Bibliography: leaves 194-233.

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The events in the formation of the components of the mammalian sperm flagellum have been elucidated, in an analysis of rat spermiogenesis, by electron microscopy and EM radioautography using ('3)H-proline and ('3)H-cystine. The connecting piece forms by deposition of dense material around the centrioles during steps 8-15. Newly-synthesized proteins are incorporated into this structure throughout this period. The outer dense fibers exist in step 8-14 spermatids as slender fibrils associated with the axonemal doublets. During step 16, they undergo rapid growth, assuming the form of the mature fibers. This results from massive deposition of proline- and cystine-containing proteins onto the fibrils. The fibrous sheath develops from a framework comprised of two longitudinal columns and a series of circumferentially-oriented ribs which is assembled during steps 11-15 in a distal-to-proximal direction along the flagellum. New ribs originate from proline-rich fuzz-coated filaments which arise within the flagellar cytoplasm.

A morphological and functional investigation of the enamel organ and enamel was carried out on the incisor of the rat. Using transmission electron microscopy and other electron optical techniques, the ultrastructure of enamel hydroxyapatite crystallites and the morphology of the cells of the enamel organ related to these crystallites were examined. In the enamel secretion zone, putative cell communication via matched approaches of rough endoplasmic reticulum to the ameloblast cell membrane was not confirmed. Throughout the enamel organ, extracellular permeability was assessed using radiolabeled proteins as tracers. Regional differences were found, especially related to the two types of maturation ameloblasts. Several modified histochemical techniques were successfully applied to the enamel such that the functional contribution of each type of ameloblast was ascertained. In this way it was demonstrated that several functional cell subpopulations exist and that they can be correlated with different calcium and protein distributions within the enamel. In vivo injection of vinblastine, and in vitro treatments with other drugs, all severely modified the enamel maturation staining pattern and $ sp{45}$Ca uptake. In addition, it was found that ruffle-ended maturation zone ameloblasts possess higher levels of specific transferrin receptor sites relative to smooth-ended ameloblasts, a finding that may be directly related to the deposition of iron within the enamel.

The objective of the thesis was to examine the distribution, biogenesis and assembly of basement membrane components in situ. This goal was achieved by immunolocalizing laminin, collagen IV, heparan sulfate proteoglycan and other components using 5 and 15nm colloidal gold particles. / The distribution of these components, showed them to be ubiquitously localized throughout the thickness of all basement membranes examined. In "thick" basement membranes: Reichert's membrane and the matrix of the mouse EHS tumor, and in the "thin" common basement membranes, the components were localized to the cord network (Inoue et al., 1985). Despite some variations between tissues, quantitation of gold particles indicated a tendency for the molar ratio of laminin:collagen:proteoglycan to be 1:1:0.2 in the thick and 1:1:1 in the thin basement membranes. / The biogenesis of laminin and collagen IV was examined in the endodermal cells producing Reichert's membrane. Both were co-localized in the rough endoplasmic reticulum, Golgi apparatus and secretory granules, corresponding to the pathway followed during processing. / Since the components are believed to self-aggregate after secretion, the molar ratios were used as guidelines to combine the three molecules in vitro, at 35$ sp circ$C. A precipitate formed, which in the electron microscope showed three main structures, one of these had the thickness, immunohistochemical and fine, ultrastructural characteristics of authentic basement membrane. Hence, basement membrane was reconstructed in vitro.

[...] We will briefly review the subjeet focusing our attention on the spermatogonial cella in the rat, and occasionally in other species. [...]

Vibrations of the tibia induced during the tibial resection procedure of Total Knee Arthroplasty are studied. Experimental modal analysis, performed on cadaver specimens, shows that natural frequencies of the in-situ tibia occur at 250, 350, and 650 Hz. A finite element beam model of the tibia, which consists of 3-D elements with varying material and geometrical properties, is used. The model indicates that the first bending mode of the in-situ tibia may occur below 100 Hz. The cadaver specimens are then cut with an oscillating saw to observe the effect of the oscillating saw on the vibrational characteristics. When the tibial resection is performed with the oscillating saw, it is shown that the oscillating saw excites the resonant frequencies of the in-situ tibia.