Single trabecula

It is a fact that in all studies up to now the bone or bones removed from the carcass for analyses have been treated as one unit. The result of Nicolaysen and Jansen s work indicates that each single trabecula contains less mineral per cubic unit in vitamin D deficiency. There was much more bone (Albright and Reifenstein, 1948) in the vitamin D-free rats. It might consequently be contended, in purely descriptive terminology, that the rachitic bone takes up as much minerals as the normal bone when identical amounts of Ca and P are supplied to it, because the defective mineralization of each matrix unit is compensated for by the formation of more, or by the destruction of less, matrix. 

Microstructure 10-500 mm Haversian system, osteons, single trabeculae... 

The mechanical properties of bone are related to its complex hierarchical structure. Several levels of structural organization, from macro- to subnanostructure, can be identified (a) the macrostructure (cancellous and cortical bone) (b) the microstructure (from 10 to 500 mm Haversian systems, osteons, single trabeculae) (c) the submicrostructure (1-10 mm lamellae) (d) the nanostructure (from a few hundred nanometers to 1 mm fibrillar Col and embedded mineral) and (e) the subnanostructure (below a few hundred nanometers the molecular structure of constituent elements, such as mineral, collagen, and non-collagenous organic proteins). The hierarchical structural organization of bone is shown in Fig. 1 [12]. 

Cancellous bone accounts for roughly 20% of the total mass of the skeleton. It exhibits a quite isotropic cellular structure, made by interconnected network of plates (trabeculae). Such network provides a low-density, open-cell structure, whereas a single trabecula gives high-density, virtually closed cells [2]. 

Mechanical Properties of a Single Trabecula in Bovine Femur by the Three Point Bending Test... 

In contrast to the increase in submaximal force, AB KO trabeculae had a decrease in maximal force with saturating Ca2+ or tetanus (-20-40% lower). Ca2+ transients were unchanged, indicating that the decreased force was caused by impaired myofilament function. The exact abnormality is unknown, but one possibility is a reduction in amount of myofibrils. The relative contribution of the A and the B to development of normal force generation also is unknown. Maximal force was also reduced in single A KO trabeculae (-20%), although this was not significant statistically (42). 

The lymphoid system, because of its rapidly proliferating tissues, is susceptible to PAH-induced toxicity. The mechanism of action for this effect is most likely inhibition of DNA synthesis. No adverse effects on this system associated with PAH exposure have been reported in humans, but several accounts of lymphoid toxicity in animals are available. A single intraperitoneal injection of benzo[a]pyrene to mice resulted in a small spleen with marked cellular depletion, prominent and edematous trabeculae, and large lymphocytes. These lesions resulted in death (Shubik and Porta 1957). The Shubik and Porta (1957) study was severely limited by the following the benzo[a]pyrene was only partly in solution, only one dose was employed, there was a small size, the purity of benzo[a]pyrene was not specified, only one sex was tested, and the presence of benzo[a]pyrene in the peritoneal cavity indicates inadequate absorption. No other similar studies were found in the literature. 

Townsend RR., Rose R.M., and Radrn E.L. 1975. Budding studies of single human trabeculae. /. Biomech. 8 199. 

Fig. 14. A photomicrograph of a five-month old irrfant mandible, showing the complete fusion of the mental ossicle (mo) with the hemimandibles (hem) forming a single bony trabecula (b). Rostrally, remains of the symphyseal tissue (m) still separate the hemimandibles. The arrows show the direction of fusion between the mental ossicle and each hemimandible. (Haematoxylin and Eosin x 100).

Fig. 16. A photomicrograph of a one-year old infant mandible, showing a complete closure of the symphysis menti resulting in a single mandible. Notice the complete midline encroachment (line) by bony trabeculae (b). (Haematoxylin and Eosin x 20).

Niedergerke, R., and Page, S., 1977, Analysis of catecholamine effects in single atrial trabeculae of the frog heart, Proc. R. Soc. London, Ser. B 197 333-362. 

The theory of Frey-Wyssling postulates the existence of monomolecular polypeptide filaments which must be about 20 A thick. However the electron microscope has revealed the presence in the C3rtoplasm of an endoplasmic reticulum made up of trabeculae 30 to 40 m/i in length, hollow tubes joining together vesicles 100 to 300 m/u in diameter. Attached to this system there are basophilic particles. In addition the cytoplasm contains fibres either singly or in bundles, which make up the contractile material of the cell and by means of a slow but continuous motion maintain the various organelles suspended in the cellular fluid. 

Fig. 2 Effects of stimulus frequency (0.2 Hz and 2.0 Hz), muscle length (100% Lo, 92% Lo and 84% Lo) and [Ca ]o (1 mM and 2 mM) on the heat rate and stress production of a representative trabecula. The left side of the record shows a single twitch stress at 0.2 Hz...

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