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Biomedical subjects

E Foresti

Publications and source records attributed to E Foresti.

10 recordsLinked to original sources
PubMed1998

X-ray diffraction on cyclically loaded osteons.

The results of a study on the fine structural distortion due to the two previously observed types of degradation in cyclically loaded single osteons (i.e., stiffness degradation and pinching effect) are presented. Fully calcified longitudinal and alternate osteons were isolated from 350-microns-thick longitudinal sections of human femoral cortical bone. The samples were prepared from 500-microns-long central cylindrical portions of an osteon, whose two ends were penetrating into rectangular lugs for fixation to an electromechanical device that cyclically loaded the samples. This device was connected to a microwave micrometer and a recorder. The structural distortions induced by cyclic loading were investigated by high- and low-angle X-ray diffraction on conventional and synchrotron radiation sources. Cyclic loading results in a reduction in the degree of orientation of apatite crystallites, especially in longitudinal osteons, in which the most abundant longitudinal lamellae are not protected against buckling by transverse lamellae as they are in alternate osteons. In contrast, the degree of orientation of collagen fibrils does not seem to be affected by cycling loading in the two osteon types, possibly because the disorientation of collagen fibrils is, within limits, a reversible process. Finally, the contrast between the disorientation of inorganic crystallites and the apparently unaltered distribution of collagen fibrils suggests that the degradation of cyclically loaded osteons may be due to a separation of the crystallites from the fibrils.

Adult↗
PubMed1992

The role of magnesium on the structure of biological apatites.

X-ray diffraction, infrared absorption spectroscopy, and chemical investigation have been carried out on deproteinated samples of turkey leg tendon at different degrees of calcification. The inorganic phase consists of poorly crystalline B carbonated apatite. On increasing calcification, the apatite crystal size, as well as its thermal stability, increase while the relative magnesium content is reduced. On the other hand, synchrotron X-ray diffraction data clearly indicate that apatite lattice parameters do not change as the crystals get larger. At the last stage of calcification the crystal size, chemical composition, and thermal conversion of the apatite crystallites approximate those of bone samples, which have been examined for comparison. The results provide a quantitative relationship between relative magnesium content and extent of apatite conversion into B-tricalcium phosphate by heat treatment. Furthermore, they suggest that the smaller crystallites laid down inside the gap region of the collagen fibrils are richer in magnesium than the longer ones that fill the space between collagen fibrils.

Animals↗
PubMed1988

Structure and molecular orbital study of ergoline derivatives. 1-(6-Methyl-8 beta-ergolinylmethyl)imidazolidine-2,4-dione (I) and 2-(10-methoxy-1,6-dimethyl-8 beta-ergolinyl)ethyl 3,5-dimethyl-1H-2-pyrrolecarboxylate toluene hemisolvate (II) and comparison with nicergoline (III).

(I): C19H22N4O2 (Registry No. 95688-34-9), m.p. greater than 573 K, Mr = 338.4, orthorhombic, P2(1)2(1)2(1), a = 8.392 (2), b = 13.004 (2), c = 15.676 (5) A, V = 1710.7 (7) A3, Z = 4, Dx = 1.31 Mg m-3, Mo Ka radiation, lambda = 0.71069 A, mu = 0.08 mm-1, F(000) = 720, T = 293 K, final R = 0.051 for 990 independent reflexions. (II): C26H33N3O3.1/2C7H8 (Registry No. 54370-23-9), m.p. 427-429 K, Mr = 481.64, monoclinic, P2(1), a = 11.595 (4), b = 14.274 (2), c = 16.103 (4) A, beta = 100.19 (3) degrees, V = 2623 (1) A3, Z = 4, Dx = 1.22 Mg m-3, Mo Ka radiation, lambda = 0.71069 A, mu = 0.07 mm-1, F(000) = 1036, T = 293 K, final R = 0.064 for 2738 independent reflexions. Two independent molecules constitute the asymmetric unit, together with a toluene molecule. Parallel investigations of the title compounds by single-crystal X-ray analysis and theoretical calculations have converged in showing an extended configuration of the side chain attached at the C8 atom of the ergoline nucleus.

Chemical Phenomena↗
PubMed1988

Structural and chemical characterization of inorganic deposits in calcified human mitral valve.

X-ray diffraction, i.r. absorption, and chemical analyses have been carried out on the mineral deposits of calcified human mitral valves and glutaraldehyde-preserved porcine aortic grafts. The mineral deposits isolated from highly calcified mitral valves and porcine aortic grafts are constituted of type B-carbonate apatite. Magnesium substituted beta-tricalcium phosphate is present, together with an apatitic phase similar to dahllite, in the ashes of poorly calcified mitral valves. The contraction of the unit cell of beta-tricalcium phosphate due to magnesium incorporation is compared with the variation of the lattice constants of synthetic beta-tricalcium phosphate at different degree of magnesium substitution for calcium. The results reveal the important role of magnesium on the calcification of human valves. In fact, the apatitic phase deposited at the beginning of the calcification process, when there is a high magnesium content, converts completely into beta-tricalcium phosphate by heat treatment at 1,000 degrees C. On the other hand, when the calcification becomes massive, magnesium content appears highly reduced, and the deposited apatitic phase is characterized by a high thermal stability.

Calcinosis↗
PubMed1984

Thermal behavior of bone and synthetic hydroxyapatites submitted to magnesium interaction in aqueous medium.

The thermal behavior of the products obtained from magnesium interaction with powdered femoral bone and carbonate containing synthetic hydroxyapatite under conditions of pH fluctuation in aqueous medium has been investigated. The products, heat treated at different temperatures from 100 to 1300 degrees C, have been characterized by infrared spectroscopy and X-ray diffraction technique. The results show that the interaction with magnesium ion destabilizes the apatitic structure and favours its thermal conversion into beta-tricalcium phosphate (beta-TCP). The replacement of magnesium with calcium in the beta-TCP crystal lattice hinders its subsequent thermal conversion into the alpha form. The influence of magnesium on the thermal stability is much more evident for carbonate-containing synthetic hydroxyapatite than for bone apatite.

Animals↗
PubMed1980

[X-ray diffraction analysis of collagen fibers processed with glutaraldehyde and glycerol].

Rat tail tendon collagen fixed with glutaraldehyde and treated with glycerol has been studied by X-ray diffraction technique. The evaluation of the distribution of the areas at higher and less density of molecular packing in the collagen fibrils has been carried out through the analysis of the intensity distribution of the low angle X-ray diffraction maxima. The results show that this treatment usually employed in the freeze-etching technique induces a modification of the degree of order in specific regions inside the axial period D.

Aldehydes↗
PubMed1980

[Study of rat tail tendon by x-ray diffraction and freeze-etching technics].

Rat tail tendon collagen processed according to different fixation and cryoprotection treatments has been examined by small angle X-ray diffraction and freeze-etching techniques. The results show some differences in the axial period and in the degree of disorder of the molecular packing as a function of the applied treatment.

Animals↗