2,232 research outputs found
Human Induced Pluripotent Stem Cells Derived From Adult And Fetal Hepatocytes For The Study And Treatment Of Liver Metabolic Diseases
Hepatocyte transplantation has been used to treat liver disease. The availability of cells for these procedures is quite limited. hESCs and hiPSCs may be a useful source of hepatocytes for basic research and transplantation if efficient and effective differentiation protocols were developed and problems with tumorigenicity could be overcome. Recent evidence suggests that the cell of origin may affect hiPSC differentiation. Thus, hiPSCs generated from hepatocytes may differentiate back to hepatocytes more efficiently than hiPSCs from other cell types. We examined the efficiency of reprogramming adult and fetal human hepatocytes. The present studies report the generation of 40 hiPSC lines from primary human hepatocytes under feeder-free conditions (37 from fetal hepatocytes, 2 from normal adult hepatocytes and 1 from adult hepatocytes of a patient with Crigler-Najjar Syndrome, Type-1). All lines were confirmed reprogrammed and expressed markers of pluripotency by gene expression, flow cytometry, immunofluorescence, and teratoma formation. Fetal hepatocytes were reprogrammed at a frequency over 50-fold higher than adult hepatocytes. Adult hepatocytes were only reprogrammed with 6 factors, while fetal hepatocytes could be reprogrammed with 3 or 4 factors. The increased reprogramming efficiency of fetal cells was not due to increased transduction efficiency or vector toxicity.
We also report the transplantation and differentiation of human fetal hepatocyte-derived iPSCs. We show preliminary data that undifferentiated cells can engraft in mouse livers of FRG and NOD/SCID mice. Engraftment was based on human DNA presence in liver tissue. Furthermore we differentiated these cells to definitive endoderm and transplanted them to FRG mice. Human DNA and human albumin were present in mouse livers and mouse serum respectively. Finally, full hepatic differentiation was performed, although we show limited results in terms of the cells’ ability to express liver specific genes and perform liver-specific metabolism. Taken together, these studies confirm that hiPSCs can be generated from adult and fetal hepatocytes, including those with genetic diseases, and differentiated back to the hepatocyte lineage. Fetal hepatocytes reprogram much more efficiently than adult, although both could serve as useful sources of hiPSC-derived hepatocytes for basic research or transplantation if an efficient hepatic differentiation protocol could be developed
Temperature effects on the magnetization of quasi-one-dimensional Peierls distorted materials
It is shown that temperature acts to disrupt the magnetization of Peierls
distorted quasi-one-dimensional materials (Q1DM). The mean-field finite
temperature phase diagram for the field theory model employed is obtained by
considering both homogeneous and inhomogeneous condensates. The tricritical
points of the second order transition lines of the gap parameter and
magnetization are explicitly calculated. It is also shown that in the absence
of an external static magnetic field the magnetization is always zero, at any
temperature. As expected, temperature does not induce any magnetization effect
on Peierls distorted Q1DM.Comment: 11 pages, 2 figure
A Moving Bump in a Continuous Manifold: A Comprehensive Study of the Tracking Dynamics of Continuous Attractor Neural Networks
Understanding how the dynamics of a neural network is shaped by the network
structure, and consequently how the network structure facilitates the functions
implemented by the neural system, is at the core of using mathematical models
to elucidate brain functions. This study investigates the tracking dynamics of
continuous attractor neural networks (CANNs). Due to the translational
invariance of neuronal recurrent interactions, CANNs can hold a continuous
family of stationary states. They form a continuous manifold in which the
neural system is neutrally stable. We systematically explore how this property
facilitates the tracking performance of a CANN, which is believed to have clear
correspondence with brain functions. By using the wave functions of the quantum
harmonic oscillator as the basis, we demonstrate how the dynamics of a CANN is
decomposed into different motion modes, corresponding to distortions in the
amplitude, position, width or skewness of the network state. We then develop a
perturbative approach that utilizes the dominating movement of the network's
stationary states in the state space. This method allows us to approximate the
network dynamics up to an arbitrary accuracy depending on the order of
perturbation used. We quantify the distortions of a Gaussian bump during
tracking, and study their effects on the tracking performance. Results are
obtained on the maximum speed for a moving stimulus to be trackable and the
reaction time for the network to catch up with an abrupt change in the
stimulus.Comment: 43 pages, 10 figure
Miniaturização da análise de açúcares livres em tecido foliar pelo método de fenol-ácido sulfúrico.
Resumo
Introdução ao cultivo in vitro de Guanandi (Calophyllum brasiliense Camb.) oriundos de Morretes e Paranaguá, PR.
EVINCI. Resumo 003
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