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31.
Pei-Hsun Cheng Brooke Snyder Dimitri Fillos Chris C Ibegbu Anderson Hsien-Cheng Huang Anthony WS Chan 《BMC cell biology》2008,9(1):20
Background
Chimpanzee dental pulp stem/stromal cells (ChDPSCs) are very similar to human bone marrow derived mesenchymal stem/stromal cells (hBMSCs) as demonstrated by the expression pattern of cell surface markers and their multipotent differentiation capability. 相似文献32.
Hatters DM MacRaild CA Daniels R Gosal WS Thomson NH Jones JA Davis JJ MacPhee CE Dobson CM Howlett GJ 《Biophysical journal》2003,85(6):3979-3990
Amyloid fibrils have historically been characterized by diagnostic dye-binding assays, their fibrillar morphology, and a "cross-beta" x-ray diffraction pattern. Whereas the latter demonstrates that amyloid fibrils have a common beta-sheet core structure, they display a substantial degree of morphological variation. One striking example is the remarkable ability of human apolipoprotein C-II amyloid fibrils to circularize and form closed rings. Here we explore in detail the structure of apoC-II amyloid fibrils using electron microscopy, atomic force microscopy, and x-ray diffraction studies. Our results suggest a model for apoC-II fibrils as ribbons approximately 2.1-nm thick and 13-nm wide with a helical repeat distance of 53 nm +/- 12 nm. We propose that the ribbons are highly flexible with a persistence length of 36 nm. We use these observed biophysical properties to model the apoC-II amyloid fibrils either as wormlike chains or using a random-walk approach, and confirm that the probability of ring formation is critically dependent on the fibril flexibility. More generally, the ability of apoC-II fibrils to form rings also highlights the degree to which the common cross-beta superstructure can, as a function of the protein constituent, give rise to great variation in the physical properties of amyloid fibrils. 相似文献
33.
Background
SXT is an integrating conjugative element (ICE) originally isolated from Vibrio cholerae, the bacterial pathogen that causes cholera. It houses multiple antibiotic and heavy metal resistance genes on its ca. 100 kb circular double stranded DNA (dsDNA) genome, and functions as an effective vehicle for the horizontal transfer of resistance genes within susceptible bacterial populations. Here, we characterize the activities of an alkaline exonuclease (S066, SXT-Exo) and single strand annealing protein (S065, SXT-Bet) encoded on the SXT genetic element, which share significant sequence homology with Exo and Bet from bacteriophage lambda, respectively.Results
SXT-Exo has the ability to degrade both linear dsDNA and single stranded DNA (ssDNA) molecules, but has no detectable endonuclease or nicking activities. Adopting a stable trimeric arrangement in solution, the exonuclease activities of SXT-Exo are optimal at pH 8.2 and essentially require Mn2+ or Mg2+ ions. Similar to lambda-Exo, SXT-Exo hydrolyzes dsDNA with 5'- to 3'-polarity in a highly processive manner, and digests DNA substrates with 5'-phosphorylated termini significantly more effectively than those lacking 5'-phosphate groups. Notably, the dsDNA exonuclease activities of both SXT-Exo and lambda-Exo are stimulated by the addition of lambda-Bet, SXT-Bet or a single strand DNA binding protein encoded on the SXT genetic element (S064, SXT-Ssb). When co-expressed in E. coli cells, SXT-Bet and SXT-Exo mediate homologous recombination between a PCR-generated dsDNA fragment and the chromosome, analogous to RecET and lambda-Bet/Exo.Conclusions
The activities of the SXT-Exo protein are consistent with it having the ability to resect the ends of linearized dsDNA molecules, forming partially ssDNA substrates for the partnering SXT-Bet single strand annealing protein. As such, SXT-Exo and SXT-Bet may function together to repair or process SXT genetic elements within infected V. cholerae cells, through facilitating homologous DNA recombination events. The results presented here significantly extend our general understanding of the properties and activities of alkaline exonuclease and single strand annealing proteins of viral/bacteriophage origin, and will assist the rational development of bacterial recombineering systems. 相似文献34.
Callus cultures were established in three commercial sugarcane varieties viz., CoJ 64, CoJ 83 and CoJ 86 from spindle explants on MS + 2,4-D (4 mg l?1) + BAP (0.5 mg l?1) medium. Shoots were regenerated from two-month-old calli on MS + BAP (0.5 mg l?1) medium. Callus and callus derived shoots were treated with gamma (γ) radiation at 20, 40, 60 and 80 Gray (Gy). Per cent shoot regeneration from y-irradiated calli in the three varieties ranged from 90 to 93.8 at 20 Gy, 83.3 to 87.5 at 40 Gy, 30 to 36.4 at 60 Gy and 0 at 80 Gy. Upon irradiating shoots, subsequent shoot proliferation in the three varieties ranged from 90.9 to 93.1% at 20 Gy, 82.6 to 84.0% at 40 Gy and 27 to 32.3% at 60 Gy, whereas 80 Gy dose was 100% lethal. Thus, 60 Gy dose of y-radiation was found to be optimum for carrying out mutagenesis of both callus and callus derived shoots. In the field, different irradiated clones of the same variety exhibited huge variability with respect to number of canes, cane girth, cane height and sucrose content. 相似文献
35.
Yonekawa H; Moriwaki K; Gotoh O; Miyashita N; Matsushima Y; Shi LM; Cho WS; Zhen XL; Tagashira Y 《Molecular biology and evolution》1988,5(1):63-78
The Japanese mouse, Mus musculus molossinus, has long been considered an
independent subspecies of the house mouse. A survey of restriction- site
haplotypes of mitochondrial DNA (mtDNA) showed that Japanese mice have two
main maternal lineages. The most common haplotype is closely related to the
mtDNA of the European subspecies M. m. musculus. The other common haplotype
and two minor ones are closely related to each other and to the mtDNA of an
Asiatic subspecies, M. m. castaneus. Two other rare variants are probably
the result of recent contamination by European M. m. domesticus. The
musculus type of mtDNA is found in the southern two-thirds of Japan,
whereas the common castaneus type is found in the northern third and the
minor variants are found sporadically throughout Japan. The castaneus mtDNA
lineage had a few minor variants, whereas the musculus lineage was
completely monomorphic. By contrast, the native population of M. m.
castaneus and the Chinese and Korean musculus populations were highly
polymorphic. These results suggest that M. m. molossinus is a hybrid
between ancestral colonies, possibly very small, of M. m. musculus and M.
m. castaneus, rather than an independent subspecies.
相似文献
36.
Flagellar adhesion in chlamydomonas induces synthesis of two high molecular weight cell surface proteins 总被引:2,自引:2,他引:0
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Because our previous studies (Snell, W.J., and W.S. Moore, 1980, J. Cell Biol. 84:203- 210) on the mating reaction of chlamydomonas reinhardtii showed that there was an adhesion-induced turnover of proteins whose synthesis is induced during aggregation. Analysis by SDS PAGE and autoradiography showed that proteins of 220,000 M(r) and 165, 000 M(r) (designated A(1) and A(2) respectively) consistently showed a high rate of synthesis only in flagella or flagellar membrane-enriched fractions prepared from aggregating gametes. Since the two proteins were soluble in the non-ionic detergent NP-40 and were removed from intact cells by a brief pronase treatment, it is likely that A(1) and A(2) are membrane proteins expose on the cell surface. A(1) and A(2) were each synthesized by gametes of both mating types (mt(-) and mt(+)) and synthesis of these two proteins could be detected in the normal mating reaction (wild type mt(-) and mt(+)), in mixtures of mt(-) and impotent mt(+) gametes (which could aggregate but not fuse), and in mixtures of gametes of a single mating type with isolated flagella of the opposite mating type. Cells aggregating in tunicamycin, an inhibitor of protein glycosylation, lost their adhesiveness during aggregation and did not synthesize the 220,000 M(r) protein but instead produced a protein (possibly an underglycosylated form of A(1)) of slightly lower mol wt. The 220,000 and 165,000 M(R) proteins appeared to be flagellar proteins and not cell wall proteins because A(1) and A(2) did not co-migrate with previously identified cell wall proteins, and synthesis of the two proteins could not be detected in flagella-less (bald-2) mutant cells. Analysis of the adhesive activity of sucrose gradient fraction of detergent (octyl glucoside)-solubilized flagellar membranes revealed that fractions containing A(1) and A(2) did not have detectable adhesive activity. The possibility remains that A(1) and A(2) are adhesion molecules whose activity could not be measured in the assay we used. Alternatively, the 220,000 and 165,000 M(r) proteins may be inactivated adhesion molecules or else they may be flagellar surface proteins involved only indirectly in the adhesion process. 相似文献
37.
Lymphocyte locomotion and attachment on two-dimensional surfaces and in three-dimensional matrices 总被引:9,自引:3,他引:6
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The adhesion and locomotion of mouse peripheral lymph node lymphocytes on 2-D protein- coated substrata and in 3-D matrices were compared. Lymphocytes did not adhere to, or migrate on, 2-D substrata suck as serum- or fibronectin-coated glass. They did attach to and migrate in hydrated 3-D collagen lattices. When the collagen was dehydrated to form a 2-D surface, lymphocyte attachment to it was reduced. We propose that lymphocytes, which are poorly adhesive, are able to attach to and migrate in 3-D matrices by a nonadhesive mechanism such as the extension and expansion of pseudopodia through gaps in the matrix, which could provide purchase for movement in the absence of discrete intermolecular adhesions. This was supported by studies using serum-coated micropore filters, since lymphocytes attached to and migrated into filters with pore sizes large enough (3 or 8 mum) to allow pseudopod penetration but did not attach to filters made of an identical material (cellulose esters) but of narrow pore size (0.22 or 0.45 mum). Cinematographic studies of lymphocyte locomotion in collagen gels were also consistent with the above hypothesis, since lymphocytes showed a more variable morphology than is typically seen on plane surfaces, with formation of many small pseudopodia expanded to give a marked constriction between the cell and the pseudopod. These extensions often remained fixed with respect to the environment as the lymphocyte moved away from or past them. This suggests that the pseudopodia were inserted into gaps in the gel matrix and acted as anchorage points for locomotion. 相似文献
38.
WS Watkins R Thara BJ Mowry Y Zhang DJ Witherspoon W Tolpinrud MJ Bamshad S Tirupati R Padmavati H Smith D Nancarrow C Filippich LB Jorde 《BMC genetics》2008,9(1):1-17
Background
Major population movements, social structure, and caste endogamy have influenced the genetic structure of Indian populations. An understanding of these influences is increasingly important as gene mapping and case-control studies are initiated in South Indian populations.Results
We report new data on 155 individuals from four Tamil caste populations of South India and perform comparative analyses with caste populations from the neighboring state of Andhra Pradesh. Genetic differentiation among Tamil castes is low (RST = 0.96% for 45 autosomal short tandem repeat (STR) markers), reflecting a largely common origin. Nonetheless, caste- and continent-specific patterns are evident. For 32 lineage-defining Y-chromosome SNPs, Tamil castes show higher affinity to Europeans than to eastern Asians, and genetic distance estimates to the Europeans are ordered by caste rank. For 32 lineage-defining mitochondrial SNPs and hypervariable sequence (HVS) 1, Tamil castes have higher affinity to eastern Asians than to Europeans. For 45 autosomal STRs, upper and middle rank castes show higher affinity to Europeans than do lower rank castes from either Tamil Nadu or Andhra Pradesh. Local between-caste variation (Tamil Nadu RST = 0.96%, Andhra Pradesh RST = 0.77%) exceeds the estimate of variation between these geographically separated groups (RST = 0.12%). Low, but statistically significant, correlations between caste rank distance and genetic distance are demonstrated for Tamil castes using Y-chromosome, mtDNA, and autosomal data.Conclusion
Genetic data from Y-chromosome, mtDNA, and autosomal STRs are in accord with historical accounts of northwest to southeast population movements in India. The influence of ancient and historical population movements and caste social structure can be detected and replicated in South Indian caste populations from two different geographic regions. 相似文献39.
Rabindra Sandhu Varindra Pandhir Aparna Das S. S. Gosal 《Journal of plant biochemistry and biotechnology.》2003,12(2):159-162
Callus was initiated on Murashige and Skoog (MS) medium containing different combinations of growth regulators or different concentrations of vitamins from pericarp of six varieties of Capsicum annuum differing in their capsaicin content. Callus derived from pericarp of low capsaicin containing varieties was snowy white, friable and showed excellent growth. Callus initiation was delayed (10-15 days) in Punjab Lal, which had very high fruit capsaicin content (7.0 mg g?1 DW). It also showed relatively slow proliferation although callus obtained was white and friable. Several different media were tried to improve the initiation and the proliferation of the callus in this variety. Callus growth improved greatly by doubling the concentration of MS salts. Initiation time was reduced to 4-6 days by adding 10 mg l?1 NAA and 0.5 mg l?1 Kin in MS medium. Other combinations of growth regulators or increase in concentration of vitamins or activated charcoal (0.1%) resulted in poor callus growth and callus texture. Of all media tried, MS medium containing 2 mg l?1 2,4 D and 0.5 mg l?1 Kin was the best for callus initiation and proliferation. 相似文献
40.
Pauly M; Andersen LN; Kauppinen S; Kofod LV; York WS; Albersheim P; Darvill A 《Glycobiology》1999,9(1):93-100
A full-length c-DNA encoding a xyloglucan-specific endo -beta-1, 4-
glucanase (XEG) has been isolated from the filamentous fungus Aspergillus
aculeatus by expression cloning in yeast. The colonies expressing
functional XEG were identified on agar plates containing azurine-dyed
cross-linked xyloglucan. The cDNA encoding XEG was isolated, sequenced,
cloned into an Aspergillus expression vector, and transformed into
Aspergillus oryzae for heterologous expression. The recombinant enzyme was
purified to apparent homogeneity by anion- exchange and gel permeation
chromatography. The recombinant XEG has a molecular mass of 23,600, an
isoelectric point of 3.4, and is optimally stable at a pH of 3.4 and
temperature below 30 degreesC. The enzyme hydrolyzes structurally diverse
xyloglucans from various sources, but hydrolyzes no other cell wall
component and can therefore be considered a xyloglucan-specific endo
-beta-1, 4-glucanohydrolase. XEG hydrolyzes its substrates with retention
of the anomeric configuration. The Kmof the recombinant enzyme is 3.6
mg/ml, and its specific activity is 260 micromol/min per mg protein. The
enzyme was tested for its ability to solubilize xyloglucan oligosaccharides
from plant cell walls. It was shown that treatment of plant cell walls with
XEG yields only xyloglucan oligosaccharides, indicating that this enzyme
can be a powerful tool in the structural elucidation of xyloglucans.
相似文献