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61.
62.
Seyed Sajad Mohseni Salehi Monfared Shirin Pournourmohammadi 《Biological trace element research》2010,133(2):236-241
Islet transplantation has become a promising treatment in the therapy of type 1 diabetes. Its function improvement, after
isolation and before transplantation, is crucial because of their loss both in number and function of islets after isolation
procedures. Trace elements sodium orthovanadate (SOV) and sodium molybdate (SM), as well as medicinal plant Teucrium polium L. (TP), showed and possessed high beneficial antioxidative potential and even hypoglycemic properties via their effect on
islets. We evaluated the effect of these components in combination on cultured islet function in order to improve pancreatic
islet transplantation. Rat pancreatic islets were cultured for 24 h then incubated with different concentrations of TP (0.01
and 0.1 mg/mL) alone and in combination with SOV (1 mM) or SM (1 mM). Insulin concentration in buffer media was measured as
islet secretory function. Administration of TP (0.01 mg/mL), SM, and SOV alone or in combination with each other significantly
increased insulin secretion at high glucose concentration (16.7 mM); insulin secretion was significantly greater in the group
containing both TP and SM than other treated groups (p < 0.05). The combination of the mentioned trace elements especially molybdate with TP could improve islet cells function before
transplantation. 相似文献
63.
Although it has been known for nearly a century that strains of Trypanosoma cruzi, the etiological agent for Chagas'' disease, are enzootic in the southern U.S., much remains unknown about the dynamics of its transmission in the sylvatic cycles that maintain it, including the relative importance of different transmission routes. Mathematical models can fill in gaps where field and lab data are difficult to collect, but they need as inputs the values of certain key demographic and epidemiological quantities which parametrize the models. In particular, they determine whether saturation occurs in the contact processes that communicate the infection between the two populations. Concentrating on raccoons, opossums, and woodrats as hosts in Texas and the southeastern U.S., and the vectors Triatoma sanguisuga and Triatoma gerstaeckeri, we use an exhaustive literature review to derive estimates for fundamental parameters, and use simple mathematical models to illustrate a method for estimating infection rates indirectly based on prevalence data. Results are used to draw conclusions about saturation and which population density drives each of the two contact-based infection processes (stercorarian/bloodborne and oral). Analysis suggests that the vector feeding process associated with stercorarian transmission to hosts and bloodborne transmission to vectors is limited by the population density of vectors when dealing with woodrats, but by that of hosts when dealing with raccoons and opossums, while the predation of hosts on vectors which drives oral transmission to hosts is limited by the population density of hosts. Confidence in these conclusions is limited by a severe paucity of data underlying associated parameter estimates, but the approaches developed here can also be applied to the study of other vector-borne infections. 相似文献
64.
The Wageningen Delivery of Functionality symposium covered all aspects involved with food structural design to arrive at high-quality
foods which meet demanding customer expectations and regulatory requirements. The symposium integrated aspects from the structural
organization of foods at molecular and supramolecular scales to dedicated techniques required to describe and visualize such
structures, the gastro-intestinal events and how to model these in a laboratory setting, and finally the impact those food
structures and ingredients have on the consumer’s physiology and on the human perception. As an interdisciplinary platform,
bringing together more than 160 researchers from academia and industry, the symposium meanwhile fulfills an important role
in the food science community. 相似文献
65.
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
66.
Christopher N. Anderson Gregory F. Grether 《Proceedings. Biological sciences / The Royal Society》2010,277(1700):3669-3675
Aggression between species is a seldom-considered but potentially widespread mechanism of character displacement in secondary sexual characters. Based on previous research showing that similarity in wing coloration directly influences interspecific territorial aggression in Hetaerina damselflies, we predicted that wing coloration would show a pattern of character displacement (divergence in sympatry). A geographical survey of four Hetaerina damselfly species in Mexico and Texas showed evidence for character displacement in both species pairs that regularly occurs sympatrically. Hetaerina titia, a species that typically has large black wing spots and small red wing spots, shifted to having even larger black spots and smaller red wing spots at sites where a congener with large red wing spots is numerically dominant (Hetaerina americana or Hetaerina occisa). Hetaerina americana showed the reverse pattern, shifting towards larger red wing spots where H. titia is numerically dominant. This pattern is consistent with the process of agonistic character displacement, but the ontogenetic basis of the shift remains to be demonstrated. 相似文献
67.
Elisabeth Hansson Ingemar Jacobson Richard Venema Åke Sellström 《Journal of neurochemistry》1980,34(3):569-573
Abstract: The lipophilic cation [3 H]triphenylrnethylphosphonium bromide ([3 H]TPMP+ ) was investigated as a measure of the membrane potential of synaptosomes. Conditions under which [3 H]TPMP+ achieved an equilibrium distribution were tested. The toxicity of TPMP has been studied relative to its inhibitory effects on [3 H]y-aminobutyric acid ([3 H]GABA) transport. In some experiments the distribution of 86 RbZ+ and [3 H]TPMP+ was changed upon incubation in the presence of elevated levels of K+ , ouabain, or KCN, or at 0°C in a way that would be expected from the membrane potential. In normal incubation conditions a membrane potential of ∼−60 mv was calculated. 相似文献
68.
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
69.
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
70.
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