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31.
The role of double-stranded break repair in the creation of phenotypic diversity at cereal VRN1 loci 下载免费PDF全文
Nonhomologous repair of double-stranded breaks, although fundamental to the maintenance of genomic integrity in all eukaryotes, has received little attention as to its evolutionary consequences in the generation and selection of phenotypic diversity. Here we document the role of illegitimate recombination in the creation of novel alleles in VRN1 orthologs selected to confer adaptation to annual cropping systems in barley and wheat. 相似文献
32.
Background
Both active smoking and environmental tobacco smoke exposure are associated with pregnancy complications. In March 2006, Scotland implemented legislation prohibiting smoking in all wholly or partially enclosed public spaces. The aim of this study was to determine the impact of this legislation on preterm delivery and small for gestational age.Methods and Findings
We conducted logistic regression analyses using national administrative pregnancy data covering the whole of Scotland. Of the two breakpoints tested, 1 January 2006 produced a better fit than the date when the legislation came into force (26 March 2006), suggesting an anticipatory effect. Among the 716,941 eligible women who conceived between August 1995 and February 2009 and subsequently delivered a live-born, singleton infant between 24 and 44 wk gestation, the prevalence of current smoking fell from 25.4% before legislation to 18.8% after legislation (p<0.001). Three months prior to the legislation, there were significant decreases in small for gestational age (−4.52%, 95% CI −8.28, −0.60, p = 0.024), overall preterm delivery (−11.72%, 95% CI −15.87, −7.35, p<0.001), and spontaneous preterm labour (−11.35%, 95% CI −17.20, −5.09, p = 0.001). In sub-group analyses, significant reductions were observed among both current and never smokers.Conclusions
Reductions were observed in the risk of preterm delivery and small for gestational age 3 mo prior to the introduction of legislation, although the former reversed partially following the legislation. There is growing evidence of the potential for tobacco control legislation to have a positive impact on health. Please see later in the article for the Editors'' Summary 相似文献33.
Immune protection against experimental autoimmune encephalomyelitis: optimal conditions and analysis of mechanism 总被引:3,自引:0,他引:3
Protection against experimental autoimmune encephalomyelitis (EAE) was studied in the guinea pig and the Lewis rat. Basic protein of myelin (BPM) injected in incomplete Freund's adjuvant (IFA) gave solid protection against subsequent challenge with normally encephalitogenic doses of BPM in complete Freund's adjuvant (CFA). Protection depended on the amount of BPM in IFA injected and on the duration of the interval between protection and encephalitogenic challenge with BPM in CFA. Notably, protection was long lasting; it remained demonstrable, to some degree for 52 weeks in guinea pig and 32 weeks in rats, these being the longest intervals tested.Protection could not be correlated with serum antibody levels to BPM, and was afforded in the guinea pig by the injection, in IFA, of a synthetic peptide matching residues 112–122 of human BPM; this peptide produced no detectable serum antibody to BPM. Protected guinea pigs had intact cell-mediated immunity to BPM, as measured by inhibition of macrophage migration in vitro. The mechanism of protection may involve the production, following injection of BPM in IFA, of a class of suppressor thymic lymphocytes capable of overriding otherwise encephalitogenic thymic lymphocytes. 相似文献
34.
Litman GW; Rast JP; Shamblott MJ; Haire RN; Hulst M; Roess W; Litman RT; Hinds- Frey KR; Zilch A; Amemiya CT 《Molecular biology and evolution》1993,10(1):60-72
Immunoglobulins are encoded by a large multigene system that undergoes
somatic rearrangement and additional genetic change during the development
of immunoglobulin-producing cells. Inducible antibody and antibody-like
responses are found in all vertebrates. However, immunoglobulin possessing
disulfide-bonded heavy and light chains and domain-type organization has
been described only in representatives of the jawed vertebrates. High
degrees of nucleotide and predicted amino acid sequence identity are
evident when the segmental elements that constitute the immunoglobulin gene
loci in phylogenetically divergent vertebrates are compared. However, the
organization of gene loci and the manner in which the independent elements
recombine (and diversify) vary markedly among different taxa. One striking
pattern of gene organization is the "cluster type" that appears to be
restricted to the chondrichthyes (cartilaginous fishes) and limits
segmental rearrangement to closely linked elements. This type of gene
organization is associated with both heavy- and light-chain gene loci. In
some cases, the clusters are "joined" or "partially joined" in the germ
line, in effect predetermining or partially predetermining, respectively,
the encoded specificities (the assumption being that these are expressed)
of the individual loci. By relating the sequences of transcribed gene
products to their respective germ-line genes, it is evident that, in some
cases, joined-type genes are expressed. This raises a question about the
existence and/or nature of allelic exclusion in these species. The
extensive variation in gene organization found throughout the vertebrate
species may relate directly to the role of intersegmental
(V<==>D<==>J) distances in the commitment of the individual
antibody-producing cell to a particular genetic specificity. Thus, the
evolution of this locus, perhaps more so than that of others, may reflect
the interrelationships between genetic organization and function.
相似文献
35.
Marks SC Lundmark C Christersson C Wurtz T Odgren PR Seifert MF Mackay CA Mason-Savas A Popoff SN 《The International journal of developmental biology》2000,44(3):309-316
The pacemaker of endochondral bone growth is cell division and hypertrophy of chondrocytes. The developmental stages of chondrocytes, characterized by the expression of collagen types II and X, are arranged in arrays across the growth zone. Mutations in collagen II and X genes as well as the absence of their gene products lead to different, altered patterns of chondrocyte stages which remain aligned across the growth plate (GP). Here we analyze GP of rats bearing the mutation toothless (tl) which, apart from bone defects, develop a progressive, severe chondrodystrophy during postnatal weeks 3 to 6. Mutant GP exhibited disorganized, non-aligned chondrocytes and mineralized metaphyseal bone but without cartilage mineralization or cartilaginous extensions into the metaphysis. Expression of mRNA coding for collagen types II (Col II) and X (Col X) was examined in the tibial GP by in situ hybridization. Mutant rats at 2 weeks exhibited Col II RNA expression and some hypertrophied chondrocytes (HC) but no Col X RNA was detected. By 3rd week, HC had largely disappeared from the central part of the mutant GP and Col II RNA expression was present but weak and in 2 separate bands. Peripherally the GP contained HC but without Col X RNA expression. This abnormal pattern was exacerbated by the fourth week. Bone mineralized but cartilage in the GP did not. These data suggest that the tl mutation involves a regulatory function for chondrocyte maturation, including Col X RNA synthesis and mineralization, and that the GP abnormalities are related to the Col X deficiency. The differences in patterning in the tl rat GP compared to direct Col X mutations may be explained by compensatory effects. 相似文献
36.
37.
38.
I Suzuki D Lee B Mackay L Harahuc J K Oh 《Applied and environmental microbiology》1999,65(11):5163-5168
The oxidation of elemental sulfur by Thiobacillus thiooxidans was studied at pH 2.3, 4.5, and 7.0 in the presence of different concentrations of various anions (sulfate, phosphate, chloride, nitrate, and fluoride) and cations (potassium, sodium, lithium, rubidium, and cesium). The results agree with the expected response of this acidophilic bacterium to charge neutralization of colloids by ions, pH-dependent membrane permeability of ions, and osmotic pressure. 相似文献
39.
M. J. Kennard B. J. Pusey A. H. Arthington B. D. Harch S. J. Mackay 《Hydrobiologia》2006,572(1):33-57
Multivariate predictive models are widely used tools for assessment of aquatic ecosystem health and models have been successfully
developed for the prediction and assessment of aquatic macroinvertebrates, diatoms, local stream habitat features and fish.
We evaluated the ability of a modelling method based on the River InVertebrate Prediction and Classification System (RIVPACS)
to accurately predict freshwater fish assemblage composition and assess aquatic ecosystem health in rivers and streams of
south-eastern Queensland, Australia. The predictive model was developed, validated and tested in a region of comparatively
high environmental variability due to the unpredictable nature of rainfall and river discharge. The model was concluded to
provide sufficiently accurate and precise predictions of species composition and was sensitive enough to distinguish test
sites impacted by several common types of human disturbance (particularly impacts associated with catchment land use and associated
local riparian, in-stream habitat and water quality degradation). The total number of fish species available for prediction
was low in comparison to similar applications of multivariate predictive models based on other indicator groups, yet the accuracy
and precision of our model was comparable to outcomes from such studies. In addition, our model developed for sites sampled
on one occasion and in one season only (winter), was able to accurately predict fish assemblage composition at sites sampled
during other seasons and years, provided that they were not subject to unusually extreme environmental conditions (e.g. extended
periods of low flow that restricted fish movement or resulted in habitat desiccation and local fish extinctions). 相似文献
40.
Chromosomal Proteins and Cytokinesis: Patterns of Cleavage Furrow Formation and Inner Centromere Protein Positioning in Mitotic Heterokaryons and Mid-anaphase Cells 总被引:8,自引:1,他引:8 下载免费PDF全文
D. Mark Eckley Alexandra M. Ainsztein Alastair M. Mackay Ilya G. Goldberg William C. Earnshaw 《The Journal of cell biology》1997,136(6):1169-1183
After the separation of sister chromatids in anaphase, it is essential that the cell position a cleavage furrow so that it partitions the chromatids into two daughter cells of roughly equal size. The mechanism by which cells position this cleavage furrow remains unknown, although the best current model is that furrows always assemble midway between asters. We used micromanipulation of human cultured cells to produce mitotic heterokaryons with two spindles fused in a V conformation. The majority (15/19) of these cells cleaved along a single plane that transected the two arms of the V at the position where the metaphase plate had been, a result at odds with current views of furrow positioning. However, four cells did form an additional ectopic furrow between the spindle poles at the open end of the V, consistent with the established view. To begin to address the mechanism of furrow assembly, we have begun a detailed study of the properties of the chromosome passenger inner centromere protein (INCENP) in anaphase and telophase cells. We found that INCENP is a very early component of the cleavage furrow, accumulating at the equatorial cortex before any noticeable cortical shape change and before any local accumulation of myosin heavy chain. In mitotic heterokaryons, INCENP was detected in association with spindle midzone microtubules beneath sites of furrowing and was not detected when furrows were absent. A functional role for INCENP in cytokinesis was suggested in experiments where a nearly full-length INCENP was tethered to the centromere. Many cells expressing the chimeric INCENP failed to complete cytokinesis and entered the next cell cycle with daughter cells connected by a large intercellular bridge with a prominent midbody. Together, these results suggest that INCENP has a role in either the assembly or function of the cleavage furrow. 相似文献