R. Strocchi

Human Achilles Tendon: Morphological and Morphometric Variations as a Function of Age

Aging of human Achilles tendon results in changes in both cellular and fibrous components. Cells flatten and become less numerous. Their thin and long cytoplasmatic projections tend to shorten and diminish in number. Tendon fibers lose their typical undulating appearance and become quite straight. Collagen fibril diameter, small and uniform in the neonatal period, becomes large and extremely variable from adolescence onwards. Age related morphometric changes include a decrease in the average, maximum diameter and density of collagen fibrils and an increase of fibril concentration. In our opinion these morphological and morphometric variations are strictly related to functional requirements.

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.

Collagen Fibril Patterns in Compact Bone: Preliminary Ultrastructural Observations

A comparative study of the Haversian architecture was carried out on compact bone derived from the anterior and posterior edges of the diaphysis of horse radius, regions which have different mechanical requirements in vivo. Samples were heat-deproteinated prior to SEM analysis, a treatment which effectively removes cells and vascular structures as well as exposing large areas of the mineralization front along the walls of the haversian canals. Bone subject to tensile stress revealed a prevalent alignment of its collagen fibrils in the stress direction, and the vast majority of its osteons were composed of fibrils running almost parallel and crossing at very acute angles. Bone subject to compressive forces showed either an orthogonal alternation of collagen lamellae or a multidirectional arrangement corresponding to the twisted plywood pattern described by other authors. Our observations substantiate both the classical model of the osteon and the twisted plywood concept, and suggest that osteon ultrastructure is modulated according to biomechanical requirements.

Histological and ultrastructural evaluation of Leeds-Keio ligament six years after implant: A case report

Abstract We examined by light and electron microscopy study a Leeds-Keio ligament removed from a patient 6 years and 4 months after implant following rupture. The new ligament presented an outer capsule made up of bundles of collagen fibres running mainly perpendicular to the long axis of the ligament. Septa were seen emerging from the capsule and composed of bundles of collagen fibres surrounding the bundles of Dacron fibres. Each thread of Dacron was surrounded by a layer of connective tissue containing periodic acid-Schiff (PAS)-positive cells. The bundles of collagen fibres making up the outer capsule, the septa and the layer of connective tissue surrounding the Dacron threads were positive for anti-type I collagen antibody. The rehabitated Leeds-Keio ligament presented a specific organization at the septa zone, showing a layer of collagen fibrils alternating with a layer of cells. Our remodelling findings suggest a shoelace effect of the artificial ligament. On the other hand, the presence of type I collagen could be responsible for the good functional behaviour of this composite system. In conclusion, the factors that play an important role in determining this remodelling process and its mechanical function are unknown.

Proteoglycans and their relationship with the other components of the rabbit aorta wall observed in two different experimental conditions

An electron microscopic study of the aorta wall of rabbit was carried out employing electron microscopic histochemical methods aimed at examining the distribution of proteoglycans and their correlation with the other structural components of the aorta wall. The ultrastructural evidence of the proteoglycans has been obtained by treating the arterial wall with alcian blue stain and supporting this staining procedure with control enzyme treatments. Moreover, in order to attain a better interpretation of the ultrastructural findings, the arterial wall has been studied under 2 different experimental conditions, the 1st one being represented by an accentuated contraction of the vases wall, following immersion in the fixator, the other one by an extreme distension of the wall, reached prior to fixation, subjecting the tissue to its tension limit of 700 dyn/mm2. This type of electron microscopic visualization of the proteoglycans following alcian blue treatment leads on to think that at least 2 distinct macromolecular entities of proteoglycans exist, each one having an unusual relationship with the other components of the arterial wall. Different site and types of interaction are to be noted for each of the 2 distinct ultrastructural proteoglycans entities.

Particular Structure of the Anterior Third of the Human True Vocal Cord

The histological aspects of the true vocal cord mucosa change in the anterior third compared with the posterior two thirds. The anterior third is characterized by an epithelium where the ridges, marked in the posterior two thirds, are very slight or even absent. The underlying basement membrane, which is thin in the posterior two thirds, here appears particularly thick. At the ultrastructural level in this area, beneath a normally thickened basal lamina, a thick layer of finely granulated electron-dense material, interspersed with thin and randomly scattered collagen fibrils and proteoglycan filaments, is detectable. Beneath this thickened basement membrane, a layer of small undulated collagen fibril bundles with very numerous interspersed oxytalan fibres is found. The collagen fibrils, small in diameter (30-40 nm), seem to continue with the collagen fibrils of the basement membrane. In this layer numerous blood vessels with a very thick, delaminated basement membrane are also observed. The underlying area is characterized by the vocal cord ligament, composed by large compact collagen fibril bundles with interspersed elastic fibres. The particular features of the thick basement membrane, the thick-walled and delaminated vessels and the modular distribution of the elastic system together may well form the basic structure enabling the functional integration of the vocal ligament into the overlying mucosa and the underlying vocal muscle.

Sister Chromatid Exchanges (SCEs) and Proliferation Rate Index (PRI): The Application of Cytogenetic Methods in Biocompatibility Field

Cytologically visible damage in human chromosome detected as Sister Chromatid Exchanges (SCEs) or other structural chromosomal aberrations is one of the “In Vitro” steps to assess the biocompatibility of some materials to be used in orthopaedy or dentistry. The utility of these observations is that they point out that similar alterations may have occurred in other tissues, either somatic or germinal cells, evenience with possible clinical implications. The absence of effects on the DNA of replicating human lymphocytes cultivated in presence of three different types of Alumina (105 NS, 105 SFP and 130 SF, Metco Ind.) and an Hydroxyapatite, at different concentrations, let these materials to be classified as “negative”, (from the point of view of being a possible genotoxic substance), as they failed to induce a significant increase in SCEs. They result also not inducing effects on the proliferation rate index (PRI) on the same cell type.