To evaluate and compare the effect of raw and processed pyritum on tibial defect healing, 32 male Sprague Dawley rats were randomly divided into four groups. After tibial defect, animals were produced and grouped: sham and control group were orally administrated with distilled water (1 mL/100 g), while treatment groups were given aqueous extracts of raw and processed pyritum (1.5 g/kg) for successive 42 days. Radiographic examination showed that bone defect healing effect of the treatment groups was obviously superior compared to that of the control group. Bone mineral density of whole tibia was increased significantly after treating with pyritum. Inductively coupled plasma-optical emission spectrometry showed that the contents of Ca, P, and Mg in callus significantly increased in the treatment groups comparing with the control. Moreover, serological analysis showed that the concentration of serum phosphorus of the treatment groups significantly increased compared with that of the control group. By in vitro study, we have evaluated the effects of drug-containing serum of raw and processed pyritum on osteoblasts. It was manifested that both the drug-containing sera of raw and processed pyritum significantly increased the mRNA levels of alkaline phosphatase and collagen type I. Protein levels of phosphorylated Smad2/3 also increased. The mRNA levels of osteocalcin and transforming growth factor β (TGF-β) type I and II receptors, as well as the protein levels of TGF-β1 in the processed groups, were higher than those in the control. In summary, both raw and processed pyritum-containing sera exhibited positive effects on osteoblasts, which maybe via the TGF-β1/Smad signaling pathway. Notably, the tibia defect healing effect of pyritum was significantly enhanced after processing. 相似文献
A continuum hypothesis-based model is developed for the simulation of the (long term) contraction of skin grafts that cover excised burns in order to obtain suggestions regarding the ideal length of splinting therapy and when to start with this therapy such that the therapy is effective optimally. Tissue is modeled as an isotropic, heterogeneous, morphoelastic solid. With respect to the constituents of the tissue, we selected the following constituents as primary model components: fibroblasts, myofibroblasts, collagen molecules, and a generic signaling molecule. Good agreement is demonstrated with respect to the evolution over time of the surface area of unmeshed skin grafts that cover excised burns between outcomes of computer simulations obtained in this study and scar assessment data gathered previously in a clinical study. Based on the simulation results, we suggest that the optimal point in time to start with splinting therapy is directly after placement of the skin graft on its recipient bed. Furthermore, we suggest that it is desirable to continue with splinting therapy until the concentration of the signaling molecules in the grafted area has become negligible such that the formation of contractures can be prevented. We conclude this study with a presentation of some alternative ideas on how to diminish the degree of contracture formation that are not based on a mechanical intervention, and a discussion about how the presented model can be adjusted. 相似文献
Long-term assessments of species assemblages are valuable tools for detecting species ecological preferences and their dispersal
tracks, as well as for assessing the possible effects of alien species on native communities. Here we report a 50-year-long
study on population dynamics of the four species of land flatworms (Platyhelminthes, Tricladida, Terricola) that have colonized
or become extinct in a 70-year-old Atlantic Forest regrowth remnant through the period 1955–2006. On the one hand, the two
initially most abundant species, which are native to the study site, Notogynaphalliaernesti and Geoplana multicolor have declined over decades and at present do not exist in the forest remnant. The extinction of these species is most likely
related with their preference for open vegetation areas, which presently do not exist in the forest remnant. On the other
hand, the neotropical Geoplaninae 1 and the exotic Endeavouria septemlineata were detected in the forest only very recently. The long-term study allowed us to conclude that Geoplaninae 1 was introduced
into the study area, although it is only known from the study site. Endeavouria septemlineata, an active predator of the exotic giant African snail, is originally known from Hawaii. This land flatworm species was observed
repeatedly in Brazilian anthropogenic areas, and this is the first report of the species in relatively well preserved native
forest, which may be evidence of an ongoing adaptive process. Monitoring of its geographic spread and its ecological role
would be a good practice for preventing potential damaging effects, since it also feeds on native mollusk fauna, as we observed
in lab conditions.
Júlio Pedroni: Granted by CNPQ–Brazil. 相似文献
Some P-450 systems, notably aromatase and 14-demethylase catalyse not only the hydroxylate reaction but also the oxidation of an alcohol into a carbonyl compound as well as a C---C bond cleavage process. All these reactions occur at the same active site. A somewhat analogous situation is noted with 17-hydroxylase-17,20-lyase that participates in hydroxylation as well as C---C bond cleavage process. The C---C bond cleavage reactions catalysed by the above enzymes conform to the general equation:
It is argued that all three types of reaction catalyzed by these enzymes may be viewed as variations on a common theme. In P-450 dependent hydroxylation the initially formed FeIII---O---O. species is converted into FeIII---O---OH and the heterolysis of the oxygen—oxygen bond of the latter then gives the oxo-derivative for which a number of canonical structures are possible; for example FeV = O ↔ (+.)FeIV = O ↔ FeIV---O.. One of these, FeIV---O. behaves like an alkoxyl radical and participates in hydrogen abstraction from C---H bond to produce FeIV---OH and carbon radical. The latter is then quenched by the delivery of hydroxyl radical from FeIV---OH. The latter species may thus be regarded as a carrier of hydroxyl radical. We have proposed that the C---C bond cleavage reaction occurs through the participation of the FeIII---O---OH species that is trapped by the electrophilic property of the carbonyl compound giving a peroxide adduct that fragments to produce an acyl—carbon cleavage. Scientific developments leading up to this conclusion are considered. In the first author's views,
“The study of mechanisms is not a scientific but a cultural activity. Mechanisms do not aim at an absolute truth but are intended to be a “running” commentary on the status of knowledge in a field. As the structural knowledge in a field advances Mechanisms evolve to take note of the new findings. Just as a constructive “running” commentary provides the stimulus for higher standards of performance, so Mechanisms call for better and firmer structural information from their practitioners”. 相似文献
Human ornithine δ-aminotransferase (hOAT) (EC 2.6.1.13) is a mitochondrial pyridoxal 5′-phosphate (PLP)-dependent aminotransferase whose deficit is associated with gyrate atrophy, a rare autosomal recessive disorder causing progressive blindness and chorioretinal degeneration. Here, both the apo- and holo-form of recombinant hOAT were characterized by means of spectroscopic, kinetic, chromatographic and computational techniques. The results indicate that apo and holo-hOAT (a) show a similar tertiary structure, even if apo displays a more pronounced exposure of hydrophobic patches, (b) exhibit a tetrameric structure with a tetramer-dimer equilibrium dissociation constant about fivefold higher for the apoform with respect to the holoform, and (c) have apparent Tm values of 46 and 67?°C, respectively. Moreover, unlike holo-hOAT, apo-hOAT is prone to unfolding and aggregation under physiological conditions. We also identified Arg217 as an important hot-spot at the dimer–dimer interface of hOAT and demonstrated that the artificial dimeric variant R217A exhibits spectroscopic properties, Tm values and catalytic features similar to those of the tetrameric species. This finding indicates that the catalytic unit of hOAT is the dimer. However, under physiological conditions the apo-tetramer is slightly less prone to unfolding and aggregation than the apo-dimer. The possible implications of the data for the intracellular stability and regulation of hOAT are discussed. 相似文献
It is widely believed that environmental variability is the main cause for fluctuations in commercially exploited small pelagic
fish populations around the world. Nevertheless, density-dependent factors also can drive population dynamics. In this paper,
we analyzed thirteen years of a relative abundance index of two clupeoids fish populations coexisting in the central-south
area off Chile, namely the common sardine, Strangomera bentincki, and anchovy, Engraulis ringens. We applied the classical diagnostic tools of time series analysis to the observed time-series. Also, the realized per capita
population growth rate was studied with the aim of detecting the feedback structure that is characterizing the population
dynamics of the two species. The analysis suggests that population fluctuations of the two species have an important density-dependent
component, displaying first-order (direct density-dependent) and second-order (delayed density-dependent) simultaneously.
The density-dependent component explained 70.5 and 55.6 % of the realized per capita population growth rate of common sardine
and anchovy, respectively. The deterministic skeleton model showed an asymptotic convergence to equilibrium density. In presence
of a stochastic environment, fluctuations were reproduced for the species showing a component of fluctuation with a period
of 4 year. The intrinsic dynamics of each species is typical of interacting species resulting from trophic interactions. It
is postulated that the second-order dynamics of S. bentincki and E. ringens in central-south Chile, may be the result from interactions with a specialist predator (the fishing fleet), interacting with
exogenous environmental factors. 相似文献
Having been investigated for over 40 years, some aspects of the biology of terrestrial gastropod’s olfactory system have been challenging and highly contentious, while others still remain unresolved. For example, a number of terrestrial gastropod species can track the odor of food, while others have no strong preferences toward food odor; rather they find it by random encounter. Here, while assessing the most recent findings and comparing them with earlier studies, the aspects of the food selection based on olfactory cues are examined critically to highlight the speculations and controversies that have arisen. We analyzed and compared the potential role of airborne odors in the feeding behavior of several terrestrial gastropod species. The available results indicate that in the foraging of most of the terrestrial gastropod species odor cues contribute substantially to food finding and selection. The results also suggest, however, that what they will actually consume largely depends on where they live and the species of gastropod that they are. Due to the voluminous literature relevant to this object, this review is not intended to be exhaustive. Instead, I selected what I consider to be the most important or critical in studies regarding the role of the olfaction in feeding of terrestrial gastropods. 相似文献