C-band variants of telocentric chromosomes in swine: evidence and inheritance studies

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Heat and fluid flow in a scraped-surface heat exchanger containing a fluid with temperature-dependent viscosity

Scraped-surface heat exchangers (SSHEs) are extensively used in a wide variety of industrial settings where the continuous processing of fluids and fluid-like materials is involved. The steady non-isothermal flow of a Newtonian fluid with temperature-dependent viscosity in a narrow-gap SSHE when a constant temperature difference is imposed across the gap between the rotor and the stator is investigated. The mathematical model is formulated and the exact analytical solutions for the heat and fluid flow of a fluid with a general dependence of viscosity on temperature for a general blade shape are obtained. These solutions are then presented for the specific case of an exponential dependence of viscosity on temperature. Asymptotic methods are employed to investigate the behaviour of the solutions in several special limiting geometries and in the limits of weak and strong thermoviscosity. In particular, in the limit of strong thermoviscosity (i.e., strong heating or cooling and/or strong dependence of viscosity on temperature) the transverse and axial velocities become uniform in the bulk of the flow with boundary layers forming either just below the blade and just below the stationary upper wall or just above the blade and just above the moving lower wall. Results are presented for the most realistic case of a linear blade which illustrate the effect of varying the thermoviscosity of the fluid and the geometry of the SSHE on the flow

Establishment of Rat Embryonic Stem Cells and Making of Chimera Rats

The rat is a reference animal model for physiological studies and for the analysis of multigenic human diseases such as hypertension, diabetes, neurological disorders, and cancer. The rats have long been used in extensive chemical carcinogenesis studies. Thus, the rat embryonic stem (rES) cell is an important resource for the study of disease models. Attempts to derive ES cells from various mammals, including the rat, have not succeeded. Here we have established two independent rES cells from Wister rat blastocysts that have undifferentiated characters such as Nanog and Oct3/4 genes expression and they have stage-specific embryonic antigen (SSEA) -1, -3, -4, and TRA-1-81 expression. The cells were successfully cultured in an undifferentiated state and can be possible over 18 passages with maintaining more than 40% of normal karyotype. Their pluripotent potential was confirmed by the differentiation into derivatives of the endoderm, mesoderm, and ectoderm. Most importantly, the rES cells are capable of producing chimera rats. Therefore, we established pluripotent rES cell lines that are widely used to produce genetically modified experimental rats for study of human diseases

The Liberation of Embryonic Stem Cells

Mouse embryonic stem (ES) cells are defined by their capacity to self-renew and their ability to differentiate into all adult tissues including the germ line. Along with efficient clonal propagation, these properties have made them an unparalleled tool for manipulation of the mouse genome. Traditionally, mouse ES (mES) cells have been isolated and cultured in complex, poorly defined conditions that only permit efficient derivation from the 129 mouse strain; genuine ES cells have not been isolated from another species in these conditions. Recently, use of small molecule inhibitors of glycogen synthase kinase 3 (Gsk3) and the Fgf-MAPK signaling cascade has permitted efficient derivation of ES cells from all tested mouse strains. Subsequently, the first verified ES cells were established from a non-mouse species, Rattus norvegicus. Here, we summarize the advances in our understanding of the signaling pathways regulating mES cell self-renewal that led to the first derivation of rat ES cells and highlight the new opportunities presented for transgenic modeling on diverse genetic backgrounds. We also comment on the implications of this work for our understanding of pluripotent stem cells across mammalian species

Studies of synaptonemal complexes in farm mammals - a review

For the last 10 years extensive studies of synaptonemal complexes in farm mammals were carried out. In this article a survey of the obtained results is presented. Studies on synaptic behavior of chromosomes at pachytene substage of meiotic prophase I in carriers of centric fusions (cattle, sheep, goat, pig, and blue fox) showed that the trivalent is rarely involved in an association with the sex bivalent. In carriers of reciprocal translocations (pig and cattle) a wide range of synaptic configurations were found. Besides the expected cross-shaped quadrivalent, the following configurations were observed: open quadrivalent, trivalent plus univalent, and two heteromorphic bivalents. The latter configurations were quite frequently involved in the association with XY bivalent. Studies of synaptonemal complexes in interspecies hybrids (cattle x zebu, river x swamp buffalo, blue fox x silver fox) revealed a wide range of synaptic disturbances. Cases of pericentric inversions, aneuploidy, and chromosomal polymorphisms are also reviewed. This survey shows that synaptonemal complex analysis is a very useful tool in studies on causes of altered fertility in carriers of abnormal chromosome complemen

Non-Newtonian flow behaviour in narrow annular gap reactors

In this paper local flow investigations under isothermal conditions have been established for a narrow annular gap reactor (NAGR, given by a rotor/stator system with a radius ratio of ri/ro=0.8) including two wall scraper blades of different geometry. Two-dimensional laminar flow fields are considered (with Reynolds numbers below Re \u3c 82.6), based on numerical flow simulations, where validations with experimental velocity measurements are in good agreement. Comparisons of the macroscopic flow structuring behaviour are shown for Newtonian and inelastic shear-thinning fluids based on velocity profiles, secondary flows, hydrodynamic pressure contours, shear stress and energy dissipation, by varying the rotor velocity (described in terms of a characteristic rotational Reynolds number Re), the scraper blade angle (β) and the non-Newtonian flow behaviour (power-law exponent n). © 2001 Elsevier Science Ltd. All rights reserved