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171.
Today’s scientific interest in tissue engineering for organ transplantations and regeneration from stem cells, allied with recent observations on biostimulation of tissues and cells by laser radiation, stands as a strong motivation for the present work, in which we examine the effects of the low power laser radiation onto planarians under regenerative process. To investigate those effects, a number of 60 amputated worms were divided in three study groups: a control group and two other groups submitted to daily 1 and 3 min long laser treatment sections at 910 W/m2 power density. A 685 nm diode laser with 35 mW optical power was used. Samples were sent to histological analysis at the 4th, the 7th and the 15th days after amputation. A remarkable increase in stem cells counts for the fourth day of regeneration was observed when the regenerating worms was stimulated by the laser radiation. Our findings encourage further research works on the influence of optical radiation onto stem cells and tissue regeneration.  相似文献   
172.
A validated method was developed for determination of diclofenac sodium, considered a model hydrophilic drug for in vitro permeation studies, in Eagle's Minimum Essential Medium (MEM) with Earle's balanced salt solution. Liquid chromatography was used to determine diclofenac sodium. This method was developed with a reversed-phase column Supercosil LC 18, DB 25 cm x 4.5 mm; the mobile phase was methanol with 3% (v/v) acetic acid-Milli-Q water (74 + 26), and detection was at 283 nm. The detection and quantitation limits were 2.41 x 10(-8) and 3.31 x 10(-5) microg/microL, respectively. The accuracy within-day (n = 3) and day-to-day (n = 7) was 98.83%; the mean variation coefficient for inter- (n = 7) and intraday precision (n = 3) was 12.20%, thus, not exceeding 15%. This method can be used as an analytical procedure for the determination of diclofenac sodium in MEM for in vitro permeation studies.  相似文献   
173.
A theory of globally convergent trust-region methods for self-consistent field electronic structure calculations that use the density matrices as variables is developed. The optimization is performed by means of sequential global minimizations of a quadratic model of the true energy. The global minimization of this quadratic model, subject to the idempotency of the density matrix and the rank constraint, coincides with the fixed-point iteration. We prove that the global minimization of this quadratic model subject to the restrictions and smaller trust regions corresponds to the solution of level-shifted equations. The precise implementation of algorithms leading to global convergence is stated and a proof of global convergence is provided. Numerical experiments confirm theoretical predictions and practical convergence is obtained for difficult cases, even if their geometries are highly distorted. The reduction of the trust region is performed by a strategy that uses the structure of the energy function providing the algorithm with a nice practical behavior. This framework may be applied to any problem with idempotency constraints and for which the derivative of the objective function is a symmetric matrix. Therefore, application to calculations based both on Hartree–Fock or Kohn–Sham density functional theory are straightforward.  相似文献   
174.
A lattice model is used to study mutations and compacting effects on protein folding rates and folding temperature. In the context of protein evolution, we address the question regarding the best scenario for a polypeptide chain to fold: either a fast nonspecific collapse followed by a slow rearrangement to form the native structure or a specific collapse from the unfolded state with the simultaneous formation of the native state. This question is investigated for optimized sequences, whose native state has no frustrated contacts between monomers, and also for mutated sequences, whose native state has some degree of frustration. It is found that the best scenario for folding may depend on the amount of frustration of the native structure. The implication of this result on protein evolution is discussed.  相似文献   
175.
The compounds 1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl)methyl nitrate (C1), (1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl)ethyl nitrate (C2), 3-(1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl)benzyl nitrate (C3), 4-(1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl)-N-hydroxy-benzenesulfonamide (C4), 4-(1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl)benzyl nitrate (C5), and 2-[4-(1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl)phenyl]ethyl nitrate (C6) were evaluated with a micronucleus test using mouse peripheral blood to identify new candidate drugs for the treatment of sickle cell disease (SCD) that are safer than hydroxyurea. The compounds induced an average frequency of micronucleated reticulocytes (MNRET) of less than six per 1,000 cells at 12.5, 25, 50, and 100 mg/kg, whereas hydroxyurea induced an average MNRET frequency of 7.8, 9.8, 15, and 33.7 per 1000 cells respectively, at the same concentrations. Compounds C1-C6 are new non-genotoxic in vivo candidate drugs for the treatment of SCD symptoms.  相似文献   
176.
Unusually structure-selective growth of single-walled carbon nanotubes (SWNTs) has been attained using a CVD method with a solid supported catalyst. In this method, CO feedstock disproportionates on silica-supported catalytic nanoclusters of Co that are formed in situ from mixed salts of Co and Mo. The nanotube products are analyzed by spectrofluorimetry to reveal distributions resolved at the level of individual (n,m) structures. Two structures, (6,5) and (7,5), together dominate the semiconducting nanotube distribution and comprise more than one-half of that population. The average diameter of produced SWNTs is only 0.81 nm, and a strong propensity is found favoring chiral angles near the armchair limit.  相似文献   
177.
Abstract— In 1, 1, 2-trichlorotrifluoroethane solution biliverdin physically quenches singlet oxygen at a rate of 8 × l0sM-1s-1 and reacts chemically at 6 × 10 5M-1s-1 to give a red product. In D, O solution the rate constants are PD dependent and range from 1.5–6 times 1010M-1s-1 for quenching and the chemical rate varies from 3–5 × 108 M-1 s-1 to give colorless products.  相似文献   
178.
The aliphatic heterocycles piperidine and morpholine are core structures of well-known antifungals such as fenpropidin and fenpropimorph, commonly used as agrofungicides, and the related morpholine amorolfine is approved for the treatment of dermal mycoses in humans. Inspired by these lead structures, we describe here the synthesis and biological evaluation of 4-aminopiperidines as a novel chemotype of antifungals with remarkable antifungal activity. A library of more than 30 4-aminopiperidines was synthesized, starting from N-substituted 4-piperidone derivatives by reductive amination with appropriate amines using sodium triacetoxyborohydride. Antifungal activity was determined on the model strain Yarrowia lipolytica, and some compounds showed interesting growth-inhibiting activity. These compounds were tested on 20 clinically relevant fungal isolates (Aspergillus spp., Candida spp., Mucormycetes) by standardized microbroth dilution assays. Two of the six compounds, 1-benzyl-N-dodecylpiperidin-4-amine and N-dodecyl-1-phenethylpiperidin-4-amine, were identified as promising candidates for further development based on their in vitro antifungal activity against Candida spp. and Aspergillus spp. Antifungal activity was determined for 18 Aspergillus spp. and 19 Candida spp., and their impact on ergosterol and cholesterol biosynthesis was determined. Toxicity was determined on HL-60, HUVEC, and MCF10A cells, and in the alternative in vivo model Galleria mellonella. Analysis of sterol patterns after incubation gave valuable insights into the putative molecular mechanism of action, indicating inhibition of the enzymes sterol C14-reductase and sterol C8-isomerase in fungal ergosterol biosynthesis.  相似文献   
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