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131.
132.
133.
Leaf mass per unit area (LMA), carbon and nitrogen contents, leaf construction cost, and photosynthetic capacity (P
max) of Adiantum reniforme var. sinensis, an endangered fern endemic to the Three Gorges region in southwest China, were compared in five populations differing in
habitat such as soil moisture and irradiance. The low soil moisture and high irradiance habitat population exhibited significantly
higher LMA, area-based leaf construction (CCA), and carbon content (CA), but lower leaf nitrogen content per unit dry mass (NM) than the other habitat populations. The high soil moisture and low irradiance habitat populations had the lowest CCA, but their cost/benefic ratios of CCA/P
max were similar to the medium soil moisture and irradiance habitat population due to their lower leaf P
max. Hence A. reniforme var. sinensis prefers partially shaded, moist but well-drained, slope habitats. Due to human activities, however, its main habitats now
are cliffs or steeply sloped bare rocks with poor and thin soil. The relatively high energy requirements and low photosynthetic
capacity in these habitats could limit the capability of the species in extending population or interspecific competition
and hence increase its endangerment. 相似文献
134.
Redox-active iron mediates amyloid-beta toxicity 总被引:12,自引:0,他引:12
Rottkamp CA Raina AK Zhu X Gaier E Bush AI Atwood CS Chevion M Perry G Smith MA 《Free radical biology & medicine》2001,30(4):447-450
While amyloid-beta toxicity is mediated by oxidative stress and can be attenuated by antioxidants, the actual biochemical mechanism underlying neurotoxicity remains to be established. However, since aggregated amyloid-beta can interact with transition metals, such as iron, both in vitro and in vivo, we suspected that bound iron might be the mediator of toxicity such that holo- and apo-amyloid would have differential effects on cellular viability. Here we demonstrate that when amyloid-beta is pretreated with the iron chelator deferoxamine, neuronal toxicity is significantly attenuated while conversely, incubation of holo-amyloid-beta with excess free iron restores toxicity to original levels. These data, taken together with the known sequelae of amyloid-beta, suggest that the toxicity of amyloid-beta is mediated, at least in part, via redox-active iron that precipitates lipid peroxidation and cellular oxidative stress. 相似文献
135.
X. Pochon L. Garcia-Cuetos A. C. Baker E. Castella J. Pawlowski 《Coral reefs (Online)》2007,26(4):867-882
Recent molecular studies of symbiotic dinoflagellates (genus Symbiodinium) from a wide array of invertebrate hosts have revealed exceptional fine-scale symbiont diversity whose distribution among
hosts, regions and environments exhibits significant biogeographic, ecological and evolutionary patterns. Here, similar molecular
approaches using the internal transcribed spacer-2 (ITS-2) region were applied to investigate cryptic diversity in Symbiodinium inhabiting soritid foraminifera. Approximately 1,000 soritid specimens were collected and examined during a 12-month period
over a 40 m depth gradient from a single reef in Guam, Micronesia. Out of 61 ITS-2 types distinguished, 46 were novel. Most
types found are specific for soritid hosts, except for three types (C1, C15 and C19) that are common in metazoan hosts. The
distribution of these symbionts was compared with the phylotype of their foraminiferal hosts, based on soritid small subunit
ribosomal DNA sequences, and three new phylotypes of soritid hosts were identified based on these sequences. Phylogenetic
analyses of 645 host-symbiont pairings revealed that most Symbiodinium types associated specifically with a particular foraminiferal host genus or species, and that the genetic diversity of these
symbiont types was positively correlated with the genetic diversity found within each of the three host genera. Compared to
previous molecular studies of Symbiodinium from other locations worldwide, the diversity reported here is exceptional and suggests that Micronesian coral reefs are
home to a remarkably large Symbiodinium assemblage. 相似文献
136.
Zhao FP Jiang L Gao HJ Ding XD Zhang Q 《Animal : an international journal of animal bioscience》2009,3(8):1075-1084
Marker-assisted gene pyramiding provides a promising way to develop new animal breeds or lines, in which genes responsible for certain favorable characters identified in different breeds or lines are incorporated. In consideration of features of animal populations, we proposed five schemes for pyramiding three genes, denoted Scheme A-E, and five schemes for pyramiding four genes, denoted Scheme F-J. These schemes are representative of the possible alternatives. We also provided an algorithm to compute the population sizes needed in each generation. We compared these schemes with respect to the total population size and the number of generations required under different situations. The results show that there is no scheme that is optimal in all cases. Among the schemes for pyramiding three genes from three lines (L1, L2 and L3), Scheme D (a three-way cross between the three lines are first performed, followed by a backcross to L1 and a subsequent intercross to obtain the desired genotype) has a significant advantage over the other schemes when the recombination rate between adjacent genes ranges from 0.1 to 0.4, while Scheme A (a two-way cross between L1 and L2 and a subsequent intercross are performed, followed by a cross with L3 and a subsequent intercross to obtain the desired genotype) is optimal when recombination rate is 0.5. Among schemes for pyramiding four genes from four lines (L1, L2, L3 and L4), Scheme I (seperately, a two-way cross between L1 and L2 (L3 and L4) followed by a backcross to L1 (L3) and a subsequent intercross are performed, then the offspring from the two sides are crossed and followed by a backcross to L1 and a subsequent intercross to obtain the desired genotype) is optimal when the recombination rate ranges from 0.1 to 0.4, while Scheme F (cross and subsequent intercross between the four lines are performed successively) is the optimal when the recombination rate is 0.5. We also disscuss how the animals' reproductive capacity, the probabilities of obtaining the desired genotypes and genetic distance between adjacent genes would affect the design of an optimal scheme. 相似文献
137.
We investigated the role of the cell adhesion molecule NrCAM for axonal growth and pathfinding in the developing retina. Analysis of the distribution pattern of NrCAM in chick embryo retina sections and flat-mounts shows its presence during extension of retinal ganglion cell (RGC) axons; NrCAM is selectively present on RGC axons and is absent from the soma. Single cell cultures show an enrichment of NrCAM in the distal axon and growth cone. When offered as a substrate in addition to Laminin, NrCAM promotes RGC axon extension and the formation of growth cone protrusions. In substrate stripe assays, mimicking the NrCAM-displaying optic fibre layer and the Laminin-rich basal lamina, RGC axons preferentially grow on NrCAM lanes. The three-dimensional analysis of RGC growth cones in retina flat-mounts reveals that they are enlarged and form more protrusions extending away from the correct pathway under conditions of NrCAM-inhibition. Time-lapse analyses show that these growth cones pause longer to explore their environment, proceed for shorter time spans, and retract more often than under control conditions; in addition, they often deviate from the correct pathway towards the optic fissure. Inhibition of NrCAM in organ-cultured intact eyes causes RGC axons to misroute at the optic fissure; instead of diving into the optic nerve head, these axons cross onto the opposite side of the retina. Our results demonstrate a crucial role for NrCAM in the navigation of RGC axons in the developing retina towards the optic fissure, and also for pathfinding into the optic nerve. 相似文献
138.
The recent genome-wide association study identified a link between vitiligo and genetic variants in the ribonuclease T2 (RNASET2) gene; however, the functional roles of RNASET2 in vitiligo pathogenesis or in melanocyte apoptosis have yet to be determined. The current study was designed to investigate the vitiligo-related expression pattern of RNASET2 and its molecular function involving apoptosis-related signaling proteins and pathways. The results showed overexpression of RNASET2 in epidermis specimens from 40 vitiligo patients compared with that from matched healthy controls. In addition, in vitro analyses indicated that overexpression of RNASET2 was inducible in cultured primary human melanocytes and keratinocytes by stress conditions, that is, exposure to UV irradiation, hydrogen peroxide, and inflammatory factors, respectively, and led to increased cell apoptosis via the tumor necrosis factor receptor-associated factor 2 (TRAF2)–caspases pathway through the physical interaction of RNASET2 with TRAF2. Thus, RNASET2 may contribute to vitiligo pathogenesis by inhibiting TRAF2 expression and, as such, RNASET2 may represent a potential therapeutic target of vitiligo. 相似文献
139.
Summary. Protein histidine phosphorylation is now recognized as an important form of post-translational modification. The acid-lability
of phosphohistidine has meant that this phosphorylation has not been as well studied as serine/threonine or tyrosine phosphorylation.
We show that phosphohistidine and phosphohistidine-containing phosphopeptides derived from proteolytic digestion of phosphohistone
H4 are detectable by ESI-MS. We also demonstrate reverse-phase HPLC separation of these phosphopeptides and their detection
by MALDI-TOF-MS. 相似文献
140.
The shaved right hind feet of male rabbits weighing 2.5 to 3.0 kg were immersed in −25 °C alcohol to produce experimental severe frostbite. The changes in tissue temperature were recorded by a thermocouple probe inserted subcutaneously.In the first experiment the therapeutic effects of repeated immersion of frostbitten feet in 40 °C 0.1% chlorhexidine (CHX) were observed. The average survival area (ASA) in the untreated control group was 15.6% and in the CHX group, 69.4%. The difference between them is significant.In the second experiment the effects of rapid thawing in 40 °C water when the feet were frozen and the effects of CHX were compared; ASA of both groups (49.0 and 60.4%) was greater than that of the control group (18.6%), but there was no distinct difference between these therapeutic groups.Results of the third experiment demonstrated that repeated immersion in 40 °C water for 6 days was not only useless, but was also harmful (13.6%). At the same time, repeated immersion in 20 °C 0.1% CHX solution was useless as well. Only when the two factors (warmer temperature and CHX) were combined, i.e., repeated immersion in 40 °C rather than 20 °C 0.1% CHX solution were the effects obvious (58.4%).Experiment 4 investigated the relationship between the first immersion time and the therapeutic effects. Results showed that even with the first immersion at 72 hr after thawing, repeated immersion in 40 °C 0.1% CHX solution was still useful; the ASA (53.0%) was greater than that of the control group (17.6%).Experiment 5 concerned the relationship between therapeutic effects and continual days of immersions. The ASA values in control and 1-, 3-, and 6-day groups were 14.2, 36.6, 58.4, and 69.4%, respectively.In the final experiment, the effects of CHX-Cl and CHX-Ac were compared. The ASA values were 71.3 and 77.7%; there was no significant difference between them.All of the above experiments proved that repeated immersions in 40 °C 0.1% CHX solution is a useful therapeutic measure in treatment of severe experimental frostbite of rabbit feet. It is useful even when the first immersion is at 72 hr after thawing of the frozen limbs. 相似文献