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Biomedical subjects

A Bigi

Publications and source records attributed to A Bigi.

At least 55 records · Page 3Linked to original sources
PubMed1988

The oral allergy syndrome.

We have studied 262 patients suffering from hay fever and oral allergy syndrome after fruit and vegetable ingestion. The history and the results of RAST and skin test for pollen showed a contemporary presence of systemic and local symptoms in most of the patients; a close connection between age of onset of hay fever and oral allergy syndrome; a frequent association between allergy to some pollens and some vegetables, such as between apple, carrot, pear, cherry with birch pollen and tomato, melon, watermelon with grass pollen.

Adolescent↗
PubMed1987

IgE-mediated food allergy.

The behaviour of some immunologic parameters was studied in order to explain the presence or the lack of symptomatology in subjects with IgE specific to foods. In particular, we compared the levels of serum and salivary IgA and IgE antibody specific to apple in 33 patients allergic to birch and with anti-apple IgE, of whom 24 had oral allergy syndrome after eating apple and nine were apple tolerants. We found no differences in the IgE-related parameters such as levels of anti-apple IgE antibody in serum and secretions, mean size of apple skin prick test, and number of patients with a positive histamine release from peripheral basophils stimulated by apple. Similarly, we detected no statistically significant differences in serum and salivary total IgG and total anti-apple IgA antibody of the two groups. We could, however, observe a significantly higher anti-apple salivary IgA/anti-apple serum IgE and anti-apple salivary IgA/anti-apple serum IgA ratios and a significant correlation between the same parameters in tolerant patients when compared with the intolerants. These results seem to suggest that the presence of appropriate levels of secretory anti-apple IgA associated to anti-apple IgE might be one of the factors playing a key role in the prevention of clinical symptoms in atopic subjects.

Food Hypersensitivity↗
PubMed1986

Differences in the fibril structure of corneal and tendon collagen. An electron microscopy and X-ray diffraction investigation.

A detailed analysis of the D-period and axial electron density distribution of cornea and tendon collagen was carried out by means of X-ray diffraction and electron microscopy. Ultrastructural observations were made on replicas of freeze fractured and deep-etched specimens. Synchrotron radiation was used to obtain high resolution small angle X-ray diffraction patterns. The data provide evidence that D-period and intraperiod distances in cornea are shorter than in tendon collagen fibrils. The observed different banding observed is interpreted on the basis of the different morphological arrangement of the microfibrils in the two tissues: "helicoidal" in cornea and "straight" in tendon microfibrils.

Animals↗
PubMed1985

A low-angle X-ray diffraction analysis of osteonic inorganic phase using synchrotron radiation.

Using synchrotron radiation the low-angle X-ray diffraction method has been applied to single osteon samples to yield new data on the texture of the inorganic bone fraction. Two sample types--cylindrically shaped osteonic samples and osteonic radial hemisections--were prepared from longitudinal and alternate osteons at both the initial and final stages of calcification. The results indicate that the diffraction pattern is due to the inorganic phase, which reveals the same axial periodicity as native collagen fibrils and fits into the main band. No change is appreciable as osteons pass from the initial to the final stage of calcification. This means that when crystallites covering much more than a collagen axial period are observed under the electron microscope, they do not appreciably affect the calcified banding of collagen fibrils. The osteonic axis corresponds to the main direction of collagen orientation both in longitudinal and alternate osteons. The degree of orientation, however, is lower in alternate osteons than in longitudinal ones, where only few thin, incomplete transversal lamellae are found.

Adult↗
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↗
PubMed1983

Arrangement of microfibrils in collagen fibrils of tendons in the rat tail. Ultrastructural and x-ray diffraction investigation.

The microfibrillar arrangement in collagen fibrils of tendons in the tail of the rat was examined by electron microscopy and X-ray diffraction. Fresh and air-dried collagen fibers were examined in unstretched and stretched conditions. The results demonstrate that the microfibrils have a course parallel to the longitudinal axis of the collagen fibrils. The influence of stretching and hydration of the samples on the orientation of fibrils and microfibrils is also assessed.

Animals↗
PubMed1983

X-ray diffraction analysis of transversal osteonic lamellae.

When isolated osteon samples are submitted to wide-angle X-ray diffraction, it is not possible to detect any preferential orientation of the hydroxyapatite crystallites of the lamellae with transversally arranged fiber bundles. So a complete and exhaustive X-ray diffraction analysis of an osteon needs adequately prepared osteonic subunits. For the present investigation, 2 types of samples were prepared from longitudinal and alternate osteons: osteonic radial sections and isolated straightened transversal lamellae. An X-ray diffraction microcamera has been used with a rotating anode X-ray generator. In accordance with the data provided by the polarizing microscope, the orientation of crystallites runs parallel to the osteon axis in longitudinally structured osteons, whereas in alternate osteons the orientation changes by about 90 degrees in successive lamellae. Neither crystallites associated with the collagen fibrils that run alongside the osteocyte canaliculi nor those associated with the fibrils that run transversally in longitudinally structured osteons are revealed by X-ray diffraction, because there are so few of them.

Crystallization↗
PubMed1983

Light microscopy, electron microscopy, and X-ray diffraction analysis of glycerinated collagen fibers.

Light microscopy, transmission electron microscopy (freeze-fracture replicas and thin sections), and X-ray diffraction techniques were used to investigate the structure of rat tail tendon collagen fibers subjected to one of the following treatments: water, phosphate buffer, glutaraldehyde, glutaraldehyde followed by glycerol, glycerol, and glycerol followed by phosphate buffer. As seen by light microscopy, only treatment with glycerol induces a remarkable swelling of the native (untreated) collagen specimens. Replicas and thin sections show that this swelling is due to an expansion of the interfibrillar space, and to a dissociation of the collagen fibrils into microfibrils. X-Ray diffraction analysis reveals great disorder in the glycerol-swollen collagen fibers. However, this does not appreciably involve the microfibrillar and molecular structure. Light and electron microscopy as well as X-ray diffraction techniques show that the collagen fiber swelling induced by glycerol is an almost completely reversible process.

Animals↗
PubMed1982

Carotid wall as an isotropic mechanical system.

The morphological organization of the structural components in the dog carotid wall is investigated by X-ray diffraction and microscopic analysis. Histological analysis confirms an anisotropic morphology of smooth muscle cells and elastic fibers in the tissue. Collagen fibers, as revealed by X-ray diffraction technique, are organized in an isotropic network in the unstretched carotid media. Collagen fibers stretch without a preferential direction of orientation when a carotid segment is deformed in the physiological range under intraluminal pressure. A mathematical model which takes into account the isotropic distribution of the collagen fibers is developed. The validity of this model has been tested by computing several mechanical parameters using Anliker's data on the axial and radial oscillation obtained for carotids of living dogs. In spite of the anisotropic morphology of the main constituents of the carotid media layer, from a mechanical point of view the tissue can be considered as an isotropic material for the random distribution of the collagen fibers which represent the component of higher tensile strength.

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↗
PubMed1980

[Mechanical properties of the human basilar artery].

The mechanical properties of the wall of human basilar artery have been determined by tension tests. The degree of orientation of collagen fibers inside the deformed arterial wall has been evaluated by the analysis of the mechanical results and by the X-ray diffraction pattern. The results show that the wall of the muscular arteries can be considered a "composite material" which mechanical properties, at high stress, are due mainly to the collagen fibers orientation.

Basilar Artery↗
PubMed1980

[Role of the orientation of the collagen fibers on the mechanical properties of the carotid wall].

Mechanical test was applied to several carotid walls air-dried under different degree of deformation along the circumferential direction. The stress-strain curves show an increase of the elastic modulus as a function of the deformation. X-ray diffraction studies were applied to determine the degree of collagen orientation in the deformed samples. The carotid wall, in agreement with the "composite materials theory", shows that the collagen is the most responsible factor of the mechanical properties of the tissue.

Animals↗
PubMed1980

[Collagen fiber orientation in the tunica media of the aorta as a function of intraluminal pressure].

X-ray diffraction investigation and hystological analysis have been carried out on segments of pig's aortic media layer under different values of distending pressure. The roentgenografic study shows that collagen fibers aligne themselves along the circumferential direction of the vessel as a function of the intraluminal pressure and are completely oriented at systolic pressure. Hystological analysis reveales that the smooth cells orientation, as a function of intraluminal pressure, is very close to that of collagen fibers.

Animals↗
PubMed1980

[Roentgenographic study of the structural organization of the collagen fibers in the tunica media of the aorta].

X-ray diffraction tecnique was used to investigate the distribution and orientation of collagen fibers in media layer of pig aortic wall as a function of mechanical deformation. Hyistological analyses were carried out to study the behavior of smooth cells when mechanical deformation is applied to media layer. The results show a close relationship between collagen fibers and smooth cells orientation.

Animals↗
PubMed1980

Characterization of synthetic apatites for bioceramic implants.

Hydroxyapatite has been studied as a substance suitable for surgical substitution of bones and teeth with emphasis on its biocompatibility. The present work tries to identify the characteristics of this material either from the chemico-physical-structural point of view, or from the technological one, evaluating the best performance. By X-ray, i.r., thermal, chemical and SEM analyses, the relationship of different phenomena involved in the sintering was evaluated. Technological tests demonstrated the stability and the workability characteristics. In particular, the influence of CO2 was studied, in connection with the most suitable technique for hydroxyapatite (HAP) sintering, considering the eventual aims and requirements for industrial production.

Ceramics↗
PubMed1979

X-ray diffraction study of bovine lens capsule collagen.

The wide angle X-ray diffraction pattern of air-dried lens capsule collagen under tension is the same as the tendon collagen diffraction pattern with regard to the main reflections, and indicates that lens capsule collagen has the characteristic three-stranded helical structure with an axial repeat of 0.29 nm as tendon collagen. The low angle X-ray diffraction pattern shows several weak diffraction maxima corresponding to the meridional reflections of capsule collagen which show orders of 63.0 nm periodicity. This is an evidence of quarter staggered molecular assembly typical of tendon collagen even if less ordered. The results are consistent with the existence in lens capsule collagen of clearly defined molecular units, which can be oriented by stress and are packed in a poor-ordered fibrillar assembly.

Animals↗