Periosteal and endosteal control of bone remodeling under torsional loading.

The shape changes that occur in the mid-diaphysis of a long bone due to adaptive remodeling induced by increasing or decreasing the axial and/or torsional loading of the bone are investigated using a simple model. In this model the mid-diaphysis of a long bone is represented as a hollow thick-walled right-circular cylinder, and different optimal strategies for bone remodeling are considered. It is shown that if such a thick-walled right-circular cylinder capable of surface remodeling is subjected to an axial compressive load and a twisting torque, then the remodeling patterns depend on whether the periosteal surface or the endosteal surface controls the limits of the remodeling process. It is shown that the effect of increasing the torque is always opposite to the effect of increasing the compressive load. Thus, similar remodeling patterns are obtained by increasing one type of loading and decreasing the other. Aside from the restriction of idealized cylindrical geometry, the only assumptions made are that the bone tissue is linearly elastic and that there exists a finite range of remodeling equilibrium stresses. Only those loading situations which maintain the bone in remodeling equilibrium are considered in this work. It follows that the results presented are independent of the specific type of rule governing the temporal evolution of the bone shape, since any such rule applies only in situations where there is active remodeling and, hence, no remodeling equilibrium.     

Arachidonic acid distribution and release in human and rat blood platelets: importance of transacylases]

Human platelets release about 5 fold more arachidonate than rat platelets when they ar triggered with a high dose of thrombin. Total arachidonate content of the phospholipids was not significantly different between the two species. In contrast, phosphatidylcholine (PC) from human platelets exhibited twice more arachidonate than PC from rat platelet and opposite arachidonate contents were found in phosphatidylethanolamine. Moreover, rat platelet PC was very rich in disaturated species, primarily dipalmitoyl whereas high levels of oleate and linoleate were present in human platelets PC. The differences in the fatty acids content of the two species are the result of CoA-independent and CoA-dependent transacylase activities which are more efficient in rat than in human platelets and could account for the low level of arachidonate released from rat platelets.     

Margins and torsion of the human fibula

The borders and ridges of the fibula show a difficult aspect caused by the bone-forming musculature. These structures are an occasion for misunderstanding and mistaken denominations, which even had a noticeable effect on the PNA. Two thirds of all human fibulae exhibit a clearly prominent 'crista musculi tibialia posterioris', giving tendinuous attachment to the tibialis posterior muscle. In diagnosis of borders this crista may lead to errors, because it branches off from the interosseous border underneath the upper fourth of the fibula and reaches the medial crest in the middle of the bone. Most of the borders of the fibula show a twisted course corresponding to the direction of the shaping musculature and effecting a fictitious torsion of the shaft. The proper torsion of the fibula, however, is substantiated by the difference between the absolute torsion (= twist of the two ends of the bone) and the accompanying torsion (= twist enforced by the torsion of the tibia).     

Arterial blood supply to the laryngeal part of the pharynx]

The sources, anastomoses and variations of bloodsupply of the laryngeal part of the pharynx were studied in 100 corpses of different sex and age. It has been established that the fronto-lateral divisions of the laryngeal part of the pharynx are supplied with blood by pharyngeal branches of the superior and inferior paryngeal arteries. Ligation of the pharyngeal arteries during laryngectomy prior to their entering the larynx, i. e. before the divergence of the pharyngeal branches from them, as conventional, causes restriction of supply of these parts and can contribute to disjunction of the pharyngeal suture. The trunks of laryngeal arteries with their pharyngeal branches should be preserved, if possible. The posterior wall of the laryngeal part of the pharynx is divided into three zones depending on the main arterial sources (the ascending pharyngeal, superior and inferior thyroid arteries).     

Sources of the blood supply to the human bulbar conjunctiva

In 93 complex preparations of the human orbit, the sources for blood supply of the eyeball conjunctiva, types of orbital vessels, including size of their diameters, were studied. The open parts of the conjunctiva were stated to get arteries of greater diameters comparing to those supplying the subconjunctival parts. It was noted that some sources of blood supply take their origin from the external carotid artery. This fact should be taken into account when choosing the part for biomicroscopy of the eyeball conjunctiva vessels.     

The LOUVAIN rat and its importance in cancerology]

The LOUVAIN rat model is characterized by a high incidence of spontaneous tumors which is extremely rare in animals. Presently, the spectrum of monoclonal immunoglobulins synthetized by these tumors is the largest ever discovered in animals. Particularly, the LOUVAIN rat tumors produced the only IgD and IgE monoclonal immunoglobuling discovered in an animal species up to now. The contributions of this model to experimental cancerology were multiple: some of them originate in its high incidence, its anatomopathological type or its production of homogenous proteins, others, in the antigenic properties of the monoclonal immunoglobulins synthetized by these tumors, allowing the study of their natural analogues in absolutely new experimental conditions.