Metastable states of water and ice during pressure-supported freezing of potato tissue.

Different ice modifications were obtained during freezing processes at several pressure levels from atmospheric pressure up to 300 MPa. In the pressure range between 210 and 240 MPa, a metastable ice I modification area was observed, as the nucleation of ice I crystals in the thermodynamically stable region of ice III was reached. A significant degree of supercooling was obtained before freezing the tissue water to ice III, which has to be considered when designing pressure-supported freezing processes. The effect of supercooling phenomenon on the phase transition time is discussed using a mathematical model based on the solution of the heat transfer governing differential equations. Phase transition and freezing times for the different freezing paths experimented are compared for the processes: freezing at atmospheric pressure, pressure-assisted freezing, and pressure-shift freezing. Different metastable states of liquid water are defined according to their process-dependent stability.

Establishment of a monkey kidney epithelial cell line with the BARF1 open reading frame from Epstein-Barr virus.

We previously reported that the BARF1 (BamH1-A right frame 1) gene product from Epstein-Barr Virus (EBV) may have oncogenic properties since injection into new-born rats of transfected cell lines resulted in the development of BARF1 expressing tumors, which were aggressive in the case of murine fibroblasts and transient in that of human B lymphocytes. As EBV has been associated with nasopharyngeal carcinoma (NPC) and evidence of BARF1 transcription in this cancer was emerging from our biopsy analyses, we examined the effects of BARF1 transfection into primate primary epithelial cells. The expression of the BARF1 open reading frame in primary monkey kidney epithelial cells led us to the establishment of continuously dividing lines. The BARF1 transfectants showed the major characteristics of immortalized cells: morphological change, short cell doubling time, ability to divide at low cell density and continuous growth over 50 passages. Injection of BARF1 transfectants into nude mice did not induce any tumor. Established subclones were shown to be epithelial cells expressing known keratins as well as the BARF1 coded mRNA and protein. This is the first report indicating that expression of the BARF1 gene product in primary epithelial cells may contribute to the establishment of cell lines.

Culture of epithelial cells derived from the oviduct of different species.

This study proposes a procedure for the isolation and culture of oviduct epithelial cells of several species. In-vitro culture on such a feeder seems to allow full embryonic development and viability. The inner linings of Fallopian tubes from mouse, rabbit, cow and human were trypsinized and the epithelial cells were enriched with Percoll gradient. Isolated cells, obtained in high yield with good viability, were maintained in monolayer culture in B2-Menezo medium supplemented with serum, which also supports early embryonic development in vitro. The plated primary cultures reached confluence within 8 days, producing a monolayer of cohesive polygonal cells. Associated with this large epithelial cell population, ciliated cells as well as polykaryotic cells and few fibroblastic nests were observed. After the first sub-culture, the ciliated cells disappeared and the epithelial cell monolayer grew rapidly to confluence within 3 days and displayed contact inhibition. No epithelial cell growth could be obtained in culture in the absence of serum. The addition of oestrogens had no effect on any of the cultured oviductal epithelial cells. A spontaneous alteration was observed in morphology and growth after several passages, the number of which depends mainly upon the species.