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This work presents an analysis of the dynamic behaviour of a HRSG (heat recovery steam generator) during start-up. A calculation program based on a quasi-steady method is constructed. A typical high-pressure HRSG is designed conceptually and analysis is performed to examine the influence of the gas inlet condition of the HRSG on its start-up behaviour. Effects of the gas turbine operation mode and the gas bypass are analysed. In addition, the water level control during start-up, which is one of the most important facts in the real plant operation, is simulated. Through a parametric calculation, the effect of the control parameters on the start-up behaviour is analysed and examples of optimum control are demonstrated. Copyright © 2000 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Sperm mediated gene transfer (SMGT) is based on the ability of spermatozoa to bind and internalize exogenous DNA and transfer it into the oocytes at fertilization. The purpose of this study was to assess introducing exogenous DNA into boar spermatozoa by DNA solution or DNA/liposome complex under different conditions (period of incubation, exogenous DNA, liposome, and concentration of spermatozoa). Genomic DNA of sperm loaded with DNA by treatment was isolated by alkaline lysis. Quantitation of exogenous DNA amplified by PCR was analyzed by agarose electrophoresis densitometry. The quality of treated spermatozoa under the best conditions or no treatment (control) was evaluated during incubation (0, 2, 4, and 6 h) for viability (SYBR-14/PI), motility (Makler counting chamber), morphology (rose bengal staining), and acrosomal status (Coomassie staining). Sperm loaded with DNA also were used for in vitro fertilization. Immature oocytes incubated in TCM-199 medium for 44 h were fertilized in mTBM medium for 6 h and cultured in PZM-3. Cleavage and development of embryos were assessed on Days 2 and 7 of culture, respectively. Transfection rates at the blastocyst stage were assessed by PCR analysis. Data were evaluated by Duncan''s multiple-range test using the GLM procedure. In the preliminary experiment, DNA uptake of spermatozoa by DNA solution and liposome/DNA complex was completed within 90-120 min. Transfection efficiency of spermatozoa was significantly (P < 0.05) higher in the 105 spermatozoa group than in the other groups (104, 106, and 107 spermatozoa). The transfection efficiency was gradually increased by increasing the concentration of exogenous DNA. On the other hand, viability of transfected spermatozoa by all treatments (control, DNA solution, and DNA/liposome) at 0 h (72.3 0.2, 70.8 1.8, and 68.0 2.2%, respectively) of storage was significantly (P < 0.05) lower than for fresh spermatozoa (83.3 1.7%). Survival and motility of all treatments after 4 h of storage were significantly (P < 0.05) lower than at 0 and 2 h. Both abnormality and acrosome reaction of spermatozoa were gradually increased with prolonged storage periods. On the other hand, the cleavage rate of embryos by DNA/liposome complex (56.3 2.3%) was significantly (P < 0.05) lower compared to both DNA solution (64.0 1.1%) and control (67.8 2.3%). The developmental rates of blastocysts were significantly (P < 0.05) lower in the liposome/DNA complex and DNA solution groups (9.1 1.3 and 11.3 0.8%) than in the control group (22.2 0.6%). The transfection rates of blastocysts were higher in the liposome/DNA group (54.3 12.0%) than in the DNA solution group (38.7 6.6%). These results show that the SMGT method under the control conditions efficiently transfers exogenous DNA into the porcine oocytes.This work was supported by the Research on the Production of Bio-organs (No. 2005 03020302) Ministry of Agriculture and Forestry, Republic of Korea [ABSTRACT FROM AUTHOR]

P-doped ZnO was fabricated by means of the ion-implantation method. At the Raman measurement, the blue shift of the E2 high mode and A1(LO) phonon of the inactive mode were observed after the P-ion implantation. It suggested to be caused by the compressive stress. Thus, Hall effect measurement indicates that the acceptor levels exists in P-doped ZnO while still maintaining n-type ZnO. From the X-ray photoelectron spectroscopy, the chemical bond formation of the P2p3/2 spectrum consisted of 2(P2O5) molecules. Therefore, the implanted P ions were substituted to the Zn site in ZnO. From the photoluminescence (PL) spectra, P-related PL peaks were observed in the energy ranges of 3.1 and 3.5 eV, and its origin was analyzed at PZn-2VZn complexes, acting as a shallow acceptor. With increasing temperatures, the neutral-acceptor bound-exciton emission, (A0, X), shows a tendency to quench the intensity and extend the emission linewidth. From the relations of the intensity and the linewidth as a function of temperature, the broadening of linewidth was believed to the result that the vibration mode of E2 high participates in the broadening process of (A0, X) and the change of luminescent intensity was attributed to the partial dissociation of (A0, X). Consequently, these facts indicate that the acceptor levels existed in P-doped ZnO layer by the ion implantation. [ABSTRACT FROM AUTHOR]

Background and Aims In Tilia amurensis, two types of trichomes (hairy and glandular) develop from epidermal surfaces of cotyledons and hypocotyls of zygotic embryos soon after germination. Here, it is demonstrated that glandular trichome initials develop directly into somatic embryos when treated in vitro with 2,4-dichlorophenoxyacetic acid (2,4-D). Methods Zygotic embryos of Tilia amurensis were cultured on Murashige and Skoog medium with 3 % sucrose and various concentrations (0, 2·2, 4·4 and 8·8 µm) of 2,4-D. Morphological development of trichomes and somatic embryos was analysed by scanning electron microscope and light microscope after histological sectioning. Key Results In zygotic embryos cultured on medium with 4·4 µm 2,4-D, formation of hairy trichomes was completely suppressed but formation of glandular trichome initials increased. That some filamentous trichome initials developed directly into somatic embryos was confirmed by histological and scanning electron microscope observation. When explants with different stages of trichome initials (two-, four- and eight-celled filamentous and fully mature trichomes) were temporally pre-treated with 4·4 µm 2,4-D for 24 h and transferred into hormone-free medium, two-celled and four-celled filamentous trichome initials were the effective stage of trichomes for somatic embryo induction. Conclusions It is suggested that early developing filamentous trichome initials have developmental plasticity and that with 2,4-D treatment these trichome initials develop directly into somatic embryos. [ABSTRACT FROM AUTHOR]

Somatic cell nuclear transfer (SCNT) is one of the most useful methods for production of transgenic animals. While both adult and fetal fibroblasts have been used in SCNT, adult cells provide the opportunity to use donor cells from an animal with a proven high yield of milk production. In this study, in vitro development and pregnancy rates were compared following the use of transfected fibroblasts that were obtained from adult and fetal tissues. Ear and fetal fibroblasts were collected from Saanen goats and cultured in serum-starvation condition (TCM-199 + 0.5% FBS) until cell confluence. Linearized DNA containing the human granulocyte-macrophage colony-stimulating factor (hGM-CSF) gene that is targeted for expression in the mammary gland by the ?-casein promoter (pBC1/hGM-CSF) was transfected into the cells using lipofectamine 2000 (Invitrogen, Inc., Carlsbad, CA, USA). Transfected colonies were selected with G418 for 14 days. Well-separated colonies were isolated and screened for the presence of transgene by PCR and southern blotting. Recipient oocytes were surgically collected by flushing the oviducts of FSH-stimulated goats at 35 h after hCG injection. The zonae pellucidae of the oocytes were partially drilled using a laser system and each somatic cell was individually transferred into the enucleated oocyte. The couplets were electrically fused and activated by ionomycin + 6-DMAP. The reconstructed embryos were cultured in mSOF medium containing 0.8% BSA at 39C in an atmosphere of 5% CO2, 5% O2, 90% N2 for 12 to 15 h. Nuclear transfer embryos (2- to 4-cell stages) were surgically transferred into the oviducts of recipients that were in either natural or induced estrus. Pregnancy was diagnosed by progesterone assay and ultrasound on Days 21, 42, and 60 of pregnancy. The type of donor cells, ear or fetal fibroblasts, affected neither the fusion rate (54/65, 83.1% vs. 89/116, 76.7%, respectively) nor the cleavage rate (19/54, 35.2% vs. 37/89, 41.6%, respectively). A total of 55 embryos derived from ear fibroblasts and 84 embryos derived from fetal fibroblasts were transferred into 9 and 14 recipients, respectively. No pregnancy was observed in recipients that received NT embryos derived from ear fibroblasts (0/9); however, 5 (2 in natural estrus and 3 in induced estrus; 35.7%), 3 (1 in natural and 2 in induced estrus; 21.4%), and 2 (2 in induced estrus; 14.3%) of 14 recipients that received NT embryos derived from fetal fibroblasts were confirmed pregnant on Days 21, 42, and 60, respectively. These results imply that the type of donor cells for nuclear transfer may be directly correlated with the success rate. More studies will be needed to examine factors affecting production of transgenic goats and to improve results obtained using adult donor cells. [ABSTRACT FROM AUTHOR]

Human natural killer (NK) cell-mediated response plays an important role in xenograft rejection. In the case of pig-to-human xenotransplantation, it has been suggested that NK cells are involved in delayed-type rejection, which is characterized by pig endothelial cell (pEC) activation, direct lysis, and secretion of proinflammatory cytokines. NK cell activation can be a direct barrier to the potential use of pig organs for human xenograft transplantation. Therefore, it is important to suppress the NK cell activity on pig-to-human xenografts. Expression of HLA-G1 (non-classical major histocompatibility complex class I molecules) inhibits the cytotoxic activity of NK cells and has been proposed as a potential solution to overcome NK cell-mediated xenogeneic cytotoxicity in pEC. In this study, we transfected the HLA-G1 gene into mini-pig fetal fibroblasts to produce 2 HLA-G1 clonal cell lines. These cell lines were used to produce cloned HLA-G1 transgenic mini-pigs by nuclear transfer (NT). The presence of the HLA-G1 gene in transgenic mini-pigs was confirmed by PCR. The expression of HLA-G1 was detected by flow cytometry-immunohistochemistry assay. Mini-pig fibroblasts derived from a 35-day-old cloned fetus also showed characteristics similar to those of HLA-G1 clonal cell lines. The expressed HLA-G1 significantly suppressed NK-mediated cell lysis, and the rate of NK 92MI cell cytotoxicity was reduced as compared to the control group (HLA-G1: 46.7 4.5%; control: 4.6 13.3%; P < 0.05). In conclusion, transgenic cloned mini-pigs expressing HLA-G1 were produced by NT for the first time. It is expected that these mini-pigs could be used to overcome the NK cell-mediated rejection in xenotransplantation. [ABSTRACT FROM AUTHOR]

Xenotransplantation has the potential to resolve the chronic shortage of donor organs if immunological barriers can be overcome. In particular, the initial type of rejection following xenotransplantation is acute cellular rejection by host CD8+ cytotoxic T lymphocyte (CTL) cells that react to the donor class I major histocompatibility complex (MHC). The human cytomegalovirus (HCMV) glycoprotein US2 specifically targets class I MHC heavy chains for dislocation from the endoplasmic reticulum (ER) membrane to the cytosol, where they are degraded by the proteasome. In this study, the recombinant expression vector pCX-US2 was stably transfected into mini-pig fetal fibroblasts by lipofection. The integration of US2 into the host genome was confirmed by PCR and Southern blot assay. The reduction of swine leukocyte antigen class I (SLA-I, MHC protein class I) by US2 was detected by flow cytometry analysis (FACS). FACS analysis of US2 clonal cell lines demonstrated substantial reductions in SLA surface expression. The decrease in the level of class I MHC expression for US2 clonal cell lines ranged from 22 to 34% relative to the non-transfected control. US2 clonal cell lines were also tested to determine if the resulting reduction in cell surface SLA would reduce in vitro cytotoxicity by CTL. The US2 clonal cell line demonstrated 5- to 6-fold reduction of specific lysis by primed CD8+ CTL. In conclusion, US2 can directly protect pig clonal cell lines from human CTL cells. These results indicate that the expression of US2 in pig cells may provide a new approach toward overcoming CTL-mediated immunity to xenotransplantation.This work was supported by the National Livestock Research Institute (6132-211-303-1). [ABSTRACT FROM AUTHOR]

We demonstrate that the Lyman α forest flux power spectrum of ‘randomized’ quasi-stellar object (QSO) absorption spectra is comparable in shape and amplitude to the flux power spectrum of the original observed spectra. In the randomized spectra a random shift in wavelength has been added to the observed absorption lines as identified and fitted with vpfit. At the ‘3D’ power spectrum of the randomized flux agrees with that of observed spectra within the errors. At larger scales it still approaches 50 per cent of that of the observed spectra. At smaller scales the flux power spectrum is dominated by metal lines. Lines of increasing column density contribute to the ‘3D’ flux power spectrum at increasingly larger scales. Lines with dominate at the peak of the ‘3D’ power spectrum while strong absorbers with contribute at large scales, . We further show that a fraction of ≳15 per cent of the mean flux decrement is contributed by strong absorbers at . Analysis of the flux power spectrum which use numerical simulations with too few strong absorption systems calibrated with the observed mean flux may underestimate the inferred rms fluctuation amplitude and the slope of the initial dark matter power spectrum. [ABSTRACT FROM AUTHOR]