Do the research goal and databases match? A checklist for a systematic approach.

To test the appropriateness of a given database for specific research questions, we designed a checklist starting with the definition of an ideal database. This ideal database contains all relevant data on patients, providers and services. It is safe and accessible, input is always accurate, continuity is guaranteed and linkage with other information is easy. Of course no such database exists. Still these features are often taken for granted, but highly influenced by organizational processes in healthcare and prioritization. Starting with the characteristics of an ideal database, one can systematically list the required aspects for research goals and compare these with the available systems. This checklist is used to address important aspects of administrative database research and ethical issues. The increasing possibility to misuse sensitive data needs to be discussed by researchers, administrators, individuals and society. This checklist can also be valuable to others to design or interpret studies based on claims databases.

Milky spots in the greater omentum are predominant sites of local tumour cell proliferation and accumulation in the peritoneal cavity.

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 x 10(6) 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.

Ontogeny of milky spots in the human greater omentum: an immunochemical study.

BACKGROUND: Milky spots in the human greater omentum are preformed specific accumulations of primarily macrophages within the stroma of the greater omentum. To obtain a better understanding of milky spots in the human greater omentum, the development and the earliest forms of milky spots in the human greater omentum were studied, with special attention to the macrophage population. METHODS: Specimens of human greater omentum were obtained from fetuses of 20 to 40 weeks gestation and one newborn three days old (n = 6). Using mature macrophages (RFD 7), activated macrophages (RFD 1), B-lymphocytes (CD 22), and T-lymphocytes (CD 2), and immunoperoxydase labeling, the percentage of these cells in developing milky spots and the development of milky spots were studied by light microscopy. A time-dependent increase in the percentage of positive staining cells and the size of clusters was analyzed using the non-parametric Spearman rank correlation test. RESULTS: Small accumulations of cells with about 50% monocytes/macrophages were present at 20 weeks of gestation. With increasing gestational age the number of clusters of cells increased significantly (P < 0.01) as well as their size (P < 0.01). Starting at 29 weeks, vascularized clusters of cells were seen; true milky spots were present at 35 weeks. A significant (P < 0.05) increase in the percentage of mature macrophages was found in developing milky spots, whereas no activated macrophages were seen. The percentage of B-lymphocytes and T-lymphocytes found in the clusters of cells and milky spots increased significantly (P < 0.05) but did not exceed 10% of the total number of cells. CONCLUSIONS: From our data it can be concluded that milky spots are specific structures in the greater omentum formed between the 20th and 35th week of gestation. Further, we concluded that immature cells (promonocytes) mature locally in developing milky spots.

Novel isolation and purification method permitting functional cytotoxicity studies of macrophages from milky spots in the greater omentum.

Milky spots in the greater omentum are well organized perivascular infiltrates of leukocytes which are probably involved in the clearance of tumor cells from the peritoneal cavity. In milky spots, macrophages are the predominant cell type forming a distinct population of cells. To investigate whether these macrophages have a function in the control of metastatic spread in the peritoneal cavity, a novel isolation and purification method was developed in order to study the functional cytotoxicity of macrophages from milky spots in the greater omentum against tumor cells in vitro. In order to obtain a cell suspension, greater omenta of unstimulated healthy male WAG/RIJ rats were incubated in collagenase/DNase suspension and filtered. Subsequently, macrophages were isolated and purified using flow cytometry by sorting unstained cells on the basis of size and internal complexity. Macrophages and other cells were identified by routine May-Grünwald-Giemsa staining and by immunophenotyping with the specific macrophage monoclonal antibody ED 1. Furthermore, macrophage subtypes were characterized by ultrastructural analysis. Functional cytotoxicity of the isolated macrophages was assayed against the syngeneic CC 531 tumor cell line in a colorimetric MTT assay. From three greater omenta of healthy rats 1.16 +/- 0.16 x 10(6) macrophages were isolated with a purity of 83 +/- 2% and a viability of > or = 96%. The macrophages were of the exudate (monocytic), exudate-resident and resident cell type and were in equal proportions. The contaminating cells were mainly mesothelial. A maximum cytotoxicity of approximately 30% was reached with the macrophage fraction at an effector-to-target ratio of 10. Furthermore, it was established that the mesothelial cells did not exhibit cytotoxicity.

Macrophage depletion in the rat after intraperitoneal administration of liposome-encapsulated clodronate: depletion kinetics and accelerated repopulation of peritoneal and omental macrophages by administration of Freund's adjuvant.

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.

Cellular composition of milky spots in the human greater omentum: an immunochemical and ultrastructural study.

BACKGROUND: Milky spots in the greater omentum of some animals are well organized perivascular infiltrates 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 monoclonal antibodies against 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-cell 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 peritoneal macrophages when the intra-abdominal status so requires. Finally, the data from this study are compared with the data of other studies of human milky spots and those in animals.

An ultrastructural study of dopamine-immunoreactive nerve fibres in milky spots of the human greater omentum.

An ultrastructural study was performed to examine the presence and distribution of dopamine-immunoreactive nerve fibres in milky spots of the human greater omentum. Non-myelinated nerve fibres were located perivascularly as well as throughout the milky spots. Dopamine immunoreactivity was demonstrated in the nerve fibres and in a portion of the macrophage population. These results demonstrate a discrepancy between human and non-human milky spots.