Growth of normal peritoneal cells in diffusion chambers: a study in cell modulation

The Origin of Regenerating Mesothelium: A Historical Perspective

Bichat first described the mesothelium in 1827 but despite its early discovery, it has only been in recent years that its importance both in health and disease has been realised. One area still poorly understood is that of the mechanisms regulating mesothelial repair. Mesothelial cells are derived from the mesoderm but express many epithelial characteristics. However, mesothelium does not heal in the same way as other epithelial-like cells. Epithelium heals by centripetal migration, with cells at the edge of the wound proliferating and migrating into the injured area. Hertzler in 1919 noted that both large and small peritoneal injuries healed within the same time frame, concluding that the mesothelium could not heal solely by centripetal migration. The exact mechanisms involved in mesothelial regeneration following injury are controversial with a number of proposals suggested to explain the origin of the regenerating cells. This review will examine these proposals and give some insights into the likely mechanisms involved.

Peripheral blood fibrocytes contribute to the formation of the avian spleen

Chick-quail chimeric studies were made to determine the origin of the cells of splenic ellipsoid. The ellipsoid is formed by supporting and phagocytic cells, which are embedded in a well-organized extracellular matrix. Splenic and bursal anlage of 6- to 6.5-day-old quail embryos were transplanted into the coelomic cavity of 3-day-old chick embryos and further incubated for 17 days. CD45+ chicken hemopoietic cells colonized both organs. They formed the cells of the ellipsoid and the periellipsoidal white pulp of the transplanted quail spleen. Chicken-specific collagen III was produced only in the donor quail spleen, but not in the bursa of Fabricius. The CD45+/collagen I+/collagen III+ cells are probably identical with the mammalian peripheral blood fibrocytes and contribute to the formation of supporting cells, whereas the CD45+/74.2+ ellipsoid-associated macrophages are of monocytic origin. We provide, for the first time, experimental evidence that peripheral blood fibrocytes exist in the avian species; they are present in the circulation of the chicken embryo and contribute to the organogenesis of the spleen.

Margination and diapedesis of inflammatory cells in the islets of Langerhans in hamsters infected with the 139H strain of scrapie

The islets of Langerhans in hamsters infected with the 139H strain of scrapie contain large masses of red blood cells not surrounded by the usual arterial, venous or capillary wall cells. We have referred to these structures as "blood vessel cores" (BVCs). BVCs were almost always centrally located within the islets and surrounded by pancreatic B cells. Margination and diapedesis of inflammatory cells were observed at the BVC walls in 139H-infected hamsters. The cells consisted of the following types: single or clustered lymphocytes; and mixtures of lymphocytes and macrophages or neutrophils. Interaction observed between groups of inflammatory cells and B cells at the BVC walls and inside the islets of Langerhans indicated an inflammatory process. We refer to this interaction as the "linkage-reaction", and to the inflammatory cells as "linkage-inflammatory cells". These phenomena were not observed in other organs (adrenal, uterus, ovary, spleen, liver, kidney, oesophagus, trachea, intestine or pituitary) in 139H-affected hamsters or in the islets of Langerhans of animals infected with other scrapie strains (263K-infected hamsters; 139A-, ME7- and 22L-infected SJL mice). This appears to represent the first clear evidence of an inflammatory reaction in any organ in scrapie-infected animals.

The mesothelium and its reactions: a review

The origins, nature, and reactions of the mesothelium have intrigued investigators for over 100 years. Recently, the use of sophisticated techniques has clarified earlier impressions of its development, structure, and function. The structure of mesothelium reflects its functional properties, its long slender microvilli entrapping a layer of glycosoaminoglycans, providing a frictionless free surface between the parietal and visceral serosa. Transport requirements are met by various surface modifications and both inter- and intra-cellular mechanisms occur. The presence of stomatal openings in the mesothelial membrane has been established, and they may have a major role to play in the movement of cells to and from the serosal cavities. In addition, mesothelial cells can respond to situations of increased functional demand and during the course of inflammation, the mesothelium's fibrinolytic properties are of major importance in preventing the formation of adhesions and the enhancement of healing. Of all the unanswered questions the most significant is the nature, localization, and potentialities of mesothelial precursors. A mesodermal origin is readily acknowledged, but the healing process of damaged mesothelium is less clear. It seems probable that "mature" mesothelium is one source of cell renewal, but mesenchymal cells located in the submesothelial serosa are also strong contenders. Neoplastic mesothelium can adopt a spectrum of histological appearances, reflecting its mesodermal origins. In fact, overacceptance of this concept has erroneously led to the classification of other neoplasms arising in the serosal area as mesotheliomas. Although the ocogenic sequence is still obscure, asbestos is recognized as the major etiologic agent in malignant mesotheliomas. In 1955, Hartwell described differing impressions of the peritoneum as seen through the eyes of an anatomist, an histologist, and a surgeon. In this review on the mesothelium we have attempted to unravel some of its complexities as viewed by embryologists, electronmicroscopists, cell biologists, pathologists, and oncologists.

[Transformation of monocytes into fibroblasts in wound healing (author's transl)]

Recent investigations of HELPAP and CREMER 1972 seem to confirm the supposition of COHNHEIM 1867 that monocytes of the peripheral blood are transformed into firbroblasts in healing wounds. The view of VIRCHOW 1871, MARCHAND 1901 and ASCHOFF 1924 that the fibroblasts in healing wounds are of local origin seems to be supported by the invesigation on parabiotic inbred rats of ROSS et al. 1970. We thought that irradiating the whole body of rabbits could be of value in resolving these apparent contradictions about the origin of fibroblasts in healing wounds.

Cellular Responses of Mice to Diffusion Chambers I. Reactions to Intraperitoneal Diffusion Chambers Containing Listeria monocytogenes and to Bacteria-Free Chambers

Diffusion chambers made with membranes having a pore size of 0.22 μm were implanted in the peritoneal cavities of mice. Chambers that contained no cells induced splenic lymphoreticular hyperplasia and a proliferation of fibroblasts around the chambers. When the chambers contained the bacterium, Listeria monocytogenes , there was strong and continuous chemotaxis of phagocytic cells to the membrane surface. The tendency to incite fibrosis around the chambers containing bacteria produced a tissue reaction resembling a chronic abscess or granuloma. The important difference from a natural lesion was the prevention of direct parasite-host cell interactions. In studies on the pathogenesis of long persisting host-parasite relationships, one might successfully use diffusion chambers to investigate the role of humoral antimicrobial substances as well as the effects of chronic inflammation, with its local concentration of metabolic products and constituents of phagocytic cells. On the other hand, the presence of diffusion chambers in the tissues is an abnormal situation and changes arising from their presence may complicate the interpretations of some experiments.

Quantitation of strain BALB-c mouse peritoneal cells

Total and differential counts of the peritoneal cells of male and female BALB/c mice aged 10 days to over 2 years demonstrate that the increase in cell number that occurs in mice over 2 months old is due entirely to an increase in lymphocytes. The number of peritoneal macrophages in BALB/c females is maintained at a constant level for 22 months. The stability of the macrophage population in contrast to the increase in numbers of lymphocytes suggests that the body pools of these two cell types are not related.

Wound healing and collagen formation. VI. The origin of the wound fibroblast studied in parabiosis

Healing skin wounds were studied in a series of parabiotic rats. The femurs of one parabiont of each pair were shielded whilst both animals were given 800 r from a Co(60) source. The animals were wounded 3 days after irradiation. Each animal with partially shielded marrow was then given tritiated thymidine intraperitoneally daily while the cross-circulation was arrested by clamping. After the thymidine-(3)H had cleared the blood, the clamp was released. Animals were sacrificed, and wounds were prepared for radioautography 1, 2, and 6 days after wounding. In the wounds of the shielded animals thymidine-(3)H was observed in epidermis, endothelium, leukocytes, fibroblasts, and mast cells. Only neutrophilic leukocytes, monocytes, and lymphocytes were labeled, as determined by light and electron microscope radioautography, in the wounds of each nonshielded parabiont. None of the many fibroblasts present were found to contain label in the wounds of the nonshielded parabionts through the 6 day period. These observations provide further evidence that wound fibroblasts do not arise from hematogenous precursors and, therefore, must arise from adjacent connective tissue cells.

Dialysis culture of microorganisms: design, theory, and results

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