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  • 1
    ISSN: 1432-0851
    Keywords: Key words Greater omentum ; Milky spots ; Tumour cells ; Macrophages ; Solid metastasis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The role that milky spots in the greater omentum play in tumour cell spread in the peritoneal cavity is presently not fully understood. To study whether intraperitoneally injected tumour cells appear preferentially in milky spots of the greater omentum and to study the changes in the greater omentum, and especially in the cell population of milky spots after tumour cell infiltration, the following study was performed. A detailed temporal sequences of changes in morphology and cellular composition in milky spots of the greater omentum of Wag/Rij rats 5, 15, 30, 60 min, 2, 4, 8, 16, 24 h, 2, 4, 8 days and 2 and 4 weeks after intraperitoneal administration of 2.0 × 106 CC 531 tumour cells was investigated by light microscopy and electron microscopy (pre-embedding labelling). Our data showed that the milky spots in the greater omentum were the sites to which tumour cells migrated preferentially from the peritoneal cavity. The tumour cells infiltrated the milky spots and formed clusters within. The cellular population in milky spots reacted by a very rapid influx of young macrophages during the first hour and an increase of the total number of cells (P 〈 0.01). After 4 h tumour cells were also located on the greater omentum outside the area of the milky spots. Around these tumour cell deposits, new milky spots are formed, which increased the total number of milky spots. The cells present in milky spots are not capable of reversing the growth of tumours and finally a solid omental cake of tumour cells is formed.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0878
    Keywords: Macrophage ; Peritoneal cavity ; Omentum ; Depletion ; Repopulation ; Freund's adjuvant ; Rat (Wistar)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The purpose of this study was to develop a method for the depletion of macrophages from the peritoneal cavity and the omentum of the rat. Rats received two intraperitoneal injections (at days 0 and 3) with liposome-encapsulated clodronate (dichloromethylene bisphosphonate: Cl2MBP-liposomes). This treatment resulted in complete elimination of mature tissue macrophages (ED2-positive macrophages) from the peritoneal cavity and the omentum within 2 days. The elimination included the strongly ED2-positive spindle-shaped cells of the omental membrane. Repopulation of the omental ED2-positive macrophages was not seen within the next 23 days. Whereas ED2-positive macrophages were completely depleted, few ED1-positive cells remained and repopulation of ED1-positive cells was faster. The treatment further depleted macrophages from the spleen, especially from the red pulp, parathymic lymph nodes and liver. Freund's incomplete adjuvant administered one day after the last injection of Cl2MBP-liposomes considerably accelerated repopulation in the omentum. The protocol described might be used to investigate the contribution of mature tissue macrophages to the induction of immune responses, drug metabolism and the elimination of intestinal tumours.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0878
    Keywords: Key words: Macrophage ; Peritoneal cavity ; Omentum ; Depletion ; Repopulation ; Freund’s adjuvant ; Rat (Wistar)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. The purpose of this study was to develop a method for the depletion of macrophages from the peritoneal cavity and the omentum of the rat. Rats received two intraperitoneal injections (at days 0 and 3) with liposome-encapsulated clodronate (dichloromethylene bisphosphonate: Cl2MBP-liposomes). This treatment resulted in complete elimination of mature tissue macrophages (ED2-positive macrophages) from the peritoneal cavity and the omentum within 2 days. The eliminatio n included the strongly ED2-positive spindle-shaped cells of the omental membrane. Repopulation of the omental ED2-positive macrophages was not seen within the next 23 days. Whereas ED2-positive macrophages were completely depleted, few ED1-positive cells remained and repopulation of ED1-positive cells was faster. The treatment further depleted macrophages from the spleen, especially from the red pulp, parathymic lymph nodes and liver. Freund’s incomplete adjuvant administered one day after the last i njection of Cl2MBP-liposomes considerably accelerated repopulation in the omentum. The protocol described might be used to investigate the contribution of mature tissue macrophages to the induction of immune responses, drug metabolism and the elimination of intestinal tumours.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0003-276X
    Keywords: Human greater omentum ; Milky spots ; Macrophages ; Lymphocytes ; Light microscopy ; Electron microscopy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Background: Milky spots in the greater omentum of some animals are well organized perivascular infiltrated of leucocytes, and are considered to have characteristics of secondary lymphoid tissue. To determine whether milky spots in the human greater omentum can also be regarded as secondary lymphoid tissue, we studied milky spots in an unstimulated state.Methods: Patients were selected on the basis of absence of disease in the peritoneal cavity that might influence the state of the milky spots. Using monoclonel antibodies aganist macrophages, B-lymphocytes and T-lymphocytes, and immunoperoxidase labeling, the number of these cells and their location in milky spots were studied by light microscopy. However, the stromal components of the greater omentum, especially those within the milky spots, were studied by electron microscopy.Results: Milky spots in the human greater omentum are relatively uniform vascularized accumulations of mononuclear cells comprising macrophages (67.9% ± 9.4, mean ± standard deviation), B-cells (10.1% ± 3.4), T-cells (10.2% ± 3.7), and mast cells. However, no special B-cells and T-cell areas could be distinguished. On the ultrastructural level it was demonstrated that macrophages are present in different stages of maturation and can enter or leave the milky spots. Furthermore, no cells characteristic of secondary lymphoid organs, such as interdigitating cells or follicular dendritic cells, were seen.Conclusions: These data indicate that unstimulated milky spots in the human greater omentum are to a great extent just a preformed specific accumulation of primarily macrophages within the stroma of the greater omentum, and therefore, cannot be regarded as true secondary lymphoid tissue. Milky spots could serve as a gateway for, as well as a provider of pertioneal macrophages when the intra-abdominal status so requires.Finally, the data from this study are compard with the data of other studies of human milky spots and those in animals. © 1995 Wiley-Liss, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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