Biomedical subjects

A Ruggeri

Publications and source records attributed to A Ruggeri.

At least 73 records · Page 4Linked to original sources

PubMed1992

The dependency of collagen fibrillogenesis in vitro on fibroblast culture conditions. Fibroblasts in mono- and multi-layers.

The extracellular matrix produced by monolayer and tridimensional cultures of fibroblasts was investigated using histochemical and ultrastructural methods. In monolayer cultures, collagen and proteoglycans produced by fibroblasts could not be organized into morphologically recognizable structures. Tridimensional fibroblast cultures produced a well organized matrix with periodic, parallel ordered collagen fibrils of 50 nm diameter, criss-crossed by alcianophylic segments 6-10 nm thick in diameter and 100-300 nm in length, parallel to each other, perpendicular to the collagen fibrils and spaced 67 nm from each other. Some alcianophylic segments lay perpendicular to the above described ones, with maximum lengths of 65-70 nm. Alcianophylic segments are the ultrastructural evidence of structural proteoglycans. These observations suggest that the culture conditions influence the collagen and proteoglycans secretion, so that the final organization of the matrix results quite different.

Alcian Blue↗

PubMed1992

Ultrastructure of the extracellular matrix of bovine dura mater, optic nerve sheath and sclera.

The sclera, the outermost sheath of the optic nerve and the dura mater have been investigated histologically and ultrastructurally. Although these tissues appear very similar under the light microscope, being dense connective tissues mainly composed of collagen bundles and a limited amount of cells and elastic fibres, they exhibit subtle differences on electron microscopy. In the dura and sclera collagen appears in the form of large, nonuniform fibrils, similar to those commonly found in tendons, while in the optic nerve sheath the fibrils appear smaller and uniform, similar to those commonly observed in reticular tissues, vessel walls and skin. Freeze-fracture also reveals these fibrils to have different subfibrillar architectures, straight or helical, which correspond to 2 distinct forms of collagen fibril previously described (Raspanti et al. 1989). The other extracellular matrix components also vary with the particular collagen fibril structure. Despite their common embryological derivation, the dura mater, optic nerve sheath and sclera exhibit diversification of their extracellular matrix consistent with the mechanical loads to which these tissues are subjected. Our observations indicate that the outermost sheath of the optic nerve resembles the epineurium of peripheral nerves rather than the dura to which it is commonly likened.

Animals↗

PubMed1992

The human anterior cruciate ligament: histological and ultrastructural observations.

In transverse and longitudinal paraffin-embedded sections, the human anterior cruciate ligament (ACL) is made up of wavy bundles of collagen fibres arrayed in various directions, the majority around the axis of the ligament with a few running parallel to it. The fascicles making up the larger bundles are also characterised by this undulating appearance. In thin sections 2 types of collagen fibrils are observed: small (with a single diameter peak at 45 nm) and large (3 peaks at 35, 50 and 75 nm respectively), organised into distinct areas made up of either large or small bundles of fibrils. The numerous fibroblasts that are present appear elongated in the direction of the bundles with branches and short cytoplasmic processes. The elastic system is made up of both elastic and oxytalan fibres. The varied orientation of the bundles in the ACL, the complex ultrastructural organisation and the abundant elastic system make it very different from other ligaments and tendons, providing a structure able to withstand the multiaxial stresses and varying tensile strains imposed upon it.

Anterior Cruciate Ligament↗

PubMed1991

Calcium phosphate materials containing alumina: Raman spectroscopical, histological, and ultrastructural study.

Variable alumina quantities were added to two types of calcium phosphate materials-hydroxyapatite ceramics with Ca/P = 1.67 and calcium metaphosphate glass with Ca/P = 1--in order to increase their mechanical properties. Raman spectroscopy shows that alumina interacts with the phosphate group of these materials, while thermomechanical analysis shows that their elastic modulus has a value similar to that of bone. Histological sections demonstrate that the surface in close contact with ceramic materials shows a good integration between bone and biomaterial. All ceramic specimens are penetrated by well-stained, presumably glycoprotein, matrix, that consistently forms a thin network in close contact with the implant. After 6 weeks bone growing on both ceramic and glass shows signs of maturation with a lamellar structure and an apparently normal mineralization. In the case of the glass, inside this newly formed bone, were often observed two layers, the internal one showing a well defined lamellar structure.

Aluminum Oxide↗

PubMed1991

A reduced sampling schedule for estimating the parameters of the glucose minimal model from a labeled IVGTT.

The minimal model of tracer glucose disappearance allows the measurement in man of important metabolic parameters from a labeled IVGTT (intravenous glucose tolerance test). Usually 30 blood samples are drawn to measure the insulin and the labelled glucose concentration time courses, which provide the data base for the model identification. In this paper, we address the problem of reducing the number of blood samples withdrawn without, however, deteriorating parameter estimation. By using a stepwise approach, largely based on optimal experiment design theory, we have derived a reliable reduced sampling schedule, which comprises only 14 total samples. The practical application of this reduced schedule has been validated by applying it in a new set of human experiments, completely independent of the ones used in the design phase.

Blood Glucose↗

PubMed1991

Ultrastructure of the bovine nuchal ligament.

Nuchal ligament is composed almost exclusively of elastic fibres and collagen fibrils, interwoven very closely and lying parallel to the main ligament axis. Elastic fibres are very large, straight and roughly cylindrical; the collagenous matrix consists of septa of diminishing size forming a 3-dimensional matrix that envelops fibre bundles as well as individual elastic fibres. In all areas examined, collagen fibrils are of very uniform size and, on replicas, they reveal a spiral subfibrillar arrangement with an inclination angle of 17 degrees. Collagen fibrils appear to adhere to the elastic fibres very closely, conforming to their irregular shape. Sometimes they impinge directly upon the elastic fibres, while in other cases a space is visible between collagen fibrils and elastic fibres that contains a rich fabric of intermediate filaments. The collagen-elastin complex of the ligamentum nuchae may be considered a fibre-reinforced composite material comprising tough fibres immersed in an amorphous elastic matrix. Its mechanical behaviour is the result of the combined properties of its components and their interactions.

Animals↗

PubMed1991

Tricalcium phosphate endosseous implants in dentistry: ultrastructural findings.

beta-Tricalcium phosphate magnesium substituted (beta-TCMP), consisting of one part small unsintered and one part large sintered granules was placed in upper and lower jaw surgical cavities of monkeys. At light and transmission electron microscope the biopsies taken at 2, 4, 8 and 24 weeks showed that both sintered and unsintered granules were well tolerated by the host tissue and result biodegradable over time. beta-TCMP may stimulate the direction of bone growth enhancing osteoblasts activity and new bone deposition in direct contact and in the micropores of the biomaterial. beta-TCMP containing Mg ions reabsorbs slowly when in sintered granules form and rapidly as unsintered granules. When it is placed in bone cavities, if bone reabsorption is biologically necessary, the biomaterial can be reabsorbed with bone, while if osteogenesis is required beta-TCMP provides a more durable matrix to support new bone growth.

Animals↗

PubMed1991

Histologic and ultrastructural findings of tissue ingrowth. The Leeds-Keio prosthetic anterior cruciate ligament.

A light and electron microscopy investigation was performed on a Leeds-Keio ligament removed because of rupture 18 months after implantation to repair an anterior cruciate ligament. The investigation showed fibrous connective tissue on the plane of the main stress force. There was elastin and adequate vascularization interspersed with Type I collagen fibrils in the area most distant from the ligament. The tissue near the Dacron fibers was highly cellular with a matrix of infrequent, thin collagen fibrils and abundant fine granular material. The growth of the host tissue occurred in and around a Leeds-Keio ligament in response to tensile stresses.

Adult↗

PubMed1990

Distribution of elastic system fibres in the rat tail tendon and its associated sheaths.

The distribution of elastic, elaunin and oxytalan fibres in tendons and tendon sheaths was studied by means of light and electron microscopy. The different fibres were characterised by comparing their typical ultrastructural pictures with a combination of selective staining techniques for light microscopy with the appropriate enzymatic digestions. Since it was observed that the rat tail tendon and its associated sheaths are not homogeneous structures from the point of view of the distribution of the elastic system fibres, a systematic description of the differential distribution of the oxytalan, elaunin and elastic fibres in the tendon and in the endo-, peri-, epi- and paratendineum is presented. Mature elastic fibres are present in the tendon and in the para-, epi- and endotendineum, whereas these fibres could not be detected in the peritendineum. Very many elaunin fibres are characteristically recognised in the endotendineum; these fibres are present in the peritendineum and in the tendon fascicles too, while the epi- and paratendineum are devoid of elaunin fibres. The peri- and endotendineum contain numerous oxytalan fibres, whereas these fibres are absent from the tendon fascicles and the epi- and paratendineum. The functional implications of the foregoing findings are discussed.

Animals↗

PubMed1990

Subfibrillar architecture and functional properties of collagen: a comparative study in rat tendons.

Collagen fibrils from different rat tendons have been investigated by freeze-fracture and transmission electron microscopy. In all cases, marked differences in both fibril morphology and subfibrillar organisation have been consistently found between the tendon core (composed of large and heterogeneous fibrils comprising tightly-packed, straight, parallel molecules) and sheath (showing small, uniform collagen fibrils with a helical arrangement of the molecules). The bio-mechanical requirements to which these tissues are subjected suggest, as do previous observations on other tissues, that a causal correlation exists between substructure and collagen fibril function.

Animals↗

PubMed1989

[beta-TCP and beta-TCMP osteoregenerators. New perspectives].

The Authors present personal histological findings on a beta-tricalcium phosphate Mg substituted (beta-TCMP) prepared as sintered granules and unsintered powder. A mixture of these materials was used to fill bone cavities or defects in oral surgery. The beta-TCMP represents a biocompatible ceramic material able to accelerate and enhance bone repair of bone defects. It provides a completely biodegradable matrix for new bone growth as well as releasing mineral ions into the tissue during mineralization. Newly formed bone tissue is described in direct contact with residual beta-TCMP granules. No connective tissue layer is present between the new bone and the surface of the alloplastic material.

Animals↗

PubMed1989

[Class V cavities for composites. New preparation principles].

The aim of this study is to establish with the help of a computer a new type of Class V cavity that would ensure minimal marginal gap of restoration work using restorative resins. Comparison of computer graphics has shown that the ideal Class V cavity for restorative resins is cone-like with the apex or smaller base pointing towards the pulp and the walls slightly convex towards the free surface of the cavity. To prepare this sort of cavity new specular-type burrs are required.

Composite Resins↗

PubMed1989

[A new lining material, B-tricalcium phosphate MG substitute].

Powder of not-sintered beta-tricalcium phosphate granules was used as capping material in deep cavities of monkey and human teeth. The authors have demonstrated by SEM with E-DAX the dispersion of beta-TCP in the dentinal tubules and in predentin. Histological sections didn't show any inflammation or degeneration of the pulp.

Animals↗

PubMed1989

[Surface polishing of posterior composites].

In this research we have valued at SEM the smoothness degree of the surface obtained in vitro on three kinds of composite resins for posterior restoration (P-30, P-50, Clearfil Photo Posterior); then we have compared it with the result obtained in vitro with an alloy not gamma-2 (Dispersalloy). The surfaces of the composite restorations show at SEM irregularities more or less accentuated for the presence of particles of filling got in comparison with the matrix. The surface of alloy restorations results on the contrary perfectly polished and completely comparable with the enamel surface.

Bicuspid↗

PubMed1989

[Surface polishing of anterior composites].

In this research it has been valued at SEM the smoothness degree of the surface obtained in vitro on three kinds of composite resins for anterior restorations (Lumifor, Silux, Pekalux). The surface has been polished and finished with abrasive disks (Sof Lex Pop On XT). The composite resin Lumifor presents at SEM a good finished surface. Far better results have been obtained with the microfilled composite resins Silux and Pekalux, which show at SEM surfaces perfectly polished and homogeneous.

Composite Resins↗

PubMed1989

Different architectures of the collagen fibril: morphological aspects and functional implications.

Several tissues known to contain collagen fibrils with a 'helical' arrangement were studied by t.e.m. and freeze-fracture. In all the tissues examined, the diameter of the collagen fibrils appeared to be tissue-specific and fairly constant within the same tissue. No statistical differences, on the contrary, were detectable in the coiling angle which appeared similar in all the tissues and independent of both diameter and age of the fibril. Rat tail tendon was also examined under the same technical conditions and showed collagen fibrils of large and very heterogeneous diameter and with a consistent 'straight' arrangement. These data seem to suggest that the 'helical' and 'straight' arrangements may actually identify different types of collagen fibrils. The authors discuss the possible functional significance of these arrangements and present two hypotheses on the three-dimensional structure of the 'helical' fibril.

Animals↗

PubMed1989

Collagen fibril surface structures: freeze-etching data and computer modelling.

In order to investigate the correlation between primary structure and surface profile of collagen, freeze-fractured and deep-etched (dehydrated) collagen fibrils have been compared with a fibril model built directly from the amino acid sequence. The model appeared to be almost identical to the freeze-etched collagen fibril with respect to the most relevant features, such as the gap-overlap ratio and the location of the two main intraperiod ridges (X3 and X2). However, it did not show the minor ridges observed in the gap zone (X1 and Y1), thus suggesting that these structures, although consistently present in collagen fibrils, may in fact be due to post-translational modifications or to non-collagenic material adhering to the fibril.

Amino Acid Sequence↗

PubMed1989

Optimal design of sampling schedules for studying glucose kinetics with tracers.

Minimum size sampling schedules for estimating glucose kinetic parameters from an impulsive (bolus) tracer injection in normal humans and rats are presented. Glucose kinetics are described by a two-compartment linear model, and reference values of the parameters are estimated from a data base with many samples. The optimal sampling schedule (OSS) is determined in each individual by using a D-optimal criterion and consists of four samples. A population optimal sampling schedule (POSS) applicable to all the individuals of a given population is then determined, and its reliability and efficiency in recovering kinetic parameters (e.g., rate constants, plasma clearance rate, and mean residence time) is assessed. The influence of model and measurement error on OSS is discussed. Moreover, the adoption of an enhanced POSS (EPOSS, 8 samples) is shown to improve accuracy and precision of parameter estimates in a predictable manner. Finally some suggestions are given for obtaining more information from turnover studies using a constant infusion of tracer, with or without a priming pulse of tracer.

Animals↗