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41.
Evergreen boreal plant species express high variability in their leaf traits. It remains controversial whether this within-species
variability is constrained to the same leaf trait relationships as has been observed across species. We sampled leaves of
three boreal evergreen woody species along a latitudinal gradient (from 57o56′N to 69o55′N). Leaf longevity (LL) of Pinus sylvestris L. and Vaccinium vitis-idaea L. correlated negatively with mean annual air temperature (MAT), whereas the LL of Ledum palustre L. was not affected by MAT. V. vitis-idaea and L. palustre had a negative relationship between leaf mass per area (LMA) and MAT. In P. sylvestris, the LMA–MAT relationship was positive. A negative correlation between LL and LMA was significant only for P. sylvestris. Leaf nitrogen concentration was positively related to leaf phosphorus concentration in all three species. Leaf potassium
concentration was related to nitrogen concentration only in L. palustre, and to phosphorus concentration in P. sylvestris and L. palustre. Our results demonstrate that although within the studied species the variation in some of the leaf traits may have the same
degree as interspecific variation, there is no such intercorrelation of leaf traits within the studied species as has been
observed across species. 相似文献
42.
The effect of insulin on phosphatidylcholine biosynthesis in cultured rat liver cells was assessed by measuring changes in the activity of the first enzyme in the choline pathway of phosphatidylcholine biosynthesis, choline kinase (ATP: cholinephosphortransferase, EC 2.7.1.32), in the presence or absence of the hormone. Choline kinase specific activity in liver cells incubated for 18 hours in the presence of 10?7M insulin increased two-fold from 3.4 ± 0.3 nmoles phosphorylcholine formed/min/mg protein to 7.5 ± 0.6 nmoles/min/mg protein. This effect was dose dependent and reversed by the addition of actinomycin D and cycloheximide. It is concluded that the increase in specific activity is due to synthesis of new enzyme rather than activation of existing enzyme. 相似文献
43.
Jianhua Zhang Mei Liu Hongjian Jin Liandong Deng Jinfeng Xing Anjie Dong 《AAPS PharmSciTech》2010,11(2):894-903
Lactate esters are widely used as food additives, perfume materials, medicine additives, and personal care products. The objective
of this work was to investigate the effect of a series of lactate esters as penetration enhancers on the in vitro skin permeation of four drugs with different physicochemical properties, including ibuprofen, salicylic acid, dexamethasone
and 5-fluorouracil. The saturated donor solutions of the evaluated drugs in propylene glycol were used in order to keep a
constant driving force with maximum thermodynamic activity. The permeability coefficient (K
p), skin concentration of drugs (SC), and lag time (T), as well as the enhancement ratios for K
p and SC were recorded. All results indicated that lactate esters can exert a significant influence on the transdermal delivery
of the model drugs and there is a structure-activity relationship between the tested lactate esters and their enhancement
effects. The results also suggested that the lactate esters with the chain length of fatty alcohol moieties of 10–12 are more
effective enhancers. Furthermore, the enhancement effect of lactate esters increases with a decrease of the drug lipophilicity,
which suggests that they may be more efficient at enhancing the penetration of hydrophilic drugs than lipophilic drugs. The
influence of the concentration of lactate esters was evaluated and the optimal concentration is in the range of 5∼10 wt.%.
In sum, lactate esters as a penetration enhancer for some drugs are of interest for transdermal administration when the safety
of penetration enhancers is a prime consideration. 相似文献
44.
Hugues Bersini 《Origins of life and evolution of the biosphere》2010,40(2):121-130
There is a long tradition of software simulations in theoretical biology to complement pure analytical mathematics which are
often limited to reproduce and understand the self-organization phenomena resulting from the non-linear and spatially grounded
interactions of the huge number of diverse biological objects. Since John Von Neumann and Alan Turing pioneering works on
self-replication and morphogenesis, proponents of artificial life have chosen to resolutely neglecting a lot of materialistic
and quantitative information deemed not indispensable and have focused on the rule-based mechanisms making life possible,
supposedly neutral with respect to their underlying material embodiment. Minimal life begins at the intersection of a series
of processes which need to be isolated, differentiated and duplicated as such in computers. Only software developments and
running make possible to understand the way these processes are intimately interconnected in order for life to appear at the
crossroad. In this paper, I will attempt to set out the history of life as the disciples of artificial life understand it,
by placing these different lessons on a temporal and causal axis, showing which one is indispensable to the appearance of
the next and how does it connect to the next. I will discuss the task of artificial life as setting up experimental software
platforms where these different lessons, whether taken in isolation or together, are tested, simulated, and, more systematically,
analyzed. I will sketch some of these existing software platforms: chemical reaction networks, Varela’s autopoietic cellular
automata, Ganti’s chemoton model, whose running delivers interesting take home messages to open-minded biologists. 相似文献
45.
Biogeographical analyses are applied to skipper (Hesperioidea) presence/absence data from the Western Mediterranean mainland
and the three largest islands (Sardinia, Corsica and Sicily) in order to identify potential conservation issues. The analyses
performed on species, both collectively and individually, indicate that regional species richness and occurrence in the Mediterranean
zone are largely predicted by latitude and area but that islands have impoverished faunas. Several species, predicted to be
present on these islands from logistic regression of their continental distributions, are actually absent. The number of species
predicted to be present from logistic regression analyses for each island, closely matched the number of species predicted
to occur in regional-focused multiple regression analysis. This suggests that missing species have been identified. When compared
with species that occur in Sicily and Corsica, the missing species are shown to differ for ecological traits, mainly those
linked to altitudinal tolerance. No ecological distinctions were disclosed for Sardinian skippers suggesting a mainly stochastic
colonisation. These results, and those from an analogous study carried out on Papilionoidea, point to Hesperioidea having
(i) overall more impoverished faunas on islands and (ii) being subject to stochastic or historical colonisation events more
than Papilionoidea. Species not predicted to occur on islands based on their mainland distributions and ecological traits,
are foci for conservation attention. However, as many species becoming extinct on the islands may be irreplaceable, all species,
in particular the Sardinian ones, deserve to be conserved. 相似文献
46.
47.
Hiroyuki Kozu Isao Kobayashi Mitsutoshi Nakajima Kunihiko Uemura Seigo Sato Sosaku Ichikawa 《Food biophysics》2010,5(4):330-336
This paper uses computational fluid dynamics to simulate and analyze intragastric fluid motions induced by human peristalsis.
We created a two-dimensional computational domain of the distal stomach where peristalsis occurs. The motion of the gastric
walls induced by an antral contraction wave (ACW) on the wall of the computational domain was well simulated using a function
defined in this study. Retropulsive flow caused by ACW was observed near the occluded region, reaching its highest velocity
of approximately 12 mm/s in the narrowest region. The viscosity of the model gastric contents applied in this study hardly
affected the highest velocity, but greatly affected the velocity profile in the computational domain. The shear rate due to
gastric fluid motion was calculated using the numerical output data. The shear rate reached relatively high values of approximately
20 s−1 in the most occluded region. The shear rate profile was almost independent of the fluid viscosity. We also simulated mass
transfer of a gastric digestive enzyme (pepsin) in model gastric content when peristalsis occurs on the gastric walls. The
visualized simulation results suggest that gastric peristalsis is capable of efficiently mixing pepsin secreted from the gastric
walls with an intragastric fluid. 相似文献
48.
Patrizia Vaccino Heinz-Albert Becker Andrea Brandolini Francesco Salamini Benjamin Kilian 《Molecular genetics and genomics : MGG》2009,281(3):289-300
The celiac disease (CD) is an inflammatory condition characterized by injury to the lining of the small-intestine on exposure
to the gluten of wheat, barley and rye. The involvement of gluten in the CD syndrome has been studied in detail in bread wheat,
where a set of “toxic” and “immunogenic” peptides has been defined. For wheat diploid species, information on CD epitopes
is poor. In the present paper, we have adopted a genomic approach in order to understand the potential CD danger represented
by storage proteins in diploid wheat and sequenced a sufficiently large number of cDNA clones related to storage protein genes
of Triticum monococcum. Four bona fide toxic peptides and 13 immunogenic peptides were found. All the classes of storage proteins were shown to contain harmful
sequences. The major conclusion is that einkorn has the full potential to induce the CD syndrome, as already evident for polyploid
wheats. In addition, a complete overview of the storage protein gene arsenal in T. monococcum is provided, including a full-length HMW x-type sequence and two partial HMW y-type sequences.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
49.
Wojciech Leszczyński Krzysztof Ślosarek Marta Szlag 《Reports of Practical Oncology and Radiotherapy》2012,17(6):347-351
AimThe aim was to provide a dosimetric comparison between IMRT and RapidArc treatment plans with RPI index with simultaneous comparison of the treatment delivery time.BackgroundIMRT and RapidArc provide highly conformal dose distribution with good sparing of normal tissues. However, a complex spatial dosimetry of IMRT and RapidArc plans hampers the evaluation and comparison between plans calculated for the two modalities. RPI was used in this paper for treatment plan comparisons. The duration of the therapeutic session in RapidArc is reported to be shorter in comparison to therapeutic time of the other dynamic techniques. For this reasons, total treatment delivery time in both techniques was compared and discussed.Materials and methods15 patients with prostate carcinoma were randomly selected for the analysis. Two competitive treatment plans using respectively the IMRT and RapidArc techniques were computed for each patient in Eclipse planning system v. 8.6.15. RPIwin® application was used for RPI calculations for each treatment plan.Additionally, total treatment time was compared between IMRT and RapidArc plans. Total treatment time was a sum of monitor units (MU) for each treated field.ResultsThe mean values of the RPI indices were insignificantly higher for IMRT plans in comparison to rotational therapy. Comparison of the mean numbers of monitor units confirmed that the use of rotational technique instead of conventional static field IMRT can significantly reduce the treatment time.ConclusionAnalysis presented in this paper, demonstrated that RapidArc can compete with the IMRT technique in the field of treatment plan dosimetry reducing the time required for dose delivery. 相似文献
50.