52 research outputs found
The canalicular system and the osteoblast domain in human secondary osteons.
No full textThe lacunar-canalicular system in human secondary osteons was examined by two complementary techniques: light microscopy analysis of undecalcified thick sections and the SEM cortex-fractured surface technique. Unlike the earlier definitions of 'osteoblastic domain' presented as the matrix volume produced by osteoblasts in the process of osteon infilling, this study measured the domain by the length of osteoblast dendritic processes. The domain extension was defined along radial vectors advancing from the reversal line towards the central canal. According to their lengths, domains were divided into three classes: peripheral, intermediate and internal. The mean length of peripheral domains was significantly shorter than those of the intermediate and internal domains. This suggests that the infilling process is modulated by an initial preparatory phase characterised by osteoblast adhesion to the wall of the cutting cone, and a limited matrix synthesis, followed by a regular matrix volume apposition organised in concentric layers. In addition to the radial canaliculae arranged along converging vectors in planes perpendicular to the central canal, we distinguished a further class of canaliculae, the equatorial canaliculae originating from the major perimeter of the lacuna and spreading out radially in the plane of the same lacuna (therefore, perpendicularly to the radial canaliculae). The whole lacunar-canalicular network was structured as a closed system around the vascular axis of the central canal with very few canaliculae crossing the reversal line and connecting the neighbouring osteons. These anatomical observations contribute to our knowledge of lacunar-canalicular system development
Morphometric analysis of osteonal architecture in bones from healthy young human male subjects using scanning electron microscopy.
No full textThe shape and structure of bones is a topic that has been studied for a long time by morphologists and biologists with the goal of explaining the laws governing their development, aging and pathology. The osteonal architecture of tibial and femoral mid-diaphyses was examined morphometrically with scanning electron microscopy in four healthy young male subjects. In transverse sections of the mid-diaphysis, the total area of the anterior, posterior, lateral and medial cortex sectors was measured and analysed for osteonal parameters including osteon number and density, osteon total and bone area and vascular space area. Osteons were grouped into four classes including cutting heads (A), transversely cut osteons (B), longitudinally cut osteons (C) and sealed osteons (D). The morphometric parameters were compared between the inner (endosteal) and outer (periosteal) half of the cortex. Of 5927 examined osteons, 24.4% cutting heads, 71.1% transversely cut osteons, 2.3% longitudinally cut osteons and 2.2% sealed osteons were found. The interosteonic bone (measured as the area in a lamellar system that has lost contact with its own central canal) corresponded to 51.2% of the endosteal and 52.4% of the periosteal half-cortex. The mean number of class A cutting heads and class B osteons was significantly higher in the periosteal than in the endosteal half-cortex (P < 0.001 and P < 0.05, respectively), whereas there was no significant difference in density. The mean osteon total area, osteon bone area and vascular space area of both classes A and B were significantly higher (P < 0.001 for all three parameters) in the endosteal than in the periosteal half-cortex. The significant differences between the two layers of the cortex suggest that the osteoclast activity is distributed throughout the whole cortical thickness, with more numerous excavations in the external layer, but larger resorption lacunae closer to the marrow canal. A randomly selected population of 109 intact class B osteons was examined at higher magnification (350×) to count osteocyte lacuna and to analyse their relationship with osteon size parameters. The distribution frequency of the mean number of osteocyte lacunae increased with the increment in the sub-classes of osteon bone area, whereas the density did not show significant differences. The number of osteocyte lacunae had a direct correlation with the osteon bone area and the mean osteon wall thickness, as well as the mean number of lamellae. The osteocyte lacunae density showed an inverse relationship. These data suggest a biological regulation of osteoblast activity with a limit to the volume of matrix produced by each cell and proportionality with the number of available cells in the space of the cutting cone (total osteon area). The collected data can be useful as a set of control parameters in healthy human bone for studies on bone aging and metabolic bone diseases
The dependency of collagen fibrillogenesis in vitro on fibroblasts culture conditions. Fibroblasts in mono- and multi- layers
No full textThe 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
Morphology of epiphyseal apparatus of a ranid frog (Rana Esculenta)
No full textMorphological, histochemical and ultrastructural investigations on epiphyseal apparatus of Rana Esculenta were made. The most important findings were the following: 1) metaphyseal cartilage is localized inside proximal diaphyseal compact bone as a plug; 2) metaphyseal cartilage do not reduce in thickness during ageing; 3) metaphyseal cartilage do not show vascular invasion and do not mineralize in degenerative zone; 4) trabecular bone was not at all evident in this animal; 5) external periosteum is well vascularized and proliferates in correspondence to marginal epiphyseal end of the diaphyseal. From these results the hypothesis that the ranid frog bone growth is not due to metaphyseal metabolism (as in avian and mammals) but to bone periosteal marginal mineralization is reached
The foreign body reaction in total hip arthroplasties. A correlated light-microscopy, SEM, and TEM study.
No full textAn in vivo histological and ultrastructural study of the cellular reaction to particulate material currently used in orthopaedic surgery produced evidence that, on a strictly cellular level, the main damage is done by the smallest particles produced by hip prostheses, i.e. metal particles, irrespective of differences in their chemical composition. Particle size and release rate are the critical factors, although other mechanisms of cellular damage may be active once granulation tissue is formed
Recognition of cell surface modulation by elliptic Fourier analysis.
No full textA development of elliptic Fourier analysis, consisting in an alignment of harmonics according to their clockwise or counter-clockwise rotation, resolves the discrepancy between calculated harmonic frequencies and observed morphological periodicities. The new technique is supported by consistent data of empiric and fractal contours, comparatively analyzed and visualized with and without harmonic alignment. The method is particularly suitable for the recognition of periodic modulations of the cell surface. A preliminary analysis of two different cell populations (echinocytes and chondrocytes) shows distinct patterns of surface modulation that allow an effective discrimination of the cell type, while providing relevant information about the respective cytological configurations
- …
