Normale und pathologische Anatomie最新文献

The variations of the joint shape are first analyzed in the acetabulum and the ulnar trochlear notch of man. Then an attempt is made to explain the basic shape of the lunate surface and the types of articular surface diverging from it with regard to causal histogenesis and the general theory of joint stress (Pauwels), as well as the theoretical distribution of stress in the perfect ball and socket joint (Kummer). Certain statements are made about the position, size, changes in direction and course of the resultant forces at the joint, statements which seem very likely to be accurate when compared to facts already known about the hip joint in man. Under these preconditions, the various forms of the observed articulating surfaces may be theoretically reconstructed in every case. In this connection, it is first shown that the preservation of the joint cartilage is also dependent on the period of time during which the resultant force is effective in the various areas of the articular surface. The term "relative constancy" is used to express this time factor. Two functional explanations are given for the presence of incisions and divisions in the lunate surface and in the trochlear notch: 1. It is assumed that the "relative constancy" of the resultant forces is of varying magnitude in the different areas of the articular surface. The incisions and divisions in the joint cartilage are thus seen as areas in which the resultant joint stress does not rise above the minimum value for preservation of the articular cartilage. 2. The radius of the convex articular surface can be slightly larger than the radius of the concave articular surface. Because of this incongruity no pressure will be transmitted in an area of the lunate surface or of the trochlear notch because of the defective contact. It follows that the cartilage-preserving stimulating pressure is also absent from this area. According to Pauwels, the magnitude and distribution of the stresses arising in the articulating surfaces may be determined from the varying density distribution of the subchondral bony tissue, as seen in x-rays. The density distribution of the subchondral bone at the ulnar socket shows clear basic parallels to the extent of the surface covered by joint cartilage. The relatively low density in the area of the notch is seen as being the result of lower stress, in accordance with the functional explanation of division of the cartilage surfaces. In photoelastic model experiments, the dependence of the degree of relative stress on the form of the articular surface is illustrated by means of the number of isochromes. Here, the distribution of density of the subchondral bony tissue corresponds to the local magnitude of stress in the corresponding model joint. Functional analysis of the tangential fiber layer of the joint cartilage at the femoral head and the elbow joint, shows basic agreement between the split line patterns and the trajectoral pattern, as described in articulati

The increasing intraneuronal accumulation of lipofuscin has been linked to the aging process by a striking linear correlation between the degree of accumulation and chronological age. It has been established that age pigments are soluble in polar and nonpolar solvents; the pigment is autofluorescent and stains with PAS, Sudan black B, Nile blue osmic acid and ferric ferricyanide techniques. Whether all pigments exhibiting these properties are identical, or at least closely related, regardless of the surrounding tissue, animal species and age of the individual, is debatable. Pigment formation has been demonstrated in young and aged animals as well as in individual subjected to experimental stress and to dietetic and environmental interference. Electron microscopic studies in animals have shown a considerable variability in the fine structure of individual lipofuscin granules but the presence of "lucent vacuoles" surrounded by a unit membrane is one of the characteristic features of neuronal lipofuscin in the aged. Recently, electron microscopy, utilizing the freeze-etching technique, has provided convincing evidence which disproves the earlier view that lucent vacuoles are the remnant of lipid material dissolved and removed during the preparation of the tissues for microscopic examination. These vacuoles have also been demonstrated in freshly frozen material not previously fixed or immersed. Vacuolated pigment granules occur earlier in the area postrema than in other regions of the rat brain (Hasan and Heyder 1974). Regional differences in the time sequence of pigment deposition are present.