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Abstract Background We previously reported the usefulness of the αGal epitope as a target molecule for gene therapy against cancer. To induce cancer cell specific transcription of the αGal epitope, an expression vector which synthesizes the αGal epitope under the control of a promoter region of the human telomerase reverse transcriptase (hTERT), NK7, was constructed. Methods NK7 was transfected into a human pancreatic carcinoma cell line, MIA cells, and telomerase-negative SUSM-1 cells served controls. Expression of the αGal epitope was confirmed by flow cytometry using IB4 lectin. The susceptibility of transfected MIA cells to human natural antibodies, was examined using a complement-dependent cytotoxic cross-match test (CDC) and a flow cytometry using annexin V. Results The αGal epitope expression was detected only on the cell surfaces of NK7-transfected MIA cells, i.e., not on naive MIA cells or telomerase negative SUSM-1 cells. The CDC results indicated that MIA cells transfected with NK7 are susceptible to human natural antibody-mediated cell killing, and the differences, as compared to NK-7 transfected telomerase negative SUSM-1 cells or telomerase positive naïve MIA cells, were statistically significant. The flow cytometry using annexin V showed a higher number of the apoptotic cells in NK-7 transfected MIA cells than in naïve MIA cells. Conclusions The results suggest that αGal epitope-expression, under the control of the hTERT-promoter, may be useful in cancer specific gene therapy.

A multi-layered satellite network (MLSN) appears to be a promising network for providing global ubiquitous broadband communication. To utilize the abundant network resources of the MLSNs, fair traffic distribution among its satellite layers is, indeed, important. In this paper, we propose a routing method to optimally distribute traffic load among the layers (i.e., the satellite layers in the MLSN). The load balancing scheme of the proposed routing method is developed by adopting a traffic distribution model, which is based upon network capacity estimation and theoretical analysis of the congestion rate in each layer. The performance of the proposed routing method has been validated through extensive computer simulations, which demonstrate that our traffic distribution model is reliable enough to characterize the traffic behavior in the MLSN. Furthermore, in contrast with the basic routing approach, our proposed routing method is more effective in terms of improved throughput and lower packet drops, which are optimized by the theoretical parameter setting. [ABSTRACT FROM PUBLISHER]

The proven pluripotency of ES cells is expected to allow their therapeutic use for regenerative medicine. We present here a novel suspension culture method that facilitates the proliferation of pluripotent ES cells without feeder cells. The culture medium contains polyvinyl alcohol (PVA), free of either animal-derived or synthetic serum, and contains very low amounts of peptidic or proteinaceous materials, which are favorable for therapeutic use. ES cells showed sustained proliferation in the suspension culture, and their undifferentiated state and pluripotency were experimentally verified. DNA microarray analyses showed a close relationship between the elevated expression of genes related to cell adhesions. We suggest that this suspension culture condition provides a better alternative to the conventional attached cell culture condition, especially for possible therapeutic use, by limiting the exposure of ES cells to feeder cells and animal products. Developmental Dynamics 237:2129-2138, 2008. © 2008 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Neural crest cells migrate throughout the embryo and differentiate into diverse derivatives: the peripheral neurons, cranial mesenchymal cells, and melanocytes. Because the neural crest cells have critical roles in organogenesis, detailed elucidation of neural crest cell differentiation is important in developmental biology. We recently reported that melanocytes could be induced from mouse ESCs. Here, we improved the culture system and showed the existence of neural crest-like precursors. The addition of retinoic acid to the culture medium reduced the hematopoiesis and promoted the expression of the neural crest marker genes. The colonies formed contained neural crest cell derivatives: neurons and glial cells, together with melanocytes. This suggested that neural crest-like cells assuming multiple cell fates had been generated in these present cultures. To isolate the neural crest-like cells, we analyzed the expression of c-Kit, a cell-surface protein expressed in the early stage of neural crest cells in vivo. The c-Kit-positive (c-Kit+) cells appeared as early as day 9 of the culture period and expressed the transcriptional factors Sox10 and Snail, which are expressed in neural crest cells. When the c-Kit+ cells were separated from the cultures and recultured, they frequently formed colonies containing neurons, glial cells, and melanocytes. Even a single c-Kit+ cell formed colonies that contained these three cell types, confirming their multipotential cell fate. The c-Kit+ cells were also capable of migrating along neural crest migratory pathways in vivo. These results indicate that the c-Kit+ cells isolated from melanocyte-differentiating cultures of ESCs are closely related to neural rest cells. [ABSTRACT FROM AUTHOR]

In 1993, a proposal at the Japan-US Science, Technology, and Space Applications Program (JUSTSAP) workshop led to a subsequent series of satellite communications experiments and demonstrations, under the title of Trans-Pacific High Data Rate Satellite Communications Experiments. The first phase of which was a joint collaboration between government and industry teams in the United States and Japan that successfully demonstrated distributed high definition video (HDV) post-production on a global scale using a combination of high data rate satellites and terrestrial fiber optic asynchronous transfer mode (ATM) networks. This was followed by the Phase-2 Internet Protocol (IP) based experiments and demonstrations [4–6] in tele-medicine and distance education, using another combination of two high data rate satellites and terrestrial fiber optic networks. The Visible Human tele-medicine and Remote Astronomy distance education demonstrations and their use of distributed systems technologies afforded an opportunity for people around the world to work together as a virtual team under one roof, using resources thousands of miles away as if they were next to each other. The visible human activity demonstrated global-scale interactive biomedical image segmentation, labeling, classification, and indexing using large images; the remote astronomy activity demonstrated collaborative observation and distance education at multiple locations around the globe and the transparent operations of distributed systems technologies over a combination of broadband satellites and terrestrial networks. The use of Internet Protocol related technologies allowed the general public to be an integral part of the exciting activities, helped to examine issues in constructing a global information infrastructure with broadband satellites, and afforded an opportunity to tap the research results from the (reliable) multicast and distributed systems communities. This paper summarizes the Phase-2... [ABSTRACT FROM AUTHOR]

This paper presents the network architecture, engineering tests and their results for the Trans-Pacific Demonstrations (TPD). The experimental network was configured using an Intelsat satellite, N-STAR, and terrestrial networks in Japan, Canada and the United States. The TransPAC, submarine fiber-optic link was also used as a backup for the Intelsat link. We began to establish the full-scale experimental network in May 2000, and performed the engineering tests during about a two-month period of the TPD. We verified the connectivity of the satellite links, ATM connections, IP and higher layers, and then measured satellite link performance, ATM transmission performance, TCP/XTP performances and so on. As the result of the engineering test, we found that networks that include one or two satellite links can be used as network infrastructure for high data rate applications. [ABSTRACT FROM AUTHOR]

A high data rate (HDR) satellite communication system is essential for developing the network configuration of a Global Information Infrastructure (GII) because of its features, such as wide area coverage, flexibility of network configuration and multicast connection capability. From this point of view, Communications Research Laboratory (CRL) is conducting research and development of a Gigabit satellite system [1] that has an on-board ATM switch and gigabit-class capacity. We have developed a hardware simulator in order to investigate how satellite links influence on-board ATM switching and network performance, such as a long delay and burst error. In this paper, we describe the simulation results for the TCP layer performance and the SVC connection set-up performance. [ABSTRACT FROM AUTHOR]

This paper discusses the measurement of the excitation amplitude and phase of each element antenna of phased arrays in satellite orbit. In a phased array, the excitation amplitude and the phase of each element antenna deviate from the desired values, due to the nearby satellite structure, the error of attachment to the satellite, and thermal deformation in the orbit. The errors in the amplitude and the phase must be known for beam scanning and the synthesis of various antenna patterns. The rotating element electric field vector method is useful in measuring the amplitude and the phase of phased arrays. In this method, the amplitude and the phase of the element antenna can be determined simply by varying the phase of the element antenna by a phase-shifter and measuring the amplitude change of the electric field as a result of composition by the array. This is suited to the measurement of phased arrays in satellite orbit, where direct measurement of the phase is difficult. In this study, the above method is used to measure the excitation amplitude and phase of the phased array installed on Engineering Test Satellite VI in orbit. Based on the measured phase, the phase is corrected to realize the designed value. The accuracy of the beam directivity is examined and the validity of the measurements is evaluated. © 1998 Scripta Technica. Electron Comm Jpn Pt 1, 81(1): 1–13, 1998 [ABSTRACT FROM AUTHOR]

The development of melanocytes from neural crest-derived precursor cells depends on signaling by the receptor tyrosine kinase KIT and the G protein-coupled endothelin receptor B (EDNRB) pathways. Loss-of-function mutations in either of these two signaling receptor molecules cause a loss or a marked reduction in the number of melanocyte precursors in the embryo and finally lead to loss of the coat color. Using cultures of embryonic stem (ES) cells to induce melanocyte differentiation in vitro, we investigated the requirement for EDNRB signaling during the entire developmental process of the melanocyte, in association with that for KIT signaling. During the 21-day period necessary for the induction of mature melanocytes from undifferentiated ES cells, endothelin 3 (EDN3), a ligand for EDNRB, increased the number of melanocytes in proportion to the period during which it was present. We tested the compensatory effect of EDNRB signaling on KIT signaling in vivo by using Kit(W-LacZ)/Kit(W-LacZ) ES cells and confirmed that the ectopic expression of EDN3 in the skin reduced the white spotting of Kit(W57)/Kit(W57)mice. KIT ligand (KITL) and EDN3 worked synergistically to induce melanocyte differentiation in vitro; however, the complete lack of EDNRB signaling attained by the use of EDN3-/- ES cells and an EDNRB antagonist, BQ788, revealed that the resulting failure of melanocyte development was not compensated by the further activation of KIT signaling by adding KITL. Simultaneous blockade of EDNRB and KIT signalings eliminated melanocyte precursors completely, suggesting that the maintenance or survival of early melanocyte precursors at least required the existence of either EDNRB or KIT signalings., (Copyright 2005 Wiley-Liss, Inc)

Embryonic stem cells have the potential to give rise to all cell lineages when introduced into the early embryo. They also give rise to a limited number of different cell types in vitro in specialized culture systems. In this study, we established a culture system in which a structure consisting of lens, neural retina, and pigmented retina was efficiently induced from embryonic stem cells. Refractile cell masses containing lens and neural retina were surrounded by retinal pigment epithelium layers and, thus, designated as eye-like structures. Developmental processes required for eye development appear to proceed in this culture system, because the formation of the eye-like structures depended on the expression of Pax6, a key transcription factor for eye development. The present culture system opens up the possibility of examining early stages of eye development and also of producing cells for use in cellular therapy for various diseases of the eye., (Copyright 2003 Wiley-Liss, Inc.)