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91.
Periosteum is a thin fibrous layer that covers most bones. It resides in a dynamic mechanically loaded environment and provides a niche for pluripotent cells and a source for molecular factors that modulate cell behaviour. Elucidating periosteum regenerative poten-tial has become a hot topic in orthopaedics. This review discusses the state of the art of osteochondral tissue engineering rested on periosteum derived progenitor cells(PDPCs) and suggests upcoming research direc-tions. Periosteal cells isolation, characterization and migration in the site of injury, as well as their differen-tiation, are analysed. Moreover, the role of cell mecha-nosensing and its contribution to matrix organization, bone microarchitecture and bone stenght is examined. In this regard the role of periostin and its upregulation under mechanical stress in order to preserve PDPC sur-vival and bone tissue integrity is contemplated. The re-view also summarized the role of the periosteum in the field of dentistry and maxillofacial reconstruction. The involvement of microRNAs in osteoblast differentiation and in endogenous tissue repair is explored as well. Fi-nally the novel concept of a guided bone regenerationbased on the use of periosteum itself as a smart mate-rial and the realization of constructs able to mimic the extracellular matrix features is talked out. Additionally, since periosteum can differentiate into insulin produc-ing cells it could be a suitable source in allogenic trans-plantations. That innovative applications would takeadvantage from investigations aimed to assess PDPCimmune privilege. 相似文献
92.
Costantino V Fattorusso E Imperatore C Mangoni A Freigang S Teyton L 《Bioorganic & medicinal chemistry》2008,16(4):2077-2085
Corrugoside (1a), a new immunostimulatory triglycosilated alpha-galactoglycosphingolipid, was isolated from the marine sponge Axinella corrugata, and its structure determined by spectral analysis and chemical degradation. Compound 1a activated murine NKT cells in vitro, with a potency of about 2 logs lower than that of alphaGalCer. Four stereoisomeric glycosphingolipids (2a-2d) were also obtained, beta-glucosylceramides bearing unusual endoperoxide and allylic hydroperoxide functionalities on the sphinganine chain. They were shown to be photooxidation artifacts of the known glycosphingolipids 3, also present in the sponge. A possible role of compound 3 as a singlet oxygen scavenger to protect the organism from oxidative damage is proposed. 相似文献
93.
Karl E. Havens Antonia Concetta Elia Maria Illuminata Taticchi Rolland S. FultonIII 《Hydrobiologia》2009,628(1):165-175
This study compares and contrasts the dynamics of phytoplankton, zooplankton, and nutrients in two of the largest shallow
lakes in the USA (Lake Apopka, Florida) and Europe (Lago Trasimeno, Umbria, Italy) and considers particularly the biomass
ratio of zooplankton to phytoplankton (BZ:BP) in relation to nutrient levels and in the context of data from other subtropical
and temperate lakes. Lake Apopka is hypereutrophic with higher concentrations of total phosphorus (TP), nitrogen (TN), and
nearly an order of magnitude higher BP than Lago Trasimeno. However, combined data from the two lakes can be fit to a single
log–log regression model that explains 72% of the variability in BP based on TP. In contrast, BZ has a significant positive
log–log relationship with TP only for Lago Trasimeno, and is much lower than expected based on the TP concentrations observed
in Lake Apopka. Lake Apopka has a fish assemblage that includes high densities of gizzard shad (Dorosoma cepedianum) and threadfin shad (D. petenense), similar to other eutrophic Florida lakes that also have extreme low BZ. The ratio BZ:BP is below 0.01 in Lake Apopka, 10-fold
lower than in Trasimeno and among the lowest values reported in the literature. Although stress of high water temperature
and a greater proportion of inedible cyanobacteria may be contributing factors, the collective results support an emerging
view that fish predation limits the biomass of crustacean zooplankton in subtropical lakes.
Handling editor: S. I. Dodson 相似文献
94.
Characterization of Demographic Expansions From Pairwise Comparisons of Linked Microsatellite Haplotypes
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This work extends the methods of demographic inference based on the distribution of pairwise genetic differences between individuals (mismatch distribution) to the case of linked microsatellite data. Population genetics theory describes the distribution of mutations among a sample of genes under different demographic scenarios. However, the actual number of mutations can rarely be deduced from DNA polymorphisms. The inclusion of mutation models in theoretical predictions can improve the performance of statistical methods. We have developed a maximum-pseudolikelihood estimator for the parameters that characterize a demographic expansion for a series of linked loci evolving under a stepwise mutation model. Those loci would correspond to DNA polymorphisms of linked microsatellites (such as those found on the Y chromosome or the chloroplast genome). The proposed method was evaluated with simulated data sets and with a data set of chloroplast microsatellites that showed signal for demographic expansion in a previous study. The results show that inclusion of a mutational model in the analysis improves the estimates of the age of expansion in the case of older expansions. 相似文献
95.
96.
Hydrogen peroxide, nitric oxide and cytosolic ascorbate peroxidase at the crossroad between defence and cell death 总被引:14,自引:0,他引:14
de Pinto MC Paradiso A Leonetti P De Gara L 《The Plant journal : for cell and molecular biology》2006,48(5):784-795
An increase in the production of reactive oxygen species (ROS) is a typical event occurring during different stress conditions and activating conflicting responses in plants. In order to investigate the relevance of different timing and amounts of ROS production, tobacco (Nicotiana tabacum) Bright Yellow-2 (TBY-2) cells were incubated with different amounts of glucose plus glucose oxidase, for generating H(2)O(2) during time, or directly with known amounts of H(2)O(2). Data presented here indicate that, in TBY-2 cells, a difference in H(2)O(2) level is a critical point for shifting metabolic responses towards strengthening of antioxidant defences, or their depletion with consequent cell death. Timing of ROS production is also critical because it can determine programmed cell death (PCD) or necrosis. Depending on the different kinds of activated cell death, ascorbate (ASC) and glutathione (GSH) pools are altered differently. Moreover, an H(2)O(2)-dependent activation of nitric oxide synthesis is triggered only in the conditions inducing PCD. Ascorbate peroxidase (APX) has been analysed under different conditions of H(2)O(2) generation. Under a threshold value of H(2)O(2) overproduction, a transient increase in APX occurs, whereas under conditions inducing cell necrosis, the activity of APX decreases in proportion to cell death without any evident alteration in APX gene expression. Under conditions triggering PCD, the suppression of APX involves both gene expression and alteration of the kinetic characteristics of the enzyme. The changes in ASC, GSH and APX are involved in the signalling pathway leading to PCD, probably contributing to guaranteeing the cellular redox conditions required for successful PCD. 相似文献
97.
Alais D Morrone C Burr D 《Proceedings. Biological sciences / The Royal Society》2006,273(1592):1339-1345
Current models of attention, typically claim that vision and audition are limited by a common attentional resource which means that visual performance should be adversely affected by a concurrent auditory task and vice versa. Here, we test this implication by measuring auditory (pitch) and visual (contrast) thresholds in conjunction with cross-modal secondary tasks and find that no such interference occurs. Visual contrast discrimination thresholds were unaffected by a concurrent chord or pitch discrimination, and pitch-discrimination thresholds were virtually unaffected by a concurrent visual search or contrast discrimination task. However, if the dual tasks were presented within the same modality, thresholds were raised by a factor of between two (for visual discrimination) and four (for auditory discrimination). These results suggest that at least for low-level tasks such as discriminations of pitch and contrast, each sensory modality is under separate attentional control, rather than being limited by a supramodal attentional resource. This has implications for current theories of attention as well as for the use of multi-sensory media for efficient informational transmission. 相似文献
98.
Effects of storage temperature on viability, germination and antioxidant metabolism in Ginkgo biloba L. seeds. 总被引:1,自引:0,他引:1
Franca Tommasi Costantino Paciolla Maria Concetta de Pinto Laura De Gara 《Plant Physiology and Biochemistry》2006,44(5-6):359-368
The behaviour of the Ginkgo biloba L. seeds was studied during storage at 4 and 25 degrees C. When stored at 25 degrees C, all the seeds died in 6 months. Cold temperatures preserved seed tissue viability for 1 year but did not preserve their capability to germinate, since such capability decreased after 6 months. A significant increase in lipid peroxidation occurred in the seed both in the embryo and in the endosperm. During storage a progressive deterioration of the endosperm tissues was evident. The two major water soluble antioxidants, ascorbate (ASC) and glutathione (GSH), showed different behaviour in the two conditions of storage and in the two main structures of the seed, the embryo and the endosperm. The ASC content of embryos and endosperms remained quite unchanged in the first 9 months at 4 degrees C, then increased. At 25 degrees C a significant decrease in the ASC content in the embryos was evident, whereas it remained more stable in the endosperm. The GSH pool decreased at both storage temperatures in the embryos. As far as the ASC-GSH redox enzymes are concerned, their activities decreased with storage, but changes appeared to be time-dependent more than temperature-dependent, with the exception of the endosperm ascorbate free radical (AFR) reductase (EC 1.6.5.4), the activity of which rapidly decreased at 25 degrees C. Therefore overall the antioxidant enzymes were scarcely regulated and unable to counteract oxidative stress occurring during the long-term storage. 相似文献
99.
100.
Pavan S Schiavulli A Appiano M Marcotrigiano AR Cillo F Visser RG Bai Y Lotti C Ricciardi L 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2011,123(8):1425-1431
The powdery mildew disease affects several crop species and is also one of the major threats for pea (Pisum sativum L.) cultivation all over the world. The recessive gene er1, first described over 60 years ago, is well known in pea breeding, as it still maintains its efficiency as a powdery mildew
resistance source. Genetic and phytopathological features of er1 resistance are similar to those of barley, Arabidopsis, and tomato mlo powdery mildew resistance, which is caused by the loss of function of specific members of the MLO gene family. Here, we describe the obtainment of a novel er1 resistant line by experimental mutagenesis with the alkylating agent diethyl sulfate. This line was found to carry a single
nucleotide polymorphism in the PsMLO1 gene sequence, predicted to result in premature termination of translation and a non-functional protein. A cleaved amplified
polymorphic sequence (CAPS) marker was developed on the mutation site and shown to be fully co-segregating with resistance
in F2 individuals. Sequencing of PsMLO1 from three powdery mildew resistant cultivars also revealed the presence of loss-of-function mutations. Taken together, results
reported in this study strongly indicate the identity between er1 and mlo resistances and are expected to be of great breeding importance for the development of resistant cultivars via marker-assisted
selection. 相似文献