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M N Walters

Publications and source records attributed to M N Walters.

9 recordsLinked to original sources
PubMed1979

Macrophage polykarya.

Multinucleated giant cells are commonly found in a wide variety of inflammatory reactions. They are formed at sites of tissue injury by fusion of freshly exuded monocytes, the rate of fusion being dependent on a range of extracellular and intracellular factors. Electron miscroscopy shows that the pooled components of the fused monocytes are not randomly dispersed in the syncytium, but are highly reorganized into a functioning unit. In addition, histochemical and biochemical profiles of cell populations containing these polykarya display a range of metabolic activities, including DNA synthesis, which, on occasions, is followed by successful mitotic division and the formation of polyploid daughter cells. Fusion results in the loss of some surface receptors which in turn interferes with the phagocytic performance of polykarya, which is generally less pronounced than their mononuclear precurses. In addition, polykarya are not as actively motile as macrophages although phenomena of contact inhibition are less obvious. On the other hand, the multinucleate giant cells display prominent exocytosis which may aid in the degradation of extracellular material. The properties of macrophage polykarya contrast with macrophage homokarya produced in vitro. The latter are actively phagocytic, do not synthesize DNA, and have a longer half-life than the syncytia produced in chronic inflammatory reactions. It may well be that the polykarya in such reactions are not true homokarya.

Animals↗
PubMed1978

An ultrastructural examination of the interaction between macrophages and Cryptococcus neoformans.

The interaction of mononuclear phagocytes with Cryptococcus neoformans was examined in vitro and in vivo using ultrastructural techniques. Immune serum roughens the surface of the yeast and in the first 2 hr, increases the number of organisms attaching to the macrophage surface, as well as the number of contacts between individual yeasts and the phagocyte. Contact is established by means of thin filopodia and cytoplasmic flaps. During the next few days the macrophages increase in size, and, by intimate apposition of their contiguous cell surfaces, a cellular barrier surrounds the now enclosed yeast. These events are accompanied by thinning of fungal capsule, degradation of the enclosed cryptococcus, and the formation of macrophage polykaryons. Electron cytochemical techniques for peroxidase reveal that these multinucleated cells are formed predominantly by the fusion of stimulated macrophages. Destruction of the enclosed yeast probably results from the secretion of various agents by the surrounding cells.

Animals↗
PubMed1978

The inhibitory effects of high molecular levan on transport across the vascular wall stimulated by histamine.

Administration of levan to mice and rats inhibited the passage of intravenously injected trypan blue into the area of skin injected with histamine. In the mouse, the optimal dose of levan was about 5 mg/25 g body weight; higher doses, on the other hand, enhanced diffusion. In the rat, the inhibitory effect was directly related to the dose of levan, the optimal dose being five times higher than for mice. Treatment of rats with levan caused a marked reduction in the uptake and transport of colloidal carbon. In normal and histamine- or turpentine-injected cremaster muscles, treatment with levan prevented carbon from being adsorbed and endocytosed by the endothelial cells. Levan itself was frequently attached to the lumenal surface of endothelial cells, or less frequently was enclosed within pinocytic vesicles. Occasionally, transport across the interendothelial junction was also seen, but the impression gained was that the frequency and extent of patent junctions were reduced in animals receiving phlogistic stimuli and treated with levan. Carbon particles were generally aggregated in the central zone of vessels and were seldom seen near the endothelial cells, within endothelial cells or within any open junctions, presumably because of the coating effect of levan. With partly depolymerised levan, carbon particles were found in endothelial cells and intercellular spaces, but at lower concentrations than in non-levanised control animals. It is suggested that levan acts by altering the rheologic patterns in the microcirculation, by modifying the surface of endothelial cells and by influencing their behaviour, and, finally, by changing the constitution of the ground substance and basement lamina.

Animals↗
PubMed1978

The tissue reaction to implanted foreign bodies in levan-treated mice.

The effect of local administration of levan on the reaction to foreign bodies was studied in the subcutaneous tissues of mice implanted with sterile cotton wool pellets or Melenex plastic coverslips. Treatment with levan reduced leucocytic invasion of the implanted pellets as well as the vasoproliferative response of the surrounding tissue. Reduction in the thickness of the capsule surrounding the implant in levan-treated mice provided further evidence for the latter. Assessment of cells attached onto implanted coverslips showed that levan treatment diminished the number of macrophages attaching to the plastic and significantly reduced the number of nuclei within the multinucleate giant cells formed at the site of implantation. This reduction indicates that levan also exerts an inhibitory action on fusion between macrophages.

Animals↗
PubMed1978

Phagocytosis: a review.

Primitive unicellular organisms depend greatly on internalization of particulate matter for nourishment. In metazoa, this process is further developed to play a major role in mechanisms of defense. This review analyzes, mainly in mammalian systems, the various phenomena surrounding the phagocytic act. Much of the emphasis is placed on experimental work which has recently elucidated some of its features. Both the structural and functional aspects of phagocytosis are considered throughout the review, which is subdivided into an examination of chemotaxis and the various agents inducing it, the mode of recognition of particles to be phagocytized, and the mechanisms of ingestion. The last includes a discussion of the possible means whereby recognition is translated into ingestion, the modes of adhesion of particles onto the surface of phagocytes, the formation and fusion of pseudopodia during engulfment and ingestion, and process and significance of degranulation. In addition, the metabolic changes in phagocytes during the processes of chemotaxis, ingestion, and digestion are described. A discussion of the various ways phagocytes may destroy microorganisms incorporates an appreciation of the importance of the microbicidal action of the acidic environment of the phagosome, the various lysosomal contents, hydrogen peroxide, superoxide, singlet oxygen, and chemiluminescence. The interdependence and interrelationship of the induction and cooperation of these mechanisms are examined.

Animals↗
PubMed1976

The surface morphology of the phagocytosis of micro-organisms by peritoneal macrophages.

Scanning electron-microscopic studies of phagocytosis of various micro organisms by murine peritoneal macrophages has been made. Bacillus cereus, Staphylococcus aureus, and Brewer's yeast were easily ingested, whereas Cryptococcus neoformans was not. The development of intricate and tenuous filopodia preceded close-surface attachment, after which both thin and thicker lamellipodia invested the micro-organisms. Loss of the normal surface ridges characterised the replete cell. The technique of scanning electron microscopy is easily reproducible and adds a new parameter to the morphological appreciation of a fundamental biological phenomenon.

Animals↗
PubMed1976

Bone marrow metastases in disseminated alveolar rhabdomyosarcoma: case report with ultrastructural study and review.

A case of desseminated alveolar rhabdomyosarcoma in an 18-year-old male with leuco-erythroblastic anaemia is described. Numerous bizarre malignant cells, including frequent multinucleated giant cells, were seen in bone marrow aspirates, and osteolytic lesions appeared late in the clinical course. The primary site of the neoplasm remained undertermined during life and also at necropsy, which revealed minute pulmonary metastases and extensive lymph nodal, pleural and skeletal deposits. The diagnosis was confirmed on necropsy tissue by ultrastructural examination which demonstrated numerous thin (5 nm) and thick (15 nm) intracytoplasmic filaments in tumour cells, sometimes organized in bundles; scattered dense Z-band-like bodies, and rod-shaped structures were also seen. The fine structure of the rhabdomyosarcoma in the present case is compared with previous ultrastructural studies. Elongated, thick intracytoplasmic filaments whose diameter corresponds to that of myosin myofilaments are strong evidence for rhabdomyoblastic differentiation and are considered to be the sine qua non of a positive electron microscopic diagnosis of rhabdomyosarcoma. Orgaized bundles of filaments and Z-band-like dense bodies are usually present, and rod-shaped structures are found infrequently, but none of these are necessary for the ultrastructural diagnosis.

Adolescent↗
PubMed1975

An analysis of the Phagocytic potential of multinucleate foreign body giant cells.

Multinucleate giant cells were collected by subcutaneous implantation of plastic films into mice. The attached cells were challanged in vitro with staphylococci, yeasts and sheep erythrocytes treated with either glutaraldehyde or isologous or heterologous antiserum. Cells containing more than seven nuclei rarely phagocytized yeasts or staphylococci, and the uptake and ingestion of sheep erythrocytes treated with heterologous antiserum was equally infrequent. Many sheep erythrocytes treated with isologous antiserum or glutaraldehyde attached to giant cells. When the adherent erythrocytes were related to the increased size of the multinucleate cell by dividing the number attaching by the number of nuclei in the giant cell, a progressive relative reduction was demonstrated as the nuclear content increased. It is suggested that these phenomena are due to the loss of surface receptors subsequent to fusion during the formation of multinucleate cells.

Animals↗