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991.
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Godfrey C. Akani Luca Luiselli Edem A. Eniang Charity C. Amuzie Nwabueze Ebere 《African Journal of Ecology》2008,46(4):533-539
The ecology of the blindsnake, Typhlops punctatus punctatus in five selected study plots in the River Niger Delta (Port Harcourt, Nigeria) was investigated. A total of 207 specimens were collected, 43% occurring under stones, 30% under leaf litter and 15% under logs. The number of snakes found under cover objects was significantly influenced by the number of cover objects lifted up. GLM analysis revealed that there was no difference in terms of number of snakes observed, once the relative effect of the different number of cover objects lifted up was taken into account, either among study plots or among types of cover objects. These snakes appeared to have a strong affinity for loamy soils, with moisture content of 8–18%, high organic matter (1–6%) and slightly acid pH of 5.4–6.9. Stomach content analysis revealed that these snakes fed mainly upon ants and termites. A case of predation by the toad Bufo maculatus on a juvenile blindsnake was also reported. 相似文献
994.
Rhodobacter capsulatus contains lhaA and pucC genes that have been implicated in light-harvesting complex 1 and 2 (LH1 and LH2) assembly. The proteins encoded by these
genes, and homologues in other photosynthetic organisms, have been classified as the bacteriochlorophyll delivery (BCD) family
of the major facilitator superfamily. A new BCD family phylogenetic tree reveals that several PucC, LhaA and Orf428-related
sequences each form separate clusters, while plant and cyanobacterial homologues cluster more distantly. The PucC protein
is encoded in the pucBACDE superoperon which also codes for LH2 α (PucA) and β (PucB) proteins. PucC was previously shown to be necessary for formation
of LH2. This article gives evidence indicating that PucC has a shepherding activity that keeps the homologous α and β proteins
of LH1 and LH2 apart, allowing LH1 to assemble properly. This shepherding function was indicated by a 62% reduction in LH1
levels in ΔLHII strains carrying plasmids encoding pucBA along with a C-terminally truncated pucC gene. More severe reductions in LH1 were seen when the truncated pucC gene was co-expressed in the presence of C-terminal PucC::PhoA fusion proteins. It appears that interaction between truncated
PucC::PhoA fusion proteins and the truncated PucC protein disrupts LH1 assembly, pointing towards a PucC dimeric or multimeric
functional unit. 相似文献
995.
The 16S and 18S rRNA genes of planktonic organisms derived from five stations with nutrient gradients in Lake Donghu, China, were studied by PCR–denaturing gradient gel electrophoresis (DGGE) fingerprinting, and the relationships between the genetic diversity of the plankton community and biotic/abiotic factors are discussed. The concentrations of total nitrogen (TN), total phosphorus (TP), NH4 -N and As were found to be significantly related ( P <0.05) to morphological composition of the plankton community. Both chemical and morphological analyses suggested that temporal heterogeneity was comparatively higher than spatial heterogeneity in Lake Donghu. Although the morphological composition was not identical to the DGGE fingerprints in characterizing habitat similarity, the two strongest eutrophic stations (I and II) were always initially grouped into one cluster. Canonical correspondence analysis suggested that the factors strongly correlated with the first two ordination axes were seasonally different. The concentrations of TN and TP and the densities of rotifers and crustaceans were generally the main factors related to the DGGE patterns of the plankton communities. The study suggested that genetic diversity as depicted by metagenomic techniques (such as PCR-DGGE fingerprinting) is a promising tool for ecological study of plankton communities and that such techniques are likely to play an increasingly important role in assessing the environmental conditions of aquatic habitats. 相似文献
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Ivanov R Tiedemann J Czihal A Schallau A Diep le H Mock HP Claus B Tewes A Bäumlein H 《Developmental biology》2008,313(1):93-106
EFFECTORS OF TRANSCRIPTION2 (ET) are plant-specific regulatory proteins characterized by the presence of two to five C-terminal DNA- and Zn-binding repeats, and a highly conserved cysteine pattern. We describe the structural characterization of the three member Arabidopsis thalianaET gene family and reveal some allelic sequence polymorphisms. A mutation analysis showed that AtET2 affects the expression of various KNAT genes involved in the maintenance of the undifferentiated state of cambial meristem cells. It also plays a role in the regulation of GA5 (gibberellin 3-beta-dioxygenase) and the cell-cycle-related GASA4. A correlation was established between AtET2 expression and the cellular differentiation state. AtET-GFP fusion proteins shuttle between the cytoplasm and nucleus, with the AtET2 product prevented from entering the nucleus in non-differentiating cells. Within the nucleus, AtET2 probably acts via a single strand cutting domain. A more general regulatory role for ET factors is proposed, governing cell differentiation in cambial meristems, a crucial process for the development of plant vascular tissues. 相似文献
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Tissue-engineered fibrocartilage could become a feasible option for replacing tissues such as the knee meniscus or temporomandibular joint disc. This study employed five growth factors (insulin-like growth factor-I, transforming growth factor-beta1, epidermal growth factor, platelet-derived growth factor-BB, and basic fibroblast growth factor) in a scaffoldless approach with costal chondrocytes, attempting to improve biochemical and mechanical properties of engineered constructs. Samples were quantitatively assessed for total collagen, glycosaminoglycans, collagen type I, collagen type II, cells, compressive properties, and tensile properties at two time points. Most treated constructs had lower biomechanical and biochemical properties than the controls with no growth factors, suggesting a detrimental effect, but the treatment with insulin-like growth factor-I tended to improve the constructs. Additionally, the 6-week time point was consistently better than that at 3 weeks, with total collagen, glycosaminoglycans, and aggregate modulus doubling during this time. Further optimization of the time in culture and exogenous stimuli will be important in making a more functional replacement tissue. 相似文献