A. van den Hooff

Stromal Involvement In Malignant Growth

Publisher Summary This chapter describes various modes of interaction between malignant cells and stroma. Malignant cells are shown to produce various lytic enzymes, which attack the stroma or to induce fibroblasts to synthesize collagenolytic, elastolytic, and glycosaminoglycan-degrading enzymes. In some cancers tumor cells stimulate fibroblasts to produce stromal components—collagen, elastin, and glycosaminoglycans. Migration of tumor cells is partly determined by versatile adhesive glycoproteins in the stroma. Wound healing and especially fibrosis (scars) appear to be possible auxiliary factors in carcinogenesis. Stromal cells (local or generalized) may exhibit subtle alterations similar to transformed cells. Stromal alterations preceding manifest malignancy contribute to carcinogenesis. In vitro data point to intricate interdependencies between cancer cells and fibroblasts resulting in synthesis of collagenolytic enzymes. Normal ontogenesis depends on a complex of interactions between various tissues among which the stroma plays an essential role. Epithelial–stromal interactions are also important in the adult organism. In cancer growth, the microenvironmental signals constitute an essential category of influences contributing to malignancy.

Fine structure of fibroblasts in the periodontal ligament of the rat incisor and their possible role in tooth eruption

Abstract To determine whether the movement of the tooth-related part of the periodontal ligament of rodent incisors might be due to mechanical activity of the cells, the fine structure of the fibroblasts in the lingual part of the periodontal ligament of male rat lower incisors was studied; particularly the fibroblasts in the tooth-related part contain systems of microfilaments and microtubules. In these cells, microfilaments are arranged in networks as well as in bundles in the peripheral parts of the cytoplasm. Filaments, possibly in coordination with microtubules, might be associated with cell locomotion. The significance of these and other findings are discussed with respect to the mechanism of eruption. A model for the eruption of the rat incisor is proposed: fibroblasts in the tooth-related part of the periodontal ligament, while migrating in an occlusal direction, possibly guided by oxytalan fibres, pull the tooth with them by means of the collagenous framework. Data are presented which support the view that fibroblasts in the periodontal ligament of the incisor, apart from synthesizing collagen, are also engaged in degrading collagen fibres. This dual activity is necessary to maintain the structural integrity of the ligament in a dynamic situation.

Fine structure and possible function of cells containing leptomeric organelles in the periodontal ligament of the rat incisor

Abstract In the alveolar zone of the periodontal ligament of the rat incisor, cells occur which are characterized by the presence of cross-banded structures composed of filamentous material. These structures, having a periodicity of about 160 nm, resemble leptomeric organelles in muscle spindles. The cells in which these structures were found contain many vesicles and are surrounde by basement membrane-like material. They are localized in close apposition to nerve endings. Although these cells might be concerned in the mechanism of eruption, they may have sensory functions.

The Influence of Acrylic Cement on the Femur of the Dog: A Histological Study

Using dogs as experimental animals, polymerizing methylmethacrylate was inserted into the marrow cavity of the femur. The influence on bone over a period of 21 months was studied by means of histological techniques and microradiography. To distinguish the effect of the methacrylate proper from the circulatory disturbance resulting from the operation, control experiments were performed in which the marrow cavity was emptied, but no acrylic cement was inserted. Polymerization of the methacrylate in vivo resulted in a local rise in temperature to about 58 degrees C. In the femurs containing the acrylic cement a consistent picture developed, consisting of: a) necrosis and removal of the central part of the cortex and b) apposition of a thick layer of bone on the outer surface of the cortex, c) deposition of a cylindrical bone sleeve in contact with the methacrylate. In the control experiments only a minimal resorption at the inside surface of the cortex and the deposition of a thin layer of bone at the outside of the cortex were observed. It is concluded inter al. that circulatory distrubance contributes only slightly to the total reaction of bone to the insertion of methacrylate.

Long-term results of the implantation of glutaraldehyde-fixed tissue

Abstract Glutaraldehyde-fixed autologous young connective tissue was implanted in rabbits for periods of 4, 6, 8, and 12 months, respectively, to evaluate the long-term effects of glutaraldehyde fixation. It was concluded that the implants elicit very little reaction in the surrounding tissues and that the fixed tissue is slowly invaded by vital cells and probably evokes an immune response. It is likely that, although glutaraldehyde-fixed dead tissue provokes less reaction than both unfixed and formaldehyde-fixed dead tissue, in the long term it is also broken down and phagocytized.

Tissue reaction to implantation of unfixed and glutaraldehyde-fixed heterologous tissue

Renewed interest in the use of aldehydes in endodontics has made it necessary to find out if the antigenic properties of foreign proteins can be attenuated by glutaraldehyde fixation. Untreated and glutaraldehyde-fixed heterologous tissue was, therefore, implanted in rabbits. The local tissue reaction to the implants as well as the reaction in the lymph nodes draining the implant site was examined. The experimental results do not support the view that glutaraldehyde fixation, in the long term,attenuates the antigenic properties of proteins.

Histological evaluation of biocompatible orthopaedic polymer

The biocompatibility of biocompatible orthopaedic polymer implant materials was studied in subcutaneous and bony tissue of rats and rabbits. The tissue response was evaluated by histological techniques. No bone induction capacity of biocompatible orthopaedic polymer could be observed. In rabbits, the presence of plasma cells was significantly higher than in rats. The biomaterial showed some signs of biodegradation and was not very biocompatible.

The response of the living organism to dead and fixed dead enclosed homologous tissue

Polyethylene tubes at both ends and with four perforations in the side walls were filled with untreated homologous necrotic muscle tissue or formaldehyde-fixed or glutaraldehyde-fixed homologous necrotic tissue and implanted subcutaneously in rats. The cell reaction in the tissues surrounding the differently filled tubes was examined. It was found that the inflammatory reaction to untreated necrotic homologous tissue was the least severe.

Short-term tissue reactions to enclosed glutaraldehyde-fixed tissue

Polyethylene tubes closed at both ends and with four perforations in the sidewalls were filled with glutaraldehyde-fixed isologous tissue and implanted subcutaneously in rats. The cell reaction during the first 12 days in the tissues adjacent to the tubes was histologically examined. The reaction was compared to the reaction around tubes implanted empty. The examination showed a severe inflammatory reaction with probably immunologic aspects in the tissues adjacent to the filled tubes. The reaction around the empty tubes was slight and transient.

An electron microscope study of L forms of group a streptococci

Tile morphology of tile L forms of bacteria has been tile sul)ject of many studies, which have been reviewed among others by DIENES and \u (1951) and by KLIENEBERC, ER-NOBEL (1956). Tile electron microscope has been used relatively seldom, possibly because of technical problems. The obvious method of choice is ultrathin sectioning. A prerequisite for this technique is the capacity of tile object to withstand vigorous dehydration during tile embedding process. Becatlse of tile high fragility of these organisms artifacts are easily introduced. In tile present study we made use of the property of tile L forms of streptococci to grow into the medium (fig. I) a feature, common to L forms in general instead of the surface growth of tile bacterial form: the L forms have embedded themselves as it were in the medium. Intact L colonies were therefore fixed together with the surrounding medium in osmimn tetroxide, followed by tile routine methacrylate procedure. Although so far only two strains of streptococcal L forms have been studied with this technique, it seems likely that the procedure may have a wide applicability for the investigation of L forms in general and related phenomena.