Henry P. Schwarcz

Bone is constructed of mineral platelets surrounding and lying between collagen fibrils. TEM images of ion-beam milled sections of long bones of humans and other terrestrial vertebrates cut normal to the axes of collagen fibrils display ~5nm thick polycrystalline mineral platelets (MPs) arranged either as stacks of MPs wrapping closely around collagen fibrils, or as stacks of curved MPs lying between the fibrils. Previous finite-element modelling showed that circular cylinders composed of MPs would contribute to the torsional and bending stiffness of bone. Here we used TEM to study sections of cortical bone of long bones cut normal to collagen fibrils. We found closed loops up to 570 nm in diameter on their long axis. They consist of stacks of2-5 MPs, and are mostly elliptical in form; while some are almost circular. They enclose random arrangements of cylindrical collagen fibrils closely surrounded by thicker stacks of MPs. The loops are cross sections of quasi-cylindrical columns extending for unknown distances above and below the plane of the section. The columns make up about 1/3 of the volume of cortical bone. They would contribute to the stiffness of the bone with respect to torsion and bending, and presumably evolved for that reason.

Bone is constructed of mineral platelets surrounding and lying between collagen fibrils. TEM images of ion-beam milled sections of long bones of humans and other terrestrial vertebrates cut normal to the axes of collagen fibrils display ~5nm thick polycrystalline mineral platelets (MPs) arranged either as stacks of MPs wrapping closely around collagen fibrils, or as stacks of curved MPs lying between the fibrils. Previous finite-element modelling showed that circular cylinders composed of MPs would contribute to the torsional and bending stiffness of bone. Here we used TEM to study sections of cortical bone of long bones cut normal to collagen fibrils. We found closed loops up to 570 nm in diameter on their long axis. They consist of stacks of2-5 MPs, and are mostly elliptical in form; while some are almost circular. They enclose random arrangements of cylindrical collagen fibrils closely surrounded by thicker stacks of MPs. The loops are cross sections of quasi-cylindrical columns extending for unknown distances above and below the plane of the section. The columns make up about 1/3 of the volume of cortical bone. They would contribute to the stiffness of the bone with respect to torsion and bending, and presumably evolved for that reason.

Bone is one of the most important organs of mammals, consisting of collagen and apatite. Various diseases, such as osteoporosis, can affect the components of bone tissue, their chemical composition and bone ultrastructure, which leads to changes in properties. In this paper, the effect of initial osteoporosis on the chemical composition of bone apatite and the ultrastructure of bone tissue from a mineralogical point of view is analyzed using rat femurs as an example. The chemical composition of bone apatite was studied using SEM, EDS and FTIR-ATR spectroscopy. The bone ultrastructure was examined using a transmission electron microscope. An increase in the content of carbonate ion in the position of the phosphorus group and a change in the orientation of apatite crystals inside mineral plates were revealed against the background of initial osteoporosis, which can affect not only the mechanical properties of bone, but also the stability of apatite under biological conditions.

Purpose Transmission electron microscopy (TEM) is widely used to study the ultrastructure of bone. The mineral of bone occurs as polycrystalline mineral plates about 3 to 6 nm in thickness. A problem in using TEM to make quantitative analyses of bone is that the orientation of the plates with respect to the plane of the section being imaged is expected to affect their apparent thickness. The purpose of this study was to test if this was true, if the apparent thickness of plates changed substantially as a result of tilt of the section. Methods We prepared TEM sections of samples of cortical human bone by ion beam milling, orienting one section parallel to the collagen fibril axes and one perpendicular to them. We obtained TEM bright field and HAADF images of these sections, tilting the sections up to ± 20° at 2° intervals and measuring the apparent thickness of individual mineral platelets at each angle of tilt. Results Thickness appears to double as section is tilted ± 20°. True thickness of plates is determined by tilting the section along an axis parallel to the plate orientation and determining the minimum apparent thickness. However, as plates are tilted away from minimum-thickness orientation, they become less well-resolved, disappearing when tilted more than 20°. We therefore also measured apparent thickness of only the darkest (most electron scattering) plate images in an untilted section and obtained the same average thickness as that obtained by tilting. Conclusion We conclude that tilting of the section is not necessary to obtain an accurate measurement of the thickness of mineral plates.

Hominins emerging from Africa in the Pleistocene required sources of vitamins in addition to sources of energy and substance (carbohydrates, proteins and fats). Most of their vitamin requirements could be provided by eating the flesh of herbivores but vitamin C is in low concentrations in animal muscle tissue. Lack of vitamin C causes fatal disease of scurvy. In southern Eurasia hominins would have been able to harvest fruits and vegetables throughout the year but as they migrated further to the north, they would encounter regions in which no plants were growing in mid-winter. Vitamin C is enriched in organ meats but their mass was probably too low for adequate provision. Storage of summer crops of fruit was possible. Hominins could however fulfil ascorbic acid requirements by drinking aqueous extracts from the needles of pines and other conifers which contain adequate amounts of vitamin C to satisfy human needs. We show evidence of pine needle and related consumption in Paleolithic sites.