In Vivo Biological Behavior of Polymer Scaffolds of Natural Origin in the Bone Repair Process

Autologous bone grafts, used mainly in extensive bone loss, are considered the gold standard treatment in regenerative medicine, but still have limitations mainly in relation to the amount of bone available, donor area, morbidity and creation of additional surgical area. This fact encourages tissue engineering in relation to the need to develop new biomaterials, from sources other than the individual himself. Therefore, the present study aimed to investigate the effects of an elastin and collagen matrix on the bone repair process in critical size defects in rat calvaria. The animals (Wistar rats, n = 30) were submitted to a surgical procedure to create the bone defect and were divided into three groups: Control Group (CG, n = 10), defects filled with blood clot; E24/37 Group (E24/37, n = 10), defects filled with bovine elastin matrix hydrolyzed for 24 h at 37 °C and C24/25 Group (C24/25, n = 10), defects filled with porcine collagen matrix hydrolyzed for 24 h at 25 °C. Macroscopic and radiographic analyses demonstrated the absence of inflammatory signs and infection. Microtomographical 2D and 3D images showed centripetal bone growth and restricted margins of the bone defect. Histologically, the images confirmed the pattern of bone deposition at the margins of the remaining bone and without complete closure by bone tissue. In the morphometric analysis, the groups E24/37 and C24/25 (13.68 ± 1.44; 53.20 ± 4.47, respectively) showed statistically significant differences in relation to the CG (5.86 ± 2.87). It was concluded that the matrices used as scaffolds are biocompatible and increase the formation of new bone in a critical size defect, with greater formation in the polymer derived from the intestinal serous layer of porcine origin (C24/25).     

Fluoride effect on the palladium–phenanthroline catalyzed carbonylation of nitroarenes to carbamates

Fluorides promote the palladium–phenanthroline catalyzed carbonylation of nitroarenes to carbamates. The effect is more evident on the rate of the reaction at short reaction times, but a positive effect on selectivity is also observed under certain conditions. The effect is observed even under conditions under which chloride inhibits the reaction. Tetraethylammonium is a better countercation than sodium. Copyright © 2007 John Wiley & Sons, Ltd.     

PHEMA hydrogels obtained by a novel low-heat curing procedure with a potential for in situ preparation

In this work, we report on poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogels obtained by a low heat curing reaction. These materials are suitable for in situ preparation and therefore endowed with a potential for several biomedical applications. The novel procedure adopted involves as the first step the synthesis of a soluble oligomeric PHEMA precursor containing polymerizable functions as side substituents. As the second step, the precursor is dissolved in equal amounts of 2-hydroxyethyl methacrylate (HEMA) and water, to form a viscous but still injectable syrup. A low temperature water soluble initiator is then added. The curing reaction starts promptly and is completed within few minutes. During the entire process the internal temperature never rises above 40 degrees C. Preliminary mechanical characterizations performed on the hydrogels in their water-swollen state and diffusion tests in absorption/desorption experiments clearly indicated that on all respects the novel hydrogels are comparable with conventional PHEMA hydrogels obtained according to literature from HEMA in the presence of divinyl crosslinkers. However, the much shorter curing time combined with the far lower curing temperature endow the new hydrogels with a higher potential in view of specific surgical requirements, and particularly for in situ preparation.     

Solid-state equilibrium relations in the Ternary Systems TeO2?MoO3?MoO2 and TeO2?MoO3?Te

In a study of the solid-state reactions in the ternary systems TeO₂? MoO₃? MoO₂ and TeO₂? MoO₃? Te, approximately 70 selected compositions were sintered at 550°C to attain equilibrium conditions, and solid-state equilibrium relations were characterized by x-ray diffraction. In a large composition range, the interaction of TeO₂ and MoO₃ with the reducing agents MoO₂ or Te leads to the reduced ternary oxide TeMo₄O₁₃ (m. p. 748°C), in addition to Te₂MoO₇, Te and (intermediate) molybdenum oxides. The compatibility relations for the binary systems TeO₂? MoO₂ and MoO₃? Te are presented for the first time. In the TeO₂? MoO₂ system, three-phase regions are found: (Te₂MoO₇? TeO₂? Te) on the TeO₂? and (TeMo₄O₁₃? MoO₂? Te) on the MoO₂-rich sides with (TeMo₄O₁₃? Te₂MoO₇? Te) in the intermediate region. In the MoO₃? Te system, three-phase regions (TeMo₄O₁₃? MoO₂? Te), (TeMo₄O₁₃? Mo₄O₁₁? MoO₂) and (TeMo₄O₁₃? MoO₃? Mo₄O₁₁) were detected. TeMo₄O₁₃ presents two allotropic forms (α′ for T < 450°C, α for T > 450°C). Both structures have been characterized by I.R. and optical reflectance spectroscopy. Unit cell dimensions are also given.     

Gas chromatographic--mass spectrometric determination of phenylacetic acid in human blood

Phenyl acetic acid, a metabolite of 2-phenyl ethylamine, acts as a neuromodulator in the nigrostriatal dopaminergic pathway stimulating the release of dopamine. The evaluation of phenyl acetic acid concentration in the biological fluid reflects phenyl ethylamine levels thus allowing the assessment of the modulatory role of this endogenous substance. Changes in biological fluids levels of 2-phenylethylamine and/or in its metabolite have been reported in affective disorders, such as depression and schizophrenia. Recently, the occurrence of the "attention deficit hyperactivity syndrome" has been frequently reported in childhood population and involvement of dopaminergic dysfunction in this disease has been suspected. A fast, reliable and reproducible method for the determination of phenyl acetic acid in human blood, is therefore needed in order to have a screening tool for monitoring both healthy childhood population and suspected "attention deficit hyperactivity syndrome" patients. The gas chromatographic-mass spectrometric method here described makes use of a deuterated internal standard in order to overcome problems related to the lack of reproducibility often encountered when a derivatization step is performed.     

The Binary Oxide System TeO2?MoO3

Phase analysis of the mixed oxide system TeO₂? MoO₃ by means of x-ray diffraction and optical microscopy indicates the formation of a new phase, α-Te₂MoO₇, stable at room temperature. Below 500°C mixtures of crystalline products are obtained or complete devitrification can easily be induced in the system TeO₂? MoO₃. Above this temperature, tendency to glass formation is observed under the conditions employed, due to the liquidus temperature effect. Quenching of a melt of Te₂MoO₇ yields a dark yellow glass, α-Te₂MoO₇. X-ray and density measurements were used to explore the range of stoichiometry and exclude formation of solid solutions in the system; no apparent relationship exists between the crystal structures of the component oxides and the binary compound.     

Solvent effects on the O-neophyl rearrangement of 1,1-diarylalkoxyl radicals. A laser flash photolysis study

[reaction: see text] A laser flash photolysis study has been carried out to assess solvent effects on the O-neophyl rearrangement of 1,1-diarylalkoxyl radicals. The rearrangement rate constant k decreases by increasing solvent polarity and an excellent correlation with negative slope is obtained between log k and the solvent polarity parameter E(T)N. These evidences are in full agreement with the previous indication that the extent of internal charge separation decreases on going from the starting 1,1-diarylalkoxyl radical to the transition state.     

Acyclic stereoselection in the reaction of nucleophilic reagents with chiral N-acyliminium ions generated from N-

Optically active N-[1-(phenylsulfonyl)alkyl]imidazolidin-2-ones react at low temperature in the presence of tin tetrachloride to give acyclic N-acyliminium ions. These electrophilic substrates give addition products upon reaction with pi-nucleophiles. Allyltrimethylsilane affords the corresponding allylated products in good yields and high diastereoselectivity. The stereochemical outcome of this process can be rationalized by taking into account the preference of the intermediate N-acyliminium ion for an E configuration that favors the attack of the nucleophile from the si-si face. Disappointing results are obtained using silyl ketene acetals; conversely trimethylsilyl enol ether of acetophenone gives the corresponding adducts in high diastereoselectivity. The utilization of trimethylsilyl enol ether of 2-acetylfuran is particularly interesting since the corresponding adducts are obtained with good diastereoselectivity and the furan ring could be amenable of further synthetic transformations.     

CH...O and CH...F links form the cage structure of dioxane-trifluoromethane

The molecular beam Fourier transform microwave spectrum of 1,4-dioxane-trifluoromethane has been assigned and measured. The two subunits form a cage stabilized by one C-H...O and two C-H...F weak hydrogen bonds. The C-H...O link involves the axial lone pair of one of the two equivalent ring oxygens, while the two C-H...F bridges connect trifluoromethane to the two axial hydrogens in positions 3 and 5. The dissociation energy has been estimated from the D(J) centrifugal distortion parameter to be approximately 6.8 kJ/mol.     

Indium(III) chloride catalyzed one step synthesis of some new dibenzo(d,f)(1,3)dioxepines and 12H-dibenzo(d,g)(1,3)dioxocin derivatives

In the presence of catalytic amount of indium(III) chloride (10 mol %), 2,2′-dihydroxybiphenyl and bis(2-hydroxyphenyl)methane react quickly, without using any solvent, with ketones or β-keto esters possessing at least one hydrogen atom in α to the ketone-carbonyl group, to afford some new dibenzo(d,f)(1,3)dioxepines and some 12H-dibenzo(d,g)(1,3)dioxocin derivatives, respectively.