排序方式: 共有127条查询结果,搜索用时 15 毫秒
1.
2.
Morchella species ascocarps (morels) are sought-after edible mushrooms that exhibit pyrophilous behavior, proliferating in fire-affected soils of certain types of forests. The factors governing fruiting in this habitat are poorly understood. An observational approach was used to determine the spatial distribution on preferred micro-sites of black morel fruiting in a forest after a summer fire, subjected to different post-fire forestry management activities. Clearing the burnt tree stumps from the site, compaction of the burnt soil by heavy machinery (bulldozers) and covering the soil with chopped wood created preferred micro-sites for black morel fruiting. Fewer fruit bodies developed on untouched burnt soil, and almost none on non-burnt soil at the same site. These observations enhance understanding the ecological principles underlying the distribution and abundance of morel ascocarp development in natural habitats; such an understanding could contribute to conservation and management of morel fruiting in the wild. 相似文献
3.
Morgan UM Monis PT Xiao L Limor J Sulaiman I Raidal S O'Donoghue P Gasser R Murray A Fayer R Blagburn BL Lal AA Thompson RC 《International journal for parasitology》2001,31(3):289-296
Avian isolates of Cryptosporidium species from different geographic locations were sequenced at two loci, the 18S rRNA gene and the heat shock gene (HSP-70). Phylogenetic analysis of the sequence data provided support for the existence of a new avian species of Cryptosporidium infecting finches and a second species infecting a black duck. The identity of Cryptosporidium baileyi and Cryptosporidium meleagridis as valid species was confirmed. Also, C. baileyi was identified in a number of isolates from the brown quail extending the host range of this species. 相似文献
4.
Somjen D Kohen F Gayer B Knoll E Limor R Baz M Sharon O Posner GH Stern N 《The Journal of steroid biochemistry and molecular biology》2004,(1-5):397-399
In cultured human vascular smooth muscle cells (VSMC), estradiol-17beta (E2) induced a biphasic effect on DNA synthesis, i.e., stimulation at low concentrations and inhibition at high concentrations. Additionally, E2 increased the specific activity of creatine kinase (CK) in these cells. Observations that novel protein-bound membrane impermeant estrogenic complexes could elicit inhibition of DNA synthesis, suggested interaction via membranal binding sites. Nevertheless other effects, such as increasing CK activity were only seen with native E2 but not with E2-BSA, thus indicating that the classical nuclear receptor pathway was involved. In the present report, we confirm that human VSMC express both ERalpha and ERbeta. Further, pretreatment of cultured VSMC with the Vitamin D non-calcemic analog JK 1624 F2-2 (JKF) increased ERalpha mRNA (100-200%) but decreased ERbeta mRNA (30-40%) expression as measured by real time PCR. ERalpha protein expression assessed by Western blot analysis increased (25-50%) in parallel, whereas ERbeta protein expression declines (25-55%). Using ovalbumin bound to E2 (Ov-E2) linked to Eu (Eu-Ov-E2), to assess specific membrane binding sites, we observed that membranal binding was down regulated by JKF by 70-80%. In contrast, total cell binding of 3[H] E2, that nearly entirely represents intracellular E2 binding, was increased by 60-100% by the same Vitamin D analog. The results provide evidence that the effects of JKF on ERalpha/ERbeta as well as on membranal versus nuclear binding of estrogen are divergent and show differential modulation. 相似文献
5.
Xiao L Ryan UM Graczyk TK Limor J Li L Kombert M Junge R Sulaiman IM Zhou L Arrowood MJ Koudela B Modrý D Lal AA 《Applied and environmental microbiology》2004,70(2):891-899
The genetic diversity of Cryptosporidium in reptiles was analyzed by PCR-restriction fragment length polymorphism and sequence analysis of the small subunit rRNA gene. A total of 123 samples were analyzed, of which 48 snake samples, 24 lizard samples, and 3 tortoise samples were positive for Cryptosporidium: Nine different types of Cryptosporidium were found, including Cryptosporidium serpentis, Cryptosporidium desert monitor genotype, Cryptosporidium muris, Cryptosporidium parvum bovine and mouse genotypes, one C. serpentis-like parasite in a lizard, two new Cryptosporidium spp. in snakes, and one new Cryptosporidium sp. in tortoises. C. serpentis and the desert monitor genotype were the most common parasites and were found in both snakes and lizards, whereas the C. muris and C. parvum parasites detected were probably the result of ingestion of infected rodents. Sequence and biologic characterizations indicated that the desert monitor genotype was Cryptosporidium saurophilum. Two host-adapted C. serpentis genotypes were found in snakes and lizards. 相似文献
6.
VEGF162, a new heparin-binding vascular endothelial growth factor splice form that is expressed in transformed human cells 总被引:5,自引:0,他引:5
Lange T Guttmann-Raviv N Baruch L Machluf M Neufeld G 《The Journal of biological chemistry》2003,278(19):17164-17169
The splice forms of vascular endothelial growth factor (VEGF) differ in biological properties such as the receptor types that they recognize and their interaction with heparan sulfate proteoglycans. We have identified a new VEGF mRNA splice form encoding a VEGF species containing 162 amino acids (VEGF(162)) in human A431 ovarian carcinoma cells. This novel mRNA contains the peptides encoded by exons 1-5, 6A, 6B, and 8 of the VEGF gene. Recombinant VEGF(162) is biologically active. It induces proliferation of endothelial cells in vitro and angiogenesis in vivo as determined by the alginate bead assay. VEGF(162) binds less efficiently than VEGF(145) but more efficiently than VEGF(165) to a natural basement membrane produced by corneal endothelial cells. VEGF(138), an artificial VEGF form that contains exon 6B but lacks exons 6A and 7, did not bind to this basement membrane at all, indicating that exon 6B probably interferes with the interaction of exon 6A with heparin and heparan sulfate proteoglycans. 相似文献
7.
We developed schemes for rapid identification of Mycobacterium species and strain typing using a microfluidic labchip instrument. A 439-bp region of the gene that codes for the 65-kDa heat shock protein (hsp65), which has sequence polymorphisms specific for most mycobacterial species, was examined using PCR-restriction analysis (PRA). We performed PRA in duplicate, using 2 strains each of 12 species, and observed that fragment sizes (bp) determined automatically by the instrument were consistently smaller than the correct sizes for each of the species as determined by sequence analysis (mean variance, < 7 bp). Mycobacterium tuberculosis isolates were typed with the labchip instrument using mycobacterial interspersed repetitive unit-variable number tandem repeat (MIRU-VNTR) typing, which determines the number of copies of repeated units at 12 loci in the genome based on product size after PCR amplification. Seven strains with one to six repeat copies at each locus were examined. Sizes were smaller by a mean of 13.47 bp compared with correct sizes predicted by sequence analysis, but could be used to correctly identify all strains types. Isolates of Mycobacterium chelonae and Mycobacterium abscessus were typed using randomly amplified polymorphic DNA (RAPD) electrophoresis, and patterns obtained using the labchip instrument were compared with multilocus enzyme electrophoresis (MEE) types. Patterns were distinct and reproducible for all strains except those with closely related MEE types. The labchip instrument is a versatile alternative for sizing mycobacterial DNA fragments. 相似文献
8.
Broday DM 《Bulletin of mathematical biology》2000,62(5):891-924
Focal adhesions play a major role in maintaining the cell shape and motility, and in regulating numerous cellular processes.
Observations suggest that the functioning of focal adhesions is possible due to their dynamic nature, yet the mechanisms that
govern their motion are not well understood. This study addresses the process of focal adhesion remodeling using two distinct
theoretical approaches. Namely, adhesion sites are modeled as clusters of integrins that are either bound to cytoskeletal
elements or dissociated and temporarily free of any attachments. In the first approach effects of cluster size and permeability
on the diffusion of mobile adhesion structures are studied using Brinkman’s effective medium approach. Diffusion coefficients
calculated by this hydrodynamic model significantly decrease with the increase in contact area (the effective size of the
focal adhesion). In the second approach focal adhesions are modeled as clusters of transmembrane proteins tightly connected
to the cytoskeleton, but still capable of motion. The remodeling of these clusters is coupled to the deformation of the cytoskeleton
by means of equating energies at the end states of a reversible elastodynamic interaction. Due to large uncertainty of the
plasma membrane and the cytoskeleton properties, predicted diffusion coefficients vary within several orders of magnitude.
However, a reasonable set of parameters for each model yields diffusion coefficients that compare favorably with those measured
by single-particle tracking (SPT), fluorescence recovery after photobleaching (FRAP), and fluorescence digital imaging (FDI).
The estimated Young’s modulus of the stress fibers is also in good agreement with measurements. To assess the relevance of
the models to focal adhesion remodeling and to improve their predictions, further data on the morphology of focal adhesions
and on properties of the plasma membrane and the cytoskeleton are required. 相似文献
9.
Cryptosporidium spp. in domestic dogs: the "dog" genotype 总被引:3,自引:0,他引:3
Morgan UM Xiao L Monis P Fall A Irwin PJ Fayer R Denholm KM Limor J Lal A Thompson RC 《Applied and environmental microbiology》2000,66(5):2220-2223
Genetic and phylogenetic characterization of Cryptosporidium isolates at two loci (18S rRNA gene and heat shock gene) from both Australian and United States dogs demonstrated that dog-derived Cryptosporidium isolates had a distinct genotype which is conserved across geographic areas. Phylogenetic analysis provided support for the idea that the "dog" genotype is, in fact, a valid species. 相似文献
10.
To further validate the observation of the existence of host-adapted strains of Cryptosporidium parvum, we genetically characterized an isolate of Cryptosporidium parasite from a black bear. Sequence analysis of the ribosomal RNA small subunit and the 70-kDa heat shock protein (HSP70) showed that this parasite represents a new genotype of C. parvum and is related to the C. parvum dog genotype. This finding is helpful for clarifying Cryptosporidium taxonomy. 相似文献