield of
DNA ranged from 50–500 μg/g of sample. DNA was suitable for PCR and RFLP analyses and long-term storage. Recently, the procedure
was used to isolate DNA from withered old leaves of more than 20 tropical and subtropical fruit crops. 相似文献
6.
de Mattos JC Lage C Dantas FJ Moraes MO Nunes AP Bezerra RJ Faria MV Leitão AC Caldeira-de-Araujo A 《Molecular and cellular biochemistry》2005,280(1-2):173-179
Stannous chloride (SnCl2) is a reducing chemical agent used in several man-made products. SnCl2 can generate reactive oxygen species (ROS); therefore, studies have been carried out in order to better understand its damaging
action in biological systems. In this work, calf thymus DNA, triphosphate nucleotides and isolated bases were incubated with
SnCl2 and the results were analyzed through UV spectrophotometry. The presence of stannous ions altered the absorption spectra
of all three isolates. The amount of stannous ions associated to DNA was measured by atomic absorption spectrophotometry.
Data showed that more than 40% of the initial SnCl2 concentration was present in the samples. Our results are in accordance with the damaging potential of this salt and present
evidence that stannous ions can complex with DNA, inducing ROS in its vicinity, which may be responsible for the observed
lesions. (Mol Cell Biochem xxx: 173–179, 2005) 相似文献
7.
Nuclear DNA content (2C) is used as a new criterion to investigate nearly all species of the genus Nerine Herb. The species have the same chromosome number (2n = 2x = 22), with the exception of three triploid plants found. The
nuclear DNA content of the diploids, as measured by flow cytometry with propidium iodide, is demonstrated to range from 18.0–35.3
pg. This implies that the largest genome contains roughly 2 × 1010 more base pairs than the smallest. The species, arranged according to increasing genome size, fell apart in three groups
if growth cycle and leaf width were also considered. A narrow-leafed, evergreen group with a DNA content between 18.0 and
24.6 pg contains thirteen species, a broad-leaved winter growing group with four species has a DNA content from 25.3–26.2
pg and a broad-leafed summer growing group has a DNA content of 26.8–35.3 pg and contains six species. If the presence of
filament appendages and hairiness of the pedicels were also considered, the thirteen evergreen species could be further divided
into a group without filament appendages or hairy pedicels with a DNA content of 18.0–18.7 pg. A second group without filament
appendages but with hairy pedicels had a DNA content of 19.7–22.3 pg. And a third group with both filament appendages and
hairy pedicels had a DNA content of 22.0–24.6 pg. The exception is N. marincowitzii that, despite a low DNA content and narrow leaves is summer growing. The broad-leafed group is further characterised by the
absence of filament appendages and the absence of strongly hairy pedicels. The exception here is N. pusilla that, despite a high DNA content, has narrow leaves and minutely hairy pedicels. Nuclear DNA content as measured by flow
cytometry is shown to be relevant to throw new light on the relationships between Nerine species. 相似文献
8.
A rapid and efficient DNA minipreparation suitable for screening transgenic plants 总被引:10,自引:0,他引:10
Rong-Cheng Lin Zai-Song Ding Liang-Bi Li Ting-Yun Kuang 《Plant Molecular Biology Reporter》2001,19(4):379-379
We present a modified method for DNA minipreparation suitable for large-scale screening of transgenic plants. The method is
rapid and efficient—one person can prepare DNA from approximately 50 samples per day. The average yield was about 40 μg DNA
per 100 mg of fresh tissue, and the A260/A280 was 1.89–2.03. The total DNA extracted by this method could be used for PCR, restriction enzyme digestion, and Southern blotting. 相似文献
9.
Somaclonal variation in oil palm (Elaeis guineensis Jacq.): the DNA methylation hypothesis 总被引:2,自引:0,他引:2
Elaeis guineensis Jacq.) currently hampers the scaling-up of clonal plant production. In order to investigate the relationship between the
“mantled” somaclonal variant and possible alterations in genomic DNA methylation rate, two complementary approaches have been
used. HPLC quantification of relative amounts of 5-methyl-deoxycytidine has shown that global methylation in leaf DNA of abnormal
regenerants is 0.5–2.5% lower than in their normal counterparts (20.8% vs 22%, respectively). When comparing nodular compact
calli and fast growing calli, yielding respectively 5% and 100% of “mantled” plantlets, this decrease was up to 4.5% (from
23.2 to 18.7%). An alternative method, the SssI-methylase accepting assay, based on the enzymatic saturation of CG sites with methyl groups, gave convergent results. This
work demonstrates that a correlation exists between DNA hypomethylation and the “mantled” somaclonal variation in oil palm.
Received: 9 July 1999 / Revision received: 15 October 1999 / Accepted: 26 October 相似文献
10.
In this study,we determined species-specific variations by analyzing the mitochondrial 12S rRNA gene sequence variation(~440 bp) in 17 newly obtained sequences and 90 published cattle,yak,buffalo,goat,and pig sequences,which represent 62 breeds and 17 geographic regions.Based on the defined species-specific variations,two endonucleases,Alu I and Bfa I,were selected for species authentication using raw meat/tissue samples and the PCR-RFLP method.Goat and pig were identified using the Alu I enzyme,while cattle,yak,and buffalo were identified by digestion with Bfa I.Our approach had relatively high detection sensitivity of cattle DNA in mixed cattle and yak products,with the lowest detectable threshold equaling 20% of cattle DNA in a mixed cattle/yak sample.This method was successfully used to type commercial beef jerky products,which were produced by different companies utilizing various processing technologies.Our results show that several yak jerky products might be implicated in commercial fraud by using cattle meat instead of yak meat. 相似文献
11.
D. P. Kelly Erko Stackebrandt Jutta Burghardt Ann P. Wood 《Archives of microbiology》1998,170(2):138-140
Thiobacillus halophilus and Thiobacillus hydrothermalis share 98.7% similarity in 16S rRNA sequence, possess similar gross DNA composition (64.2 and 67.4 mol% G+C values, respectively),
and have similar physiological properties. While this might have indicated that they were strains of a single species, DNA-DNA
hybridization between the type strains of the two species showed only 59% hybridization, indicating the organisms to be different
at the species level. Thiobacillus neapolitanus is the phylogenetically nearest neighbour of T. halophilus and T. hydrothermalis (91.6–92.1% similarity in 16S rRNA sequence) and is the only other Thiobacillus in the γ-subclass of the Proteobacteria that can be regarded as exclusively related to these two species. The 16S rRNA gene
sequences of these three species are so different from those of the other thiobacilli in the γ-subclass that they justify
recognition as a distinct phyletic group. Their comparative properties are summarized.
Received: 23 February 1998 / Accepted: 23 April 1998 相似文献
12.
I. Métais C. Aubry B. Hamon D. Peltier R. Jalouzot 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1998,97(1-2):232-237
We describe the cloning and the characterization of a 130-bp DNA fragment, called OPG9-130, amplified from bean (Phaseolus vulgaris L.) genomic DNA. This fragment corresponds to a minisatellite DNA sequence containing seven repeats of 15 bp which differ
slightly from each other in their sequence. Southern analysis showed that the core sequence of 15 bp is repeated in clusters
dispersed throughout the genome. The use of this fragment as a probe allowed us to identify common bean lines by their DNA
fingerprints. We suggest that OPG9-130 will be useful for line identification as well as for the analysis of genetic relatedness
between bean species and lines.
Received: 14 February 1998 / Accepted: 10 February 1998 相似文献
13.
Kim M Singh D Lai-Hoe A Go R Abdul Rahim R Ainuddin AN Chun J Adams JM 《Microbial ecology》2012,63(3):674-681
Recent work has suggested that in temperate and subtropical trees, leaf surface bacterial communities are distinctive to each
individual tree species and dominated by Alpha- and Gammaproteobacteria. In order to understand how general this pattern is,
we studied the phyllosphere bacterial community on leaves of six species of tropical trees at a rainforest arboretum in Malaysia.
This represents the first detailed study of ‘true’ tropical lowland tree phyllosphere communities. Leaf surface DNA was extracted
and pyrosequenced targeting the V1–V3 region of 16S rRNA gene. As was previously found in temperate and subtropical trees,
each tree species had a distinctive bacterial community on its leaves, clustering separately from other tree species in an
ordination analysis. Bacterial communities in the phyllosphere were unique to plant leaves in that very few operational taxonomic
units (0.5%) co-occurred in the surrounding soil environment. A novel and distinctive aspect of tropical phyllosphere communities
is that Acidobacteria were one of the most abundant phyla across all samples (on average, 17%), a pattern not previously recognized.
Sequences belonging to Acidobacteria were classified into subgroups 1–6 among known 24 subdivisions, and subgroup 1 (84%)
was the most abundant group, followed by subgroup 3 (15%). The high abundance of Acidobacteria on leaves of tropical trees
indicates that there is a strong relationship between host plants and Acidobacteria in tropical rain forest, which needs to
be investigated further. The similarity of phyllosphere bacterial communities amongst the tree species sampled shows a significant
tendency to follow host plant phylogeny, with more similar communities on more closely related hosts. 相似文献
14.
The use of comet assay in measuring DNA damage and repair efficiency in child,adult, and old age populations 总被引:1,自引:0,他引:1
Piperakis SM Kontogianni K Karanastasi G Iakovidou-Kritsi Z Piperakis MM 《Cell biology and toxicology》2009,25(1):65-71
In the present study, we used the Comet assay to estimate basal DNA damage in three distinct populations aged 5–10, 40–50,
and 60–70 years old. The DNA damage induced by hydrogen peroxide and γ-irradiation in the lymphocytes of these populations,
as well as their repair activity, was also studied. Finally, we measured apoptosis and necrosis after the effect of these
agents. Our results indicate that the older population (60–70 years old) showed higher basal levels of DNA damage and was
more sensitive to the effects of the DNA-damaging agents than the adult one (40–50 years old), who, in turn, was more sensitive
than the younger population (5–10 years old). A decline of the repair efficiency with age to the DNA damage induced by the
two agents was also observed. Apoptosis and necrosis were also affected by age. 相似文献
15.
Host DNA from hungry males and females of Ixodes persulcatus (a total of 143 specimens) collected in the wild in April–May 2008 and 2009 was identified by means of the PCR method. Amplification
of each sample was performed using a primer species-specific by the 12S rRNA mitochondrial gene. Four species of small mammals
(Apodemus uralensis, Clethrionomys glareolus, Microtus arvalis, and Sorex araneus) and two species of passerine birds (Fringilla coelebs and Parus major) were analyzed. Hosts were established for 44 samples (30.8% of the material); in five cases (3.5%), feeding on more than
one host was revealed. 相似文献
16.
Approximately 43–60% of the total genome in bovine, goat and sheep consisted of interspersed repeated and single copy DNA
sequences. Most of the interspersed repeated DNA sequences were 1500–2400 nucleotide pair long while a minor portion was more
than 4000 nucleotide pair long in goat and sheep and 3200 nucleotide pair long in bovine. About 1/3rd of single copy sequence
were interspersed and their length was in the range of 1000–1500 nucleotide pairs. 相似文献
17.
Primary production in many ephemeral waters peaks soon after inundation, but the extent to which the algal biomass generated
by this process is immediately available to aquatic herbivores as a food source has not been extensively studied. To examine
this, we exposed natural epilithon from two permanent and two recently rewetted temporary reaches of an intermittent stream
to grazing by small, presumably newly hatched, Limnodynastes tasmaniensis tadpoles and compared the algal content of tadpole feces to that of the assemblages on which they grazed. Rocks from the
temporary sites, one colonized by tadpoles and one not, supported relatively flocculent, diatom-rich (79.7–85.7%) epilithon
of similar biomass and taxonomic content. Epilithon from the permanent sites (one with and one without tadpoles) were more
cohesive, contained fewer diatoms (57.0–60.7%), and differed in species composition from that of the temporary sites, and
from one another. Feces and epilithon were more taxonomically similar when epilithon originated from temporary reaches than
from permanent sites. This implies that grazing tadpoles accessed a greater percentage of the algal assemblages from recently
rewetted sites. Algal species differed in susceptibility to ingestion by small tadpoles, but these differences were not consistent
among habitats; susceptibility to ingestion was not predictable based solely on species growth habit, but was likely also
affected by physiognomic differences in mat structure among habitats. A large percentage of algal cells ingested by tadpoles
survived gut passage. `Live' cells (those with full chloroplasts) comprised 43.8–66.6% of all diatoms from epilithic samples
and 27.4–42.7% of those in feces of small tadpoles. In contrast, only 12.8–14.9% of the diatoms in feces produced by large
L. tasmaniensis tadpoles collected from the two tadpole-colonized sites contained full chloroplasts, suggesting higher digestion efficiency
in large tadpoles than in small ones. Distinct, gut-passage-induced transitions from `live' diatoms to empty frustules or
single diatom valves (`dead' cells) were evident when grazed material originated from temporary reaches. In contrast, `live'
diatoms in epilithon from permanent sites were more likely to emerge in tadpole feces with reduced or fragmented chloroplasts.
Thus, algae from temporary reaches appeared to be more efficiently digested than those from permanent reaches. While digestibility
of individual taxa varied among sites, some algae (e.g., Synedra ulna) were clearly more digestible than others. Our results suggest that temporary stream reaches in arid-zone catchments are
important sources of readily digestible autotrophic biomass for anuran species in these regions.
Received: 5 March 1998 / Accepted: 9 November 1998 相似文献
18.
J. -Y. Fann A. Kovarik V. Hemleben N. I. Tsirekidze T. G. Beridze 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2001,103(6-7):1068-1073
Highly repeated satellite DNA (stDNA) of citric plants was characterized by cloning and sequencing 10–14 repeats of each plant
(Citrus limon, C. sinensis, C. ichangensis, Poncirus trifoliata). The monomers are mostly 181 bp in length with a GC-content between 60% and 68% (significantly higher than the average GC-content
of the citrus group genomes). Similarity among the repeats indicates that they belong to a satellite family that underwent
species-specific modifications, which are reflected in the phylogenetic relationships. Curvature provoked by dA-stretches
of the repeats analyzed by gel shifts revealed structural conservation, even though the nucleotide sequences vary among species,
thereby probably supporting the heterochromatic structure of stDNA. We show that the species-specific modification of the
satellite consensus involves changes in the position and number of dA tracts. The molecule shapes of satellite oligomeres
predicted by computer modelling indicate a superhelical structure of the tandem repeats which is in a good agreement with
the satellite sequence dendrogram. The contribution of DNA bending elements to the evolution of plant satellite repeats is
discussed.
Received: 27 November 2000 / Accepted: 12 January 2001 相似文献
19.
Liquid handling robotics and capillary electrophoresis genetic analyzers now offer high-throughput solutions for 2 of the
4 key steps in PCR-based DNA marker-assisted fingerprinting (DNA extraction, PCR amplification, electrophoresis, data analysis).
Thus, DNA extraction remains the most significant bottleneck at the bench for large-scale applications in plant breeding and
germplasm characterization. We report on a rapid and low-cost method for relatively high-throughput extraction of high-quality
DNA from young and mature leaves of sorghum, pearl millet, chickpea, groundnut, and pigeonpea. The procedure uses a modified
CTAB/β-mercaptoethanol method for DNA extraction in a 96-well plate. The quantity and quality of the DNA extracted per sample
is adequate for more than 1000 PCR reactions. A relatively high throughput of 96–384 samples per person per day can be achieved,
depending on the crop. A major timesaving aspect of the protocol is the absence of a manual sample-grinding step. Finally,
the cost is a magnitude lower than commercial plate-based kits, and, as such, is likely to have substantial application in
tropical molecular breeding programs. 相似文献
20.
Ranjana Bhattacharjee Maria Kolesnikova-Allen Peter Aikpokpodion Sunday Taiwo Ivan Ingelbrecht 《Plant Molecular Biology Reporter》2004,22(4):435-436
DNA extraction is a time-consuming and expensive component of molecular marker analysis, constituting about 30–60% of the
total time required for sample processing. Furthermore, the procedure for extracting high-quality DNA from tree species such
as cocoa differs from extraction protocols suitable for other crop plants. This is accompanied by problems in collecting leaf
tissues from field-grown cocoa trees, where storage facilities are not available and where transporting samples to laboratory
for immediate refrigeration is usually impossible. We preserved cocoa leaf tissues in the field in an NaCl-CTAB-azide solution
(as described in Rogstad, 1992), which did not require immediate refrigeration. This method also allowed preservation of leaf
tissues for a few days during transportation and protected leaf tissues from bacterial and fungal attacks. Once transported
to the laboratory, the samples were stored at 4°C for almost 1 y. To isolate good-quality DNA from stored leaf tissues, a
rapid semiautomated and relatively high-throughput protocol was established. The procedure followed a modified CTAB/β-mercaptoethanol
method of DNA extraction in a 96-well plate, and an automated system (i.e., GenoGrinder 2000) was used to grind the leaf tissues.
The quality of DNA was not affected by long storage, and the quantity obtained per sample was adequate for about 1000 PCR
reactions. Thus, this method allowed isolation of about 200 samples per day at a cost of $0.60 per sample and is a relatively
high-throughput, low-cost extraction compared with conventional methods that use manual grinding and/or expensive kits. 相似文献