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.     

Application of color image segmentation to estrusc detection

Automatic segmentation and classification of color images is a problem of great practical interest in different areas. This paper presents an algorithm for this purpose which is divided in three steps. Firstly, the regions of interest are isolated from the rest of the image based on threshold functions defined in theYUV andYIQ color spaces, producing a set of connected components. Then, a set of features is computed to enable a quantitative evaluation of the segmented objects. Finally, the image is classified by means of a decision rule based on the analysis of the differences between the computed measures and a set of ideally segmented images, according to experts’ assessment. The algorithm was applied to a decision support tool for estrus detection in cattle. This approach constitutes a valuable alternative to improve this process, as it may replace the visual observation by the automatic analysis of pictures taken to cows in controlled environments. Experimental results show that the segmentations obtained with this method are highly satisfactory and they allow a precise classification of the images with low computational complexity.     

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.     

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.     

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.     

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.     

Carbohydrate and alditol analysis by high-performance anion-exchange chromatography coupled with electrochemical detection at a cobalt-modified electrode

A cobalt oxyhydroxide film dispersed on a carbon electrode surface was characterized and proposed as an amperometric sensor for determination of alditols and carbohydrates in flowing streams. Complex mixtures of carbohydrates were separated by anion-exchange chromatography using a moderately alkaline solution as mobile phase. The cobalt modified electrode (GC-Co) was employed under a constant applied potential of 0.5 V (vs Ag/AgCl). Under these experimental conditions the detection limits (S/N=3) for all analyzed electroactive molecules ranged between 0.3 micromol L(-1) and 1.5 micromol L(-1) and the dynamic linear ranges spanned generally three orders of magnitude above the relevant detection limits. Analytical determinations of carbohydrates and alditols in red and white wines, are reported.     

Synthesis, Electrochemistry and Crystal Structure of the [Ni36Pt4(CO)45]6− and [Ni37Pt4(CO)46]6− Hexaanions

The [Ni₃₆Pt₄(CO)₄₅]^6- and [Ni₃₇Pt₄(CO)₄₆]^6- clusters have been obtained in mixture upon reaction in acetonitrile of [Ni₆(CO)₁₂]^2- salts with K₂PtCl₄ in a 2.5:1 molar ratio. The two hexaanions were indistinguishable by spectroscopic techniques. Crystallization of their trimethylbenzylammonium salts led to crystals of composition 0.5[NMe₃CH₂Ph]₆[Ni₃₆Pt₄(CO)₄₅]-0.5[NMe₃CH₂Ph]₆[Ni₃₇Pt₄(CO)₄₆]·C₃H₈O, hexagonal,space group P6₃ (No. 173), a=17.853(9), c=27.127(13) Å, Z=2; final R=0.057. The metal core of the [Ni₃₆Pt₄(CO)₄₅]^6- anion consists of a Pt₄ tetrahedron fully encapsulated in a shell of 36 Ni atoms belonging to a very distorted and incomplete ₅ tetrahedron. The [Ni₃₇Pt₄(CO)₄₆]^6- hexaanion derives from the former by capping the unique triangular face of the metal polyhedron with an additional Ni(CO) fragment. The [Ni₃₆Pt₄(CO)₄₅]^6--[Ni₃₇Pt₄(CO)₄₆]^6- mixture is rapidly degraded to the known [Ni₉Pt₃(CO)₂₁]^4- cluster by exposure to carbon monoxide. Its reaction with protic acids initially affords the corresponding [H_6-nNi₃₆Pt₄(CO)₄₅]^n--[H_6-nNi₃₇Pt₄(CO)₄₆]^n- (n=5, 4) derivatives, and eventually leads to rearrangement to the known [H_6-n Ni₃₈Pt₆(CO)₄₈]^n- species. Both [Ni₃₆Pt₄(CO)₄₅]^6--[Ni₃₇Pt₄(CO)₄₆]^6- and [HNi₃₆Pt₄(CO)₄₅]^5--[HNi₃₇Pt₄(CO)₄₆]^5- mixtures have been chemically and electrochemically reduced to their corresponding [Ni₃₆Pt₄(CO)₄₅]^n--[Ni₃₇Pt₄(CO)₄₆]^n- (n=7–9) and [HNi₃₆Pt₄(CO)₄₅]^n--[HNi₃₇Pt₄(CO)₄₆]^n- (n=6–8) mixtures.