[Influence of hydrophobicity on the negative staining of collagen fibrils].
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Animals↗
Biomedical subjects
M Raspanti
Publications and source records attributed to M Raspanti.
[Existence of a superposition for negative and positive staining of collagen fibrils].
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Animals↗
Localization of different alcian blue-proteoglycan particles in the intervertebral disc.
A histochemical investigation was carried out on proteoglycans of bovine intervertebral disc. Samples obtained from the "annulus fibrosus" (A.F.) and "nucleus pulposus" (N.P.) were treated with Alcian blue (AB) diluted in solutions of MgCl2 at critical electrolyte concentrations (CEC); some samples were incubated in testicular hyaluronidase before AB treatment. At least four types of elongated AB-proteoglycan particles were recognized: a) in A.F. lamellae and N.P., 1 nm rod-like particles were arranged orthogonally to the collagen fibrils and spaced at a distance equivalent to the fibril D-period (Figs. 1-5); b) within the A.F. lamellae, other 16-20 nm particles formed a close network among the collagen fibrils (Figs. 1,2,3,5); c) in the A.F. interlamellar crevices, 30-50 nm leaf-like particles were present (Fig. 6); d) in the N.P.Z., 20-30 nm leaf-like particles formed a wide-mesh (Fig. 4). The alcianophylic particle sizes suggest they may correspond to proteoglycan monomers in the A.F. lamellae and mostly proteoglycan aggregates in A.F. interlamellar crevices and N.P.. Both alcianophylia degrees at MgCl2 CEC solutions and enzymatic susceptibility indicate the presence of chondroitin sulphate and keratan sulphate and that the large particles in the A.F. interlamellar crevices are the keratan sulphate richest proteoglycans. The features of the observed AB-proteoglycan particles are consistent with previous morphological data reported for other tissues as well as some biochemical data for the intervertebral disc and may be correlated to the composite mechanical properties of this tissue.
Alcian Blue↗
Striae albae: a morphological study on the human skin.
Specimens of abdomen skin, comprising alternate areas of striae albae and healthy skin, were removed during surgical lipectomy from multiparous and obese women between the ages of 24 and 53 years. A flattening and thinning of the striae albae surface and the almost complete disappearance of dermal papillae was observed in paraffin and thin sections. The papillary dermis was found to be almost completely replaced by straight bundles of collagen fibres running parallel to the skin surface. Immunofluorescence data revealed in these bundles high positivity for type I collagen. The underlying reticular dermis was also found to contain large densely packed bundles of collagen fibres running parallel to the skin surface. Both papillary and reticular dermis collagen fibres were mainly arranged orthogonally to the main axis of the stria. Furthermore, the density of the collagen fibre bundles and the diameter of the collagen fibrils was found to be greater than that of the clinically healthy skin. A larger number of elastic fibres, which presented an abnormal ultrastructural appearance, were visible in pathological papillary and reticular dermis.
Adolescent↗
[Distribution of proteoglycans in the sclera].
The Authors have studied, with histochemical methods, the manner of proteoglycans distribution in superficial and deep layers of the sclera, which are characterized by structural differences regarding collagen. The pictures, on one hand, are in agreement with biochemical data which indicate the presence of dermatan-sulfate, chondroitin-sulfate and hyaluronic acid, on the other hand, show a marked glycosaminoglycans distribution in the deep layers and a lessening of their distribution relative to the superficiality of the layers. Furthermore alcianophilic particles are visualized at the electron microscope. In the superficial layers such particles are in direct relation, often periodically, with the collagen fibrils, while in the deep layers particles without this direct relationship are also observable. The Authors point out a topographic coincidence between variations regarding the proteoglycans distribution and variations regarding collagen. Moreover, the obtained pictures suggest the existence of a particular proteoglycans-collagen interaction corresponding to the deep layers where fibrillogenesis occurs.
Animals↗
[Ultrastructure of collagen fibers in the sclera].
The Authors have studied the microfibrillar packing of the scleral collagen fibrils on thin sections of samples treated with a dissociant agent and on replicas of freeze-fractured fibrils. The only difference in observing the fibrils between the external and internal layers is relative to the diameter, evidencing in general, lower dimensions in the latter. The microfibrillar packing is characterized by a lightly spiralized or wavy running of filamentous subunits and the same is evident in fibrils of different diameter. The ultrastructural pictures are similar to those obtained in the other tissues, such as tendons, fibrous cartilages, fibrous capsules of parenchymatous organs and ligaments, in which the collagen is predominantly type I, like in the sclera.
Animals↗
Plexiform vascular structures in the human digital dermal layer: a SEM--corrosion casting morphological study.
This study aimed to describe the impressive diversity of vascular plexiform structures of the hypodermal layer of human skin. We chose the human body site with the highest concentration of dermal corpuscles, the human digit, and processed it with the corrosion casting technique and scanning electron microscopy analysis (SEM). This approach proved to be the best tool to study these microvascular architectures, free from any interference by surrounding tissues. We took high-definition pictures of the vascular network of sweat glands, thermoreceptorial and tactile corpuscles, the vessels constituting the glomic bodies and those feeding the hair follicles. We observed that the three-dimensional disposition of these vessels strictly depends on the shape of the corpuscles supplied. We could see the tubular vascularization of the excretory duct of sweat glands and the ovoid one feeding their bodies, sometimes made up of two lobes. In some cases, knowledge of these morphological data regarding the normal disposition in space and intrinsic vascularization structure of the dermal corpuscles can help to explain many of the physiopathological changes occurring during chronic microangiopathic diseases.
Capillaries↗
Intertwined Sharpey fibers in human acellular cementum.
We had carried out a detailed morphological study on the human acellular extrinsic fiber cementum (AEFC) in order to support the exclusively extrinsic origin of matrix collagen bundles. Mesial and distal cervical third of fresh premolars from young individuals were examined. Semi-thin and thin section clearly show the Sharpey fibres entering in the cementum at right-angle to the root surface and coursing throughout the cementum to the cemento-dentinal junction. On their way to the dentin the Sharpey fibres divide into smaller bundles which, coursing obliquely or tangentially, intersect with others deriving from neighbouring Sharpey fibres. Both de-proteinated and decalcified samples observed at SEM present Sharpey fibres along the fractured surfaces entering and running trough the cementum perpendicularly to the root surface. Fibril bundles are seen branching out from the main body of a single Sharpey fibre and coursing obliquely or perpendicularly to the original fibre. These morphological evidences obtained both at TEM and SEM further confirm that in AEFC fibril bundles running parallel or obliquely to the root surface are branches of Sharpey fibres and not intrinsic cementum fibres.
Adolescent↗
Peri-implant medullary cisternae at the interface of bone-smooth surface titanium endosseous implant.
A histological and ultrastructural study was carried out on the spongy bone response to smooth titanium oral implant surfaces. The samples obtained both from monkeys and from patients at various times from the implant insertion revealed that the bone-implant integration developed through different morphological aspects. The implant surface appeared in contact with medullary lacunae, as well as with osteoid tissue or directly with bone matrix. The complementary ultrastructural techniques employed have shown that the medullary lacunae appeared as wide and flattened cisternae delimited by a continuous single layer of flattened cells forming a thin lamina adhering to the implant and an endosteal lamina facing the bone surface. For their position and flattened shape we named them peri-implant medullary cisternae. The presence of blood vessels, reticular cells and myeloid cells in their lumen suggested that these peri-implant medullary cisternae were functional sites of new bone formation.
Animals↗
Connective tissues in the optic nerve and in peripheral nerves: ultrastructural observations.
The connective tissues of the bovine optic nerve and left recurrent nerve have been investigated at the ultrastructure level by TEM and freeze-fracture. The outermost of three concentric sheaths enveloping the nerve appear very similar; the intermediate sheaths appear different enough to suggest different functionalities, while the innermost sheaths are completely dissimilar. The ultrastructural aspects of the extracellular matrix suggest that all the connective tissues may mainly play a passive role as a packing material for the nerve fibers, while none of the sheaths seems apt to withstand mechanical stresses.
Animals↗
[The elastic component of the stria alba. A morphometric and ultrastructural analysis].
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Adult↗
Structure and ultrastructure of the bone/ligament junction.
The tibial insertion of the patellar ligament of rat was investigated at light microscopy, scanning electron microscopy and transmission electron microscopy. Until the point of insertion, the patellar ligament showed the typical structure of a tendon. In proximity to the insertion, the ligament increased in diameter and was gradually infiltrated by a different, cartilage-like matrix. Its tenocytes became progressively rounded and displayed some characteristics of chondrocytes. Tendon fibres crossed this fibrocartilage and arrived well beyond the mineralization front. Finally, they appeared to interweave with the tibial diaphysis bone. These fibres were always distinct from the interposed extracellular matrix and exhibited a different pattern of mineralization from the matrix. Our observations indicate that fibrocartilage does not supersede tendon but merely infiltrates it. Thus, the tendon does not splay during articular movement and the tensile stress is redistributed across the insertion area by increasing the mechanical coupling among adjacent fibres. At the same time, this mechanism provides a structural, uninterrupted connection from tendon to bone which is consistent with the biomechanical requirements it has to withstand.
Animals↗
Age-related changes in human anterior cruciate ligament (ACL) collagen fibrils.
The correlation between anterior cruciate ligament (ACL) collagen fibril diameter and aging were studied in subjects aged 15 to 87 years. The samples processed for light and electron microscopy showed statistically significant differences in collagen fibril diameter among young (< 20 years), adult (20-60) and elderly subjects (> 60 years). In the young, the ACL was made up of collagen fibrils which were highly variable in size (range 20-180 nm); the diameter distribution curve was very asymmetrical (mean asymmetry +0.895). In adults and elderly subjects, the maximum diameter had decreased remarkably (120 and 110 nm, respectively) and the diameter distribution curve had become less asymmetrical (mean asymmetry +0.527 and +0.297 respectively). Fibril concentration increased considerably from young (68 fib/mu 2) and elderly subjects (140 fib/mu 2). This reduction in diameter and the relative change in collagen fibril concentration may be related to changes in elastic stiffness. The increase in small collagen fibrils and the marked rise in their concentration may make the ligament more pliable. These findings are similar to those we obtained in Achilles tendon. They demonstrate that both ACL and Achilles tendon, a tissue which responds to unidirectional mechanical forces more than ACL does, show a reduction in diameter value during ageing. These data further suggest that collagen fibril diameter is related to the aging process.
Achilles Tendon↗