Dynamics of an ultra-discrete SIR epidemic model with time delay.

We propose an ultra-discretization for an SIR epidemic model with time delay. It is proven that the ultra-discrete model has a threshold property concerning global attractivity of equilibria as shown in differential and difference equation models. We also study an interesting convergence pattern of the solution, which is illustrated in a two-dimensional lattice.

Establishment of a human malignant fibrous mesothelioma cell line and the biological characteristics compared with malignant epithelial mesothelioma cell line.

Two human malignant mesothelioma cell lines, which we designated "epithelial mesothelioma cells" and "fibrous mesothelioma cells", were established from the pleural fluid containing malignant mesothelial cells of a 72-year-old Japanese man. These cell lines were separated by the colonial techniques from the initiation of the primary cultures and grew well without interruption for 12 years. They were characterized as producing hyaluronic acid. These cell lines displayed different biological characteristics, including morphology, heterotransplantability and genetics using with BAC array CGH. The epithelial mesothelioma cells were epithelial in shape and transplantable into the subcutis of nude mice, while the cells of the fibrous mesothelioma line were fibroblast-like and transplantable into the submucosa of Hamster's cheek pouches but not into the subcutis of nude mice. The mesotheliomas are classified into three types: epithelial mesothelioma, fibrous mesothelioma and mixed type. The gene copy number losses observed on 9p21.3, 9p21.2, 9p21.1, among others may be a major mechanism of malignant mesothelioma carcinogenesis. We considered and supported the combination theory for the histogenesis of malignant mesothelioma.

Establishment and characterization of a human liposarcoma cell line (HTLS) from the retroperitoneal liposarcoma.

A cell line designated HTLS was established from the retroperitoneal liposarcoma. The HTLS line showed stable proliferation without interruption for 2 years and subcultivated over 35 times. The cells were elongated fibrous and spindle in shape, and neoplastic and pleomorphic features. The multinucleated giant cells with fine cytoplasm were seen. The cells proliferated slowly and the population doubling time was about 90 hours. The chromosome number showed a wide distribution of aneuploidy, the mode was hyperdiploid range (51-52), and many marker chromosomes were observed. The cells were transplantable into the submucosa of immunesuppressed hamster's cheek pouch and produced liposarcoma, while were not transplantable into subcutis of nude mice

Establishment and characterization of human malignant lymphoma cell line derived from uterine cervix.

Human uterine cervical malignant lymphoma (B-cell type) was cultured and the cell line (HIUML) was newly established. The HIUML cells were round in shape and had a tendency to make floating clusters. The cells had a smooth surface or protrusion on the margin of the cytoplasm, and proliferate in floatation. The population doubling time was about 32 hours and 42 or more passages were successfully observed in two years. The HIUML cells were not transplantable into nude mice but were successfully done in the cheek pouch of hamster with formation of malignant lymphoma. Epstein-Barr virus was detected in the HIUML cells.

Establishment and characterization of human glioblastoma cell line (HUBT-n).

We succeeded in primary culture of 3 in 4 cases of glioblastomas. The long-term passage cultures were not done from the primary cultures of original tumor, but glioblastoma cell line (HUBT-n) was established from a xenograft of nude mouse. This line grew well without interruption for 4 years and was subcultivated over 120 times. The cells were spindle like or round in shape and neoplastic and pleomorphic features contained glial fibrillar acid protein (GFAP) and S-100 protein and grew multilayering without contact inhibition. A bough-shaped long projection was noted from a small cell. One of the characteristics of the HUBT-n cells was existence of well developed intermediate filaments in their cytoplasm. The cells proliferated rapidly, and the population doubling time was about 32 hours. The chromosome number showed a narrow distribution of diploid range. Abnormal constitution was observed in all cells by G-band karyotyping. The culture cells were easily transplanted into the subcutis of nude mouse and produced the tumor resembling the original tumor.

Establishment and characterization of a human malignant choroids plexus papilloma cell line (HIBCPP).

A cell line designated "HIBSPP" was established from a human malignant choroids plexus papilloma of 29-year-old Japanese woman. This line grew well without interruption for 3 years and was subcultivated over 70 times. The cells were spindle, oval, and polygonal in shape, and neoplastic and pleomorphic features, a jigsaw puzzle-like arrangement, multilayering and forming papillary structures without contact inhibition. The cells proliferated slowly, and the population doubling time was about 69 hours. The chromosome number showed a wide distribution of aneuploidy. The mode was in the hypotetraploid range, and many marker chromosomes were observed. The culture cells were easily transplanted into the subcutis of nude mice and produced the tumor resembling the original tumor.

In vitro culture of various typed meningiomas and characterization of a human malignant meningioma cell line (HKBMM).

We placed on culture the 13 cases of meningiomas, succeeded in making a primary culture of 10 cases and maintained 5 cases in vitro over considerable period of time (over three month), and one cell line derived from a malignant meningioma were established. In the early period of the primary culture, meningioma cells were spindle- or round-shaped cells. In the case of psammomatous type, the cultured cells were characterized as forming psammoma bodies. A cell line designated "HKBMM" was established from a human malignant meningioma occurred from frontal lobe. This line grew well without interruption for 5 years and was subcultivated over 120 times. The cells were spindle and fibrous in shape, and neoplastic and pleomorphic features, and multilayering without contact inhibition. The cells proliferated rapidly, and the population doubling time was about 29 hours. The chromosome number showed a wide distribution of aneuploidy. The mode was in the diploid range. The culture cells were easily transplanted into the subcutis of nude mice and produced the tumor resembling the original tumor.